[ oxygen ]
Read the full White Paper This article is a condensed version of Parker’ s White Paper on oxygen compatibility and design considerations for electrolysers. Scan the QR code to access the complete document.
Fig. 5. Comparison of costs between Inconel and stainless steel 316L across a range of feedstocks ¹³
There are few, if any, materials that are fundamentally 100 % safe for oxygen service across all operating parameters whilst also being suitable as construction materials for oxygen systems.
Many materials that exhibit improved resistance to ignition in oxygen service – such as Inconel 625 – and possess good mechanical properties are also significantly more expensive. For example, Inconel 625 can be six times the price of 316 stainless steel.¹² Materials with poorer oxygen compatibility can, and often are, used in oxygenenriched environments, provided additional design validations are carried out.
The available material data is invariably based on pure substances. However, during production, installation, assembly, etc., contaminants may be introduced into materials or components. It is not uncommon for hydrocarbons in the form of greases or oils to be present in or on pipes and components. To reduce the likelihood of a fire in the oxygen system, all equipment must be properly cleaned and verified before use.
System design and installation
Oxygen system design should first evaluate what are the lowest operating parameters( concentration, pressure, and temperature) that will provide a viable solution for the intended application. Within an electrolyser, system parameters are largely – or entirely – determined by the stack technology employed, meaning the operating parameters of the oxygen system cannot be adjusted.
Various associations worldwide provide standards and guidelines for design rules, best practices, and installation procedures:
• European Industrial Gases Association – EIGA Doc 13: Oxygen Pipeline and Piping Systems
• European Industrial Gases Association – EIGA Doc 33: Cleaning of Equipment for Oxygen Service
Table 5. Example of extinguishing diameters for various arbitrary alloys and test pressures 10
Arbitrary Alloy Designation |
Test Sample Max Diameter( mm) |
|
|
|
|
Test Pressure( MPa) |
Number of Tests |
Taper Angle(°) |
|
Extinguishment Diameter( avg ± std dev)( mm) |
A |
20 |
6.30 |
5 |
62.6 |
7.3 ± 2.4 |
B |
9.5 |
13.79 |
10 |
80.5 |
7.0 ± 0.5 |
B |
12.7 |
13.79 |
10 |
76 |
6.7 ± 0.5 |
C |
12.7 |
3.45 – 6.89 |
5 |
76 |
7.5 ± 2.9 |
C |
15.9 |
6.89 – 8.62 |
5 |
73 |
10.1 ± 2.1 |
C |
15.9 |
8.62 – 10.34 |
4 |
73 |
12.6 ± 3.0 |
C |
22.2 |
13.79 – 17.24 |
5 |
70 |
17.7 ± 1.9 |
Hydrogen Tech World | Issue 21 | April 2025 47