Bonding of Bulk Delivery Vehicles

This article, related to the requirements of bonding bulk delivery vehicles, first appeared in the 2014 Nov/Dec edition of Propane Canada Magazine.

Bonding Clamp

I have recently been involved in a project that looked at the regulatory requirements for bonding between a propane delivery vehicle and the propane container being filled.

The project’s scope included a review of the following documents:

  • Transportation of Dangerous Goods Regulations – Part 1 Classification, Clauses 2.13 & 2.14;
  • CSA-B622-03 Selection and Use of Highway Tanks, Multi-Unit Tank Car Tanks, and Portable Tanks for the Transportation of Dangerous Goods;
  • CSA-B620-09 Highway and TC Portable Tanks for the Transportation of Dangerous Goods;
  • CAN/CSA-B149.1-10 Natural Gas & Propane Installation Code Sections 7 & 8;
    Canadian Electrical Code;
  • National Fire Code of Canada Clause 4.1.8 (4.1.8.2);
  • Alberta OHS Code;
  • Alberta OHS Explanation Guide;
  • BC OHS Regulation;
  • NFPA 58 LP Gas Code Handbook Clauses 3.7.1.3 & A3.7.1.3;
  • United States OHSA Regulations; and
  • Static Electricity in the Propane Industry published by the Propane Education & Research Council (PERC).

Acts, Regulations, Standards & Codes

Transportation of Dangerous Goods Act & Regulations
1075 PlacardThe handling and transportation of propane is governed by the Transportation of Dangerous Goods (TDG) Act and Regulations. The regulations govern the construction of bulk transport vehicles with respect to the propane tank and attached components used in the transfer to or from the bulk transport vehicle.  The TDG Regulations also govern the loading and unloading of the bulk transport vehicle. The TDG Regulations classify propane as a Class 2.1 Flammable Gas.

CSA-B622-09
This Standard is adopted by the TDG Regulations and states under the heading of Loading and Unloading, that “a means of containment shall not be used where a fire hazard exists; precautions have been taken to prevent a difference in electrical potential between conductive surfaces and to ensure safe dissipation of static electricity through bonding or grounding, or both, as appropriate”.

Comment: The Standard stipulates that a container cannot be used where a fire hazard exists and requires that precautions be taken to prevent electrostatic discharge.

CAN/CSA-B149.2 Propane Storage & Handling Code
The Code applies, for purposes of this document, to the storage, handling, and transfer of propane and the installation of containers and equipment to be used for propane at customer locations.

The Code states that all tank trucks, tank trailers, and cargo liners must be designed, fabricated, and marked in accordance with the requirements of CSA B620.

The electrical requirements of the Code and the sections dealing with propane cylinder and tank filling are silent on the subject of controlling static electric charges during the propane transfer between the containers and a propane bulk transport vehicle. However, the Code does state that, where specified for the prevention of fire or explosion during normal operation, ventilation is considered adequate where provided in accordance with the provisions of the Code.

The Code requires that propane is transferred from one container to another by a person who is the holder of a certificate recognized by the authority having jurisdiction. The propane container must be filled in a location that is well ventilated.

Comment: For purposes of this document the CSA-B149.2 Code is silent and does not provide any regulatory requirements with respect to the issues of static electric charge during the process of transferring propane from a propane bulk transport to a consumer’s propane cylinder or tank.

The National Fire Code
The Code does speak to the control of static electric charge, however, the Code states that it does not apply to the transportation of flammable liquids or combustible liquids under the TDG Regulations.

Comment: For purposes of this document the National Fire Code requirements do not apply. The Code references the TDG Regulations when it comes to handling and transporting propane.

Canadian Electric Code
The objective of the Code is to establish safety standards for the installation and maintenance of electrical equipment. The scope of the Code covers all electrical work and electrical equipment operating or intended to operate at all voltages in electrical installations for buildings, structures, and premises. This includes factory built relocatable and non-relocatable structures, and self-propelled marine vessels stationary for periods exceeding five months and connected to shore supply of electricity continuously or from time to time.

Comment: For purposes of this document the Canadian Electrical Code requirements do not apply. The Code does not specifically address the issues of controlling static electric charge during the process of transferring propane from a propane bulk transport vehicle to a consumer’s propane cylinder or tank.

Alberta OHS Code
The Alberta OHS Code states that “if the work requires that the contents of metallic or conductive containers be transferred from one container to another, an employer must ensure that static electricity is controlled while the contents are being transferred.”

Comment: The OHS Explanation Guide when referring to Section 163 (2.1) states that “when transferred into or out of containers, flammable liquids can cause a static charge to build up on the container. This charge could create a difference in voltage potential between the containers, creating the possibility of an incendive spark igniting the vapours from the liquid. Effective control of static electricity can include actions such as grounding and bonding.”

The OHS Explanation Guide published on the Alberta Human Services website clarifies that the product under discussion in Part 10 Section 163 (2.1) is flammable liquids, not a flammable gas such as propane.

For purposes of this document the Alberta OHS Code Part 10 Section 163 (2.1) requirements do not apply. The Code requirements for bonding or grounding are for flammable liquids, not flammable gases such as propane.

B.C. OHS Regulation
The Regulation states that metallic or conductive containers used to transfer flammable liquids must be electrically bonded to each other or electrically grounded while their contents are being transferred from one container to the other.

Comment: While the B.C. OHS Regulations discuss the requirement for Flammable Gases in other clauses within the same section, the specific clause for grounding or bonding references Flammable Liquids only, not Flammable Gases.

For purposes of this document the B.C. OHS Regulations requirements do not apply as they only require bonding or grounding for flammable liquids, not flammable gases such as propane.

NFPA 58 Code
NFPA 58 is an American Code that is not mandated for use in Canada. That being said, NFPA Codes and Standards are often used when an equivalent Canadian Code or Standard does not exist or for comparison of requirements where a Canadian Code or Standard does exist.

On the subject of grounding or bonding, NFPA 58 Code stipulates that grounding or bonding is not required. The NFPA 58 Handbook explains “because liquefied petroleum gas is contained in a closed system of piping and equipment, the system need not be electrically conductive or electrically bonded for protection against static electricity.”

American Occupational Health & Safety Administration (OHSA) Regulations
These regulations state that “since liquefied petroleum gas is contained in a closed system of piping and equipment, the system need not be electrically conductive or electrically bonded for protection against static electricity.”

Observations

Static Electricity
Static electricity is generated when liquids move and come into contact with other materials. If the accumulation of static is sufficient, a spark may occur in the presence of a flammable vapour-air mixture, and ignition may result. Where a static spark and flammable mixture may occur simultaneously, suitable preventative measures are required to avoid ignition.

Static Electricity Danger 01Propane industry experience has shown that there have been a number of fires and explosions in which an electrostatic charge was the source of ignition. For this to occur liquid propane must be released at a high velocity, creating a mixture of liquid drops, then vapour, air, and water drops (due to condensation of water vapour in the air from the refrigerating effect of vaporizing liquid) can generate an electrostatic charge. This charge might be of sufficient energy to cause ignition of the mixture.

High-pressure propane liquid releases as described in the previous paragraph can occur when the pressure relieve valve (PRV) on a liquid-full propane container releases the liquid propane to the atmosphere due to over pressurization of the propane container. PRVs are installed within the 20 percent vapour zone on top of the liquid propane. This type of electrostatic charge is not created during the normal propane transfer process from a bulk transport vehicle to a consumer’s propane cylinder or tank.

Fire Hazard Analysis
Fire TriangleFor a fire hazard to exist, three components – fuel, air and an ignition source must be present. The ignition source must occur simultaneously with the fuel vapours and air being mixed at the point of ignition within the fuel’s range of flammability.  For propane, the flammability range is 2.4 to 9.5 percent volume in air, and requires an ignition temperature of 493⁰ to 549⁰ C. Below 2.4 per cent, the mixture is too lean to ignite. Above 9.5 percent, the mixture is too rich to ignite. Removing one or more of the three components removes the fire hazard.

Propane Liquid Transfer
The transfer of propane liquid between the bulk transport vehicle and the consumer’s cylinder or tank is a closed system with the delivery hose fill nozzle being threaded to create a leak tight seal to the fill valve of the propane container prior to the transfer of liquid propane taking place.

A minimal amount of controlled propane vapour/liquid is released to the atmosphere during the filling process through the fixed liquid level gauge. The gauge indicates when the propane container is filled to its maximum permitted volume. Once the container is filled, the gauge is shut off, stopping the release of propane vapour to the atmosphere.

Filling ASME Storage tankThe fill nozzle releases a legislated amount of propane liquid, approximately 2 to 4 cc to the atmosphere when the nozzle is first loosened from the container’s fill valve. This propane, along with any released from the fixed liquid level gauge, is well dispersed by the time the fill nozzle is removed from the fill valve of the container. If a static electric arc should occur at this point, there is no fuel to ignite.

Preventing Fire Hazards
Fire hazards, when filling customer’s propane containers, are controlled in several ways:

  1. Fill valves on the propane cylinders and tanks are made of brass, eliminating sparks from metal-to-metal contact;
  2. The metal propane-receiving cylinders and tanks are installed in contact with the ground;
  3. The actual transfer of liquid propane to the cylinder or tank is a threaded connection within a closed system, eliminating a static electric charge build-up due to liquid flow from arcing during the fill process;
  4. The B149.2 Code governs the distances that cylinders and tanks must be located from a source of ignition;
  5. Propane cylinders and tanks are filled outdoors in well-ventilated areas;
  6. Propane released during the filling process is low pressure and well dissipated by the time the fill nozzle is disconnected from the brass fill valve; and
  7. Operators are required to wear clothing which will not generate static electric charge while transferring propane.

The seven items listed above prevent the three essential components occurring simultaneously, which are needed to have an area or process classified as a fire hazard.
Therefore, the volume filling of a consumer’s cylinder or tank does not create a fire hazard. In addition, the existing operating procedures and equipment utilized satisfy the requirement that precautions are to be taken to prevent electrostatic discharge during the transfer process.

Conclusions

Current industry practices provide suitable preventative measures to avoid ignition of any propane released to the atmosphere during the filling of consumer propane containers. Therefore the need for bonding between a propane bulk transport vehicle and propane containers during the transfer process is not required.

There are no legislative requirements that require a person to bond between a propane bulk transport and a customer’s cylinders or tanks during the transfer process. The only legislated requirement to ground or bond is provided in the TDG Regulations where a fire hazard exists or precautions to prevent electro-static discharge have not been taken.

As stated above, current industry practices provide suitable preventative measures to avoid ignition of any propane released to the atmosphere during the filling of consumer propane containers. Therefore, the TDG Regulations do not apply and the need for bonding between a propane bulk transport vehicle and propane containers during the transfer process is not required.

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Bonding of the Gas System

Since 2010, the B149.1 Natural Gas and Propane Installation code requires propane and natural gas systems to be bonded. This article, which first appeared in the Mar/Apr 2013 edition of Propane Canada magazine, discusses how bonding of the gas system is achieved and includes key definitions related to bonding.

Since writing the article entitled “The Need for Bonding of Corrugated Stainless Steel Tubing (CSST) Systems”, which first appeared in the Jan/Feb 2013 edition of Propane Canada magazine, I’ve had several requests for additional information explaining how one actually goes about bonding propane and natural gas systems.

When the 2010 CSA B149.1 Natural Gas and Propane Installation Code was published and adopted by provincial regulation, the bonding of propane and natural gas piping systems became a requirement of the Code.

Key Definitions

The following terms and definitions are commonly used to describe technical requirements:

Bonded (Bonding)
Connected to establish electrical continuity and conductivity.

Bonding Jumper
A reliable conductor to ensure the required electrical conductivity between metal parts required to be electrically connected.

Grounded (Grounding)
Connected (connecting) to ground or to a conductive body that extends the ground connection.

Grounding Electrode Conductor
A conductor used to connect the system grounded conductor or the appliance to a grounding electrode or to a point on the grounding electrode system.

Grounding Electrode System
Electrodes can be a metal rod/pipe/plate driven into the ground; the metal frame of a building; buried metal or copper water line into the building; a ground ring of copper wire; or a concrete encased foundation electrode.

Clause 4.7.3 of the Code requires that all interior metal gas piping that may become energized must be made electrically continuous and bonded in accordance with the requirements of the local electrical code or, in the absence of such, the Canadian Electrical Code, Part 1.

The 2012 Canadian Electrical Code Clause 10-400 (4) has the same wording as clause 4.7.3 in the CSA – B 149.1. Clause 6.14.6 of the Code does not permit propane and natural gas piping or tubing to be used for an electrical ground.  The clause states that an electric circuit cannot utilize piping or tubing in lieu of wiring, except for a low-voltage control circuit, ignition circuit, or electronic flame detection device circuit incorporated as part of an appliance.

The Canadian Electrical Code requires the house’s electrical system have a connection to earth to provide for its safe operation.  When other systems are connected to the electrical system and its grounding, those systems are “bonded” to the electrical ground.

Bonding is provided primarily to prevent a possible electric shock hazard for persons coming into contact with the gas piping and other metal objects that are connected to the grounding system, but which may be energized at a different level of electrical potential.

Gas piping can become energized by an electrical fault in the branch circuit of a gas appliance connected to the piping system.  Nearby lightning strikes can also result in an unbalanced voltage build-up and a resulting high electrical potential difference.

An electrical bond is an intentionally installed electrically conductive and continuous path from the gas piping to the grounding electrode system.  The systems that are bonded to the electrical system will have roughly the same electrical potential, so that if energized, they will all be energized at the same rate and at the same speed.  Thus, when the electrical system and the bonded systems are energized by an electrical fault or lightning, the possibility that the electrical energy will arc or jump from one system to the other is reduced because all those systems are at an equal electrical state.

A bonding wire from one metal component to another allows stray electricity to equalize through the wire so that one metal component will not have a greater voltage in it than another metal component, preventing arcing between the two metal components. However, if metal systems in the house are not bonded to the electrical ground, they will have a different electrical potential from other conductive systems in the house.

In the event those systems are energized by a high voltage event like lightning, then it is possible that the electricity being conducted and travelling on one metal system may come to a point where it is close to an adjacent metal system that offers a lower resistance or impedance path to ground.

It is possible that if the energy has enough voltage, it may jump over the air gap between the two adjacent metal systems, and use the second path to go to ground.  When the energy jumps that air gap, it generates an electrical arc that has a high voltage.

Photo #1 provides an example of grounding the house’s electrical system. The copper underground water service that runs from the water main in the street to the house acts as the in-situ grounding electrode.

Bonding Gas Systems 1

Photo #1 – 1) Underground water service line at entrance to house. 2) Bare grounding wire connecting electrical panel & water line. 3) Grounding clamp attached to water service line. 4) Water service shut-off valve. 5) Water meter.

Bonding is achieved by installing a wire of sufficient size from the bonded component to the electrical system ground.  Equipotential bonding is achieved when all metallic systems in a structure are bonded to the electrical system ground.

Minimum bond wire should be a number 6 AWG copper wire.  The bonding clamp must be attached such that metal to metal contact is achieved with the steel pipe component. Remove any paint or applied coating on the pipe surface beneath the clamp.

As discussed in my previous article on bonding of Corrugated Stainless Steel Tubing (CSST), the bonding clamps must be attached to the brass fitting, to a steel manifold or to a rigid pipe component attached to the CSST.  The corrugated stainless steel portion of the tubing system must not be used as the bonding attachment.

Bonding Gas Systems 2

Photo #2 – 1) Bare bonding wire. 2) Steel propane/natural gas piping. 3) Copper wire line to water heater. 4) Bonding clamps.

Photo #2 above, shows the bonding wire attached to the steel gas piping and the copper cold water line feeding the water heater.  The bonding connection is by mechanical clamps. UL-467-approved bonding clamps can be used.

Under no circumstances is any underground natural gas utility service line or the underground supply line from a propane storage tank to be used as a grounding electrode because grounding electrodes are intended to carry large currents.

This can expose the piping to the possibility of sparking which can create a hazardous condition if the service piping is undergoing any type of maintenance.

 

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Bonding of CSST Systems

Corrugated Stainless Steel Tubing (CSST) has become a popular material for gas installations.  This article, which first appeared in the January/February 2013 edition of Propane Canada magazine, discusses the importance of bonding (CSST) systems to avoid electrical arcing which could perforate the tubing.

I have recently been retained to investigate two incidents where it is believed that unbounded Corrugated Stainless Steel Tubing (CSST) has been subjected to electrical arcing, resulting in the wall of the CSST being perforated. The leaking propane was ignited by the electric arc that perforated the tubing wall. The resulting fires caused extensive damage to the structures in which they were installed. I would, therefore, like to take the opportunity in this article to raise awareness of the need for bonding of CSST gas systems.

The material requirements for tubing first listed CSST in the 2005 edition of the CSA/BI49.1 Natural Gas and Propane Installation Code. The previous codes and editions contained a clause that permitted the use of materials not specified in the Code if they conformed to a nationally recognized standard or to a test report of a nationally recognized certification organization. Information on file indicates that CSST has been installed in Canada since at least 1998. This was prior to the bonding requirements being put into the manufacturer’s installation instructions and training programs.

Each manufacturer of CSST requires that a certified propane technician take an installation training program, which is required as part of ANSI LC 1-2013 / CSA 6.26-2013, Fuel Gas Piping Systems Using Corrugated Stainless Steel Tubing. The training courses are to ensure that only qualified propane technicians install CSST. The training requirement will also prevent CSST from being available at home improvement stores.

What is CSST?

In Canada, CSST is certified by ANSI LC 1-2013 / CSA 6.26-2013, Fuel Gas Piping Systems Using Corrugated Stainless Steel Tubing. CSST consists of stainless steel corrugated tubing that may or may not be sheathed by a polymer conformal coating.  Each manufacturer appears to have developed their own system for achieving couplings/connections.

CSSTThe flexible tubing comes in 100-foot rolls that can be cut to length, and be bent and conformed by hand, allowing for quick and easy installation with a limited number of connections.  Simple economics have contributed to CSST popularity since its introduction in 1997; the product is less expensive and requires far less time and skill to install.  CSST tubing cuts easily with a standard tube cutter and requires no threading or welding, and no special tools to seal the fittings. The CSST gas line also weighs far less than rigid gas pipe and is less bulky to store, transport, and handle. During the installation process, the flexible CSST product can make turns without the need for installing threaded and sealed pipe elbows.

The CSST gas line is extremely thin, with walls typically around 0.008″ in thickness. Black iron gas pipe is typically 0.12″ thick, making the walls of black iron pipe 15 times thicker than the walls of CSST tubing. Conversely, the amount of electrical energy needed to perforate the wall of traditional black iron pipe is about 15 times more than the energy needed to perforate the much thinner walls of CSST tubing.

Electrical Arcing on CSST

The thin wall thickness, required to permit easy routing of the tubing, has resulted in a material that is easily punched through by electrical arcing. Once the tubing has been perforated, it is possible for the escaping gas to be ignited by the arcing process or by adjacent open flames.

One manufacturer’s installation instructions state that although the tubing provides significant advantages over more rigid gas delivery systems, its wall dimensions may make it more likely than steel pipe to be punctured by a nail or other sharp objects, or damaged by other extraordinary forces such as a lightning strike.

CSST-damagedIt is well known that lightning is a highly destructive force. Therefore, the user must ensure that the system is properly bonded and grounded. In order to maximize protection of the entire structure from lightning damage, the user should consider installation of a lightning protection system.

The installation instructions go on to require that the gas tubing system be bonded to the electrical earth grounding system of the structure through the use of a bonding clamp and wire.

The section further states that “proper grounding and bonding may reduce the risk of damage and fire from lightning strikes. Even a nearby lightning strike that does not strike a structure directly can cause systems in the structure to become energized. If the systems are not properly bonded, the difference in potential between the systems may cause the charge to arc to another system. Arcing can cause damage to C55T. Correct bonding and grounding should reduce the risk of arcing and related damage”.

One other possible cause of electrical arcing perforating the CSST is a failure of the structure’s electrical system, resulting in the wiring’s protective coating being damaged, exposing the bare wires to the CSST.

In this type of scenario, the resulting ignited propane leak would not be the primary or secondary cause of the structural damage but a third result of the fire origin. The fire origin could have been started by the electrical wiring or a source that resulted in the fire origin compromising the electrical wiring system within the building.

When installing CSST, care should be taken to maintain as much separation as possible from other electrically conductive systems in the structure. With respect to determining which electrical source actually caused the perforations in the CSST, the author of a recent article wrote: “We must state, however, that in our opinion, the perforated gas line can normally stand on its own in terms of evidentiary value; we know of no other phenomenon that would create a clean arced hole other than lightning. If a copper wire arced to the stainless steel tubing, there should be copper remnants found. Likewise, the melting point of stainless steel will not be reached in most fires.”

Electrical Bonding and Grounding

The house’s electrical system must have a connection to earth to provide for its safe operation.  When other systems are connected to the electrical system and its grounding, those systems are “bonded” to the electrical ground.

Bonding is achieved by installing a wire of sufficient size from the bonded component to the electrical system ground.  Equipotential bonding is achieved when all metallic systems in a structure are bonded to the electrical system ground.  The systems that are bonded to the electrical system will have roughly the same electrical potential, so, if energized, they will all be energized at the same rate and at the same speed.

Thus, when the electrical system and the bonded systems are energized by lightning, the possibility that the lightning energy will arc or jump from one system to the other is reduced because all of those systems are at an equal electrical state.

A bonding wire from one metal component to another allows stray electricity to equalize through the wire so that one metal component will not have a greater voltage in it than another metal component, preventing arcing between the two metal components.

However, if metal systems in the house are not bonded to the electrical ground, they will have a different electrical potential from other conductive systems in the house.  In the event those systems are energized by a high voltage event, like lightning, then it is possible that the electricity being conducted and traveling on one metal system may come to a point where it is close to an adjacent metal system that offers a lower resistance or impedance path to ground.

It is possible that if the energy has enough voltage, it may jump over the air gap between the two adjacent metal systems, and use the second path to go to ground.  When the energy jumps that air gap, it generates an electrical arc that has a high voltage.

CSST bonding requirements provide an effective electrically continuous path in an effort to conduct stray voltage/current safely to the ground.  The bonding point must be in close proximity to the electrical panel as practical.  The wire gauge for this bond must be sized, at a minimum, for the full amperage available through the electric service.

For attachment to the CSST, bonding clamps must be attached to the brass fitting, to a steel manifold or to a rigid pipe component attached to the CSST.  The corrugated stainless steel portion of the tubing system must not be used as the bonding attachment. CSST or other gas piping system components must not be used as a grounding electrode or as a grounding path for appliances or electrical systems.

One manufacturer, Omegaflex, has developed a CSST product called “Counterstrike”, which is specifically designed to dissipate the energy from electrical arcing by enclosing the flexible tubing with a proprietary jacket (black in colour), made from a material which is both thicker and conductive.

The product is designed to spread the electrical energy over the entire length of the run, allowing it to dissipate rather than concentrate at anyone point on the CSST.  In theory, at least, this should reduce the potential for breaching of the gas line during instances where the CSST is energized by an electrical source.  Counterstrike’s installation instructions still require bonding to a ground.

In conclusion, it is imperative to read and follow the manufacturer’s installation instructions to make sure you are installing the CSST properly and that you have followed the manufacturer’s installation instructions to reduce the likelihood of electric arcing damaging the CSST.

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