OSHA bases their position on which section of 1910.106 would be applicable; if the plant is an industrial (covered under 1910.106 (e)) or a processing plant (covered under 1910.106(h)). If the operation is an incidental activity covered by §1910.106(e)(2), paragraph §1910.106(e)(2)(iv)(d) allows transfer of flammable or combustible liquids into vessels, containers, and portable tanks within a building only:
- through a CLOSED PIPING; or
- from SAFETY CANS; or
- by means of a device DRAWING THROUGH THE TOP; or
- from a container or portable tanks by gravity THROUGH AN APPROVED SELF-CLOSING VALVE
Therefore, pouring (i.e., one means of gravity transfer) flammable and combustible liquids into an open manway of a process tank/vessel would be allowed (for operations covered under 1910.106(e)(2)) per the language of the standard, "from SAFETY CANS" or "from a container or portable tanks by gravity through an APPROVED SELF-CLOSING VALVE."
However, during such a pouring operation, the employer MUST take measures for protection against static sparks (see §1910.106(e)(6)(i)), through bonding and grounding methodologies, e.g., by electrically interconnecting the transfer nozzle of the pouring container and the tank and by ascertaining that the receiving tank is grounded to dissipate any potential static current that may have generated during the pouring operation.
However, if the operation in question is part of a UNIT PHYSICAL OPERATION covered under §1910.106(e)(3), then §1910.106(e)(3)(vi) (which refers to §1910.106(h)(4)), indirectly PROHIBITS the use of gravity flow, except as required in process equipment. See §1910.106(h)(4)(iii)(a). If an employer claims this exception, versus providing pumps or water displacement for transfer through piping, as required under this paragraph, they must be prepared to demonstrate why the process equipment necessitates gravity flow through piping in lieu of the pumping.
In either case, whether the transfer is by means of gravity flow or by means of a pump, open-pouring of large quantities flammable or combustible liquids (which will not involve piping) into tanks will be in violation of §1910.106(h)(4)(iii)(a). Section 1910.106(h)(4)(iii)(a)'s requirement for pumps or water displacement comes from NFPA 30-1969, which was adopted in 1971 by OSHA into 1910.106. In commentary on this requirement, the NFPA stated that it was intended to prohibit transfer by pouring in such circumstances.
Additionally, if the operation in question is part of a processing plant covered by §1910.106(h), as stated above, §1910.106(h)(4)(iii)(a) PROHIBITS the gravity transfer of large quantities of flammable and combustible liquids into an open manway of a process tank. Since open pouring involves transfer without piping, such pouring will be in VIOLATION of §1910.106(h)(4)(iii)(a).