- Standard Number:
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.
June 4, 2018
Mr. Anthony J. Cope
Fluor Enterprises, Inc.
One Fluor Daniel Drive
Greenville, South Carolina 29607
Dear Mr. Cope:
Thank you for your September 6, 2017 letter on the Occupational Safety and Health Administration’s (OSHA) standards related to positive displacement (PD) pumps in flammable liquid service. This letter constitutes OSHA's interpretation only of the requirements discussed and may not be applicable to any questions not delineated within your original correspondence. Your letter’s scenarios and questions have been renumbered and paraphrased.
Scenario 1: The first scenario you described has the following attributes:
- Your firm is engaged in the design and construction of a manufacturing (processing) facility which includes OSHA Category 2, 3, and 4 flammable liquids as raw materials and processing intermediates.
- The Food and Drug Administration and countries in Europe, the Middle East, and Africa regulate the facility due to the manufacture of injectable biologics and pharmaceuticals. The facility must meet strict cleaning and contamination-prevention regulations.
- The facility uses PD pumps for transferring flammable liquids from storage to processing units and from process vessels to other process vessels or processing equipment.
- Flammable liquids are handled at temperatures below their flash points and boiling points.
- Quantities of flammable liquid in storage exceed 10,000 pounds as do quantities of flammable liquid outside of storage (i.e., downstream of storage processs(es)).
Question 1A: Does OSHA consider a transfer pump used to transfer flammable liquids from a storage tank to a process unit to be a process pump or a storage pump? Does OSHA view the two types of pumps differently?
Response 1A: Unless covered by OSHA’s Process Safety Management (PSM) of Highly Hazardous Chemicals standard, 29 CFR 1910.119, OSHA generally does not regulate pumps differently based on a pump’s location or function in a process (i.e., regardless of whether a pump is a “process pump” used to transfer flammable liquids from a storage tank to processing or a “storage pump” used to transfer flammable liquids between storage tanks). However, OSHA does have specific standards related to pumping into storage tanks. For example, the provisions that may apply to your process include 29 CFR 1910.106(c)(6)  and 1910.106(f)(3)(ii). Please note that the flammable liquid storage, transfer, and handling activities you describe must comply with 29 CFR 1910.106(h)(4) regardless of whether the facility is an “industrial plant” covered by 29 CFR 1910.106(e) or a “processing plant” covered by 29 CFR 1910.106(h)., , , 
Also, because your facility handles flammable liquids in quantities exceeding 10,000 pounds, OSHA’s PSM standard may apply to your storage and processing of flammable liquids. OSHA strongly recommends that you review 29 CFR 1910.119(a) on the application of the PSM standard to determine whether the standard applies to your process based on the amount and flashpoint of the flammable liquids in your process. 29 CFR 1910.119(a)(1)(ii)(B) provides information on an exemption for the storage of flammable liquids in atmospheric tanks and will help you determine if the exemption applies to your storage tanks based on their operational characteristics (e.g., operates as an atmospheric tank, i.e., ≤ 0.5 psig, inerting pressure > 0.5 psig, mixing, chilling, etc.). OSHA recommends that you also review subsection (b) for the definition of “process” to help determine whether the PSM standard covers your process.
Please note that while OSHA’s PSM standard excepts atmospheric storage of flammable liquids, OSHA’s December 14, 1993 letter of interpretation to Mr. Paul J. Plaisance, Jr. provides context to pumps. 29 CFR 1910.119(a)(1)(B) excepts “[f]lammable liquids with a flashpoint below 100 °F (37.8 °C) stored in atmospheric tanks or transferred which are kept below their normal boiling point without benefit of chilling or refrigeration.” In the 1993 letter of interpretation, OSHA states, “This exception is limited to flammable liquids in atmospheric tanks, containers and pipes used for storage and transfer (to storage) and not connected to a process or process vessel.” Therefore, the exception does not apply to pumps connected to a process or process vessel.
Moreover, if the facility operates an enforceable PSM-covered process, recognized and generally accepted good engineering practices (RAGAGEP) may apply to the design, installation, operation, and maintenance of your pumps that transfer highly hazardous chemicals (HHC). The PSM standard’s RAGAGEP provisions require employers to document the codes and standards they employ for the design of pumps and that the equipment, including pumps, complies with the employer’s appropriately chosen RAGAGEP.
Question 1B: When PD pumps are used to transfer flammable liquids, does 29 CFR 1910.106(h)(4)(iii)(b) apply to transfers when the liquids are pumped: 1) from a process vessel to another process vessel; or 2) from a storage tank to another storage tank?
Response 1B: 29 CFR 1910.106(h)(4)(iii)(b) applies to both described functions (i.e., transfers through PD pumps between processing vessels and between storage tanks). Please note that 29 CFR 1910.106(h)(4)(iii)(b) also applies to flammable liquid transfers from storage tanks to process vessels and vice versa.
Scenario 2: The second scenario you described has the following attributes:
- Due to contamination concerns you state that the PD pump relief cannot be accomplished by discharging back to the supplying process vessel. Contamination is also an issue for your industry if the relief discharge is directed to the PD pump suction.
- You state that all known market available relief valves are of a conventional type (i.e., not balanced bellows) so backpressure is additive to the set pressure of the relief valve. In some applications the worst case upset condition in suction pressure to the pump plus the set pressure of the relief valve can exceed the capacities of some pump or piping components (e.g., seal materials).
- Routing the PD pump outlet relief valve or discharge piping to a collection system or separate tank that has a lower backpressure would be an alternative to relieving back to the supplying process vessel or to the PD pump suction.
In addition, you include the following:
- You provided references to the National Fire Protection Association’s (NFPA), Flammable and Combustible Liquids Code (NFPA 30), Section 18.4.5 and the International Fire Code (IFC), Section 5705.2.1  that provide for relieving PD pumps to alternative equipment or to locations other than the supply tank or vessel, or the pump’s suction.
- You state that, as written, the IFC and NFPA 30 requirements apply to both storage and processing applications.
- You state that OSHA’s 29 CFR 1910.106(h)(4)(iii)(b) standard does not explicitly permit the alternative PD pump relief permitted in the NFPA 30 and IFC requirements.
Question 2A: Has OSHA specifically excluded the use of relief discharge to locations other than the pump suction or suction tank/vessel, or is it permissible to discharge these relief valves to another location (e.g., relief collection system or collection tank)?
Response 2A: OSHA interprets the term “tank” in 29 CFR 1910.106(h)(4)(iii)(b) to include the supply tank or vessel or other properly designed and installed equipment or location such as a relief collection system or collection tank.
Question 2B: Is it permissible to use Safety Instrumented System (SIS) interlocks instead of relief valves for the PD pumps?
Response 2B: Yes, OSHA will accept a SIS designed, installed, operated, and maintained in accordance with the International Society of Automation (ISA) or the International Electrotechnical Commission (IEC) requirements in lieu of a relief device for PD pumps, which are required by 29 CFR 1910.106(h)(4)(iii)(b). OSHA considers the use of a SIS in this instance a de minimis violation. See OSHA’s Field Operations Manual, Ch. 4, Sec. VIII (CPL 02-00-160, August 2, 2016).
In this case, ANSI/ISA - S84.00.01 (2004) Parts 1-3 (IEC 61511 Mod), Functional Safety: Safety Instrumented Systems for the Process Industry Sector, is a consensus standard for SIS. ANSI/ISA - S84.00.01 (2004), Part 1 establishes requirements for the specification, design, installation, operation, and maintenance of a SIS. Therefore, if an employer complies with ANSI/ISA - S84.00.01 to control the hazards of fire/explosion and overpressurization related to operating a PD pump without the OSHA-required relief device, OSHA would consider this to be a de minimis condition/violation.
Conversely, the use of non-SIS interlocks would not be a de minimis condition and would not comply with 29 CFR 1910.106(h)(4)(iii)(b). SIS that complies with ANSI/ISA - S84.00.01 achieve certain minimum standards and performance levels that are not required of non-SIS interlocks. Therefore, OSHA believes that non-SIS interlocks do not clearly provide equal or greater employee protection compared to ANSI/ISA - S84.00.01 compliant SIS.
Thank you for your interest in occupational safety and health. I hope this letter has been helpful in understanding OSHA’s position on these subjects. OSHA’s requirements are set by statute, standards, and regulations. OSHA’s letters of interpretation do not create new or additional requirements; rather they explain the requirements and how they apply to particular circumstances. This letter constitutes OSHA’s interpretation only of the requirements discussed.
If you have any further questions, please do not hesitate to contact the Directorate of Enforcement Programs at (202) 693-2100.
Thomas Galassi, Director
Directorate of Enforcement Programs
 29 CFR 1910.106(c)(6) Valves. Piping systems shall contain a sufficient number of valves to operate the system properly and to protect the plant. Piping systems in connection with pumps shall contain a sufficient number of valves to control properly the flow of liquid in normal operation and in the event of physical damage. Each connection to pipelines, by which equipments such as tankcars or tank vehicles discharge liquids by means of pumps into storage tanks, shall be provided with a check valve for automatic protection against backflow if the piping arrangement is such that backflow from the system is possible.
 29 CFR 1910.106(f)(3)(ii) Category restriction. Equipment such as piping, pumps, and meters used for the transfer of Category 1 or 2 flammable liquids, or Category 3 flammable liquids with a flashpoint below 100 °F (37.8 °C), between storage tanks and the fill stem of the loading rack shall not be used for the transfer of Category 3 flammable liquids with a flashpoint at or above 100 °F (37.8 °C) or Category 4 flammable liquids.
 29 CFR 1910.106(e)(3)(i) Application. This subparagraph shall be applicable in those portions of industrial plants where flammable liquids are handled or used in unit physical operations such as mixing, drying, evaporating, filtering, distillation, and similar operations which do not involve chemical change. Examples are plants compounding cosmetics, pharmaceuticals, solvents, cleaning fluids, insecticides, and similar types of activities.
 29 CFR 1910.106(e)(1)(ii) Exceptions. Where portions of such plants involve chemical reactions such as oxidation, reduction, halogenation, hydrogenation, alkylation, polymerization, and other chemical processes, those portions of the plant shall be in accordance with paragraph (h) of this section.
 29 CFR 1910.106(h)(1) Scope. This paragraph shall apply to those plants or buildings which contain chemical operations such as oxidation, reduction, halogenation, hydrogenation, alkylation, polymerization, and other chemical processes but shall not apply to chemical plants, refineries or distilleries.
 29 CFR 1910.106(e)(3)(vi) Storage and handling. The storage, transfer, and handling of liquid shall comply with paragraph (h)(4) of this section.
 1910.119(a)(1)(ii) A process which involves a Category 1 flammable gas (as defined in 1910.1200(c)) or a flammable liquid with a flashpoint below 100 °F (37.8 °C) on site in one location, in a quantity of 10,000 pounds (4535.9 kg) or more except for . . . (B) Flammable liquids with a flashpoint below 100 °F (37.8 °C) stored in atmospheric tanks or transferred which are kept below their normal boiling point without benefit of chilling or refrigeration.
 29 CFR 1910.119(b) Definitions. Process means any activity involving a highly hazardous chemical including any use, storage, manufacturing, handling, or the on-site movement of such chemicals, or combination of these activities. For purposes of this definition, any group of vessels which are interconnected and separate vessels which are located such that a highly hazardous chemical could be involved in a potential release shall be considered a single process.
 29 CFR 1910.119(d)(3)(i)(F) [Information pertaining to the equipment in the process shall include . . .] Design codes and standards employed;
 29 CFR 1910.119(d)(3)(ii) The employer shall document that equipment complies with recognized and generally accepted good engineering practices.
 29 CFR 1910.106(h)(4)(iii)(b) Positive displacement pumps shall be provided with pressure relief discharging back to the tank or to pump suction.
 NFPA 30 (2015 and 2018), Section 18.4.5 - Positive displacement pumps shall be provided with pressure relief that discharges back to the tank, pump suction, or other suitable location or shall be provided with interlocks to prevent overpressure.
 IFC (2015), Section 5705.2.1 - Positive displacement pumps shall be provided with pressure relief discharging back to the tank, pump suction or other approved location, or shall be provided with interlocks to prevent overpressure.
 A SIS system design has to be effective as well as reliable; the safety instrumented function (SIF) must be designed according to the system’s specific safety integrity level (SIL). The response time requirements for preventing overpressure due to PD pump block-in place severe performance requirements on controls such as fast opening valves. Depending on the pump design and rotating inertia, simply killing power to the pump motor might be insufficient to protect the piping from shock loading.
 29 CFR 1910.106(h)(4)(iii)(b)