Which valve does the USAID procedure single out for low purity?

The equalisation valve: its low-purity tips include checking that it is closed during oxygen production and regeneration of the other bed.

Can a leaking valve be found with a pressure test?

The USAID RISE procedure leaves the plant isolated and pressurised, for example at 5 bar, for one hour, and traces any pressure drop with soapy water on joints, fittings, valves and regulators.

What are the signs of a failing PSA switching valve?

Q: What are the signs that a switching or pneumatic valve in a PSA oxygen generator is failing, and how is it confirmed?

PATH's 2023 review of 50 PSA plants lists leaky valves, resulting in low purity output, fire and/or noise, among the common issues of plants in disrepair; the USAID RISE procedure for Indian hospitals (2022) lists valve checks for low purity and failed purging, and Global Fund checklists record sieve bed pressures against the manual.

What are the signs that a switching or pneumatic valve in a PSA oxygen generator is failing, and how is it confirmed?

In a PSA generator, PATH's November 2023 report explains, control valves direct the clean compressed air into one of two adsorption vessels and then release the pressure, with the nitrogen-rich air, before the cycle repeats with the other vessel. Its review of 50 plants at 45 facilities found leaky valves, resulting in low purity output, fire and/or noise, among the common issues of plants in disrepair.

Valve checks in the published procedures

Low purity: the USAID RISE operating procedure for PSA plants (March 2022) lists, for low purity, checking that all valves are fully open, that the equalisation valve is closed during oxygen production and regeneration of the other bed, and that the valves are cleaned as the manual says.
Sound and exhaust: at start-up, the same procedure asks the operator to watch for abnormal sounds inside the towers, the exhaust blowdown, and dust or powder at the silencers.
Valve operation: at start-up, it asks for all valves to operate as per the PLC program in the control panel.
Plant will not purge: its troubleshooting table checks that the compressor is working, checks the solenoid valve, confirms that all manual valves, including the exhaust valve, are open, and checks that the silencers of the vent pipe are clean.
Overdrawing: the procedure warns that drawing more oxygen than the plant's capacity can cause malfunction or permanent failure of valves, sensors and gauges.

Pressure records and tests

Bed pressures: the Global Fund commissioning checklist (28 August 2024) records the minimum, maximum and equalisation pressures of both sieve beds. Its post-commissioning form (12 September 2025) asks the assessor to observe the pressure swing in the sieve beds as purity builds, note uneven maximum, minimum or equalisation pressures, cross-check them against the ranges in the manual, and video the display or gauges over a full cycle.
Trend display: WHO's technical specifications for health facility oxygen systems (December 2024) ask the control panel to show sieve bed pressure among the oxygen production parameters, trending continuously.
Leak test: the USAID procedure isolates the plant pressurised, for example at 5 bar, for one hour, then looks for the pressure drop with soapy water on joints and fittings, including the valves and regulators.
Routine checks: it checks solenoid valves for corrosion every month, and the condition of all valve seals and the drying and regeneration cycles every year.

If the tips do not resolve the problem, the USAID procedure says the manufacturer or supplier should be contacted. PATH and CHAI (July 2021) note that corrective maintenance may require rebuilding a valve assembly after a failure. For the wider low-purity checklist, see how to troubleshoot low purity.

In ULTRAOX plants

The ULTRAOX Technical Data Sheet (2022) lists a set of electro-pneumatic valves and regulators in each ULTRACON concentrator, says the cycles are widely spaced, which reduces valve operations and moving parts over the years, and gives a touch screen with a record of all contingencies and alarm information.