CGA’s P-18 Publication Guides Safe Use of Bulk Inert Gas Supply Systems

September 25, 2020

In September 2020, the Compressed Gas Association (CGA) issued the 5th edition of CGA P-18, Standard for Bulk Inert Gas Systems, an American National Standard. This recently revised safety standard provides minimum requirements for locating/siting, selecting equipment, installing, starting up, maintaining, and removing bulk inert gas supply systems.

CGA P-18 is referenced in both the National Fire Protection Association’s NFPA 55 Compressed Gases and Cryogenic Fluids Code and the International Fire Code (IFC), published by the International Code Council.

Bulk Inert Gas Systems

A bulk inert gas supply system covered by this standard is one that contains greater than 20 000 scf (566 m3) of inert gas, and operates at 15 000 psi (103.4 MPa) or less.

Inert gases – such as argon, nitrogen, and helium – do not react readily with other materials under normal temperatures and pressures.

Bulk inert gas supply systems often include the following, although not all inert gas systems include all the equipment shown:

  • cryogenic storage tanks
  • gas storage vessels (receivers)
  • vaporizers
  • valves including manual and automatic shutoff valves and check valves
  • pressure control equipment including regulators and control valves
  • piping (pipe and tubing)
  • cryogenic pumps
  • snubbers and pulsation dampeners
  • monitoring and control systems, including electrical and instrumentation

The bulk inert supply system terminates at the source valve where the gas or liquid supply first enters the supply line to the customer.

Liquid vs. Gaseous Supply Systems

This safety standard covers two types of bulk inert gas supply systems: liquid and gaseous.

In the case of a liquid system, the inert gas is delivered to the supply system and stored on-site in liquid form. The inert gas is then supplied to the customer in either liquid or gaseous form, depending on the customer’s requirement.

When required, pumps are used to increase the gas pressure before it is supplied to the customer in gaseous form. Also when required, coded vessels are used to store the gas before it is supplied to the customer in gaseous form.

The system is defined as a bulk liquid system instead of a bulk gaseous system because the gas is delivered in liquid form from the supplier to the system’s storage.

In contrast, a gaseous system is one in which the inert gas is delivered to the supply system, stored, and supplied to the customer’s requirement, all in gaseous form.

What’s New in the 5th Edition of CGA P-18

In this new edition of CGA P-18, the following content has been updated:

  • Model code compliance
  • Electrical requirements
  • Pipe joint options
  • Equipment foundations

In addition, the following new topics have been added to the 5th edition:

  • Customer and supplier responsibilities
  • Site security
  • Reciprocating pumps
  • Equipment transportation and setting
  • Temporary systems
  • Initial fill processes
  • Site management systems
  • Shutdown, repair, and start-up
  • System removal

Where to Find Additional Details

The full Table of Contents may be downloaded for free from the CGA P-18 publication details page on the CGA portal.