grounding & bonding

Grounding & Bonding

Hazardous Materials Certification Study Guide

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Definition of Terms (continued)

• Static Electricity - Electricity present on a surface of a non conductive body where electricity is trapped or prevented from escaping.


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• Static Transfer - Equalization of electrical charges. Nature wants to balance electrical charges. When there are excessive negative or positive charges they will seek ways to become neutral, which is what gives us the “shock”. This is the charges equalizing.


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• Grounding - The connection of the conductive objects to the earth.

• Bonding - The connection of two or more conductive objects together by the means of a conductor (wire cable).


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Source of Static Electricity• Static electricity can be created in all

states of matter. Conveyor belts, moving vehicles & pulverized materials through chutes are examples of solids that can generate static electricity. Liquids moving through constricted areas like pipe or transfer hoses do the same.


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Source of Static Electricity (continued)

• Gaseous generators are steam or gases flowing from an opening in a pipe. Other sources are contamination such as rust, dirt or dust in the transfer system.


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Conditions For Ignition

• Four conditions must be fulfilled in order for static electricity to be a source of ignition.– Generation of static electricity– Accumulation of static charge with no means to

discharge– Spark discharge of adequate energy– Spark discharge in an ignitable atmosphere


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Equipment Needed to Control Static Electricity

• 3 - 3/4” copper grounding rods - 4-6’

• 3 - 1/8” stainless steel grounding cables with a single point clamp at one end and an alligator clamp at the other end - 50’ length

• 2 - 1/8” stainless steel grounding cables with a single point clamp at both ends - 50’ length

• 1 ohm meter


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Ways to Control Static Electricity Hazards

• Remove the flammable mixture– Use foam or fog to reduce the ignitable

atmosphere.

• Slow down the transfer– This option probably will not be practical


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Ways to Control Static Electricity Hazards (continued)• Release or relax the charge after it has

been generated. (Ground & Bond)– By grounding & bonding, we are giving the

static charge a path in which to travel to earth without creating a spark. Ideally, the grounding rods should be 10’ in length & 5/8” in diameter. The clamps used should be screw clamps or pressure point clamps.


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Recommended Practices For Cable/Rod Connection

• Be certain to attach the cables to a part of the vehicle that is connected directly to the vessel holding the contents that you are going to transfer or otherwise work with.


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• NEVER connect the grounding cables to the following:– Bolted-on-Ladders– Bumpers– Container Jackets– Strapping holding the container to the

vehicle


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• ALWAYS connect the grounding cables to something welded to or part of the tanker itself.– Since the flow of materials through a

constricted carrier such as a pipe or transfer hose can cause static electricity to be generated, ALWAYS ground.


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General Procedures for Grounding & Bonding

• Test the area with a CGI to establish the limits of the hot zone and find a flammable atmosphere free area to connect the “ground”.


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Bonding & Grounding Sequence

NURS

ECALF

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3

4

A

B

BOND

GROUND RODS

Make connections in sequence shown to avoid sparks in potentially flammable areas

Connection A-Bcan be made anytimeprior to off-loading


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Grounding the Leaking Vehicle (Nurse)

• Place the grounding rod as far away from the vehicle as possible.

• Attach the single point clamp to the tanker.• Attach the alligator clamp to the grounding

rod.– This should be as low as possible so that it

is in the foam blanket.– The tanker is now grounded.


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Grounding the Receiving Vehicle (Calf)

• Place the grounding rod

• Attach the single point clamp

• Attach the alligator clamp to the grounding rod

• Test resistance


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Bonding the Nurse & Calf• A single point clamp is placed on the

leaking vehicle (nurse).• A single point clamp is placed on the

receiving vehicle (calf).• Test resistance.

– A delay of a minimum of 5 minutes should occur after bonding & grounding has been accomplished before any offloading should start.


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Offloading From a Damaged Tank Truck to Another Truck

• Test the area with CGI to establish the limits of the hot zone and find a flammable atmosphere free area in which to park the vehicle that will be receiving the product.

• Connect your wire (at least 8 AWG) to the leaking vessel, tank truck or other potential static source first. DO NOT hook up the receiving vehicle before you connect to the potential static source.


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Offloading From a Damaged Tank Truck to Another Truck

• Connect your wire to the receiving vehicle (in the “safe” zone). If you connect to your receiving vehicle first, the difference in electrical potential might cause a spark when you hook up to the leaking truck causing ignition of flammable vapors.

• Remember that stingers & pumps used in offloading MUST also be bonded & grounded.


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Bonding & Grounding To Off-Load a Flammable Material

Wind

Hot Zone

Cold Zone

CALF

NURSE

Grounding Cable

Bonding Cable


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306 Cargo Tank Involved Fire

• Aluminum tank

• Gasoline

• Decision to allow fire to burn

• Estimate that the rate of fuel burn to be 1 foot of fuel per hour

grounding & bonding

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