CWAQP - PCST Instrumentation 2 PDF

CONTRACTOR WORK FORCE ASSESSMENT & QUALIFICATION PROGRAM CWAQP Instrumentation INSTRUMENT TECHNICIAN REMEDIAL The purpose of this presentation is to provide remedial training and instruction to contractor Instrument Technicians It will be understood that all the necessary safety training has been completed and the mandatory test passed Under each objective there will be a brief description of the required knowledge in order to reapply for the main qualification certification test TERMINAL OBJECTIVE Will competently and safely work in oil and gas facilities as an instrumentation technician to install, troubleshoot and maintain complete instrumentation loops from field devices to the process control systems connections (e.g. DCS and PLC) ENABLING OBJECTIVES 1. IDENTIFY SAFETY EQUIPMENT,HAZARDS,PROTECTION AND RULES 1.1. Identify Operator's Responses in an Emergency/Disaster Situations. 1.2. Identify Requirements to Comply with work Permit Procedures. 1.3. Identify Requirements to Comply with Isolation & Lockout Procedures. 1.4. Identify Requirements to Comply with Personal Protective Equipment (PPE). ENABLING OBJECTIVES 2. TERMS,SYMBILS AND P&ID 2.1 Identify Instrument Loops. 2.2 Identify Instrument Drawing and Symbols. 2.3 Identify Electronic and Pneumatic Terminology. ENABLING OBJECTIVES 3.TEST EQUIPMENTS 3.1 Explain The Use of a Multimeter. 3.2 Explain The Use of a Communicator. 3.3 Identify Instrumentation Hand Tools. ENABLING OBJECTIVES 4. Instrument and control Loop Components 4.1 Identify Components, Principles of Operation and Repair of Transducers. 4.2 Explain Principles of Operation, Testing and Replacement of Solenoids. 4.3 Explain the Testing and Replacement of Transducers. 4.4 Identify Actuator and Positioner Components. 4.5 Define Piston Actuator Principles. ENABLING OBJECTIVES 4. Instrument and control Loop Components 4.6 Define Pressure Element Principles. 4.7 Diagnose Pressure Loop Problems. 4.8 Explain the Function of Switches. 4.9 Troubleshoot and Repair Electronic Transmitters. 4.10 Explain Calibration of Electronic Transmitters. ENABLING OBJECTIVES 4. Instrument and control Loop Components 4.11 Explain Calibration Switches. 4.12 Explain Function of Pressure Regulators and Signal Booster. 4.13 Repair of Pneumatic Controllers and Relays. 4.14 Troubleshooting of Pneumatic Control Loop & Relays. 4.15 Explain Calibration of valve Positioners. ENABLING OBJECTIVES 4. Instrument and control Loop Components 4.16 Explain Repair of Switches. 4.17 Define Resistance Temperature Detector Principles. 4.18 Define Thermocouple Principles. 4.19 Troubleshoot RTD and Thermocouples. Objectives 1 1.1. Identify Operator's Responses in an Emergency/Disaster Situations. 1.2. Identify Requirements to Comply with work Permit Procedures. 1.3. Identify Requirements to Comply with Isolation & Lockout Procedures. 1.4. Identify Requirements to Comply with Personal Protective Equipment (PPE). Objective 1.1 Identify Operator’s Responses in an Emergency/Disaster Situations Objective 1.1 Plant Alarms: Different plants use different sounding alarms responses to alarms are frequently practised. An operator must learn the alarms for his plant : Stop work Fire Combustible gas release Hydrogen sulfide (H2S) leak Evacuate plant Disaster All clear Objective 1.1 Fire Alarms When a fire alarm sounds, an operator must immediately report to his supervising operator The supervising operator will instruct him to : Stay at his current position. OR Direct him to another area to help in the fire fighting. Objective 1.1 Hydrocarbon Leaks If an operators discovers a hydrocarbon leak he must: 1. Report the leak immediately. 2. Stop all hot work that may create an ignition source. 3. Tell all drivers in the area to turn off their engines and stop anymore vehicles from entering the area. Objective 1.1 Hydrocarbon Leaks If an operators discovers a hydrocarbon leak he must: 1. Try to isolate the leaking equipment. (without endangering himself) 2. Stay upwind of a leak. (Hydrocarbon vapors are harmful to breathe) 6. Stay away from the vapor cloud in case it ignites. Objective 1.1 If you are driving a vehicle & you hear a gas alarm you must : Switch off the engine immediately If the engine stops on its own: Do not try to restart it, as you may be in the middle of the vapor cloud. Check the wind sock for wind direction. Get out of the vehicle and walk to a safe location crosswind or upwind of the release. Inform the plant control room of the situation. DO NOT RESTART YOUR VEHICLE UNTIL CERTAIN THERE ARE NO GAS LEAKS Objective 1.1 H2S Alarms In some plants, when the automatic detectors sense H2S in the air: An alarm will sound only in the control room. The control room will announce the H2S leak over the public address system. In other plants the H2S alarm automatically sounds outside. Objective 1.1 H2S Alarms Operator response to an H2S alarm: Contact the control room immediately to learn the location of the leak. Walk upwind of the leak, if instructed to leave the work area. If instructed to evacuate the plant : Put on a Scott Air-Pak, and move to an assembly point outside the plant area. Objective 1.1 Walk Upwind of the Leak Wind Sock Upwind Objective 1.1 H2S Leak Control After plant evacuation : The supervising operator will send 2 operators wearing Scot Air-Paks back into the general area of the reported leak. One operator enters the leak area with a portable H2S monitor to identify the exact location. 2nd operator remains on standby with spare Scott Air Pak. When the leak is located, he will isolate it by closing valves. He will report his findings and coordinate his actions with the control room. Objective 1.1 Disaster Alarm: Disasters are emergency situations that are out of control. If a fire is detected, the fire alarm sounds. If the fire becomes uncontrollable, the disaster alarm is sounded. If an emergency starts with a large problem such as a big explosion the disaster alarm will sound immediately When the disaster alarm sounds : Go immediately to the plant assembly point. At assembly points operators will receive instructions: Help control the emergency. Stay at the assembly point until all clear signal is given. Evacuate the area using the posted evacuation routes. Objective 1.1 Review Questions 1. When disaster alarm sounds what must you do? 2. Name the picture shown: 3. What instrument is used in checking the wind direction? Objective 1.1 Review Questions with Answers 1. When disaster alarm sounds what must you do? Go immediately to the plant assembly point. 2. Name the picture shown: Wind Sock 3. What instrument is used in checking the wind direction? Wind Sock Objective 1.2 Identify Requirements to Comply with Work Permit Procedures Objective 1.2 Identify the basic concepts, definitions & main responsibilities in Saudi Aramco Work Permit system. Objective 1.2 Purpose of Work Permits You must use Work Permits when working in hazardous areas. By using them, you make sure that all hazards and precautions are identified so that work can be done safely. Using Work Permits helps prevents incidents like fires, equipment damage and injuries; they make sure Issuers, Receivers and workers communicate with each other so they know what is happening and what they must do. With a Work Permit, you control the work by giving people permission to do specific work, with specific equipment, and using specific procedures. Objective 1.2 A Work Permit Issuer inspects the work site, identifies what hazards and precautions must be taken to work safely, and fills out and signs Work Permits. Receivers are the people who will do the work(maintenance technician). They have to comply with all safety precautions written on the Work Permit, and they must sign the Work Permit.(usually the work permit is obtains from operation supervisor) Both are responsible for the safety at the work site Objective 1.2 Objective 1.2 HOT WORK Permit Whenever an ignition source will be used, you must use a HOT WORK permit. Hot work creates enough heat to ignite a flammable or combustible material. This includes the use of spark or flame-producing tools, and work on live electrical equipment, heat producing equipment, and internal combustion engines. If hot work is not controlled, the workers could cause an unplanned fire or explosion. Objective 1.2 COLD WORK Permit The COLD WORK job does not create an ignition source. Cold work can include the use of hand tools, sand removal, brush painting, building scaffolding, installing shoring or carpentry work. Cold work is any work that does not create an ignition source. Objective 1.2 Objective 1.2 CONFINED SPACE Permit A confined space is… any space: tank, vessel, pipeline, vault, or excavation over 4 feet deep. which is not normally intended for human occupancy in which movement is restricted and which has the potential to contain hazardous materials. Objective 1.2 Objective 1.2 Additional Precautions Wear hearing protection Hand dig only Use a fire blanket Use a flag man Keep asbestos material wet Wear chemical suit Ensure man-way watch has a radio Ensure critical lift plan on site Objective 1.2 If the issuer and receiver cannot meet to close a work permit, it can be closed without signatures if both the issuer and receiver agree to this ahead of time and it is written on the work permit The issuer must keep all work permits on file for at least 3 months and the receiver is also encouraged to do so after work is completed. Objective 1.2 Work Permits Examples Notice that some jobs requires more than one type of permit. Objective 1.2 Review Questions 1. Which person carries the receiver certificate? 2. What environment are HOT WORK permit used in? 3. What work permit is shown? 4. What work permit is shown? 5. How long shall work permits be kept on file after work is completed? Objective 1.2 Review Questions with Answers 1. Which person carries the receiver certificate? Maintenance technician 2. What environment are HOT WORK permit used in? ignition source, spark, flame-producing tools, work on live electrical equipment 3. What work permit is shown? Cold 4. What work permit is shown? Hot 5. How long shall work permits be kept on file after work is completed? 3 moths Objective 1.3 Identify Requirements to Comply with Isolation & Lockout Procedures Objective 1.3 1. Identify how and why equipment is prepared for maintenance. 2. Identify what equipment is isolated and how it is isolated. 3. Identify the purpose of Locks/Tags & how they are used. Objective 1.3 Before you work on a piece of equipment, the Issuer must make sure the equipment is safe to work on. The Issuer must shut it down, isolate, de-energize, and purge or clean it. The order in which the operator does these things depends upon the type of equipment he is preparing: 1. Shut down and isolated. 2. Depressurized or de-energized. 3. Cleaned or purged. Objective 1.3 Equipment must be isolated Qs. Why equipment must be isolated? Isolate equipment to make sure it cannot start-up, turn, move, leak or cause an electric shock. Prevents the unexpected release of energy or hazardous materials. If the equipment starts up or moves, you or your co- workers could be injured or killed. If a valve leaks or is accidentally opened, dangerous materials may be released into a confined space or to the atmosphere. Objective 1.3 If you don’t isolate equipment correctly, a terrible incident or fire could happen. Therefore, before you issue or receive any Work Permit, you must make sure that equipment is completely isolated. Here are some examples of the equipment that we should isolate: Electrical equipment. Mechanical equipment. Hydraulic equipment. Air- or gas-operated systems. Vessels, pipes and confined spaces. Objective 1.3 Here are some methods of isolating equipment: Install blinds. Remove piping. Close and chain valves. Open electrical circuit breakers. Remove fuses or disconnect wiring. Objective 1.3 Blinds are metal plates that are installed in a pipeline or equipment. They prevent liquids or gases from coming in contact with people. Use blinds to isolate operating equipment such as tanks, vessels, pumps, compressors and pipelines. Sometimes a section of piping can be removed to isolate equipment. Objective 1.3 Use chains to prevent a valve from being opened by accident. Install locks to make sure a electrical circuit breakers cannot be closed, a valve cannot opened, or any method of isolation cannot be overcome. Locks prevent accidental start-up of equipment while work is in progress. Objective 1.3 Locks/Tags Sequence Before issuing or receiving a Work Permit, you must identify all locations where locks & tags must be installed. 1. Operations must install their locks and tags first. 1. Then, one craftsman from each work crew, who will work on the equipment, must also install his lock and tag. Objective 1.3 There must only be one key for every lock used. This way, the only person who can open the lock is the person who installed it. One lock When operators change shifts, the new operations supervisor reviews all isolated equipment. He must also review the locations of locks and tags. Operations’ locks and tags may be left installed between shift changes. The keys to operations locks may also be transferred to One key the new shift. This only applies to operations locks and tags at a shift change. Objective 1.3 When craftsmen change shifts and the work must continue. But then, the on-coming shift must install their own locks and tags. Old shift remove locks & tags New shift install new locks & tags Objective 1.3 Alternatively, when craftsmen change shifts, and the work must continue, they can leave their locks in place. Transfer keys When they do this, the keys for to new shift their locks are transferred to the new craftsmen. The new craft foreman or supervisor must review each locked location. He can then install new tags, or sign the old ones and leave them in place. New shift – new tags, or sign old tags Objective 1.3 Locks and Tags Objective 1.3 Lockout hasp Hold Tag Multiple Lockout lock in hasp Lockout Padlocks and chain Objective 1.3 Review Questions 1. Name the item shown. 2. Name the item shown. 3. Name the item shown. Objective 1.3 Review Questions with Answers 1. Name the item shown. Hot tag 2. Name the item shown. Multiple Lockout lock in hasp 3. Name the item shown. Lockout Padlocks and chain Objective 1.4 Identify Requirements to Comply with Personal Protective Equipment (PPE) Objective 1.4 Personal Protective Equipment(PPE): Objective 1.4 PPE can be defined as all equipment including clothing to protect from the weather which is intended to worn or held by a person at work, which protects against one or more risks to his health and safety. Examples of this are safety Helmets, gloves, eye protection, safety footwear etc. Objective 1.4 Types of PPE and their uses There are many types of PPE each required for a specific purpose. Different types of PPE are required to protect various body parts. For example safety footwear to protect the feet and gloves to protect the hands. The following slides illustrate the various types of PPE and their use. Objective 1.4 Foot Protection Foot Protection: Protect the feet from injury from a range of hazards including: Exposure to water or other Falling objects Slipping Penetration by sharp objects Burns Electric shock Objective 1.4 Ear Protection Ear Protection: The ears can be damaged by high levels of noise. Noise may also cause irritating sensations in the ear such as ringing, EAR MUFF accelerate the hearing loss which normally develops as we grow older. The harmful effect of noise depend on: 1- The noise Level. EAR PLUGS 2- The length of time exposed to the noise. Objective 1.4 Hearing Protection Loud noise of high and low frequency can cause permanent damage to your hearing. Ear Plugs are provided to protect your hearing. Which are best for high frequency noises. Ear Muffs are best for low frequency noise. EAR MUFF EAR PLUGS Objective 1.4 Hearing Protection A low frequency sound is about 500Hz & lower. A high frequency sound is about 2000Hz & higher. A bass drum, a “rumble,” thunder, or a man's deep voice are all examples of low frequency sounds. A shrill whistle, squeak, squeal, or a child's voice are all examples of high frequency sounds. You must wear hearing protection when you see this sign. Objective 1.4 Measurement of noise Noise is measured in Decibels (dB). Hearing protection is advised when the level reaches 85 dB over a period of 8 hrs. Examples of the noise levels during workshop activities: Hammering steel plate 95dB Using the guillotine up to 100dB Using the pedestal Grinder 95dB Objective 1.4 Respiratory protection The respiratory system includes the lungs and the breathing passages. Two main risks: Inhaling fumes or gases, causing poisoning or asphyxiation. Filter Lung damage due to inhaling dust or mask other small particles. The work area should always be well ventilated, local extraction should also be used in a confined space. Objective 1.4 Respirator masks are more complex than filter masks and can clean the air from toxic particles as you breathe. Air or oxygen packs have their own clean air supply. They are air effective protection against toxic gasses and smoke. (SCBA) Self Contained Breathing Apparatus. Objective 1.4 Eye protection The eyes are very vulnerable to a range of hazards including: Liquid splashes Flying particles such as metals, stones or glass Intense heat and light such as sparks from hot metals, electric arc or lasers Types of eye protection available include: Safety spectacles Safety goggles Face shields Objective 1.4 Hand Protection Your hands are often at the greatest risk as they get closest to machinery. They can suffer from many types of injury, including: Grazes and cuts, Temperature burns, Knocks and Blows, Chemical burns, Electric shock. Hand and arm protection includes : Gloves or mitts. Rubber gloves should be tested in the lab every 3 months. Operators must perform air test for rubber gloves prior to work. * Rubber glove must be protected by leather gloves. Objective 1.4 Hand Protection DO NOT wear gloves when operating rotating equipment such as drills as they can get caught in the machinery. Objective 1.4 Head protection Your head is at risk from hazards such as: Being hit by falling objects. Getting hair tangled in machinery. Being struck by sparks during welding. Being sprayed by chemicals from leaking pipes. Face masks to protect from chemical splashes. Objective 1.4 Body protection - Chemical spillages. - Extremes of temperature. - Colliding with a person in poor visibility. - Penetration of sharp objects. - Clothes becoming ignited or caught in machinery. Methods of protection Overalls can only protect you if they are: - Clean. - In good condition. - Fit well. Objective 1.4 Body protection Other methods include: Aprons or disposable overalls. Padded clothing. Reflective clothing for use in poor visibility. Objective 1.4 Clothing In the Workshop While working in the workshop you will: use drilling machines Use cutting fluids handle sharp material using your hands Cut material using hack saws Fill material Use a hammer for centre punching You must select the appropriate PPE whilst carrying out these activities! Objective 1.4 Fire Extinguisher Types & Colour Codes Objective 1.4 Fire Extinguisher Types & Colour Codes Objective 1.4 Review Questions Refer to the Fire extinguisher classification table, and answer the following questions: 1.What type of materials is class A fire extinguisher most suitable for? 2. What materials is class A fire extinguisher NOT suitable for? 3. What type of fire extinguisher is most suitable for Flammable gas & Flammable metal? Objective 1.4 Review Questions with Answers Refer to the Fire extinguisher classification table, and answer the following questions: 1.What type of materials is class A fire extinguisher most suitable for? Water, Foam, Dry Powder, Wet chemical 2. What materials is class A fire extinguisher NOT suitable for? CO2 3. What type of fire extinguisher is most suitable for Flammable gas & Flammable metal? Dry Powder Objective 1.4 Review Questions 4. What type of fire extinguisher is most suitable for Electrical equipment? 5. What type of fire extinguisher is most suitable for Deep fat fryer? Objective 1.4 Review Questions with Answers 4. What type of fire extinguisher is most suitable for Electrical equipment? Dry Powder & CO2 5. What type of fire extinguisher is most suitable for Deep fat fryer? Wet chemical Objective 1.4 Review Questions 6. What must the operator do before using a rubber gloves? 7. How often showed rubber gloves be tested in the lab? 7. Name the protection item shown? 8. Name the protection item shown? Objective 1.4 Review Questions with Answers 6. What must the operator do before using a rubber gloves? Air test prior to work 7. How often showed rubber gloves be tested in the lab? every 3 months 7. Name the protection item shown? Ear plug 8. Name the protection item shown? Earmuffs Objective 1.4 Review Questions 9. What breathing protection item must you use at a petrochemical industry? Objective 1.4 Review Questions with Answers 9. What breathing protection item must you use at a petrochemical industry? Respirator Do you have any questions ? Terms, symbols and P&ID Objectives 2.1 Identify Instrument Loops. 2.2 Identify Instrument Drawing and Symbols. 2.3 Identify Electronic and Pneumatic Terminology. Terms, symbols and P&ID Objective 2.1 2.1. Identify Instrumentation Loops Objective 2.1. Identify Instrumentation Loops Electronic Pressure Control Loop Objective 2.1. Identify Instrumentation Loops Electronic Pressure Control Loop Objective 2.1. Identify Instrumentation Loops Electronic Pressure Control Loop Objective 2.1. Identify Instrumentation Loops Electronic Flow Control Loop Objective 2.1. Identify Instrumentation Loops Electronic Flow Control Loop Objective 2.1. Identify Instrumentation Loops Electronic Flow Control Loop Objective 2.1. Identify Instrumentation Loops Electronic Flow Control Loop The positioner signals the actuator to open, close, or throttle as required to affect the process variable (flow). The action taken depends on the signal from the sensor (transmitter (FT)) and controller’s set point (PIC). Objective 2.1. Identify Instrumentation Loops Electronic Temperature Control Loop The temperature control loop consists of a Temperature Element (TE), transmitter (TT), temperature indicating controller (TIC), and temperature control valve (TCV). Objective 2.1. Identify Instrumentation Loops Electronic Temperature Control Loop Steam is used to heat the cold water input to the exchanger. The temperature element (TE) senses the temperature of the hot water output from the exchanger and sends a signal to the controller. The controller compares the signal from the temperature element with the set point and sends a signal to the control valve. Objective 2.1. Identify Instrumentation Loops Electronic Temperature Control Loop The control valve (TCV) consists of a positioner, actuator, and valve. The positioner receives the signal from the controller and signals the actuator to open, close, or throttle the valve as required to affect the process variable (temperature). The action taken depends on the signal from the sensor (TE) and controller. Objective 2.1. Identify Instrumentation Loops Electronic Level Control Loop The level control loop consists of the same basic components as the other loops. There is a sensor (transmitter), controller, and control valve. This is shown in below Objective 2.1. Identify Instrumentation Loops Electronic Level Control Loop LT is a differential pressure transmitter that senses the pressure created by the height of liquid in the vessel multiplied by its specific gravity. The pressure is proportional to the level of the liquid. The transmitter sends a signal to the level indicating controller, LIC. Objective 2.1. Identify Instrumentation Loops Electronic Level Control Loop The controller (LIC) operates the same as other indicating controllers. It compares the signal from the transmitter (LT) with the set point and outputs a signal to the control valve (LCV). Objective 2.1. Identify Instrumentation Loops Electronic Level Control Loop The control valve (LCV) positioner receives the signal from the controller and signals the actuator to open or close the valve as required to affect the process variable (level). The action taken depends on the signal from the sensor (transmitter) and controller. Objective 2.1. Identify Instrumentation Loops Electronic Level Control Loop Sight glass gauges LG A and B are not part of the control loop. They are used to observe the level in the tank and confirm that the level indicating controller is indicating the same level. All control loops discussed are pneumatic (powered by compressed air) and use similar devices to control the loops. Objective 2.1. Identify Instrumentation Loops Control Loop Response to process upset The measuring instruments provide continuous feedback to the controller action. The controller continues making adjustments until the temperature returns to set point. Objective 2.1. Identify Instrumentation Loops Review Questions 1. In a level control loop, What is differential pressure measured in? a. PSIG b. inches of mercury c. Fahrenheit or Centigrade d. inches of water 2. In a reverse acting controller, What will happen if an increase in the input signal? a. Decrease in system pressure b. Increase in the output signal c. Decrease in the output signal d. Increase in the valve opening Objective 2.1. Identify Instrumentation Loops Review Questions with Answers 1. In a level control loop, What is differential pressure measured in? a. PSIG b. inches of mercury c. Fahrenheit or Centigrade d. inches of water 2. In a reverse acting controller, What will happen if an increase in the input signal? a. Decrease in system pressure b. Increase in the output signal c. Decrease in the output signal d. Increase in the valve opening Objective 2.1. Identify Instrumentation Loops Review Questions 3. Which component tells the actuator to open, close, or throttle the valve? a. transmitter b. positioner c. sensor d. temperature element 4. The controller compares the signal from the transmitter with the set point and sends a signal to the_ a. Transmitter b. Sensor c. Control valve d. Temperature element Objective 2.1. Identify Instrumentation Loops Review Questions with Answers 3. Which component tells the actuator to open, close, or throttle the valve? a. transmitter b. positioner c. sensor d. temperature element 4. The controller compares the signal from the transmitter with the set point and sends a signal to the_ a. Transmitter b. Sensor c. Control valve d. Temperature element Objective 2.1. Identify Instrumentation Loops Review Questions 5. Refer to fig. What type of process control is being used? a. Cascade b. Open Loop c. Ratio d. Close loop Objective 2.1. Identify Instrumentation Loops Review Questions with Answers 5. Refer to fig. What type of process control is being used? a. Cascade b. Open Loop c. Ratio d. Close loop Objective 2.1. Identify Instrumentation Loops Review Questions 6. Refer to fig. What type of process control is being used? a. Cascade b. Open Loop c. Ratio d. Close loop Objective 2.1. Identify Instrumentation Loops Review Questions with Answers 6. Refer to fig. What type of process control is being used? a. Cascade b. Open Loop c. Ratio d. Close loop Objective 2.2 2.2. Identify instrument Drawing and symbols Objective 2.2. Identify instrument Drawing and symbols Symbols for location Line symbols are used to indicate the type of the line used by the instrument within the process. Objective 2.2. Identify instrument Drawing and symbols Symbols for location Lines through the center of symbol are used to indicate location of the instrument Objective 2.2. Identify instrument Drawing and symbols The instrument symbol will also contain the instrument’s ID and type. For example, PT 456 will look like this: P Pressure 456 Transmitter T instrument’s ID Some instruments will also have the instrument's calibrated range next to it 25-100psi P 456 T calibrated range Objective 2.2. Identify instrument Drawing and symbols Dashed lines indicate that the instrument is located behind a panel and is NOT easily accessible Objective 2.2. Identify instrument Drawing and symbols The information from instrument symbol H Name of instrument: Pressure Indicating Controller loop no. is it part of : Pressure Control loop No. 123 Objective 2.2. Identify instrument Drawing and symbols If the instrument is local only then it will also have indication of how it operates, either pneumatically or electrically or both: Objective 2.2. Identify instrument Drawing and symbols Name the valves Objective 2.2. Identify instrument Drawing and symbols Objective 2.2. Identify instrument Drawing and symbols Objective 2.1. Identify Instrumentation Loops Identifying information from the given loop below. Objective 2.2. Identify instrument Drawing and symbols Instrument Abbreviations Objective 2.2. Identify instrument Drawing and symbols Instrument Abbreviations Objective 2.2. Identify instrument Drawing and symbols Review Questions Name the line symbols Objective 2.2. Identify instrument Drawing and symbols Review Questions with Answers Name the line symbols Objective 2.2. Identify instrument Drawing and symbols Review Questions Match the number with the correct instrument symbol (1) Board (panel) mounted instrument in the control room (front of a panel) panel) (2) locally mounted instrument on a panel in the field (3) Locally mounted instrument in the field (on or near equipment) (4) Rack mounted instrument in the control room (back of a panel) Objective 2.2. Identify instrument Drawing and symbols Review Questions with Answers Match the number with the correct instrument symbol (1) Board (panel) mounted instrument in the control room (front of a panel) panel) (2) locally mounted instrument on a panel in the field (3) Locally mounted instrument in the field (on or near equipment) (4) Rack mounted instrument in the control room (back of a panel) Objective 2.2. Identify instrument Drawing and symbols Review Questions Name the valves : Objective 2.2. Identify instrument Drawing and symbols Review Questions with Answers Name the valves : Objective 2.2. Identify instrument Drawing and symbols Review Questions Write the abbreviation for each instrument in the symbol. Objective 2.2. Identify instrument Drawing and symbols Review Questions with Answers Write the abbreviation for each instrument in the symbol. Objective 2.1. Identify Instrumentation Loops Review Questions Refer to the loop below. Name the Parts 1 to 8? Objective 2.1. Identify Instrumentation Loops Review Questions with Answers Objective 2.2. Identify instrument Drawing and symbols Review Questions State the power instruments : E, F, G & H need to operate 1. 3. 2. 4. Objective 2.2. Identify instrument Drawing and symbols Review Questions with Answers State the power instruments : E, F, G & H need to operate 1. 3. 2. 4. Objective 2.2. Identify instrument Drawing and symbols Review Questions State the information from instrument symbol H 1. Name of instrument: 2. What loop no. is it part of : Objective 2.2. Identify instrument Drawing and symbols Review Questions with Answers State the information from instrument symbol H 1. Name of instrument: Pressure Indicating Controller 2. What loop no. is it part of : Pressure Control loop No. 123 Objective 2.3 2.3. Define Electronics & Pneumatic Terminology Objective 2.3. Define Electronics & Pneumatic Terminology Objective 2.3. Define Electronics & Pneumatic Terminology Objective 2.3. Define Electronics & Pneumatic Terminology Objective 2.3. Define Electronics & Pneumatic Terminology Objective 2.3. Define Electronics & Pneumatic Terminology Tuning Control loop : Is a control mode adjustments Control responses such as quarter-wave, minimum disturbance, or minimum-amplitude are obtained by these adjustments. Tuning Control loop : Is a control mode adjustments Proportion Tuning : Proportional band adjustment is a Compromise between instability and offset error. Quarter-wave : is the response that returns the process variable to the set point with the smallest deviation in the shortest amount of time. Objective 2.3. Define Electronics & Pneumatic Terminology What is PID control PID can be described as a set of rules that provide precise regulation of a closed-loop control system. Closed loop control is a method in which a real-time measurement of the process being controlled is constantly fed back to the controlling device to ensure that the desired value is obtained. The purpose of the controlling device is to make the measured value (process variable) equal to the desired value (set-point). The best way of doing this task is with the use of the control algorithm (PID). In its basic form, PID involves three mathematical control functions working together: Proportional-Integral-Derivative. Objective 2.3. Define Electronics & Pneumatic Terminology 1. Proportional Control: determines the magnitude of the difference between the set-point and the process variable (error) and then applies proportional changes (correction) to the control variable to eliminate the error. The use of proportional control alone has a large drawback offset). The offset is a sustained error that cannot be eliminated by proportional control alone. Under proportional control alone, the offset will remain until the operator manually changes the bias on the controller’s output to remove the offset. This is typically done by putting the controller in manual mode, changing its output manually until the error is zero, and then putting it back in automatic control. (operator manually “Resets” the controller.) Objective 2.3. Define Electronics & Pneumatic Terminology Because of the manual reset (Proportional Control), this led to the development of automatic reset “Integral Control” mode. 2. Integral Control: examines the offset of the set-point and the process variable over time and corrects it when and if necessary. As long as there is an error present (process variable NOT equal set point), the integral control mode will continuously increment or decrement the controller’s output to reduce the error. Integral action will drive the controller output far enough to reduce the error to zero given enough time. If the error is large, the integral mode will increment/decrement the controller output fast, if the error is small, the changes will be slower. Objective 2.3. Define Electronics & Pneumatic Terminology 3. Derivative Control: monitors the rate of change of the process variable and makes changes to the output to accommodate unusual changes. 4. PI controller: PI controller can be used to avoid large disturbances and noise presents during operation process. Objective 2.3. Define Electronics & Pneumatic Terminology Input Range PV Type Units 200–1000 psi pressure psi 100–500 °F temperature °F 0–100 "H2O pressure "H2O 3–15 psi pressure psi From above Table Input Ranges A range must have two values: minimum and maximum. For example, a range of 100°F to 500°F has a minimum of 100°F and a maximum of 500°F. Objective 2.3. Define Electronics & Pneumatic Terminology Input Range PV Type Units 200–1000 psi pressure psi 100–500 °F temperature °F 0–100 "H2O pressure "H2O 3–15 psi pressure psi From above Table Span is the difference between the minimum and maximum range. If a temperature transmitter has an input range of 100 to 500°F, the span is 500–100 which is 400°F. Objective 2.3. Define Electronics & Pneumatic Terminology Review Questions 1- Name the linear feedback control system, in which correction is applied to the control variable? 2- The difference between maximum and minimum value is known as? 3. Name the feedback control system in which the correction is applied to monitor the rate of change of the process variable and make changes to the output? Objective 2.3. Define Electronics & Pneumatic Terminology Review Questions with Answers 1- Name the linear feedback control system, in which correction is applied to the control variable? Proportional control 2- The difference between maximum and minimum value is known as? Span 3. Name the feedback control system in which the correction is applied to monitor the rate of change of the process variable and make changes to the output? Derivatives control Objective 2.3. Define Electronics & Pneumatic Terminology Review Questions 4-What control mode can add smoothing to a noisy signal effectively eliminates the offset error? Objective 2.3. Define Electronics & Pneumatic Terminology Review Questions with Answers 4-What control mode can add smoothing to a noisy signal effectively eliminates the offset error? PI controller Do you have any questions ? Test Equipment Objectives 3.1 Explain The Use of a Multimeter. 3.2 Explain The Use of a Communicator. 3.3 Identify Instrumentation Hand Tools. Test Equipment Objective 3.1 3.1 Explain The Use of a Multimeter. Objective 3.1 Explain The Use of a Multimeter Digital Multimeter A Digital multimeter is a very important test item. It can measure almost every type of process signal from voltage, current, resistance, and even frequency and capacitance. When using a multimeter always make sure you have the correct leads in the correct jack, and the switch at the right measurement for the signal you are going to measure. Keep a spare battery handy. Objective 3.1 Explain The Use of a Multimeter Review Questions What is the reading of the given gauge? Objective 3.1 Explain The Use of a Multimeter Review Questions What is the reading of the given gauge? Objective 3.1 Explain The Use of a Multimeter Review Questions What is the reading of the given gauge? Objective 3.1 Explain The Use of a Multimeter Review Questions What is the reading of the given gauge? Objective 3.1 Explain The Use of a Multimeter Review Questions What is the reading of the given gauge? Objective 3.1 Explain The Use of a Multimeter Review Questions What is the reading of the given gauge? Test Equipment Objective 3.2 3.2. Explain the use of communicator Objective 3.2. Explain the use of communicator Communicator s Objective 3.2. Explain the use of communicator Communicator s Note: HART COMMUNICATOR are connected in all parts of the control circuit during measuring or testing Does not require the loop to be disconnected. Objective 3.2. Explain the use of communicator Review Questions What is the name of the testing device shown? Where we can connect the this testing device in the _____control loop? Objective 3.2. Explain the use of communicator Review Questions with Answers What is the name of the testing device shown? HART communicator Where we can connect the this testing device in the _____control loop? Any where Test Equipment Objective 3.3 3.3. Identify instrumentation hand tools Objective 3.3. Identify instrumentation hand tools Objective 3.3. Identify instrumentation hand tools Objective 3.3. Identify instrumentation hand tools Objective 3.3. Identify instrumentation hand tools Objective 3.3. Identify instrumentation hand tools Objective 3.3. Identify instrumentation hand tools Review Questions Name the flowing tools Objective 3.3. Identify instrumentation hand tools Review Questions with Answers Name the flowing tools Tube cutter Tube bender Crimping tools Adjustable spanner Wire stripper Flaring block Do you have any questions ? Instrument and control Loop Components Objectives 4.1 Identify Components, Principles of Operation and Repair of Transducers. 4.2 Explain Principles of Operation, Testing and Replacement of Solenoids. 4.3 Explain the Testing and Replacement of Transducers. 4.4 Identify Actuator and Positioner Components. 4.5 Define Piston Actuator Principles Instrument and control Loop Components Objectives 4.6 Define Pressure Element Principles. 4.7 Diagnose Pressure Loop Problems. 4.8 Explain the Function of Switches. 4.9 Troubleshoot and Repair Electronic Transmitters. 4.10 Explain Calibration of Electronic Transmitters. Instrument and control Loop Components Objectives 4.11 Explain Calibration Switches. 4.12 Explain Function of Pressure Regulators and Signal Booster. 4.13 Repair of Pneumatic Controllers and Relays. 4.14 Troubleshooting of Pneumatic Control Loop & Relays. 4.15 Explain Calibration of valve Positioners. Instrument and control Loop Components Objectives 4.16 Explain Repair of Switches. 4.17 Define Resistance Temperature Detector Principles. 4.18 Define Thermocouple Principles. 4.19 Troubleshoot RTD and Thermocouples. Instrument and control Loop Components Objective 4.1 & 4.3 4.1 Identify Components, Principles of Operation and Repair of Transducers 4.3 Explain the Testing and Replacement of Transducers. Objective 4.1 Identify Components, Principles of Operation and Repair of Transducers & 4.3 Explain the Testing and Replacement of Transducers. I/P Transducer The I/P transducer converts the signal to what is required for the final control element and sends it as an output. For example, 4–20 mA may be converted into 3–15 psi, I/P (current to pressure). In the process industries, the I/P transducer takes a current input, usually a 4–20 mA signal, and converts it to a pressure output, a 3–15 psi signal. Objective 4.1 Identify Components, Principles of Operation and Repair of Transducers & 4.3 Explain the Testing and Replacement of Transducers. Transducer The current signal sent into the I/P transducer comes from a controller or distributed control system (DCS) that tries to keep a process variable at the set point value. The I/P transducer output typically goes to a pneumatic actuator controlling a valve, which moves the measured variable closer to the set point. Objective 4.1 Identify Components, Principles of Operation and Repair of Transducers & 4.3 Explain the Testing and Replacement of Transducers. Transducer The Honeywell model 870022 transducer is common in the plants. The major parts of the Honeywell transducer are listed below and shown figures. Objective 4.1 Identify Components, Principles of Operation and Repair of Transducers & 4.3 Explain the Testing and Replacement of Transducers. zero adjust knob: is used to set the transducer zero during calibration. A locknut locks the adjustment. span adjust :sets the span during calibration. A screw locks the span adjustment. terminal block: is where field wires connect to the transducer. force coil: produces a force proportional to the input current. Objective 4.1 Identify Components, Principles of Operation and Repair of Transducers & 4.3 Explain the Testing and Replacement of Transducers. feedback module produces a force that opposes the force generated by the force coil. Pilot valve supplies the pneumatic 3–15 psi output signal. restrictor reduces the air flow through the nozzle. valve port is the pneumatic output connection. supply port connects to the air supply. Objective 4.1 Identify Components, Principles of Operation and Repair of Transducers & 4.3 Explain the Testing and Replacement of Transducers. Operation This transducer is a single-acting, force-balancing, final control interface element. Figure below shows a functional block diagram of the transducer. Objective 4.1 Identify Components, Principles of Operation and Repair of Transducers & 4.3 Explain the Testing and Replacement of Transducers. The air-handling capacity of the transducer is determined by the one or two pneumatic stages. The single-stage model has a low air-handling capacity, and is used to transmit pneumatic signals to a relay or to a valve positioner. The two-stage model uses a high capacity relay that can actuate a pneumatic valve directly. When calibrating, make sure that the two-stage model transducer output is connected to a capacity of 50 cu. in. or more. Smaller capacities may cause cycling of the transducer. Objective 4.1 Identify Components, Principles of Operation and Repair of Transducers & 4.3 Explain the Testing and Replacement of Transducers. Transducer can be direct or reverse acting. In direct acting transducers, an increasing input current signal provides an increasing output air signal. In reverse-acting transducers, an increasing input current signal provides a decreasing output air signal. To convert the transducer to reverse action, reverse the input signal wires. Objective 4.1 Identify Components, Principles of Operation and Repair of Transducers & 4.3 Explain the Testing and Replacement of Transducers. Notes:- Testing and Replacement of an I/P transducer 1-If you remove a transducer in the field, get a work permit first, and tell operations so that the relevant control valve can be bypassed. 2- Before removing a transducer, you must safely isolate it. Objective 4.1 Identify Components, Principles of Operation and Repair of Transducers & 4.3 Explain the Testing and Replacement of Transducers. Notes:- Testing and Replacement of an I/P transducer 3-The controller output signal to the transducer must be disconnected at a nearby junction box or in the control room. 4- The instrument air supply to the transducer must be shut off. 5- The transducer can now be safely removed. Objective 4.1 Identify Components, Principles of Operation and Repair of Transducers & 4.3 Explain the Testing and Replacement of Transducers. Notes:- Testing and Replacement of an I/P transducer 6- replace with a new one. 7- Connect pneumatic lines. 8- Power up 9- Ask operations to make process in line. Objective 4.1 Identify Components, Principles of Operation and Repair of Transducers & 4.3 Explain the Testing and Replacement of Transducers. Review Questions 1. The I/P transducer takes a 4–20 mA input signal and converts it to what output signal? a. 0–50 mA b. 9–15 psi c. 3–15 mA d. 3–15 psi Objective 4.1 Identify Components, Principles of Operation and Repair of Transducers & 4.3 Explain the Testing and Replacement of Transducers. Review Questions with Answers 1. The I/P transducer takes a 4–20 mA input signal and converts it to what output signal? a. 0–50 mA b. 9–15 psi c. 3–15 mA d. 3–15 psi Objective 4.1 Identify Components, Principles of Operation and Repair of Transducers & 4.3 Explain the Testing and Replacement of Transducers. Review Questions 2. The transducer is a single-acting, force balancing, final control _________element? a. Interface b. Bypass c. Adjusting d. Amplifier Objective 4.1 Identify Components, Principles of Operation and Repair of Transducers & 4.3 Explain the Testing and Replacement of Transducers. Review Questions with Answers 2. The transducer is a single-acting, force balancing, final control _________element? a. Interface b. Bypass c. Adjusting d. Amplifier Objective 4.1 Identify Components, Principles of Operation and Repair of Transducers & 4.3 Explain the Testing and Replacement of Transducers. Review Questions 3. What must you do to convert the transducer from direct-acting to reverse-acting? a. Reverse the relay module b. Reverse the input signal wires c. Reverse the zero adjusting screw d. Reverse the pilot valve Objective 4.1 Identify Components, Principles of Operation and Repair of Transducers & 4.3 Explain the Testing and Replacement of Transducers. Review Questions with Answers 3. What must you do to convert the transducer from direct-acting to reverse-acting? a. Reverse the relay module b. Reverse the input signal wires c. Reverse the zero adjusting screw d. Reverse the pilot valve Objective 4.1 Identify Components, Principles of Operation and Repair of Transducers & 4.3 Explain the Testing and Replacement of Transducers. Review Questions 4. What is the signal range of transmitter output? a. 4–20 mA b. 5.28 mA c. 17.21 mA d. 11.8 mA Objective 4.1 Identify Components, Principles of Operation and Repair of Transducers & 4.3 Explain the Testing and Replacement of Transducers. Review Questions with Answers 4. What is the signal range of transmitter output? a. 4–20 mA b. 5.28 mA c. 17.21 mA d. 11.8 mA Objective 4.1 Identify Components, Principles of Operation and Repair of Transducers & 4.3 Explain the Testing and Replacement of Transducers. Review Questions 5. What do you do if one transducer gives error and not possible to eliminate it? Objective 4.1 Identify Components, Principles of Operation and Repair of Transducers & 4.3 Explain the Testing and Replacement of Transducers. Review Questions with Answers 5. What do you do if one transducer gives error and not possible to eliminate it? Replace it Instrument and control Loop Components Objective 4.2 4.2 Explain Principles of Operation, Testing and Replacement of Solenoids. Objective 4.2 Explain Principles of Operation, Testing and Replacement of Solenoids. Solenoids A solenoid is an electromagnetic device that can be used to convert magnetism into mechanical movement. This movement can then be attached to many other mechanical pieces to make up a control element. The most common use of a solenoid in oil and gas industry is a solenoid operated valve. These usually control the flow of instrument air or lube oil. Objective 4.2 Explain Principles of Operation, Testing and Replacement of Solenoids. Solenoid s Here the solenoid is a de- energized solenoid. Here the solenoid is energized. This movement operate a valve. Objective 4.2 Explain Principles of Operation, Testing and Replacement of Solenoids. Solenoid s Objective 4.2 Explain Principles of Operation, Testing and Replacement of Solenoids. Solenoid s Objective 4.2 Explain Principles of Operation, Testing and Replacement of Solenoids. Review Questions 1. Name the parts 5,6,7 and 8 shown in the fig. below. 2. Solenoid converted electrical energy into what type of energy? Objective 4.2 Explain Principles of Operation, Testing and Replacement of Solenoids. Review Questions with Answers 1. (7 Solenoid Blanger) (8 Spring) (6 supply leads) (5 coil) 2. Mechanical Energy Instrument and control Loop Components Objective 4.4 4.4 Identify Actuator and Positioner Components Objective 4.4 Identify Actuator and Positioner Components A valve actuator is a device that provide force to open, close ,or adjust a valve, In Saudi Aramco, the four most common types of valve actuator are :- 1- Electrical Motor Actuator 2- Pneumatic Actuator 3- Hydraulic actuator 4- Solenoid / Magnetic Actuator Objective 4.4 Identify Actuator and Positioner Components Some valves use an electric motor as an actuator. These valve are called motor-operated valve, or MOVs. The motor operated valve has tow main parts, the valve itself and a motor –driven screw stem. The motor uses two behaved gears to move the stem up and down. Objective 4.4 Identify Actuator and Positioner Components Electrical Motor Actuator Objective 4.4 Identify Actuator and Positioner Components Pneumatic Actuator Objective 4.4 Identify Actuator and Positioner Components Actuators convert pneumatic pressure into mechanical force that is used to move the control valve to the desired position. Diaphragm-type actuators use air pressure to overcome friction and process pressure to open and close a valve. These actuators normally operate with a positioner. In the positioner, the beam, bellows, and cam work together to position the flapper over the nozzle. The relay uses the back pressure created by the flapper and nozzle to send the right amount of air pressure to the actuator. And the actuator moves the valve stem to open and close the valve. Objective 4.4 Identify Actuator and Positioner Components Pressure connection is where air from the positioner is connected. The diaphragm is a flexible piece of material that flexes in response to the air input. Objective 4.4 Identify Actuator and Positioner Components The actuator spring opposes the air pressure force on the diaphragm. The actuator spring also forces the diaphragm up when air pressure decreases or fails. The spring seat holds the spring in position and provides a contact Pneumatic Actuator surface for the adjustor. Objective 4.4 Identify Actuator and Positioner Components The spring adjustor adjusts the compression of the actuator spring. The actuator stem is attached to the diaphragm plate and the valve stem. The indicator scale and travel indicator show the position of the valve. Pneumatic Actuator Objective 4.4 Identify Actuator and Positioner Components SINGLE-ACTING POSITIONERS Positioners are used to overcome the resistance to movement caused by process pressure and friction and to quickly and accurately position the valve. Objective 4.4 Identify Actuator and Positioner Components SINGLE-ACTING POSITIONERS A single-acting positioner has an air input and one output. A positioner receives a low volume 3 to 15 psi signal. The positioner changes the low volume signal into a high-volume 3 to 15 psi signal for the actuator. This is necessary to move the actuator rapidly. Objective 4.4 Identify Actuator and Positioner Components Review Questions Refer to the figure below for the following questions: 1. What is the name of the instrument shown below? 2. Name the parts labeled 1 to 7 1:________________ 2:________________ 3:________________ 4:________________ 5:________________ 6:________________ 7:________________ Objective 4.4 Identify Actuator and Positioner Components Review Questions with Answers Refer to the below to answer the following questions: 1. What is the name of the instrument shown below? Pneumatic Actuator 2. Name the parts labeled 1 to 7 1:_1Pressure connection 2:_Diaphragm 3:_Actuator spring 4:_Spring seat 5:_Spring adjustor 6:_6Actuator Stem 7:_Travel indicator Objective 4.4 Identify Actuator and Positioner Components Review Questions 3. What psi do you require to set the actuator to midpoint? ____________ 4. In _____________________ actuator air pressure forces the diaphragm down which compresses the spring and push the stem down to close the valve. 5. What component tells the actuator to open or close or throttle the valve? _______________________ Objective 4.4 Identify Actuator and Positioner Components Review Questions with Answers 3. What psi do you require to set the actuator to midpoint? _____9psi_______ 4. In ___Direct Acting___ actuator air pressure forces the diaphragm down which compresses the spring and push the stem down to close the valve. 5. What component tells the actuator to open or close or throttle the valve? ___Positioner__ Objective 4.4 Identify Actuator and Positioner Components Review Questions 6. Identify the following items: (A) Item 1 (B) Item 2 (C) Item 3 7. What range of signals will a pneumatic instruments uses to transmit or receive a signal? 8. Which of the followings is a final control element? : a. Control valve b. Pitch control unit (fin-fan) c. Louvers (cooling tower) d. All of the above Objective 4.4 Identify Actuator and Positioner Components Review Questions with Answers 6. Item 1 = actuator Item 2 = Positioner Item 3 = valve 7. 3 to 15psi 8. (a) Control valve Instrument and control Loop Components Objective 4.5 4.5 Define Piston Actuator Principles. Objective 4.5 Define Piston Actuator Principles How Actuators Work. An actuator is a motor that converts energy into torque which then moves or controls a mechanism or a system into which it has been incorporated. It can introduce motion as well as prevent it. An actuator typically runs on electric or pressure (such as hydraulic or pneumatic). Objective 4.5 Define Piston Actuator Principles Hydraulic Piston Actuator Principles: A hydraulic actuator uses the face of a pressurized liquid ,usually oil, to position the valve stem. When a hydraulic valve actuator a cylinder assembly is attached to a valve.a piston inside the cylinder moves up and down.the piston is attached to the valve stem. When a hydraulic oil is pumped to the top of the piston ,the valve will close. When the hydraulic oil is pumped to the bottom side of the piston the valve will open. Objective 4.5 Define Piston Actuator Principles Objective 4.5 Define Piston Actuator Principles Objective 4.5 Define Piston Actuator Principles Objective 4.5 Define Piston Actuator Principles Review Questions 1. Refer to the figure above. What is the name given to the device? 2 – What does the actuator converts the hydraulic energy into? Objective 4.5 Define Piston Actuator Principles Review Questions with Answers 1. Refer to the figure above. What is the name given to the device? Piston Actuator 2 – What does the actuator converts the hydraulic energy into? Mechanical energy Objective 4.5 Define Piston Actuator Principles Review Questions 3. Refer to the figure above. What does the above fig represents? Objective 4.5 Define Piston Actuator Principles Review Questions with Answers 3. Refer to the figure above. What does the above fig represents? Hydraulic Piston actuator Instrument and control Loop Components Objective 4.6 4.6 Define Pressure Element Principles Objective 4.6 Define Pressure Element Principles What is pressure? Pressure is a measure of the force applied to a unit area. Force is the pushing or pulling which can cause an object to move or change shape. Force can be applied in any direction. The relationship between pressure, force, and area is expressed by the formula: Pressure = Force ÷ Area P=F/A Objective 4.6 Define Pressure Element Principles What is pressure? If a 50 pound block measuring 10 square inches on each side is placed on a table of the same size, the pressure on the table is: P = 50 pounds / 10 square inches= 5 psi The most common expression of a unit of pressure is psi which equals pounds per square inch. Objective 4.6 Define Pressure Element Principles Atmospheric Pressure Everything on earth is exposed to atmospheric pressure. We know that air is a gas and it has weight. Because it has weight, the atmosphere (air) exerts a force on all surfaces of an object. A column of air with a base of one square inch exerts a pressure of 14.7 psi at sea level at 60°F. This is shown in figure 5. Objective 4.6 Define Pressure Element Principles Pressure Scales There are three common scales for measuring pressure. These are: Gauge Pressure Scale Absolute Pressure Scale Vacuum Pressure Scale Objective 4.6 Define Pressure Element Principles Gauge Pressure Scale Gauge pressure scales use atmospheric pressure as zero, the starting point. This means that zero on the scale is equal to 14.7 psi (atmospheric pressure). A pressure gauge open to the atmosphere will read zero. This is shown in figure 6. Gauge pressures are usually measured in pounds per square inch gauge (psig). Objective 4.6 Define Pressure Element Principles Absolute Pressure Scale The absolute pressure scale uses zero pressure in a perfect vacuum as its starting point. A perfect vacuum is the absence of pressure in a given volume. This also means the complete absence of matter. However, it is impossible to achieve a perfect vacuum. An absolute pressure gauge open to the atmosphere will read 14.7 psia at sea level. Absolute pressure is expressed as pounds per square inch absolute (psia). Objective 4.6 Define Pressure Element Principles Absolute Pressure Scale Absolute pressure is expressed as pounds per square inch absolute (psia). An absolute pressure scale is shown in figure 7. Absolute pressure equals gauge pressure plus atmospheric pressure. For example, 40 psig will equal 54.7 psia= (40 psi + 14.7 psi) Objective 4.6 Define Pressure Element Principles Vacuum Scale The vacuum scale is used to measure pressure that is lower than that of the atmosphere. Vacuum is measured in inches of mercury. One inch of mercury equals -0.491 psi. The greater the inches of mercury, the lower the pressure sensed. The maximum value is 29.92 inches of mercury which equals a perfect vacuum. Objective 4.6 Define Pressure Element Principles Vacuum Scale The vacuum scale starts at the atmospheric pressure. A reading of zero equals atmospheric pressure. Higher readings indicate lower pressures. For example, 25 inches of mercury equals a gauge pressure of about -12.3 psig. That is, -0.491 × 25 = -12.3. Absolute pressure = 14.7-12.3 =2.4 psia This is shown in figure 8. Objective 4.6 Define Pressure Element Principles Pressure Elements There are several pressure sensing elements and they are designed for different pressure ranges. The mechanical movement obtained and be used to activate switches, move needles on a dial or produce electronic signals as used in a transmitter: There are four types of devices are commonly used to measure or sense pressure: manometer Bourdon tube diaphragm bellows Objective 4.6 Define Pressure Element Principles Pressure Elements Manometer This is used for low pressure measuring environments. A simple manometer is a tube bent in the shape of a U and contains a measured amount of mercury. The manometer can be used to compare a pressure to atmospheric pressure or two different pressures. This is shown in figure 10. Objective 4.6 Define Pressure Element Principles Pressure Elements Bourdon tube The Bourdon tube is a metal tube in a spiral form and the process pressure is used to flex the metal cylinder resulting in a mechanical movement that can then be used to produce an electronic signal from that movement or simply move a gauge needle. Bourdon tubes are commonly seen in field pressure gauges and can be used in all pressure ranges Objective 4.6 Define Pressure Element Principles Pressure Elements Bourdon tube When the tube is part of a pressure gauge, the tip of the tube is connected to a gear mechanism, lever, and pointer This is shown in figure 13. When pressure is applied, the tube straightens a little. This movement causes the lever and gear mechanism to change the position of the pointer on the scale. The pointer indicates the pressure measurement Objective 4.6 Define Pressure Element Principles Pressure Elements Diaphragm Gage Diaphragm gauges can also be used to measure differential pressure. The gauge is designed to compare two input pressures. This is shown in figure 15. Inputs A and B are applied to opposite sides of the diaphragm. The difference in the two pressures is indicated by the pointer on the scale Note: The diaphragm gauge is more sensitive than a Bourdon tube. Objective 4.6 Define Pressure Element Principles Pressure Elements Diaphragm Gage The Diaphragm is a flexible metal or rubber disc that bends under the process pressure. This sensor is used for low pressure ranges. Objective 4.6 Define Pressure Element Principles Pressure Elements Bellow Gage Bellows Gauge used for measuring sensitive or low pressure In this gauge, the pressure sensing element is a flexible bellows. The bellows is a small flexible metal can that is sealed on one end and connected to a pressure source on the other end. See figure 16. When pressure is applied, the bellows expands and moves the pointer. The pointer indicates the pressure measurement. Bellows Gauge used for measuring sensitive or low pressure Objective 4.6 Define Pressure Element Principles Pressure Elements Bellow Gage Figure 17 shows how two bellows are used to compare input pressures. The pointer is attached to a rod connected to the bellows. When the input pressures are equal, the pointer is at zero. If input A is greater than the input B, the pointer moves to the right. If input B is greater than input A, the pointer moves to the left. The bellows gauge can also be used to measure differential pressure Objective 4.6 Define Pressure Element Principles Review Questions What is the reading of the given gauge? Objective 4.6 Define Pressure Element Principles Review Questions Refer to figure to answer questions 1-4. 1. Which scale is normally used for measuring pressure above atmospheric? 2. Which scale is normally used for measuring vacuum? 3. In which scales does zero equal absolute vacuum? 4. Which scale can be used for measuring both vacuum and pressure? Objective 4.6 Define Pressure Element Principles Review Questions with Answers 1. Which scale is normally used for measuring pressure above atmospheric? 2. Which scale is normally used for measuring vacuum? 3. In which scales does zero equal absolute vacuum? Answers: 4. Which scale can be used for 1-B measuring both vacuum and 2-A 3-C pressure? 4-D Objective 4.6 Define Pressure Element Principles Review Questions Name the following gages: Q1. Diaphragm Gage Burdon tube Bellow Gage Manometer Q2. Diaphragm Gage Burdon tube Bellow Gage Manometer Objective 4.6 Define Pressure Element Principles Review Questions with Answers Q1. Diaphragm Gage Burdon tube Bellow Gage Manometer Answer 1. Burdon tube 2. Diaphragm Gage Q2. Diaphragm Gage Burdon tube Bellow Gage Manometer Objective 4.6 Define Pressure Element Principles Review Questions Name the following gages: Q3. Diaphragm Gage Burdon tube Bellow Gage Manometer Q4. Diaphragm Gage Burdon tube Bellow Gage Manometer Objective 4.6 Define Pressure Element Principles Review Questions with Answers Q3. Diaphragm Gage Burdon tube Bellow Gage Manometer Answer 3. Bellow Gage 4. Manometer Q4. Diaphragm Gage Burdon tube Bellow Gage Manometer Objective 4.6 Define Pressure Element Principles Review Questions with Answers 1. Burdon tube 2. Diaphragm Gage 3. Manometer 4. Manometer Instrument and control Loop Components Objective 4.7 & 4.14 4.7 Diagnose Pressure Loop Problems & 4.14 Troubleshooting of Pneumatic Control Loop and Relays Objective 4.7 Diagnose Pressure Loop Problems & 4.14 Troubleshooting of Pneumatic Control Loop and Relays The pressure sensing element is a transmitter that outputs a 4–20 mA signal to the controller. The pressure controller compares the signal from the pressure transmitter to the set point and produces a 4–20 mA output signal to the pressure transducer, PTd. Objective 4.7 Diagnose Pressure Loop Problems & 4.14 Troubleshooting of Pneumatic Control Loop and Relays The transducer converts the 4–20 mA signals from the controller to a 3–15 psi input signal to the pressure control valve. The 3–15 psi signal enables the control valve actuator and positioner to increase or decrease the pressure depending on the pressure at the output. In the next section, we will look at the components of an electronic control loop. Objective 4.7 Diagnose Pressure Loop Problems & 4.14 Troubleshooting of Pneumatic Control Loop and Relays When PT send signal 4 to 20 mA to the controller PC ,the controller make a comparison between the set point and desired value ,the PCV will take the necessary action through the pressure transducer PTd. Note PCV will shut down (AO/AFC),when the pressure drops below the set value ,then PCV will shut down to maintain the pressure in the main line. Objective 4.7 Diagnose Pressure Loop Problems & 4.14 Troubleshooting of Pneumatic Control Loop and Relays Q. What will happen to the system when the pressure drops below the set point? PCV will be closed Q. who causes the system to shut down when the pressure drops below the set value? PT Objective 4.7 Diagnose Pressure Loop Problems & 4.14 Troubleshooting of Pneumatic Control Loop and Relays PNEUMATIC CONTROL LOOPS In a pneumatic control loop, air pressure powers the components. The sensor is a pneumatic transmitter. The transmitter senses the value of the process variable and sends a standard (3–15 psi) air signal to the controller. The controller receives the signal from the transmitter (sensor). The controller compares the signal from the transmitter with the set point. The controller then sends an output signal to the control valve. Remember, the control valve is the final control element. Objective 4.7 Diagnose Pressure Loop Problems & 4.14 Troubleshooting of Pneumatic Control Loop and Relays PNEUMATIC CONTROL LOOPS Controllers may be direct acting or reverse acting. Direct acting – when the input increase, the output increase. Reverse acting – when the input increase, the output decrease. Objective 4.7 Diagnose Pressure Loop Problems & 4.14 Troubleshooting of Pneumatic Control Loop and Relays Describe P-I-D Control Modes In an automatic control, the system is balanced when the sensor does not register more or less than that required by the control system. When the system registers a change (deviation), what happens to the control valve depends on the type of control system used. The relationship between the movement of the valve and the change in the controlled medium is known as the mode of control or control mode. There are two basic control modes. These are: On/Off – the valve is either fully open or fully closed. There are no intermediate states or throttling. Continuous – the valve can move between fully open, fully closed, or throttle (any intermediate position). Objective 4.7 Diagnose Pressure Loop Problems & 4.14 Troubleshooting of Pneumatic Control Loop and Relays Describe P-I-D Control Modes ON/OFF CONTROL The most basic type of process control is On/Off. A light switch and a thermostat are examples of an On/Off control. Figure 10 shows a water tank that uses On/Off level control. Figure 10: On/Off Level Control Objective 4.7 Diagnose Pressure Loop Problems & 4.14 Troubleshooting of Pneumatic Control Loop and Relays Describe P-I-D Control Modes Objective 4.7 Diagnose Pressure Loop Problems & 4.14 Troubleshooting of Pneumatic Control Loop and Relays Describe P-I-D Control Modes The advantages of On/Off control are that it is simple and low cost. This is why it is commonly found on domestic applications such as central heating boilers and heater fans. A major disadvantage is that the operating differential may fall outside the control tolerance required by the process. For example, on a production line, where the output is determined by precise measurements, On/Off control is not appropriate. If a more accurate control is required, the next option is the continuous control mode. Objective 4.7 Diagnose Pressure Loop Problems & 4.14 Troubleshooting of Pneumatic Control Loop and Relays Describe P-I-D Control Modes CONTINUOUS CONTROL Continuous control is often called modulating control. In this type control, the valve is capable of moving continually to change the amount of opening or closing. The three basic actions applied to continuous control are: Proportional (P) Integral (I) Derivative (D) Objective 4.7 Diagnose Pressure Loop Problems & 4.14 Troubleshooting of Pneumatic Control Loop and Relays Describe P-I-D Control Modes What is PID control? PID can be described as a set of rules that provide precise regulation of a closed-loop control system. Closed loop control is a method in which a real-time measurement of the process being controlled is constantly fed back to the controlling device to ensure that the desired value is obtained. The purpose of the controlling device is to make the measured value (process variable) equal to the desired value (setpoint). The best way of doing this task is with the use of the control algorithm (PID). Objective 4.7 Diagnose Pressure Loop Problems & 4.14 Troubleshooting of Pneumatic Control Loop and Relays Describe P-I-D Control Modes In its basic form, PID involves three mathematical control functions working together: Proportional-Integral- Derivative. Proportional Control determines the magnitude of the difference between the set point and the process variable (error).and then applies proportional changes to the control variable to eliminate the error. Integral Control examines the offset of the set point and the process variable over time and corrects it when and if necessary. Derivative Control monitors the rate of change of the process variable and makes changes to the output to accommodate unusual changes. Objective 4.7 Diagnose Pressure Loop Problems & 4.14 Troubleshooting of Pneumatic Control Loop and Relays Describe P-I-D Control Modes Each function is controlled by user-defined parameters. These parameters vary from one system to another, and needs to be adjusted to optimize the precision of control. The process of determining the values of these parameters is known as PID Tuning. PID Tuning is a well-defined process and will be covered later. We must also consider these actions in combination. That is P + I, P + D, P + I + D. It is possible to combine the different actions and produce the required response. However, remember that the integral and derivative actions are corrective functions of a basic proportional action. Let's look at three control actions. Objective 4.7 Diagnose Pressure Loop Problems & 4.14 Troubleshooting of Pneumatic Control Loop and Relays Describe P-I-D Control Modes Objective 4.7 Diagnose Pressure Loop Problems & 4.14 Troubleshooting of Pneumatic Control Loop and Relays Describe P-I-D Control Modes Objective 4.7 Diagnose Pressure Loop Problems & 4.14 Troubleshooting of Pneumatic Control Loop and Relays Describe P-I-D Control Modes SUMMARY In this part, you learned that in an automatic control, the system is balanced when the sensor does not register more or less than that required by the control system. When the system registers a change (deviation), what happens to the control valve depends on the type of control system used and the most basic type of process control is On/Off. You also learned that continuous control is often called modulating control and that the three basic actions applied to continuous control are Proportional, Integral, and Derivative and P I D can be described as a set of rules that provide precise regulation of a closed-loop control system. You learned that: Objective 4.7 Diagnose Pressure Loop Problems & 4.14 Troubleshooting of Pneumatic Control Loop and Relays Describe P-I-D Control Modes SUMMARY Proportional Control determines the magnitude of the difference between the set point and the process variable (error) and then applies proportional changes to the control variable to eliminate the error. Integral Control examines the offset of the set point and the process variable over time and corrects it when and if necessary. Derivative Control monitors the rate of change of the process variable and makes changes to the output variable to accommodate unusual. Objective 4.7 Diagnose Pressure Loop Problems & 4.14 Troubleshooting of Pneumatic Control Loop and Relays Troubleshooting steps 1. Think safety first. 2. Ask the three W’s--What, When, and Where 3. Visually inspect the equipment. 4. Have a thorough understanding of the system. Use a schematic. 5. Operate the equipment through the plant operator 6. Recheck all services to the equipment. Think safety. 7. Isolate subsystems on the equipment. 8. Make a list of probable causes. 9. Reach a conclusion about the problem. 10. Test the conclusion. 11. Repair or replace as necessary. 12. Report the findings. Objective 4.7 Diagnose Pressure Loop Problems & 4.14 Troubleshooting of Pneumatic Control Loop and Relays Review Questions 1- Refer to the figure below. Adjusting control mode settings to get optimum control loop performance is known as? Objective 4.7 Diagnose Pressure Loop Problems & 4.14 Troubleshooting of Pneumatic Control Loop and Relays Review Questions with Answer 1- Refer to the figure below. Adjusting control mode settings to get optimum control loop performance is known as? (tuning) Objective 4.7 Diagnose Pressure Loop Problems & 4.14 Troubleshooting of Pneumatic Control Loop and Relays Review Questions 2- If the pressure is less than 200 psi what will happen in the control loop below? Objective 4.7 Diagnose Pressure Loop Problems & 4.14 Troubleshooting of Pneumatic Control Loop and Relays Review Questions with Answer 2- If the pressure is less than 200 psi what will happen in the control loop below? PCV6 Close Objective 4.7 Diagnose Pressure Loop Problems & 4.14 Troubleshooting of Pneumatic Control Loop and Relays Review Questions 3- If the pressure is more than 200 psi what will happen in the control loop below? Objective 4.7 Diagnose Pressure Loop Problems & 4.14 Troubleshooting of Pneumatic Control Loop and Relays Review Questions with Answer 3- If the pressure is more than 200 psi what will happen in the control loop below? PCV6 Open Instrument and control Loop Components Objective 4.8, 4.16 & 4.11 4.8 Explain the Function of Switches 4.16 Explain Repair of Switches 4.11 Explain Calibration Switches Objective 4.8 Explain the Function of Switches 4.16 Explain Repair of Switches 4.11 Explain Calibration Switches SWITCHES Electromechanical Switch The type electromechanical switch used as a sensing switch is the single-pole double-throw (SPDT). The switch either makes or breaks a circuit, depending on how it is wired. It has a single pole and a normally open (NO) and normally closed (NC) contact. A switch and the electrical symbol are shown in the fig below. Objective 4.8 Explain the Function of Switches 4.16 Explain Repair of Switches 4.11 Explain Calibration Switches SWITCHES Mercury Switches Mercury switches are motion based and consist of a sealed glass tube with two or three contacts and a small amount of liquid mercury. A typical two contact mercury switch is shown in figure below At this point, current can flow through 5 and 6. When switch return to its original position, the connection between 5 and 6 opens and flow of current stops. The connection between 4 and 5 is closed. Objective 4.8 Explain the Function of Switches 4.16 Explain Repair of Switches 4.11 Explain Calibration Switches Temperature Sensing Element and Switch A temperature switch consists of the switch and the sensing element. This is shown in figure 16. A temperature switch assembly uses a capillary and bulb as the sensing element to supply pressure to the bellows or thermal housing. As temperature increase, pressure in the bulb and capillary also increase, moving the piston to actuate the switch. Objective 4.8 Explain the Function of Switches 4.16 Explain Repair of Switches 4.11 Explain Calibration Switches Pressure Switch The pressure sensing element consists of a housing, piston, and spring. This is shown in figure 13. When the input pressure is normal, the piston is low in the housing. When the pressure increase, the piston moves up towards the switch. When the switch pressure setting is reached, the piston actuates the switch. The switch will turn a device on or off. When the pressure decrease, the piston is forced down by the spring and the switch deactivates. Objective 4.8 Explain the Function of Switches 4.16 Explain Repair of Switches 4.11 Explain Calibration Switches Pressure Switch As you can see, the movement of the piston is controlled by the increase and decrease in pressure. Therefore, actuation of the switch is controlled by pressure. Objective 4.8 Explain the Function of Switches 4.16 Explain Repair of Switches 4.11 Explain Calibration Switches Micro Pressure Switch A micro pressure switch is a mechanical sensing element coupled with an electrical switch. The pressure sensing elements are discussed in a previous slide and it is the movement of these pressure sensing elements that operate an electrical switch which is usually of the micro-switch type. Objective 4.8 Explain the Function of Switches 4.16 Explain Repair of Switches 4.11 Explain Calibration Switches Calibrate a Pressure Switch Calibration tools A deadweight tester is a calibration standard that uses the principle of a pressure balance to calibrate pressure measuring instruments. Deadweight testers use calibrated weights to apply known pressures to a device under test for a simple and cost- effective solution that covers a wide range of pressure calibrations. Objective 4.8 Explain the Function of Switches 4.16 Explain Repair of Switches 4.11 Explain Calibration Switches Steps of Calibrate a Pressure Switch 1. Get a work permit. 2. Locate correct switch, make sure the switch is on bypass and disconnect the power. 3. Shut off process pressure. Slowly disconnect process connection to bleed of process fluid. 4. Remove switch cover and inspect for leaks and corrosion. 5. Remove wires from the switch and cover lugs with electrical tape. 6. Set the multimeter to ohms (R × 1) and connect to switch. 7. Connect pressure calibrator. 8. Apply pressure until meter (DMM) shows the switch trip point. Note: For high-pressure trip, the switch will operate on increasing pressure. For low-pressure trip, the switch will operate on decreasing pressure. Objective 4.8 Explain the Function of Switches 4.16 Explain Repair of Switches 4.11 Explain Calibration Switches Steps of Calibrate a Pressure Switch 9. Slowly bleed off pressure until meter shows the switch trip. 10. Adjust the switch to trip at the specified pressure, if required. 11. Repeat steps 8, 9, and 10 until the switch trip at the specified pressure. 12. Remove tape and replace switch wiring. 13. Replace switch cover. 14. Remove calibrator. 15. Return switch to service and check for proper operation. 16. Clean the work area and store tools and equipment in the proper location. 17. Close the work permit. Objective 4.8 Explain the Function of Switches 4.16 Explain Repair of Switches 4.11 Explain Calibration Switches Steps of Calibrate a Pressure Switch Setting up solenoids and pressure switches is straightforward. It is usually done after replacement of defective ones. A solenoid setup a mainly to make sure the solenoid is of the right type and voltage. Solenoid valves generally come complete and so the setup is to make sure the correct valve ports are connected to the right pipelines. Pressure switches will also often come complete with the pressure sensing element and so setup will consist of calibration adjustment once the unit is fitted to the process sensing line Objective 4.8 Explain the Function of Switches 4.16 Explain Repair of Switches 4.11 Explain Calibration Switches Review Questions 1- Where are control signal Pressure/flow Switches mainly used in? 2-What is the most common type of pressure switch used in control circuit? 3- What must we do before we calibrate the pressure switch? 4- In testing a pressure switch using DMM, pressure is apply until DMM shows? Objective 4.8 Explain the Function of Switches 4.16 Explain Repair of Switches 4.11 Explain Calibration Switches Review Questions with Answers 1- Where are control signal Pressure/flow Switches mainly used in? Switch ON/OFF 2-What is the most common type of pressure switch used in control circuit? SPDT 3- What must we do before we calibrate the pressure switch? De energizes and isolate 4- In testing a pressure switch using DMM, pressure is apply until DMM shows? Trip point Objective 4.8 Explain the Function of Switches 4.16 Explain Repair of Switches 4.11 Explain Calibration Switches 5-Refer to fig(4.16) below, What is the fault if a pressure switch always give infinity ohm? fig(4.16) 5-Refer to fig(4.16) above. What is the fault if a pressure switch always give infinity ohm? 6- What should you do if a switch contacts measures a 1Ω when the switch is closed and open? 7- What must you do before you calibrate a pressure switch? Objective 4.8 Explain the Function of Switches 4.16 Explain Repair of Switches 4.11 Explain Calibration Switches Review Questions with Answers 5-Refer to fig(4.16) below, What is the fault if a pressure switch always give infinity ohm? Set trip fig(4.16) 5-Refer to fig(4.16) above. What is the fault if a pressure switch always give infinity ohm? Set trip 6- What should you do if a switch contacts measures a 1Ω when the switch is closed and open? Replace the switch 7- What must you do before you calibrate a pressure switch? Set point Instrument and control Loop Components Objective 4.9 & 4.10 4.9 Troubleshoot and Repair Electronic Transmitters 4.10 Explain Calibration of Electronic transmitters Objective 4.9 Troubleshoot and Repair Electronic Transmitters 4.10 Explain Calibration of Electronic transmitters TRANSMITTERS Transmitters sense the actual value of process variables and convert these process readings into standard output signals. Output signals are sent to instrument loop controllers and other devices. Pressure transmitters are an important part of process control loops. Pressure transmitters measure the pressure in a process. In your work as a process control systems technician, you will continue to see pneumatic pressure control loops using pneumatic pressure transmitters. In the task aid, you will calibrate a pressure transmitter. Transmitters are calibrated to make sure that output signals sent to controllers accurately represent the process variables. Objective 4.9 Troubleshoot and Repair Electronic Transmitters 4.10 Explain Calibration of Electronic transmitters Pneumatic Pressure Transmitter Figure below shows a typical pneumatic pressure transmitter. Objective 4.9 Troubleshoot and Repair Electronic Transmitters 4.10 Explain Calibration of Electronic transmitters Pneumatic Pressure Transmitter The flapper/nozzle creates the back pressure to operate the control relay. The force bar is moved in two directions by the input capsule (bellows capsule). The relay converts nozzle back pressure into an output and feedback signal. The air supply connects to instrument air. The output port connects to the controller. Pressure connection connects to the process line. Objective 4.9 Troubleshoot and Repair Electronic Transmitters 4.10 Explain Calibration of Electronic transmitters Pneumatic Pressure Transmitter The feedback bellows act against the range bar to balance the force from the input pressure. The flexure connects the force bar to the range rod. The range rod is attached to the feedback bellows and the flexure connector. The range wheel forms a fulcrum, or pivot point, for the range rod. The zero adjustment screw sets the transmitter output to 3 psi. Objective 4.9 Troubleshoot and Repair Electronic Transmitters 4.10 Explain Calibration of Electronic transmitters Pneumatic Pressure Transmitter Operation of Pressure Transmitters 1-Initially,instrument air at 20 psi is input to the relay and 3 psi is output. This is shown in this figure. 2-Instrument air pressure is reduced through the restrictor. The reduced pressure goes to the relay diaphragm and nozzle. Inside the relay, back pressure on the diaphragm opens the valve enough to allow 3 psi to the output of the transmitter. Excess air is also allowed to escape through the exhaust port and the nozzle. Objective 4.9 Troubleshoot and Repair Electronic Transmitters 4.10 Explain Calibration of Electronic transmitters Pneumatic Pressure Transmitter Operation of Pressure Transmitters As long as the input pressure remains steady, the output signal will remain steady. Whenever the input pressure change, the force bar will move, the feedback bellows will oppose the movement and the output signal will stabilize at a new value. When the input pressure drops, the higher pressure in the feedback bellows pushes the range rod back. This moves the flapper away from the nozzle. The excess pressure in the bellows escape through the exhaust valve and port until the forces are balanced again. Objective 4.9 Troubleshoot and Repair Electronic Transmitters 4.10 Explain Calibration of Electronic transmitters Electronic Displacement Level Transmitters Remember the level and liquid interface is measured by a small movement of the displacer rod to produce an output in the 3–15 psi range. The electronic displacement level transmitter works on the same principle, but the displacer movement is converted to a 4–20 mA electrical output signal. Objective 4.9 Troubleshoot and Repair Electronic Transmitters 4.10 Explain Calibration of Electronic transmitters The Transmitter Face Plate During calibration, set the pointer on the dial face according to the specific gravity. The transmitter face plate is part of the circular instrument case. It is normally concealed by a cover plate. The transmitter face plate is shown in figure below. Objective 4.9 Troubleshoot and Repair Electronic Transmitters 4.10 Explain Calibration of Electronic transmitters The Transmitt

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