Bonding and grounding of plastic containers during transfer of Class I flammable liquids. | Occupational Safety and Health Administration

Standard Number:

1910.106(e)(6)(ii)

1910.106(d)(2)(iii)

NOTICE: This is an OSHA Archive Document, and may no longer represent OSHA Policy. It is presented here as historical content, for research and review purposes only.

OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at https://www.osha.gov.

March 29, 1999

Mr. Lawrence A. DeWitt
Manager of Safety Programs
Safety Management Services
Corning Incorporated
HP-ME-03-56
Corning, New York 14831

Dear Mr. DeWitt,

This is in response to your letter dated February 8, 1999. You request OSHA to provide an interpretation of our standard relating to the transfer of Class I flammable liquids. In particular, you want to know OSHA's position on the bonding and grounding of plastic containers during the dispensing or transferring of Class I flammable liquids.

The requirements for bonding and grounding of containers during the transfer of Class I flammable liquids are contained in 29 CFR 1910, paragraph (e)(6)(ii). This paragraph does not specifically address plastic containers. However, in response to previous questions, similar to yours, on this issue, OSHA issued "OSHA Instruction STD 1-5.14-A" on October 24, 1980. I am enclosing a copy of this instruction for your information.

This instruction permits the storage and use of flammable and combustible liquids in plastic containers that meet the U.S. Department of Transportation specification. It further addresses the methods of bonding and grounding such containers during the transfer of Class I flammable liquids.

Our response to your question is as follows:

Question No. 1 If the source container is metal and the receiving container is nonconductive, do the bonding and grounding requirements apply?

Reply: The bonding and grounding of two non-conductive containers would seem unnecessary since non-conductive materials are insulators and therefore they cannot conduct a current through them. However, static electrical charge can be generated when two dissimilar materials pass quickly by one another (i.e., liquids flowing through pipes, even air). OSHA recognizes that there are many factors that affect the size and strength of the static charge or potential that may develop (i.e. speed of transfer, humidity, container size, and others). OSHA is concerned that any static charge that develops between two containers be equalized, if not eliminated, so that no potential for a static discharge between the containers exists. Therefore, OSHA will permit the transfer of Class I liquids between plastic or other non-conductive containers under the following conditions:

A non-conductive container must be equipped with an approved metallic suction pump and draw tube for taking liquid from the top of a plastic container. The pump must be electrically grounded, or
The non-conductive container must be equipped with a metallic, self-closing faucet that can be grounded electrically.

We suggest you refer to the National Fire Protection Association's Standard for Recommended Practice on Static Electricity (NFPA 77-1993) for further information on the control of static electrical discharges. Please refer to sections 4-8 and 7-8 of that standard.

Question No. 2 If both containers are nonconductive, what requirements apply?

Reply: OSHA believes this situation can be covered by our response to your first question.

Question No. 3 Does the container size and/or the amount of Class I liquid being transferred in a process where nonconductive containers are used dictate whether grounding and bonding is needed?

Reply: Yes, to some extent. The transfer of Class I flammable liquids between small containers may not require the use of special bonding and grounding techniques. As stated in NFPA 77-1993, "Containers of glass or other non-conductive materials of five gallons or less capacity are usually filled without special precautions." However, for larger containers, NFPA 77-1993 suggests that special techniques should be used for the handling of flammable liquids in plastic containers having capacities of 5 to 60 gallons. OSHA would consider compliance with the suggestions of NFPA 77-1993 regarding the bonding and grounding of plastic containers holding Class I flammable liquids as compliance meeting the intent of OSHA's standards in 29 CFR 1910.106, paragraphs (e)(6)(ii) and (d)(2)(iii).

If you have any questions, please contact [the Office of General Industry Compliance Assistance at (202) 693-1850].

Sincerely,

Richard Fairfax, Director
Directorate of Compliance Program