Standard materialsStaying inside our validated conditions
Nickel-based plate and SUS316L end plates. This is the route where the published performance data applies as it stands, and it is where most reorders sit.
Quote this option→Stack hardware
Bipolar plates, gaskets and end plates for stack assembly
Parts reordered by customers who assemble or maintain our stacks themselves. Orderable individually, or as a set matched to your stack configuration and cell count.
If this is your first stack, the stack itself is what you want, not the parts. This page is for reordering and servicing a stack you already run.
WaterTreatmentCirculationCell / stackDryingAnalysisCompression- Stacks
- HXS-0 · HXS-2 · HXS-30
- Tightening torque
- HXS-2: 5 then 7 N·m
1Understand
What this part does and what decides it
Why it matters
A stack is not bolted together so much as held together under compression. The bipolar plate carries current between cells while forming the fluid channels, the gaskets contain those channels, and the end plates take the compression at either end. If any one of the three is out, the symptom shows up in the same places: a leak at a port, or spread in the cell voltages.
IN OUR OWN SYSTEMS
This is the hardware that carried HXS-2 through more than 2,400 hours of continuous operation in a 23 cell build at 0.3 M KOH, 40 °C and 50 A. It is also why stack service is a refurbish route where we replace only the MEA, the consumable part, and reuse the hardware. We have also supplied 2 kW stack hardware for a non-electrolysis application (RIST).
Background
Why these materials
Inside the stack the material question comes down to one thing: will it hold up while it sits in hot, strong alkali. On top of that each part has its own job: the bipolar plate carries current between cells and forms the flow field, the gaskets contain those channels, and the end plates take the compression. The alternative materials column lists what to take when those conditions change. On the bipolar plate, pure Ni raises the nickel purity, while titanium and platinum-coated titanium are for electrolyte and potential windows nickel does not survive. On the end plate, SUS304 is the one without the molybdenum described in the table below, and titanium and steel are for different structural requirements. Either way we start from the requirement behind the change.
- Bipolar plate, nickel-based
- It has to carry current while sitting in KOH. Nickel holds up in caustic alkali
- Film gasket, fluoropolymer
- PTFE and FEP are all but unreactive to strong bases
- O-ring gasket, EPDM
- Among elastomers, one of the better ones for alkali and heat
- End plate, SUS316L
- A structural part under compression; the molybdenum makes it more corrosion resistant than plain stainless
How the clamping load is set
A stack is not bolted together so much as pressed together, so how hard it is pressed is the figure that matters. Too little clamping raises contact resistance and lets it leak; too much crushes the porous transport layer and the membrane. The window is narrow, which is why the sequence is fixed. On HXS-2, a hydraulic press takes it to a 5 tonne gauge reading; the bolts then go up in two torque steps, 5 N·m and 7 N·m; and finally the compressed length is measured on four sides to check it has not gone in crooked. That is why reassembly needs aluminium blocks and callipers as well as the press. These figures are for the stack. Do not carry them over to a single cell or a large-area cell: the structure and the gasket arrangement differ, and the compression is set separately.
Removing a stack and opening a stack are different jobs
The tie bolts around the end plates are the compression bolts holding the stack together. Undo them and the stack opens. That is not the same job as taking the stack out of a system. Disconnecting pipework and wiring to lift the stack out is not opening it; disassembly begins the moment the compression bolts come off. The warranty turns on that distinction. Removing the stack and sending it to us is the normal return route; undoing the compression bolts is treated differently. How it is treated is set out below, under what happens to the warranty if you open the stack.
2Choose
The options and the models we handle
What you can choose
Start here and we adjust to your conditions. We can usually source what is not listed.
Change the material onlyElectrolyte or potential conditions nickel does not survive
Geometry stays and only the material changes, so this is open on HXS-2 and HXS-30 as well. Pick from the alternative materials column below; we start from the requirement behind the change.
Quote this option→Change the flow field tooWhen you design the flow field yourself
HXS-2 and HXS-30 plates are made with dedicated tooling, so the geometry is fixed. If you are designing the flow field, HXS-0 is the route.
Quote this option→Gaskets are tied to the stack rather than chosen: film gaskets on HXS-0, and on HXS-2 and HXS-30 a set of five EPDM types, six pieces per cell. The O-ring is one shape within that set.
Part by part
Not alternatives to each other — these go in together, and we supply them individually or as a set. The alternative materials column lists what we can build instead. Note that changing material means the published performance data no longer applies as it stands; we state the validated scope with the quotation.
| Model | Material | Alternative materials | Stacks | Quote this |
|---|---|---|---|---|
Bipolar plate | Nickel-based metallic plate | Pure Ni · titanium · platinum-coated titanium | HXS-0 · HXS-2 · HXS-30 | Quote this item→ |
Film gasket | PTFE, FEP and other fluoropolymers | Can be changed | HXS-0 | Quote this item→ |
EPDM gasket set (five types, six pieces per cell) | EPDM | Cannot be changed | HXS-2 · HXS-30 | Quote this item→ |
End plate | SUS316L | Titanium · SUS304 · steel | HXS-0 · HXS-2 · HXS-30 | Quote this item→ |
3Order
What to settle before a quotation
What often goes wrong
Only what has come up more than once in real enquiries.
What can actually be changed
Can the bipolar plate flow field be changed to our own design?
It depends on the product. HXS-2 and HXS-30 plates are made with dedicated tooling, so geometry stays and only material changes. For a custom flow field, HXS-0 is the route.
If we change the material to titanium, does the published performance data still apply?
Not unchanged. We state the validated scope with the quotation. We start from the requirement behind the change: electrolyte, temperature and potential window.
Opening it up and putting it back
Can we open the stack and reassemble it?
Yes, but it is compression assembled, so reassembly needs a hydraulic press, and we supply a reassembly guide with it. Tell us before you open it if you do not have a press and we will work out an approach with you. Gaskets fail most often: the O-ring rides out of its seat and the MEA gasket shrinks inwards.
What happens to the warranty if we open the stack?
Any defect confirmed before you open it stays covered. Performance and leak-tightness after you have opened it are not warranted, because reassembly quality governs the result. If you need conditions to apply after reassembly, we agree them case by case. This applies to the bare stack. On the HXB-V1 system and the HXD-V1 dryer, opening the enclosure at all counts as a modification and falls outside the warranty.
Is taking the stack out of the system already disassembly?
No. Disassembly begins the moment the compression bolts come off. MEA service runs the same route: send us the stack and we open it, replace only the MEA and reuse the hardware.
What we confirm before quoting
Once these are set, selection and quotation happen in one step. If they are not, we start there.
- Which stack and how many cells
- Which parts and how many
- Purpose: new build, replacement or spares
- For a material change: electrolyte type and concentration, temperature and potential window
Supply terms
- Supply scope
- Parts manufacture and domestic delivery. A material change is quoted separately once conditions are fixed
- Order unit
- Orderable individually; sets built to your cell count
- Reassembly needs
- Hydraulic press (5 t gauge), aluminium blocks, torque wrench, calipers
- Warranty
- We verify conformity to specification and workmanship at handover. Spare parts on their own do not carry a term warranty, and performance under your assembly and operating conditions is outside its scope
- Term warranty
- The 12-month term warranty attaches to the HXB-V1 system. It does not apply to spare parts bought on their own
Send us the checklist
Fill in only what you know. We ask about the rest.
Request a quote for this item