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Tank Car Specialist
Tank Car SpecialistTraining Support Package
November 2014
Module 11: Grounding and Bonding
Tank Car Specialist
Introduction
Static electricity is everywhere and it is likely present at the scene of any flammable liquids spill. Flammable and/or combustible liquids are major types of chemical spills we respond to as emergency responders. In order to effectively and safely mitigate an emergency involving flammable products, we need to know how to properly perform grounding and bonding.
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Tank Car Specialist
Objectives:11-1 The participant will be able describe what grounding and bonding is.
11-2 The participant will have the ability describe why we do grounding and bonding.
11-3 The participant will be able to describe the procedures for grounding and bonding.
Tank Car Specialist
Definitions
• Electricity
• Volts
• Amperes
• Ohms
• Resistance
• Static Electricity
• Conductor
• Insulator
• Joules
• Grounding
• Bonding
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Capacitance• The ability of a material to
store or hold electrical energy
• Materials vary in their storage capacity
• Relaxation time is period it takes to equalize charges
• SIZE• MATERIAL
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Relaxation Time
• Time necessary for products to dissipate buildup of stored charges
• Times differ for various materials and products
• Consult chemical specific resources
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What Is Static Electricity?
• Caused by energy trapped on surface of non conductive molecules. – Can be created by the movement of
solids, liquids, and gases.
– Can be caused by contaminants such as:• Rust• Dirt• Dust
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Why Do Grounding and Bonding?
• What products:– Assess by Hazard
Class:
If it moves, it can produce a static charge.
Hazard
Class
Yes No
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2
3
4
5
6
7
8
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Conditions for Ignition• There must be 4 conditions met
before static electricity discharge is a source:– There must be generation of static
electricity– There must be accumulation of charge – Discharge spark of sufficient energy– Discharge spark must be in flammable
atmosphere (LEL – UEL)
Tank Car Specialist
Generation of Static Electricity• Problem occurs when there is:
– Accumulation – Discharge – static measured in joules
• .02 millijoules–Hydrogen, acetylene
• .25 millijoules–LPG (propane, C3H8)
• Must be in LEL – UEL– Propane – LEL 2.2 % – UEL 9.5 %
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Generation of Static Electricity
0
0.2
0.4
0.6
0.8
1
1.2
Millijoule Propane Acetylene,Hydrogen
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Controlling Static Electricity• Remove flammable atmosphere from area
– Vapor suppression
– Vapor dispersion
• Reduce production of static energy
– Slow the transfer down
• Release or “relax” the charge
– Ground and Bond – Best method
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Factors That Affect Grounding and Bonding
• Weather• Time of year• Temperature
0
10
20
30
40
50
60
JAN MAR MAY JULY SEPT NOV
Ohms
Cool, dry weather returns
Cold, dry weather
Spring thaw…warm, moist air
Very hot, Very dry
Monsoon
• Humidity• Moisture
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Factors That Affect Grounding and Bonding
• Soil type– Clay– Loam– Sand
• Moisture in soilHigher
moisture = lower
resistance
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Minimum Equipment Needed– Ground resistance meter– Intrinsically safe ohm meter– (4) ½” dia. or > copper grounding rods– (5) 50’ ¼” stainless steel braided cables with
appropriate connecting clips• 3 – Grounding cables (pinpoint and alligator clips)
• 2 – Bonding cables (pinpoint only)PinpointAlligator
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Additional Equipment for Grounding and Bonding
– Sledge hammer/post driver
– 4 foot long 4” x 4” post
– (10) ½” dia. or > copper grounding rods
– (10) ¼” stainless steel braided cables with alligator connecting clips• Length of cable is dependent on length of
rod
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Before Grounding and Bonding
Don’t forget the basics:• Site safety• Vapor suppression (product dependent) - foam
• Detection and monitoring (product dependent)– LEL
• Operations level tactical– Damming, diking, retention, booms, pads, etc.
• Call Miss Utility, if conditions warrant
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Determining the Grounding Field• Will the soil/area absorb the charge?
– Assess the grounding field by:• Appropriate rod placement
–Maximum 50’ or length of cable <5’–Minimal traffic area
• Ground resistance meter–Different companies produce testing
devices–Operating principle is the same.
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Megger Unit
• Generates current and measures earth resistance through an internal OHM meter
• Unit is NOT intrinsically safe
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Acceptable Level for Resistance
• National Electrical Code (N.E.C.) establishes 25 ohms as ideal
• Petro Chemical of Canada sets 10 ohms
• Target is as low as practical
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Safety Considerations
1 foot
2 feet
3 feet
4 feet
5 feet
NATURAL GAS
WATER
ELECTRICAL
SEWER
PHONE, CABLE TV
ALWAYS CHECK WITH ALL UTILITIES PROVIDERS BEFORE DRIVING RODS
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Improving Ground Field• Add water to rods
• Add salt to water, copper sulfate orsodium carbonate
• Common rock salt most likely
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Location of the Fields
• Uphill and upwind
• Remote from immediate work area
• Ideally, set field 75-ft away
• Two fields offer redundancy
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Grounding and Bonding Sequence
1. Damaged/leaking container to ground
2. Receiving container to ground
3. Damaged/leaking container to receiving container
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GROUNDING FIELDS
GROUNDING CABLE
GROUNDING CABLE
BONDING CABLE
WIND
LEAKING VEHICLE
RECEIVING VEHICLE
Example of Grounding and Bonding Before Transfer
Pump
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Bolted-on Handle
PackingGaskets / O - Rings
Bolted Flanges
Bad Connection Points
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TURNBUCKLE AREA
STEP / HANDRAILS
VALVES / FITTINGS
CENTER SILL
Mixed Connection Points
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DIRECT WELD, BUT COVERED
IN PAINT, THERMAL
PROTECTION
DESIGNATED AREA
SCRAPED CLEAN
Good Connection Points
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Why Do Grounding and Bonding?• Applicable OSHA standard:
– 29 CFR 1910.106 – Flammable and Combustible Liquids (1910.106 (f) (3))
• NFPA– 30 Flammable and Combustible Liquids
Code.– 77 Recommended Practice on Static
Electricity
• NEC Article 250
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ConclusionParticipants have been given information to:
• Defined grounding and bonding and describe electricity, volts, amperes, ohms, static electricity, static transfer, static spark, conductor, insulator, breakdown voltage, capacitance, and joule. These basic terms are necessary to understand grounding and bonding
• Defined sources of static electricity, conditions of ignition, and ways to control static electricity hazards
• Listed factors that affect the ground field and describe how to check the ground field using an ohms earth tester
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Tank Car Specialist
ConclusionParticipants have been given the information to:
• Described where to locate the ground field and identify an acceptable level for resistance
• Established the recommended order for cable rod connection and container connection for grounding and bonding
• Given a situation in which grounding would be necessary, participants will be able to check the grounding field for correct resistance, demonstrate the proper sequence and position of the grounding connections, and proper location of the grounding field.
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