What to check when something looks wrong with the stack. The cause is usually in the external loop and the operating conditions rather than in the stack.
Repair and replacement of external BoP components is yours. We interpret the stack's behaviour and judge whether stack service is needed.
- FirstJudge the hazard, then make it safe
- One at a timeOne change, then re-check
- RestartingFrom low current
How to read this chapter
First timeStart with the order-of-checks section. Jumping straight to the symptoms skips making the area safe.
Done this beforeFind the line for what you are seeing in the find-by-symptom table.
On this pageThe order of checks
The order of checks
- Stop and assess the hazard level.
- Any sign of a hydrogen leak, fire, arcing, a burning smell, severe overheating or uncontrolled electrolyte leakage means follow the emergency section of the safety chapter.
- Make it safe before touching anything.
- Ramp the current to 0 A, turn off the DC output, then isolate the DC supply from the stack.
- Confirm the vent and relief lines are unobstructed, and manage residual pressure and electrolyte by your site procedures.
- Record the as-found condition.
- Record at minimum the stack current and voltage and the electrolyte flow and temperature, plus the cell voltages and hydrogen in oxygen if you measured them.
- Check the most likely external causes.
- Flow and heat: valves open, tubing not blocked, no trapped air, tank level adequate, cooling available.
- Wet outlet and backpressure: no restriction or kink in the return line.
- Electrical: cables and terminals tight, no discolouration or marks of heat.
- Apply one corrective action at a time.
- Change one thing and check whether it helps before changing the next. When you restart, begin at low current.
- Know when to stop.
- If the issue persists, repeats or suggests hardware damage, stop operating and contact us.
Find by symptom
Find the line for what you see and take the first action. Lines run from most to least severe.
| What you see | Suspect first | First action |
|---|---|---|
| Signs of a hydrogen leak, fire, arcing, a burning smell, severe overheating | — | Stop at once and follow the site emergency procedure |
| Hydrogen in oxygen above 2% | Gas crossing the membrane, low load | Stop electrolysis and shut down normally. Do not restart until the cause is found |
| A terminal or cable discoloured or hot | A loose joint, undersized cable | Stop, isolate, then check the joint and the cable size |
| One cell voltage far above the others | A fault in that cell | Stop. Do not keep restarting; contact us with your records |
| Voltage rising fast at the same current | Low temperature, dilute electrolyte, low flow | Reduce current or stop, then check temperature, concentration and flow |
| Voltage falling fast at the same current | High temperature, concentrated electrolyte | Reduce current or stop, then check temperature, concentration and level |
| Temperature keeps climbing although cooling is available | Poor circulation, not enough cooling | Reduce current or stop |
| Wetness or white crystals at a port, fitting or cell edge | A loose fitting, tubing weight on a port, a cell seal | Stop and correct the fittings and supports. If it comes from a cell edge, contact us |
| The return gurgles or keeps breaking | Line routing, backpressure, trapped gas | Correct the routing and backpressure before continuing |
| Pump noise, or the flow wanders | Low tank level, air in the loop | Stop, correct the level, then purge the air |
| Concentration falls again after a change | KOH escaping somewhere | Find the escape path first. Do not just keep changing it |
When the voltage behaves oddly
When the voltage moves quickly at the same current, look at the direction first. Up points to dilute or cold, down to concentrated or hot.
| Cause | Check | Action |
|---|---|---|
| Temperature too low | The temperature reading and the heater | Bring it back to the recommended 50 °C |
| Temperature too high | Cooling and circulation | If it cannot be controlled, stop and service the cooling |
| Electrolyte too dilute | Recent make-up and the concentration | Replace with fresh 0.1 M electrolyte |
| Electrolyte too concentrated | Tank level and DI water make-up | Bring it back to 0.1 M by your site procedure |
| Flow too low | Pump, valves, blockages, air | Remove the restriction and restore the flow |
When to contact us
Having the following ready speeds up diagnosis. If you kept the record at the end of the quick-start chapter, half of it is already done.
| Group | Contents |
|---|---|
| Identification | Model (HXS-30) and serial number |
| Conditions at the time | Stack current and voltage, electrolyte flow, temperature and concentration. If measured, cell voltages, hydrogen in oxygen and hydrogen pressure |
| Symptom | What you saw, and whether it was during start-up, while ramping, in steady running or during shutdown |
| Installation | The loop layout, pipe and vent routing, the DC supply and cables |
| Evidence | Photos, and logs of current, voltage, temperature and flow around the event |
What this chapter is based on
- HXS-30 datasheetPDF · 502 KB
- HXS-30 exterior STEP modelOn request
Ask the engineer who built it
If your case is not covered here, send us the operating condition and what you observed. The engineer who designed the system answers directly.