185 Questions
What is the primary reason for grounding and bonding in fuel handling systems?
To control hazards created by electrostatic energy
What is the process of connecting two or more metallic objects together called?
Bonding
How is protection against static charge buildup obtained?
By dissipating static charges through proper connections to the ground
What is the term for electrical currents flowing through paths other than their intended circuits?
Stray currents
What is a common source of static electricity?
Contact and separation of two materials
Why are static charges a concern in fuel handling systems?
They can create sparks that can ignite fuels
What is required for combustion to occur?
Fuel vapors and air
At what temperature do flammable vapors exist over the surface of JP-4?
Above -10ºF
What affects the static electricity characteristics of clothing materials?
Humidity
What should personnel do to dissipate static charges when wearing CWDEs?
Directly ground or bond themselves through the CWDE boot or glove
What is the purpose of touching a grounding/bonding point with a bare hand?
To dissipate static charges
Why is it important to electrostatically equalize oneself with the aircraft?
To prevent static discharges
What is the potential electrical potential of the liquid fuel surface during tank filling?
Thousands of volts
What happens to objects in a fuel tank during filling?
They become electrically charged
Why is it important to avoid touching bare electrical primers, exposed propellants, and explosive chemicals?
To prevent fuel ignition
What happens when a spark discharges from the surface of the liquid to the internal surfaces of the tank or any other object?
Ignition occurs with disastrous results
What is the acceptable electrical resistance between receptacles and clean aircraft skin?
One ohm or less
What is the minimum pull required to withdraw the plug from the receptacle?
8 pounds
What is the purpose of the locally fabricated tool assembly?
To assist in resistance testing on aircraft installed grounding/bonding receptacles
What is the characteristic of the latest assembly of receptacles?
One-half inch curved base on contact
Why would a receptacle be replaced?
If the receptacle is corroded or damaged
What is the purpose of the continuity check?
To ensure all receptacles are electrically interconnected
What should be done to the grounding/bonding cable before use?
Balance out the resistance
What is the minimum acceptable quality of the cable?
No more than one-third of the wires are broken
When would a clamp, part No.M83413/7-1, be substituted?
When there is insufficient space in a ground connection pit
What is the name of the plug used in the testing process?
Part No.MS3493
What is the primary purpose of adding a conductivity additive to fuel?
To decrease the relaxation time of electrostatic charges
What is the maximum fuel flow rate for a 2.00 inch pipe diameter to prevent hazardous levels of static electricity?
191 gallons/minute
What is the danger of lightning strikes to servicing personnel?
They can create a hazard in the surrounding area
What is the primary source of static electricity generation in operating aircraft engines?
The engine's rotor blades
What is the policy for grounding parked aircraft or aircraft fuel servicing operations?
Grounding is not required unless specified by MDS technical orders
What is the purpose of bonding aircraft to fuel servicing equipment?
To prevent static electricity generation
What should be done if a bonding wire becomes disconnected?
Reconnect the bonding wire immediately
When is grounding of aircraft or supporting servicing equipment required?
During all of the above operations
What is the duration of a lightning strike?
Approximately 1/100 second
What is the purpose of the hydrant fuel servicing vehicle's bonding to the hydrant system?
To prevent static electricity generation
What is the recommended method for personnel to ground or bond themselves when entering a fuel servicing or weapons loading area?
Touch the closest piece of grounded or bonded aircraft or equipment
What is the primary purpose of grounding or bonding when servicing fuel with personnel armor?
To prevent static charges from building up on the personnel armor
What is the effect of personnel armor on static charges during fuel servicing operations?
It generates and accumulates static charges
What should a person do if a spark occurs during bonding or grounding while wearing personnel armor?
Ground or bond more frequently during all work phases
What is the recommended method for personnel to ground or bond themselves when wearing CWDE gloves?
Ground or bond themselves directly through the CWDE glove
What is the approximate resistance of CWDE gloves?
10,000 ohms
What is attached to the plug end of the cable in the clamp-plug unit?
A warning streamer 'REMOVE BEFORE FLIGHT'
Why is the cable retainer spot welded in the two-piece plug and cap assembly design?
To prevent loosening of the cable and possible loss of continuity
What is the maximum allowable resistance of a 100-foot length of 3/32-inch diameter stainless steel cable?
10 ohms
When is a continuity test performed on installed static discharge reels?
At the time of initial installation and when a lack of continuity is suspected
What is the purpose of grounding or bonding techniques during ground servicing operations?
To dissipate or equalize static charges
Where should personnel ground or bond themselves during fuel servicing operations?
At least three feet from any aircraft fuel vent outlet
What should personnel avoid touching during fuel servicing operations?
The primers of electrically-primed munitions
When should personnel ground or bond themselves periodically?
If a spark occurs during the initial grounding or bonding procedure
Why is it necessary to ground or bond personnel during fuel servicing operations?
To reduce the risk of ignition from static sparks
When is it necessary to ground an aircraft in locations with low humidity?
After landing to dissipate static charges generated while flying through dust or precipitation
What should be checked prior to each use of the grounding reel?
The security of mounting on a rigid base and evidence of corrosion or damage
What is the purpose of the first bonding wire in overwing fuel servicing operations?
To equalize static charges that accumulate while fuel is flowing
What is not required to be grounded when stored, parked, or during other periods when in-tank work is not being accomplished?
Drop, external, ferry, and weapons bay fuel tanks
What is the purpose of a red warning streamer on a conversion jumper?
To provide a visual warning
What is the maximum resistance allowed between the body or frame of a multiple receptacle junction box and the installed female extension jacks?
10 ohms
What is the correct sequence to ground an aircraft using a clamp-plug unit?
Attach a grounding clamp to the earth grounding point, then insert the plug into the receptacle
Why are aircraft electrical receptacles inspected during maintenance intervals?
To check for corrosion and loose mounting
What is the purpose of visually inspecting aircraft electrical receptacles?
To inspect for loosely mounted receptacles and evidence of corrosion
What is not allowed when connecting multiple grounding or bonding cables?
Connecting more than one grounding or bonding cable by any means, except as specified
What is the purpose of a multiple receptacle junction box?
To reduce the number of grounding or bonding cables around a work site
What is the purpose of grounding in fuel handling systems?
To dissipate static charges through proper connections to the ground
What is the term for electrical currents flowing through paths other than their intended circuits?
Stray currents
What is a common means of producing a static charge?
Dust blowing across a surface
What is the purpose of bonding in fuel handling systems?
To equalize electrostatic potential between two or more conductive objects
Why are static charges a concern in fuel handling systems?
Because they can cause fires or explosions
What is the purpose of grounding or bonding in fuel handling systems?
To dissipate static charges through proper connections to the ground
What is required for combustion to occur?
Fuel vapors, air (oxygen), and an ignition source
What affects the static electricity characteristics of clothing materials?
Humidity
What happens to objects in a fuel tank during filling?
They collect a charge from the fuels and become similar to an electrical condenser (capacitor) plate
Why is it important to electrostatically equalize oneself with the aircraft?
To prevent damage to electronic components
What can cause a spark during tank filling?
A spark from the surface of the liquid to the internal surfaces of the tank
What should personnel avoid touching during fuel servicing operations?
Bare electrical primers, exposed propellants, and explosive chemicals
How do personnel wearing CWDEs dissipate static buildup?
By touching a grounding/bonding point through their CWDE boot or glove
What is the purpose of wearing antistatic finishes on clothing?
To reduce the risk of static electricity buildup
Why is it important to minimize static electricity buildup?
To prevent fires and explosions
What is the purpose of grounding or bonding in fuel handling systems?
To reduce the risk of static electricity buildup
What is the maximum acceptable electrical resistance between receptacles and clean aircraft skin?
One ohm or less
What is the purpose of the locally fabricated tool assembly?
To assist in resistance testing on aircraft-installed grounding/bonding receptacles
What is the characteristic of the latest assembly of receptacles?
One-half inch curved base on contact
Why would a receptacle be replaced?
If it has a weak or damaged spring
What is the minimum pull required to withdraw the plug from the receptacle?
Eight pounds
What should be done to the grounding/bonding cable before use?
Resistance should be balanced out
What is the minimum acceptable quality of the cable?
More than one-third of the wires broken
When would a clamp, part No.M83413/7-1, be substituted?
When there is insufficient space in a ground connection pit
What is the name of the plug used in the testing process?
Part No.MS3493
Why is a continuity check performed?
To ensure all receptacles are electrically interconnected
What is the purpose of momentarily connecting a cable from an earth ground to any unpainted metallic aircraft surface?
To dissipate static charges generated on the aircraft while flying through dust or precipitation.
What is required for bonding wire connections during overwing fuel servicing operations?
Two bonding wires, one between the fuel source and the aircraft, and another for each open port fuel nozzle.
Why are conversion jumpers used in overwing fuel servicing operations?
To provide bonding capability for aircraft without electrical jack assembly receptacles.
What is the purpose of a multiple receptacle junction box?
To reduce the number of grounding/bonding cables around a work site.
What is the proper connection sequence to ground an aircraft using a clamp-plug unit?
Attach the clamp to the earth grounding point, then insert the plug into an aircraft receptacle jack assembly.
Why are aircraft electrical receptacles inspected?
To check for corrosion and loose mounting.
What is the purpose of a bonding wire in overwing fuel servicing operations?
To equalize static charges that accumulate while fuel is flowing during fuel servicing operations.
What is the requirement for multiple receptacle junction boxes?
They must be built from a high-quality conductive material.
What is the resistance requirement for multiple receptacle junction boxes?
The resistance between the body or frame of the junction box and the installed female extension jacks shall not exceed 10 ohms.
What is the purpose of a continuity check on multiple receptacle junction boxes?
To ensure the junction box is electrically interconnected throughout the assembly.
What is the primary reason for the increased hazard of discharge from floating objects to the tank?
The potential required for a discharge from these objects is less than that required to cause a discharge from the liquid surface
What is the purpose of incorporating a conductivity additive to the fuel?
To decrease the relaxation time of electrostatic charges
What is the maximum fuel flow rate for a 1.50 inch pipe diameter to prevent hazardous levels of static electricity?
125 gallons per minute
What is the primary source of static electricity generation in operating aircraft engines?
The operation of the engines
What is the policy for grounding parked aircraft or aircraft fuel servicing operations?
Grounding is required only for specific MDS technical orders
What is the purpose of bonding aircraft to fuel servicing equipment?
To prevent static electricity
What should be done if a bonding wire becomes disconnected?
Reconnect it immediately
What is the duration of a lightning strike?
Approximately 1/100 second
What is the purpose of the hydrant fuel servicing vehicle's bonding to the hydrant system?
To prevent static electricity
Why are personnel inside an aircraft safe during a lightning strike?
Because the aircraft doors, hatches, and canopies are closed
What is attached to the plug end of the cable in the clamp-plug unit?
A warning streamer ‘‘REMOVE BEFORE FLIGHT’’
Why is the cable retainer spot welded in the two-piece plug and cap assembly design?
To prevent loosening of the cable and possible loss of continuity
What is the primary purpose of grounding or bonding when servicing fuel with personnel armor?
To equalize the charge on the personnel armor
What is the maximum allowable resistance of a 100-foot length of 3/32-inch diameter stainless steel cable?
10 ohms
What is the effect of personnel armor on static charges during fuel servicing operations?
It generates a static charge
When is a continuity test performed on installed static discharge reels?
At the time of initial installation and at any time a lack of continuity is suspected
Why should personnel ground or bond themselves frequently during fuel servicing operations when wearing personnel armor?
To equalize the charge on the armor
Where should personnel ground or bond themselves during fuel servicing operations?
At least three feet from aircraft fuel vent outlets
What is the recommended method for personnel to ground or bond themselves when wearing CWDE gloves?
Through the CWDE glove
What should a person do if a spark occurs during bonding or grounding while wearing personnel armor?
Ground or bond themselves frequently during all work phases
What is the purpose of grounding or bonding techniques during ground servicing operations?
To dissipate or equalize static charges that have accumulated
What should personnel avoid touching during fuel servicing operations?
The electrically-primed munitions
What is the purpose of personnel entering a fuel servicing or weapons loading area grounding or bonding themselves to the closest piece of grounded or bonded aircraft or equipment?
To dissipate static charges
When should personnel ground or bond themselves periodically?
If a spark occurs during the initial grounding or bonding procedure
What is the purpose of visual inspections of the grounding reel?
To check for security of mounting on a rigid base
What is the acceptable resistance between the plug or inside the clamp jaws to the equipment frame?
10 ohms
Why does the Air Force incorporate conductivity additives to fuel?
To decrease the relaxation time of electrostatic charges
What is the maximum fuel flow rate for a 1.50 inch pipe diameter to prevent hazardous levels of static electricity?
125 gallons/minute
What is the primary source of static electricity generation in operating aircraft engines?
All of the above
What should be done if a bonding wire becomes disconnected?
Immediately reconnect it
When is grounding of aircraft or supporting servicing equipment required?
During munitions loading/unloading operations
What is the danger of lightning strikes to servicing personnel?
A severe hazard, even if the aircraft is statically grounded
What is the purpose of bonding aircraft to fuel servicing equipment?
To prevent static electricity buildup
What is the duration of a lightning strike?
Approximately 1/100 second
Why is it important to evacuate servicing personnel during an electrical storm?
To prevent injury to personnel
What is the purpose of the hydrant fuel servicing vehicle's bonding to the hydrant system?
To bond the hydrant fuel servicing vehicle to the aircraft
What is the primary purpose of grounding and bonding in fuel handling systems?
To control hazards created by electrostatic energy
What is the result of static electricity generation when two materials are brought into contact and then separated?
A static charge is generated
What is the definition of stray currents?
Electrical currents flowing through paths other than their intended circuits
Why are stray currents a concern in Air Force fixed refueling systems?
They can flow through the conducting parts of the system
What is the purpose of bonding two or more metallic objects together?
To equalize electrostatic potential between them
What is a common means of producing a static charge?
Removing items of clothing
What is attached to the plug end of the cable in the clamp-plug unit?
A warning streamer 'REMOVE BEFORE FLIGHT'
Why is the cable retainer spot welded in the two-piece plug and cap assembly design?
To prevent loosening of the cable and possible loss of continuity
What is the maximum allowable resistance of a 100-foot length of 3/32-inch diameter stainless steel cable?
10 ohms
When is a continuity test performed on installed static discharge reels?
At the time of initial installation and at any time a lack of continuity is suspected
Where should personnel ground or bond themselves during fuel servicing operations?
At a distance of at least three feet from any aircraft fuel vent outlet
What is the purpose of grounding or bonding techniques during ground servicing operations?
To dissipate or equalize static charges that have accumulated
What should personnel avoid touching during fuel servicing operations?
Electrical primers of munitions
When should personnel ground or bond themselves periodically?
If a spark occurs during the initial grounding or bonding procedure
What is the purpose of the continuity check on locally-fabricated clamp-plug units?
To ensure continuity prior to placing into service
What should be done to the grounding/bonding cable before use?
Perform a continuity check
What is necessary for ignition to occur in fuel vapors?
Fuel vapors, air, and an ignition source
How does the wearing of multiple garment layers affect static electricity?
It has no effect on the electrostatic hazard
What is the effect of humidity on static electricity?
It decreases the electrostatic hazard
How can personnel dissipate static charges through their clothing?
By touching a grounding/bonding point with their bare hand
What is the purpose of electrostatically equalizing oneself with the aircraft?
To prevent damage to sensitive electronic components
What happens to the electrical potential of the liquid fuel surface during tank filling?
It increases to thousands of volts
What is the effect of objects in a fuel tank during filling?
They collect a charge from the fuels and become similar to an electrical condenser plate
Why is it important to avoid touching bare electrical primers, exposed propellants, and explosive chemicals?
To prevent electrostatic discharges
What is the purpose of grounding or bonding in fuel handling systems?
Not mentioned in the text
What is the effect of moisture on the electrical conductivity of clothing?
It increases the electrical conductivity
What is the minimum acceptable electrical resistance between the plug and cleaned aircraft skin?
One ohm or less
What is the purpose of the firm pull test on the plug?
To determine the minimum pull required to withdraw the plug
What is the characteristic of the latest assembly of receptacles?
One-half inch curved base on contact
What is the reason for replacing a receptacle?
If it is weak or damaged
What is the purpose of the continuity check?
To assure all receptacles are electrically interconnected through the aircraft airframe and/or skin
What should be done to the portable grounding/bonding cable before use?
Its resistance shall be balanced out prior to use
What is the minimum acceptable quality of the cable?
Less than one-third of the cable wires are broken
When would a clamp, part No.M83413/7-1, be substituted?
When the aircraft is not equipped with the jack assembly
What is the purpose of grounding or bonding oneself when wearing Chemical Warfare Defense Ensemble (CWDE) gloves?
To effectively dissipate static charges
What is the purpose of the locally fabricated tool assembly?
To assist in resistance test on aircraft installed grounding/bonding receptacles
Why should personnel avoid wearing personnel armor during fuel servicing operations except in actual combat?
To reduce the risk of static charges
What happens if a spark occurs during bonding or grounding while wearing personnel armor?
The individual should ground or bond frequently during all work phases
Where should personnel ground or bond themselves when entering a fuel servicing or weapons loading area?
To the closest piece of grounded or bonded aircraft or equipment
What is the effect of personnel armor on static charges during fuel servicing operations?
It accumulates static charges
Why is it important to ground or bond oneself before beginning fuel servicing operations?
To reduce the risk of static charges
What is the purpose of momentarily connecting a cable from an earth ground to an aircraft's unpainted metallic surface?
To dissipate static charges generated during flying through dust or precipitation
What is required for overwing fuel servicing operations?
Two bonding wires, one for each open port fuel nozzle
Why are drop, external, ferry, Benson, and weapons bay fuel tanks exempt from grounding requirements?
They do not require grounding when not in use
What is the purpose of a conversion jumper in over-the-wing fuel servicing?
To provide bonding capability for fuel servicing nozzles
What is the acceptable resistance between a multiple receptacle junction box and its installed female extension jacks?
10 ohms
What is the correct sequence for grounding an aircraft using a clamp-plug unit?
Attach clamp to earth ground, then plug into receptacle
Why are aircraft electrical receptacles inspected during maintenance intervals?
To inspect for signs of corrosion or wear
What is the purpose of a continuity check on a conversion jumper assembly?
To ensure the jumper is electrically interconnected throughout
What is the consequence of not using a bonding wire between the fuel source and the aircraft during overwing fuel servicing?
The fuel nozzle may become electrically charged
What is the purpose of a multiple receptacle junction box in grounding and bonding operations?
To reduce the number of grounding cables around a work site
Study Notes
Electrostatic Hazards and Static Grounding and Bonding
- Fire or explosion hazards are always present where fuels are handled
- Grounding and bonding are effective means of controlling hazards created by electrostatic energy
- Grounding is the process of connecting one or more metallic objects and ground conductors to ground electrodes
- Bonding is the process of connecting two or more metallic objects together by means of a conductor to equalize electrostatic potential
Electrostatic Charges
- Static electricity is frequently generated when two materials are brought into contact and then separated
- Common sources of static electricity include:
- Removing items of clothing
- Dust blowing across a surface
- Liquid flowing through a pipe
- Moving vehicles
- Protection against static charge buildup is obtained by dissipating static charges through proper connections to the ground or equalizing static charges through effective bonding
- Static electricity has been the ignition source for many petroleum fires
Stray Currents
- Electrical currents flowing through paths other than their intended circuits, or any extraneous current in the earth are stray currents
- Stray currents sometimes take paths through the conducting parts of the system
- Grounding or bonding does not eliminate stray currents
Combustion
- Combustion requires fuel vapors, air (oxygen), and an ignition source
- Flammable vapors exist over the surface of JP-4 at -10ºF and above, and aviation gasoline at -50ºF and above
- Ignition of these vapors can be caused either by a spark or flame
- Energy levels associated with electrostatic discharges may be sufficient to ignite fuel vapors
Electrostatic Charging of Personnel
- Normal activity of personnel involved in refueling operations can generate static electricity charges on their clothing
- Humidity greatly affects the static electricity characteristics of clothing materials
- The lower the humidity, the higher the electrostatic hazard
- Antistatic finishes are not permanent and are gradually removed by laundering or dry cleaning
- Wearing multiple garment layers does not cause an excessive static charge to develop
- Removing garments while in the refueling area can generate a static charge
- Insulated footwear limits the dissipation of static charges to the ground
- Gloves can dissipate static charges, but as an added precaution, personnel should touch a grounding/bonding point with their bare hand
Tank Filling
- During the tank filling process, the electrical potential of the liquid fuel surface may reach thousands of volts
- A spark may discharge from the surface of the liquid to the internal surfaces of the tank or any other object in the tank
- Objects in a fuel tank will collect a charge from the fuels and become similar to an electrical condenser (capacitor) plate
- The potential required for a discharge from these floating objects to the tank is less than that required to cause a discharge from the liquid surface to the tank
- The Air Force incorporates a conductivity additive to decrease the relaxation time of electrostatic charges in order to preclude these problems
- The use of a higher flash point fuel such as JP-8 or JP-5 in lieu of JP-4, when permitted by the applicable aircraft technical orders, reduces the vapor ignition hazard
Lightning
- Even if an aircraft were statically grounded, a severe hazard to servicing personnel could exist if lightning strikes the aircraft or within several hundred feet of the aircraft
- Servicing personnel should be evacuated from the area when there is danger of a direct or close proximity lightning strike
- Potentials in the range of several million volts exist between clouds and earth
- High points such as vertical stabilizers and antenna masts are most susceptible to strikes
- These strikes are of short duration (approximately 1/100 second duration per strike) and even though high energy levels exist, the ramp grounding system will generally conduct the energy safely to earth
Other Sources of Static Electricity
- Operating aircraft engines, rotor blades, and propeller blades can generate high static electricity voltages
- These static sources are especially hazardous because the static voltages may be generated continuously as long as the engines/blades continue to operate
Grounding and Bonding Policy
- Grounding is not required for parked aircraft or aircraft fuel servicing operations unless required by specific MDS technical orders
- Aircraft will be bonded to fuel servicing equipment at all times during fuel servicing operations
- Hydrant fuel servicing vehicles and hose carts will also be bonded to the hydrant system in addition to bonding to the aircraft
- Grounding/Bonding clamps/plugs shall not be allowed to drag across the ramp
- Clamps/plugs shall be carried to reels on equipment### Grounding and Bonding Procedures
- Personnel involved in fuel servicing or munitions loading/unloading operations must ground or bond themselves to a suitable grounding/bonding point or a bare (unpainted) portion of the aircraft.
- The bonding point should be at least three feet from any aircraft fuel vent outlet.
- If a spark occurs during the initial grounding or bonding procedure, personnel will ground or bond themselves periodically to prevent additional static charge accumulations.
- If no spark occurs, additional grounding or bonding is not necessary.
Important Safety Considerations
- Avoid grounding or bonding within three feet of aircraft fuel vent outlets.
- Personnel conducting aircraft fuel vent checks must ground or bond themselves above waist level and at least three feet from the fuel vent outlet prior to checking the vent.
- Weapons loading personnel must ground or bond themselves when entering the fuel servicing safety zone and before handling electrically-primed munitions.
- Avoid touching the primers of electrically-primed munitions (e.g., impulse cartridges and 20 MM ammunition).
Grounding and Bonding in Special Situations
- Personnel entering a fuel servicing or weapons loading area should ground or bond themselves to the closest piece of grounded or bonded aircraft or equipment.
- When wearing Chemical Warfare Defense Ensemble (CWDE) gloves, personnel can ground or bond themselves directly through the glove, which has a resistance of approximately 10,000 ohms.
- Personnel armor (Flak Vest or Individual Body Armor) should not be worn during fuel servicing operations, except in actual combat, as it acts as an electrical insulator and generates static charges.
- If wearing personnel armor, the individual must ground or bond themselves when approaching an aircraft and prior to beginning work, and repeat the process frequently during all work phases if a spark occurs.
Electrostatic Hazards and Static Grounding and Bonding
- Fire or explosion hazards are always present where fuels are handled
- Grounding and bonding are effective means of controlling hazards created by electrostatic energy
- Grounding is the process of connecting one or more metallic objects and ground conductors to ground electrodes
- Bonding is the process of connecting two or more metallic objects together by means of a conductor to equalize electrostatic potential
Electrostatic Charges
- Static electricity is frequently generated when two materials are brought into contact and then separated
- Common sources of static electricity include:
- Removing items of clothing
- Dust blowing across a surface
- Liquid flowing through a pipe
- Moving vehicles
- Protection against static charge buildup is obtained by dissipating static charges through proper connections to the ground or equalizing static charges through effective bonding
- Static electricity has been the ignition source for many petroleum fires
Stray Currents
- Electrical currents flowing through paths other than their intended circuits, or any extraneous current in the earth are stray currents
- Stray currents sometimes take paths through the conducting parts of the system
- Grounding or bonding does not eliminate stray currents
Combustion
- Combustion requires fuel vapors, air (oxygen), and an ignition source
- Flammable vapors exist over the surface of JP-4 at -10ºF and above, and aviation gasoline at -50ºF and above
- Ignition of these vapors can be caused either by a spark or flame
- Energy levels associated with electrostatic discharges may be sufficient to ignite fuel vapors
Electrostatic Charging of Personnel
- Normal activity of personnel involved in refueling operations can generate static electricity charges on their clothing
- Humidity greatly affects the static electricity characteristics of clothing materials
- The lower the humidity, the higher the electrostatic hazard
- Antistatic finishes are not permanent and are gradually removed by laundering or dry cleaning
- Wearing multiple garment layers does not cause an excessive static charge to develop
- Removing garments while in the refueling area can generate a static charge
- Insulated footwear limits the dissipation of static charges to the ground
- Gloves can dissipate static charges, but as an added precaution, personnel should touch a grounding/bonding point with their bare hand
Tank Filling
- During the tank filling process, the electrical potential of the liquid fuel surface may reach thousands of volts
- A spark may discharge from the surface of the liquid to the internal surfaces of the tank or any other object in the tank
- Objects in a fuel tank will collect a charge from the fuels and become similar to an electrical condenser (capacitor) plate
- The potential required for a discharge from these floating objects to the tank is less than that required to cause a discharge from the liquid surface to the tank
- The Air Force incorporates a conductivity additive to decrease the relaxation time of electrostatic charges in order to preclude these problems
- The use of a higher flash point fuel such as JP-8 or JP-5 in lieu of JP-4, when permitted by the applicable aircraft technical orders, reduces the vapor ignition hazard
Lightning
- Even if an aircraft were statically grounded, a severe hazard to servicing personnel could exist if lightning strikes the aircraft or within several hundred feet of the aircraft
- Servicing personnel should be evacuated from the area when there is danger of a direct or close proximity lightning strike
- Potentials in the range of several million volts exist between clouds and earth
- High points such as vertical stabilizers and antenna masts are most susceptible to strikes
- These strikes are of short duration (approximately 1/100 second duration per strike) and even though high energy levels exist, the ramp grounding system will generally conduct the energy safely to earth
Other Sources of Static Electricity
- Operating aircraft engines, rotor blades, and propeller blades can generate high static electricity voltages
- These static sources are especially hazardous because the static voltages may be generated continuously as long as the engines/blades continue to operate
Grounding and Bonding Policy
- Grounding is not required for parked aircraft or aircraft fuel servicing operations unless required by specific MDS technical orders
- Aircraft will be bonded to fuel servicing equipment at all times during fuel servicing operations
- Hydrant fuel servicing vehicles and hose carts will also be bonded to the hydrant system in addition to bonding to the aircraft
- Grounding/Bonding clamps/plugs shall not be allowed to drag across the ramp
- Clamps/plugs shall be carried to reels on equipment### Grounding and Bonding Procedures
- Personnel involved in fuel servicing or munitions loading/unloading operations must ground or bond themselves to a suitable grounding/bonding point or a bare (unpainted) portion of the aircraft.
- The bonding point should be at least three feet from any aircraft fuel vent outlet.
- If a spark occurs during the initial grounding or bonding procedure, personnel will ground or bond themselves periodically to prevent additional static charge accumulations.
- If no spark occurs, additional grounding or bonding is not necessary.
Important Safety Considerations
- Avoid grounding or bonding within three feet of aircraft fuel vent outlets.
- Personnel conducting aircraft fuel vent checks must ground or bond themselves above waist level and at least three feet from the fuel vent outlet prior to checking the vent.
- Weapons loading personnel must ground or bond themselves when entering the fuel servicing safety zone and before handling electrically-primed munitions.
- Avoid touching the primers of electrically-primed munitions (e.g., impulse cartridges and 20 MM ammunition).
Grounding and Bonding in Special Situations
- Personnel entering a fuel servicing or weapons loading area should ground or bond themselves to the closest piece of grounded or bonded aircraft or equipment.
- When wearing Chemical Warfare Defense Ensemble (CWDE) gloves, personnel can ground or bond themselves directly through the glove, which has a resistance of approximately 10,000 ohms.
- Personnel armor (Flak Vest or Individual Body Armor) should not be worn during fuel servicing operations, except in actual combat, as it acts as an electrical insulator and generates static charges.
- If wearing personnel armor, the individual must ground or bond themselves when approaching an aircraft and prior to beginning work, and repeat the process frequently during all work phases if a spark occurs.
Electrostatic Hazards and Static Grounding and Bonding
- Fire or explosion hazards are always present where fuels are handled
- Grounding and bonding are effective means of controlling hazards created by electrostatic energy
- Grounding is the process of connecting one or more metallic objects and ground conductors to ground electrodes
- Bonding is the process of connecting two or more metallic objects together by means of a conductor to equalize electrostatic potential
Electrostatic Charges
- Static electricity is frequently generated when two materials are brought into contact and then separated
- Common sources of static electricity include:
- Removing items of clothing
- Dust blowing across a surface
- Liquid flowing through a pipe
- Moving vehicles
- Protection against static charge buildup is obtained by dissipating static charges through proper connections to the ground or equalizing static charges through effective bonding
- Static electricity has been the ignition source for many petroleum fires
Stray Currents
- Electrical currents flowing through paths other than their intended circuits, or any extraneous current in the earth are stray currents
- Stray currents sometimes take paths through the conducting parts of the system
- Grounding or bonding does not eliminate stray currents
Combustion
- Combustion requires fuel vapors, air (oxygen), and an ignition source
- Flammable vapors exist over the surface of JP-4 at -10ºF and above, and aviation gasoline at -50ºF and above
- Ignition of these vapors can be caused either by a spark or flame
- Energy levels associated with electrostatic discharges may be sufficient to ignite fuel vapors
Electrostatic Charging of Personnel
- Normal activity of personnel involved in refueling operations can generate static electricity charges on their clothing
- Humidity greatly affects the static electricity characteristics of clothing materials
- The lower the humidity, the higher the electrostatic hazard
- Antistatic finishes are not permanent and are gradually removed by laundering or dry cleaning
- Wearing multiple garment layers does not cause an excessive static charge to develop
- Removing garments while in the refueling area can generate a static charge
- Insulated footwear limits the dissipation of static charges to the ground
- Gloves can dissipate static charges, but as an added precaution, personnel should touch a grounding/bonding point with their bare hand
Tank Filling
- During the tank filling process, the electrical potential of the liquid fuel surface may reach thousands of volts
- A spark may discharge from the surface of the liquid to the internal surfaces of the tank or any other object in the tank
- Objects in a fuel tank will collect a charge from the fuels and become similar to an electrical condenser (capacitor) plate
- The potential required for a discharge from these floating objects to the tank is less than that required to cause a discharge from the liquid surface to the tank
- The Air Force incorporates a conductivity additive to decrease the relaxation time of electrostatic charges in order to preclude these problems
- The use of a higher flash point fuel such as JP-8 or JP-5 in lieu of JP-4, when permitted by the applicable aircraft technical orders, reduces the vapor ignition hazard
Lightning
- Even if an aircraft were statically grounded, a severe hazard to servicing personnel could exist if lightning strikes the aircraft or within several hundred feet of the aircraft
- Servicing personnel should be evacuated from the area when there is danger of a direct or close proximity lightning strike
- Potentials in the range of several million volts exist between clouds and earth
- High points such as vertical stabilizers and antenna masts are most susceptible to strikes
- These strikes are of short duration (approximately 1/100 second duration per strike) and even though high energy levels exist, the ramp grounding system will generally conduct the energy safely to earth
Other Sources of Static Electricity
- Operating aircraft engines, rotor blades, and propeller blades can generate high static electricity voltages
- These static sources are especially hazardous because the static voltages may be generated continuously as long as the engines/blades continue to operate
Grounding and Bonding Policy
- Grounding is not required for parked aircraft or aircraft fuel servicing operations unless required by specific MDS technical orders
- Aircraft will be bonded to fuel servicing equipment at all times during fuel servicing operations
- Hydrant fuel servicing vehicles and hose carts will also be bonded to the hydrant system in addition to bonding to the aircraft
- Grounding/Bonding clamps/plugs shall not be allowed to drag across the ramp
- Clamps/plugs shall be carried to reels on equipment### Grounding and Bonding Procedures
- Personnel involved in fuel servicing or munitions loading/unloading operations must ground or bond themselves to a suitable grounding/bonding point or a bare (unpainted) portion of the aircraft.
- The bonding point should be at least three feet from any aircraft fuel vent outlet.
- If a spark occurs during the initial grounding or bonding procedure, personnel will ground or bond themselves periodically to prevent additional static charge accumulations.
- If no spark occurs, additional grounding or bonding is not necessary.
Important Safety Considerations
- Avoid grounding or bonding within three feet of aircraft fuel vent outlets.
- Personnel conducting aircraft fuel vent checks must ground or bond themselves above waist level and at least three feet from the fuel vent outlet prior to checking the vent.
- Weapons loading personnel must ground or bond themselves when entering the fuel servicing safety zone and before handling electrically-primed munitions.
- Avoid touching the primers of electrically-primed munitions (e.g., impulse cartridges and 20 MM ammunition).
Grounding and Bonding in Special Situations
- Personnel entering a fuel servicing or weapons loading area should ground or bond themselves to the closest piece of grounded or bonded aircraft or equipment.
- When wearing Chemical Warfare Defense Ensemble (CWDE) gloves, personnel can ground or bond themselves directly through the glove, which has a resistance of approximately 10,000 ohms.
- Personnel armor (Flak Vest or Individual Body Armor) should not be worn during fuel servicing operations, except in actual combat, as it acts as an electrical insulator and generates static charges.
- If wearing personnel armor, the individual must ground or bond themselves when approaching an aircraft and prior to beginning work, and repeat the process frequently during all work phases if a spark occurs.
Learn about the importance of grounding and bonding in controlling electrostatic hazards when handling fuels. This chapter covers the basics of grounding and bonding techniques to prevent fire and explosion hazards.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
