Grounding/Bonding Program
Fisher Scientific
Grounding/Bonding Program
Program 200.13
2000 Park Lane
Pittsburgh, Pennsylvania 15275
Phone 412.490.8300 • Fax 412.490.8930
Regulatory Affairs Manual Series 200
Grounding Program Program 200.13
Table of Contents
Mandatory X Discretionary
Effective Date: April 2003 Rev. # 1 Page 3 of 18
Regulatory Affairs Manual Series 200
Grounding Program Program 200.13
1 Application 1-1
2 General 2-1
2.1 Definitions 2-1
2.2 Product Transfer Procedures 2-3
2.2.1 Metal to Metal 2-3
2.2.2 Metal to Plastic 2-4
2.2.3 Metal to Glass 2-6
2.2.4 Plastic to Glass 2-7
2.2.5 Plastic to Plastic 2-8
2.2.6 Glass to Glass 2-9
2.3 Waste Transfer Procedures 2-10
2.3.1 Metal to Metal 2-10
2.3.2 Plastic to Metal 2-10
2.3.3 Glass to Metal 2-11
2.3.4 Metal to Plastic 2-11
2.3.5 Plastic to Plastic 2-12
2.3.6 Glass to Plastic 2-13
2.4 Training 2-14
Mandatory X Discretionary
Effective Date: April 2003 Rev. # 1 Page 3 of 18
Regulatory Affairs Manual Series 200
Grounding Program Program 200.13
1 Application
The Grounding/Bonding Program applies to any Fisher facility performing a flammable or combustible liquid transfer from one container to another container.
2 General
Electrostatic discharges can be a serious ignition source in any industrial operation. These discharges are created through the following sequences:
· Electrostatic charge generation
· Charge accumulation
· Electrostatic discharge
Electrostatic charges can be generated on a surface any time there is a relative motion between those two surfaces. If one surface prefers to accept electrons, it will retain electrons after the separation, becoming negatively charged. The other surface will donate electrons during contact, and be left deficient in electrons after separation. That surface will become positively charged. When an insulating liquid exits a nozzle, the separation between the liquid and nozzle results in a transfer of electrons between the liquid and the nozzle, generating a charge on the surface of the liquid and surface of the nozzle.
Electrostatic charges become a hazard when they begin to accumulate on surfaces. A grounded, conducting surface will not accumulate electrostatic charges. Insulating materials, and conductors isolated from ground will accumulate charges, and the charge can reach the high potential necessary to generate an electrostatic discharge. Continuing with this example, if a conducting liquid flows through a properly grounded nozzle, the charge will dissipate from the nozzle as quickly as it is generated, but an insulated nozzle will accumulate the electrostatic charge on its surface. If the liquid is conducting and maintains a constant stream, and flows through a grounded nozzle, the liquid will be grounded. However, if there is a splashing, or the liquid forms a spray, then droplets will be isolated, and can accumulate charge. An insulating liquid will accumulate charge whether it forms, or stays a constant stream.
2.1 Definitions
Bonding
Bonding is the interconnecting of two objects by means of a clamp and bare wire. Its purpose is to equalize the electrical potential between the objects to prevent a static discharge when transferring a flammable or combustible liquid from one container to another. Clamps that make contact with the charged object provide the conductive path and a low resistance flexible cable allows the charge to equalize.
Brush Discharge
A brush discharge is an electrostatic discharge from an insulating solid. Brush discharges can ignite a flammable vapor atmosphere.
Field Induction
Field induction is an event that can directly or indirectly generates a static charge. Whenever any object becomes electro statically charged, there is an electrostatic field associated with that charge. If a bonding wire is placed in that electrostatic field, a charge may be induced on the device. If the device is grounded while within the electrostatic field, a transfer of charge from the wire occurs.
Under the right conditions, fabric can generate static electricity. This can occur when the fabric is brought into contact with other materials and then separated, or when the fabric is rubbed on other surfaces. Most synthetic fabrics (nylon, orlon, dacron and rayon) are more active generators of static electricity than natural fabrics. Rubber and leather-soled shoes can generate static when the wearer walks on dry carpeting or other non-conductive surfaces during periods of low humidity.
The potential for a fabric to generate electricity should be considered, and appropriate steps taken to minimize the potential when developing the site specific grounding/bonding procedures.
Grounding
The procedure used to carry an electrical charge to ground through a conductive path. A typical ground may be connected directly to a conductive water pipe or to a grounding bus and ground rod.
Isolated Conductors
A conductive object has little resistance to the flow of electrostatic charge. If a conductive object is in contact with electrical ground, eliminating an electrical field from the object with electrical ground, it is grounded. This state allows any electrostatic charge on the object to easily flow to ground, eliminating an electrical field from the object. A conductor may be considered isolated and capable of accumulating a dangerous electrostatic charge if the resistance to ground is greater than 1 x 108 ohms.
Isolated conductors can create an electrostatic discharge if they are brought close to any conductor, which is at a lower electrical potential. The electric field on the isolated conductor ionizes the air between it and the grounded conductor. This ionized channel allows the charge to flow off the isolated conductor to the grounded conductor. The ionized channel is visible as a flash of light, and is accompanied by an audible noise.
A discharge between two conductors is classified as a spark discharge. Spark discharges are very energetic, and are capable of igniting flammable vapors and dust clouds.
Insulating Isolated Conductors
Isolated conductors can become insulated conductors when an insulated barrier interrupts the grounding path. Some common examples of insulators causing conductors to become isolated from ground include:
Metal table placed on a rubber mat or insulated floor
Totes on rubber wheels
Drums on pallets
Metal step ladder with rubber feet
Metal reinforcement on a plastic hose
Container on a insulated conveyor line
Insulating Solids
A solid material is classified as insulating or conducting based on its volume and surface resistivity. Insulating materials cannot conduct electrical charge, so any static charges, which are generated on them, will accumulate on them. Most plastic and rubber materials used in a plant are generally electrically insulating.
Propagating Brush Discharge
A special situation arises when insulating layers are applied to grounded conductors. The energy available for an electrostatic discharge is limited by the amount of charge present on the surface. The charge density on a surface is limited by the breakdown potential of the breakdown medium. In most cases the breakdown medium is air. However, if a thin layer of insulating material is placed on top of a grounded conductor, the charge density on the surface of the insulator may reach a much higher value. The reason is that the electric field from the surface of the insulator is directed through the insulator, rather than the air. In this situation, the breakdown medium becomes the insulating layer, not the air. The charge density is no longer controlled by the breakdown strength of the air, but rather by the breakdown strength of the insulating layer, which can be 100 to 1000 times higher than that of air.
Because the charge density is higher, the resulting discharge is also more energetic and can be very dangerous in the plant. These discharges have been known to have energies up to 10 Joules, and can be dangerous to operators. It is possible to avoid propagating brush discharges if the insulating layer is greater than 10 mm thick, or if the breakdown potential of the insulator is less.
2.2 Product Transfer Procedures
2.2.1 Metal to Metal
Hand Transfers
· The source container from which the liquid is poured is to be attached to an earthen grounding source utilizing a grounding cable designed for this purpose. The clamp will be robust and have sufficient spring force to bite through paint and dust to make a good electrical contact.
· A bonding mechanism must be connected between the source container and filling container. The bond can be in the form of:
o A bonding wire with clamps that are robust and have sufficient spring force to bite through paint and dust to make a good electrical contact.
o A design that creates a sound bond between the source and container
· Fill nozzles will be positioned such that the flammable/combustible liquid will free fall no more than one inch before making contact with the container anywhere within the process.
· The velocity of the flammable/combustible liquid entering the container is to be 3 feet/second (6.9 meters/second) or less until inlet pipe is submerged.
· Review employee operations:
o Correct attire with antistatic characteristics.
o Provide antistatic bonding.
Automated Filling
· The stationary machine is to be attached to an earthen grounding source utilizing a grounding cable designed for this purpose.
· A bond must be established between the container and filling source.
· Fill nozzles will be positioned such that the flammable/combustible liquid will free fall no more than one inch before making contact with the container anywhere within the process.
· The velocity of the flammable/combustible liquid entering the container is to be 3 feet/second (6.9 meters/second) or less until inlet pipe is submerged.
· Review employee operations:
o Correct attire with antistatic characteristics.
o Provide antistatic bonding.
2.2.2 Metal to Plastic
Hand Transfers
· The metal source container from which the liquid is poured is to be attached to an earthen grounding source utilizing a grounding cable designed for this purpose. The clamp will be robust and have sufficient spring force to bite through paint and dust to make a good electrical contact.
· The plastic container to which the liquid is poured into must be bonded. The bond can be accomplished by:
· Establish a bond between the metal fill source and the plastic fill container by:
o Place a ground rod into the container, then
o Place a bond wire onto the fill container ground rod, then
o Connect the bond wire to the fill source ground. The bonding clamps must be robust and have sufficient spring force to bite through paint and dust to make a good electrical contact.
· Fill nozzles will be positioned such that the flammable/combustible liquid will free fall no more than one inch before making contact with the container.
o When possible, direct contact of fill nozzle and container should be achieved.
o When possible liquid flow should be diverted to container side.
· The velocity of the flammable/combustible liquid entering the container is to be 3 feet/second (6.9 meters/second) or less until inlet pipe is submerged.
· Review employee operations:
o Correct attire with antistatic characteristics.
o Provide antistatic bonding.
Automated Filling
· The stationary machine is to be attached to an earthen grounding source utilizing a grounding cable designed for this purpose.
· A bond must be established between the container and filling source. A bond can be created by:
o Wetting the exterior surface of the container, maintaining a wet conveyor belt, and achieving a ground by physical contact with equipment.
o Position fill nozzle such that the flammable/combustible liquid will free fall no more than one inch before making contact with the container.
· The velocity of the flammable/combustible liquid entering the container is to be 3 feet/second (6.9 meters/second) or less until inlet pipe is submerged.
· Review employee operations:
o Correct attire with antistatic characteristics.
o Provide antistatic bonding.
2.2.3 Metal to Glass
Hand Transfers
· The metal source container from which the liquid is poured is to be attached to an earthen grounding source utilizing a grounding cable designed for this purpose. The clamp will be robust and have sufficient spring force to bite through paint and dust to make a good electrical contact
· Establish a bond between the metal fill source and the glass fill container by:
o Place a ground rod into the container, then
o Place a bond wire onto the fill container ground rod, then
o Connect the bond wire to the fill source ground. The bonding clamp must be robust and have sufficient spring force to bite through paint and dust to make a good electrical contact.
· Fill nozzles will be positioned such that the flammable/combustible liquid will free fall no more than one inch before making contact with the container.
o When possible, direct contact of fill nozzle and container should be achieved.
o When possible liquid flow should be diverted to container side.
· The velocity of the flammable/combustible liquid entering the container is to be 3 feet/second (6.9 meters/second) or less until inlet pipe is submerged.
· Review employee operations:
o Correct attire with antistatic characteristics.
o Provide antistatic bonding.
Automated Filling
· The stationary machine is to be attached to an earthen grounding source utilizing a grounding cable designed for this purpose.
· A bond must be established between the container and filling source. A bond can be created by:
o Wetting the exterior surface of the container, maintaining a wet conveyor belt, and grounding by physical contact with equipment.
o Position fill nozzle such that the flammable/combustible liquid will free fall no more than one inch before making contact with the container.
· Fill nozzles will be positioned such that the flammable/combustible liquid will free fall no more than one inch before making contact with the container.
o When possible, direct contact of fill nozzle and container should be achieved.
o When possible liquid flow should be diverted to container side.
· The velocity of the flammable/combustible liquid entering the container is to be 3 feet/second (6.9 meters/second) or less until inlet pipe is submerged.
· Review employee operations:
o Correct attire with antistatic characteristics.
o Provide antistatic bonding.