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e started except when the resistor is set in mini- c. Wye-delta starting is also an economical method of mum-speed position. reduced-voltage starting but produces a lower starting torque than the other methods. Application of wound rotor motors in petrochemical envi- ronments should be carefully rev...

e started except when the resistor is set in mini- c. Wye-delta starting is also an economical method of mum-speed position. reduced-voltage starting but produces a lower starting torque than the other methods. Application of wound rotor motors in petrochemical envi- ronments should be carefully reviewed because of the spark- d. The solid-state reduced-voltage starting method provides a ing nature of the brushes and slip smooth, stepless acceleration with current-limit control adjustable between the limits of approximately 150% and 425% of motor full-load current. 6.25 MEANS OF DISCONNECTION Means of disconnection are discussed in NFPA 70. 6.24.2 Synchronous Motor 6.26 COORDINATION OF CONTROLLER The synchronous motor is applied principally in the large horsepower class, greater than or equal to 500 HP. Because of its limited starting characteristics, the synchronous motor is APPLICATIONS WITH FUSES OR CIRCUIT BREAKERS ON LOW-VOLTAGE SYSTEMS generally started under no-load conditions with DC field 6.26.1 ’ Normal Operation and Fault Conditions excitation automatically applied when the motor approaches synchronous speed. Variable field excitation may be used dur- ing normal operation to provide power factor con-ection and should be specified if required. As is the case for squirrel-cage induction motors, full- and reduced-voltage controllers are available for starting; the selection depends on the local power source and operating conditions. There is a similarity in control except that the out- of-step protection automatically stops the motor when the motor drops out of synchronism. A controller for a synchronous motor will generally include the following functions in addition to the functions of a controller for a squirrel-cage induction motor: a. Protection of the field against overcurrents in normal or out-of-step operation. b. Automatic field application that is responsive to the definite time, the relative frequency of the current in the field and sta- tor, the power factor of the current to the stator winding, and other variables that may be used to obtain the desired result. Both AC and DC meters should be provided. 6.24.3 Wound-Rotor Induction Motor The wound-rotor induction motor meets the operating demands of controlled starting, in-rush current, and adjust- able speeds with high starting torque. It is suitable for a high- inertia load where critical operations may require closely con- trolled acceleration. Starting facilities are similar to those of the squirrel-cage induction motor, except that the motor A motor controller must be capable of starting and stop- ping its rated motor horsepower and interrupting motor locked-rotor current. Normally, the controller cannot interrupt fault currents resulting from short circuits and grounds so a circuit breaker, motor circuit protector, or a set of fuses is installed ahead of the controller. The protective devicesmust have sufficient capacity to interrupt the current safely and must be fast enough to clear the fault without damage to the contactor and overcurrent devices. They must also carry locked-rotor current long enough to allow the motor to accel- erate to rated speed without opening the motor circuit and should preferably protect against excessive locked-rotor time. In addition, they should keep motor damage to a minimum in case of a fault within the motor. The complete motor protection package normally consists of a disconnect device, fault-current protection, a contactor, time- lag overcurrent protection, and associated auxiliary devices. The disconnect and fault-current protection are often combined in a circuit breaker. Even though some components may be combined, all of these protective features must be included. 6.26.2 Fuse and Circuit Breaker Considerations NFPA 70 provides general information on fuses and circuit breakers. 6.26.2.1 Fuses Dual element (time-delay) fuses are better suited for motor branch-circuit protection than are fuses that open without delay; the time-delay feature avoids possible fuse opening during the period of high motor starting current. This allows the fuse to be sized more closely to the motor’s rated full-load current. Cun-ent-limiting fuses are also commonly used for this ser- I vice because of the following: a. For faults, they operate within I/2-cycle to reduce the dam- age caused by short-circuit current. b. The magnitude of the short-circuit current is actually lim- ited to less than the available short-circuit current, which may allow the use of smaller conductors in. branch circuits. The fast operation of most fuses, however, makes it difficult and often impossible to coordinate them with other short-circuit protective devices. c. Current-limiting fuses are not subject to aging; therefore, an ultimate false operation is avoided when these devices are used. 6.26.2.2 Circuit Breakers It is essential to select a circuit breaker capable of closing into, carrying, and interrupting the highest fault current avail- able at the point of installation. 6.27 OVERLOAD PROTECTION: SPECIAL APPLICATIONS When a motor is to be used to drive a high-inertia load that requires a long time to accelerate to normal speed, a check should be made to determine if a special form of overload protection will be required. This will usually be the case if a standard protective device, set at the maximum current value affording proper protection for the motor, trips the motor off the line during the starting period. To provide uninterrupted starting and at the same time pro- vide the desired degree of protection against sustained high starting currents, it may be necessary, in some cases, to use a thermal device that is built into the motor stator winding. In other cases, it may be necessary to use long-time induction- disk or solid-state relays that are adjustable to suit the starting conditions, or to supply current to the overload protective device through a saturable core reactor or current transformer with characteristics suitable for limiting the current to the protective device during the starting period. If one of these forms of protection will not suffice, consideration should be given to other means of providing the desired degree of pro- tection. If the ambient temperature varies, thermally compen- sated relays may be used. A speed sensor or switch coupled to the motor shaft can also be integrated into the control system, particularly with the use of timing relay(s). Many of the multifunction protec- tion relays (solid-state relays) available integrate this and other protective features. 6.28 VOLTAGE LIMITATIONS In many cases, on a privately owned industrial supply system, it is practical to tolerate voltage fluctuations some- what in excess of values that generally would be considered unacceptable on other systems. When a large motor is to be installed at a point where severe voltage dips will result, a check will determine whether the motor terminal voltage will be sufficient during the starting period to permit the motor to bring its load up to speed within a satisfactory time, and whether the resulting voltage disturbance will be acceptable, considering the requirements of other electrical equipment supplied by the system. Where the terminal volt- age will be abnormally low, approaching the value at which the undervoltage device in a standard controller is designed to operate, it is recommended that the specification for the controller include the anticipated range of voltage from the minimum during starting to the maximum during normal operation. 6.29 APPLICATION OF OUTDOOR AND INDOOR TYPES 6.29.1 Outdoor -Type It is common practice to install electric motors and driven equipment outdoors without protection from the weather, unless there is some good reason for providing a building or other form of shelter. Outdoor-type controllers may be used with these motors. The main consideration in this application is to avoid the use of buildings and other shelters as much as possible so that the possibility of an accumulation of flamma- ble vapors or gases is reduced. Enclosures for controllers installed outdoors must meet all service requirements of the location. 6.29.2 Indoor -Type Indoor-type controllers are sometimes used regardless of the location of the associated motors. It may be more eco- nomical to use indoor equipment in a building located in an unclassified area than to.provide outdoor controllers that are suitable for all conditions of service. 6.30 PUSHBUTTON STATIONS 6.30.1 Location If undervoltage protection is required, the pushbutton for operating the controller is generally of the momentary-con- tact, start-stop type and is installed in sight of and near the motor and its driven equipment and in a position that will facilitate ease and safety of operation. If a pushbutton is installed on or near a controller that is remote from the motor controlled, the pushbutton is generally of the stop- type installed only for the purpose of stopping the motor in an emergency. 7.1 PURPOSE 7.3.7 illuminance level: A prescribed amount of illumi- This section serves as a guide for the design of modern petroleum processing plant lighting facilities. It advocates the following principles: a. Establishing recommended practices for processing plant lighting will ensure adequate and efficient lighting facilities that contribute to the safe and efficient operation and mainte- nance of the plant. b. Processing plant lighting should not be considered just a necessary burden that only adds to the cost of production; rather, it should be considered an integral part of safe and effi- cient plant operation. c. Lighting design practice should be kept up-to-date with new developments such as high intensity discharge (HID) lamps. Luminaires have been developed that make effective use of metallic additive and quartz light sources. High-pres- sure sodium luminaires are commonly used where high illuminances are required and where energy cost and reduced maintenance cost are important considerations. Applications of these new developments, where suitable, may offer the most efficient lighting installation. 7.2 SCOPE nance: a. Znitial is the amount of illuminance obtained when the luminaires are new and clean and when the lamps are first energized. b. In sewice or maintained is the average amount of illumi- nance over an extended period of time. This is lower than the initial illuminance for several reasons noted under light loss factor. 7.3.8 luminaire: A complete lighting unit including the lamp, globe, reflector, refractor, housing, and support that is integral with the housing. 7.3.9 light loss factor: A’factor that represents the aver- age-to-initial illuminance ratio of a lighting system. It repre- sents the depreciation and deterioration of a lighting system caused by the following: a. Loss of lamp lumens as a result of aging. b. Decrease in lamp and luminaire output resulting from dust, dirt, insects, and chemical changes in the luminaire’s reflecting surface. c. Increased absorption of the light output of the luminaires by dust, dirt, and chemical changes in the room’s reflecting surfaces. The material in this section is intended to establish the fol- d. Differences between actual design lamp voltages. lowing: a. A general approach to the practice and principles of good lumen per square meter. lighting installation and maintenance. b. ~~i for the design of new processing plmt 7.3.11 mounting height: The distance from the bottom lighting. of the luminaire to the surface used as a reference. c. Recommended illuminances for most processing plant 7.3.12 reflection factor: The ratio of the light reflected areas. by the body to the incident light. d. A basis for estimating lighting power requirements in new processing plant design. 7.3.13 seeing or visual task The object being regarded 7.3 DEFINITION OFTERMS 7.3.14 utilization: The total flux received by a surface 7.3.1 brightness: The illuminance of a in any dwided by the total flux from the lamps illuminating it. given direction. 7.3.2 brightness ratio: The ratio of brightness of sur- faces. 7.3.3 diffusion: The breaking up of a beam of light and The data in Table 4 cover the minimum average main- the spreading of its rays in many directions by a surface. tained (in service), horizontal lighting illuminance require- ments of most processing plant areas; however, it must be 7.3.4 footcandle (ftc): A unit of illuminance. clearly understood that lighting installations should be 7.3.10 lux: The SI unit of illuminance. One lux is one and its background. 7.4 LIGHTING FACILITIES 7.4.1 Recommended Illumination 7.3.5 glare: The condition in which brightness or the con- trast of brightnesses interferes with vision. designed to meet the conditions peculiar to the tasks of each area. For instance, Table 4 indicates a minimum illuminance of 5 (ftc) in service for operating platforms on general pro- 7.3.6 illuminance: The density of luminous flux incident cess units. Obviously, ifthere are instruments -and control upon a surface. valves that must be operated constantly, the 5-ftc illumi- nance is insufficient. Supplemental lighting on the immedi- ate contro~ area or a general increase in the illuminance on that platform is necessary. In this sense, the data shown in Table 4 serve only as a guide to good lighting practice. Note: These illuminances are not intended to be mandatory by enactment into law; they are a recommended practice to be consid- ered in the design of new facilities. a. Indicates vertical illuminance. b. Refer to local Coast Guard, port authority, or governing body for required navigational lights. c. The use of many areas in petroleum and chemical plants is often different from what the designation may infer. The areas are generally small, their occupancy is low (restricted to plant personnel) and infrequent, and they are only occupied by per- sonnel trained to conduct themselves safely under unusual conditions. For these reasons, illuminances may be different from those recommended for other industries. and for com- mercial, educational, or public areas. d. Refer to local Federal Aviation Administration regulations for required navigational and obstruction lighting and marking. e. Refer to Tables 7.2A and 7.2B in API RP 14F for recom- mended illumination levels for offshore production platforms. 7.4.2 Petroleum Processing Plant Areas As shown in Table 4, the three basic areas to consider when planning lighting facilities are process areas, nonprocess areas, and buildings. Buildings peculiar to process and non- process areas have been included in Table 4. The three basic areas are broken down into more specific areas or activities. Under process areas and the more specific areas of general process units, minimum lighting require- ments are given for areas such as pump rows, heat exchang- ers, and operating platforms. 7.4.3 Lamp Types The following types of lamps are commercially available and frequently used in refinery installations: a. Incandescent, including tungsten and halogen. b. Fluorescent. c. Mercury vapor. d. Metal halide. e. High-pressure sodium. Incandescent and fluorescent lamps, including halogen and tungsten, can be used in luminaires with direct, semidi- rect, and general-diffuse outputs, while high-intensity dis- charge lamps can be used in luminaires with direct and semidirect outputs. Efficacies for incandescent lamps range from 4 to 24 lumens per watt (lm and for fluorescent lamps range from 75 to 80 (lm/W). Compared with incandescent lamps, mercury vapor lamps offer the advantages of longer average life and higher lumen output; however, with the advent of metal halide and high-pressure sodium lamps, the mercury vapor lamp is considered by many to be obsolete, except in existing plants having similar lamps. The mercury vapor lamp is consid- ered obsolete because of its rapid lumen depreciation and low lumens-per-watt (1mnV) characteristics. Also, the warm-up period and restrike may vary between 3 minutes and 7 minutes. As with other HID lamps, these ballasts have power factors in the 40% to 50% range unless corrected; capacitor correction results in power factors in the 90% range. Efficacies for mercury vapor lamps range from 38 to 63 lm, excluding ballast losses. Average lamp life is 24,000 hours, but it is recommended that lamps be replaced at 16,000 hours due to rapid lumen depreciation. Metal halide lamps are similar in construction to mercury vapor lamps. The difference is that metal halides are added to the mercury and argon in the arc tube. The efficacies are improved to the range of 75 lm/W to 125 IN, excluding bal- last loss. The color rendering is quite white and is usually superior to the phosphor-coated mercury vapor lamp. The warm-up time for metal halide lamps is 2 minutes to 4 min- utes, and restrike time varies from 5 minutes to 15 minutes, depending on the type. Power factors in the 90% range can be obtained. Lamp life varies from 3,000 hours to 20,000 hours. Metal halide lamps have more rapid lumen depreciation than do mercury vapor lamps, and have high surface operating tem- peratures which must be considered before application in clas- sified locations. The lamp life and lumen output are affected by burning position. Currently, most engineering activities by lamp manufactur- ers are focused on improvements in the overall efficiencies and life of the metal halide lamps. A series of pulse start metal halide lamps have been developed with features of improved lamp life, lumen maintenance, and the use of more efficient ballast systems. These lamps have wattages ranging from 150 W to 400 W with efficacy 90 IN to 110 le, lamp life of 15,000 to 30,000 hours; improved warm-up time of 2 minutes; and restrike time of 3 minutes to 4 minutes. A 33% improve- ment in lumen maintenance can be seen in these lamps. High-pressure sodium lamps have efficacies that range from 77 lm/W to 140 lm/W, depending on size. The color rendition is a distinct orange. Warm-up time for high-pressure sodium lamps is from 3 minutes to 4 minutes. Restrike time is less than 1 minute, and instant restrike devices are offered for 50-W to 150-W high-pressure sodium lamps. Power factors range from 40% to 99% depending on the ballast type and the age of the lamp. Lamp life is 24,000 hours. HID lighting may be supplemented by incandescent or fluorescent lighting which would provide illumination dur- ing the initial warm-up time and during the restrike time after an extinction caused by voltage dips in the 10% to 60% range, depending on ballast type. If required, a push-to-test switch can be installed with a fixture that uses the re-strike feature. This switch will allow the testing of the restrike dur- ing normal operation by interrupting power to the fixture. This testing method will ensure that the restrike will func- tion as intended after a major voltage dip or power failure. 7.5 LUMINAIRES 7.5.1 Selection In choosing a luminaire, a separate study should be made for each application. Some of the factors influencing the final selection are appearance, efficiency, glare, density of equip- ment, frequency of operation, maintenance, required color rendition, and area classification. 7.5.2 Floodlighting Floodlights provide area lighting at an economical cost. They must be located at suitable mounting heights and with unob- structed beam paths. Mounting can be on pipeways, vessel plat- forms, rigging structures, and floodlight poles. Floodlights are available with most lamp types, and with beam spreads from 10" to 18" (NEMA 1) to greater than 130" (NEMA 7). 7.5.3 Codes and Standards Local codes, national codes, federal standards, profes- sional standards, and manufacturers’ standards relate to spe- cific requirements that must be met in the construction and installation of a luminaire. Some codes and standards deal with fire and safety (electrical, mechanical, and thermal); others relate to performance and construction (materials and finishes). Conformance to the appropriate set of specifica- tion is often determined by certified laboratory tests. Certifi- cation is often denoted by an identifying label. Local code enforcement authorities may or may not require certification by an approved laboratory. 7.5.3.1 National Codes NFPA 70, the Canadian EZectricaZ Code (CEC), and simi- lar codes in most major countries state specific electrical requirements which must be met by all electrical equipment, including luminaires. 7.5.3.2 National and International Standards For electrical products, UL, CSA, and other similar organi- zations publish minimum safety standards that are in con- formance with electrical codes. Luminaires approved by these organizations will meet the standards that ensure that they are acceptable for installation and are able to provide sat- isfactory service. 7.5.3.3 Industry Standards Industry standards are published by various organizations that generally utilize national technical’ committees com- prised of representatives from industry, inspection and protec- tion agencies, and manufacturers. Conformance to these standards is not necessarily required, but it does offer many advantages to the user when conformance is specified. Stan- dards organizations include the American Society for Testing and Materials (ASTM), Certified Ballast Manufacturers (CBM)17, IEEE, ES, NEMA, andANSI. 7.5.3.4 Manufacturers’ Standards Since codes and standards deal primarily with safety and performance, the specifier should be aware of the quality standards used by the manufacturer. 7.5.4 Ballast Considerations Lamp ballasts must be taken into consideration when spec- ifying luminaires for purchase. For all lamp types requiring ballasts, there are a variety of ballasts available. The design engineer should consult with the luminaire and lamp repre- sentatives to get more details. HID luminaires may be purchased with a variety of bal- last types having a range of power factors and costs: but with the introduction of the high-pressure sodhm lamp, a new ballast consideration has been introduced. Unlike other HID lamps, the high-pressure sodium lamp is one with dynamic characteristics over its life. By carefully specifying high-pressure sodium luminaire ballast-types, the design engineer can achieve a good power factor over the life of the lamp. The design engineer’s considerations when selecting the type of ballast to be used are energy efficiency (losses), lamp life, lumen output, wiring and circuitry (number of fix- tures per circuit), and dip tolerance (ability to sustain the arc during a voltage dip). Remote mounted ballasts are available to use with mercury vapor, metal halide or high-pressure sodium lighting fixtures. The distance that the ballast can be