CGA Publishes CGA P-28, OSHA Process Safety Management and EPA Risk Management Plan Guidance Document for Bulk Liquid Hydrogen Supply Systems
August 24, 2022
Hydrogen supply systems must comply with model codes such as NFPA 2, Hydrogen Technologies Code, along with CGA standards such as CGA H-5, Standard for Bulk Hydrogen Supply Systems. As a hydrogen supply system grows in size, it must comply with additional requirements. A hydrogen supply system with more than 10,000 pounds of hydrogen storage, including any hydrogen in the supply line to end user, must meet the following regulations:
- The U.S. Occupational Safety and Health Administration (OSHA) Process Safety Management (PSM) standard and
- The U.S. Environmental Protection Agency (EPA) Risk Management Program (RMP) rule.
CGA P-28, OSHA Process Safety Management and EPA Risk Management Plan Guidance Document for Bulk Liquid Hydrogen Supply Systems, has just been released as updated edition 5 in July 2022. CGA P-28 provides details on how to comply with the PSM and RMP programs. The reason for referring to liquid hydrogen and not gas hydrogen is that it is easy to have more than 10,000 pounds of liquid hydrogen on a site. On the other hand, to have more than 10,000 pounds of gas hydrogen in a storage system would require approximately 16 jumbo tube trailers, which is an impractical number at one location.
CGA P-28 will help you work through the PSM and RMP requirements without having to read multiple pages of regulatory language. It is packed with material about the regulations and how to meet them, along with technical details for putting together a comprehensive PSM and RMP. Here is what you can find in the body of CGA P-28 and in the appendices:
Chapter 1, “Introduction,” explains the differences and similarities between PSM and RMP. Although you may use the terms interchangeably, there are some marked differences. Both regulations require that companies develop a program to prevent accidental releases of regulated toxic and flammable substances and to reduce the severity of releases, which could occur. Hydrogen is one regulated flammable substance at 10,000 pounds or more under these regulations.
Both OSHA PSM and EPA RMP regulations are intended to prevent or lessen consequences of a catastrophic release of a regulated substance. While PSM requirements focus on facility and worker safety, RMP requirements are concerned with the possible effects on the community outside the facility in the event of a catastrophic fire or loss of containment at the facility.
Chapter 2, “Purpose,” explains that CGA P-28 is designed to help owners and operators of liquid hydrogen bulk tanks comply with PSM and RMP rules in addition to the requirements of CGA H-5, Standard for Bulk Hydrogen Supply Systems.
Chapter 3, “Scope,” explains how PSM and RMP regulations apply to hydrogen supply systems (typically liquid hydrogen) that store more than 10,000 pounds of hydrogen. The chapter shows how to determine that a hydrogen supply system with an 18,000-gallon tank, a common size tank, usually does not contain more than 10,000 pounds of hydrogen. You may think that the tank can contain more than 10,000 pounds by using the nominal 18,000 gallon capacity and the density of cold hydrogen. However, an 18,000 gallon tank holds a smaller net volume, and the liquid density is less because the hydrogen warms up over time. You can find the calculation procedures for hydrogen weight in Appendix B-1, “Inventory calculation,” and table G-1, “Mass of hydrogen versus liquid volume.”
Chapter 3 also provides examples for counting the weight of hydrogen in transportation equipment in certain types of installations. Chapter 3 provides details on the exemptions for retail facilities and for hydrogen used as a fuel. Chapter 3 also points to appendix C for a list of regulatory sections and a breakdown of responsibility between the hydrogen supplier and the hydrogen customer.
Chapter 4, “Definitions,” provides technical terms used in CGA P-28.
Chapter 5, “Typical hydrogen system,” explains what is usually found in a liquid hydrogen supply system. Flow diagrams are located in appendix D, “Typical system flow diagrams.” Chapter 5 lists all the components of a liquid hydrogen supply system and how they operate.
Chapter 6, “Typical system process hazard analysis,” explains how to conduct a process hazard analysis (PHA) for a liquid hydrogen supply system using the HAZOP method. A sample PHA is found in appendix E, “Typical system HAZOP worksheets.” You should customize your PHA to include design and operational documentation, site-specific hazards, safeguards, and recommendations, and to ensure that the PHA is consistent with the process used at the hydrogen supply system. You may wish to use the HAZOP in Appendix E as the starting point for a PHA of the hydrogen system.
Chapter 7, “Hazard assessment (RMP only),” provides a methodology to determine the impacts of hydrogen releases, both worst-case and alternative release scenarios. Those distances are reported to EPA and to neighbors located within the release boundary.
The worst-case release scenario for a liquid hydrogen tank is modeled as a catastrophic release in which the entire tank content is instantaneously released to the atmosphere, forming an explosive cloud that detonates as a vapor cloud explosion (VCE). The reported distance is the radius from the hydrogen tank to the limits of a 1 psi overpressure, which is the VCE endpoint.
The alternative release scenario is a more realistic case for a leak from the largest pipe on the liquid hydrogen tank with a 20% pipe break area. The reported distance is the radius from the hydrogen tank either to the VCE endpoint or the distance to a flash fire, whichever is greater.
To work out numbers for both scenarios, you can use the following sections of CGA P-28:
- Appendix B, “Technical background,” explains how to calculate the hydrogen tank amount of storage by referring to table G-1, “Mass of hydrogen versus liquid volume.” The rest of appendix B shows the method to calculate both the worst case and the alternative release scenarios. The tables show a tabular format, while the figures show a graphical format, both for the same numbers.
- Table G-2 and figure H-1 show the worst-case scenario based on the hydrogen mass in the tank (taken from table G-1).
- Table G-3 and figure H-2 show the alternative release scenario flow rate based on tank pressure and pipe size.
- Table G-4 and figure H-3 show the alternative scenario distance for rural areas based on flow rate, which is the reportable distance.
- Table G-5 and figure H-4 show the alternative scenario distance for urban areas based on flow rate, which is the reportable distance.
Chapter 8, “Risk management plan submission,” explains how to submit the RMP to the EPA. OSHA does not require that you submit the PSM plan.