Question 1

Why does membrane feed salinity rise in a plant with ERI PX pressure exchangers?

Accepted Answer

Almost always because more brine is mixing with the seawater inside the PX. There are two usual causes: high- and low-pressure flows out of balance, which is fixed by adjusting flows, and ceramic cartridge wear, which needs a new cartridge or unit. Check flow balance before buying parts.

Question 2

What should I do if a PX pressure exchanger rotor stops or runs noisily?

Accepted Answer

Check filtration and flow before ordering a new cartridge. A slowing rotor usually means particles in the low-pressure feed or flow outside the model's range; if the cause is not fixed, a new cartridge can be damaged the same way. To quote we need the model and serial number from the nameplate.

Question 3

Can I still get spare parts for ERI PX-180, PX-220 and PX-260 (65 series)?

Accepted Answer

Yes. In 2026 we continue to quote 65-series spares. If a specific part has been discontinued, the quotation says so and gives Energy Recovery's alternative.

Question 4

What is the difference between an ERI PX pressure exchanger and a FEDCO HPB turbocharger for energy recovery?

Accepted Answer

The PX transfers brine pressure to the feed water by direct contact, with peak efficiency stated by Energy Recovery at up to 99%, and needs a separate booster pump. The turbocharger uses brine to drive a turbine that raises feed pressure: simpler to integrate, but it recovers less energy. The choice is a design decision; for spares, the installed model is what matters.

Question 5

How often should seawater RO membranes be replaced in a desalination plant?

Accepted Answer

There is no fixed interval: elements are replaced when chemical cleaning no longer recovers normalised flow, salt passage or pressure drop. The decision is made from normalised operating data, not the calendar. Many plants replace part of the elements at a time rather than a whole train at once.

Question 6

How do I tell whether a seawater membrane is fouled, scaled or oxidised by chlorine?

Accepted Answer

By where and how the problem shows. Fouling usually raises differential pressure in the lead elements; scaling lowers normalised flow in the tail elements; oxidation raises salt passage across the whole train and does not improve with cleaning. Oxidation is irreversible: DuPont sets a free chlorine limit below 0.1 ppm for FilmTec.

Question 7

Can I put new membranes next to used ones in the same pressure vessel?

Accepted Answer

You can, but it changes flow distribution: the new, more permeable element works harder than the used ones. For partial replacement, run a projection in the manufacturer's software first. To quote we ask for the installed model and the position of each element being replaced.

Question 8

Can I replace Toray membranes with FilmTec, or the other way round?

Accepted Answer

Yes, if a projection with your plant data supports it, but we do not recommend mixing brands in the same vessel. Two elements with the same active area do not perform the same if their permeability differs.

Question 9

What does the “i” mean in FilmTec models such as SW30HRLE-440i?

Accepted Answer

It means iLEC interlocking end caps. If your plant uses iLEC elements, replacements must be the same type to connect correctly.

Question 10

What is the difference between FilmTec SW30HRLE-440, SW30XHR-440 and SEAMAXX-440?

Accepted Answer

SW30HRLE-440 balances high rejection with low energy; SW30XHR-440 prioritises salt and boron rejection (99.82% and 93% according to DuPont); SEAMAXX-440 prioritises permeability to cut energy use. All three have 41 m² of active area.

Question 11

Why is my Codeline pressure vessel leaking at the head, and which part do I need?

Accepted Answer

The usual cause is a worn or badly seated head seal, and the part is that seal. If permeate is leaking at the port, it is usually the adapter O-rings. To quote we need the model and serial number from the vessel label.

Question 12

What does the bearing plate in an RO pressure vessel do, and why does it crack?

Accepted Answer

The bearing plate holds the membrane stack at the outlet end against the thrust of the flow. Excessive pressure drop across the elements increases that thrust and can crack it. When you replace it, check the vessel's differential pressure too.

Question 13

Which Codeline pressure class is used in seawater plants?

Accepted Answer

Normally the 68 bar (80E100) and 82 bar (80E120) classes. The 80E series runs from 20 to 82 bar and takes 1 to 8 eight-inch elements.

Question 14

How often does a Danfoss APP pump in a desalination plant need servicing?

Accepted Answer

Danfoss states service intervals of up to 8,000 hours and major overhauls of up to 25,000 hours. Because the pump is lubricated by the seawater it pumps, upstream filtration shortens or extends those intervals.

Question 15

What information do I need to order Danfoss APP pump spares?

Accepted Answer

The code number on the pump nameplate, plus the model and serial number. That identifies the correct service kits and wear parts.

Question 16

Why does a high-pressure pump mechanical seal fail soon after installation?

Accepted Answer

The usual causes are assembly or alignment errors, face damage during fitting, or dry running or low flow at start-up. If it fails after an emergency stop, suspect pressure spikes or water hammer.

Question 17

What is PREN and why does it matter for seawater pump parts?

Accepted Answer

PREN (%Cr + 3.3 × %Mo + 16 × %N) measures a stainless steel's resistance to pitting corrosion. High-pressure seawater service commonly calls for PREN of 40 or higher, which in practice points to super duplex. If a spare is offered in a different material, the quotation should say so.

Question 18

How do I know if a FEDCO HPB turbocharger is losing performance?

Accepted Answer

Compare measured boost with design boost at actual flow. If boost falls, the main pump makes up the difference and power consumption rises. Vibration or noise points to the bearings.

Question 19

How long does a desalination spare part take to reach Cyprus, Malta or Greece?

Accepted Answer

It depends on whether the part is in stock at a distributor or built to order, and on air versus sea freight. Kits and connections are usually in stock; complete units and large membrane lots are allocated or built to order. Shipments from stock in Spain stay inside the EU customs union, so there is no import customs clearance.

Question 20

Which critical spares should a desalination plant keep in stock?

Accepted Answer

At minimum: pressure exchanger cartridges and seal kits, a lot of membranes of the installed model with interconnectors and O-rings, service kits and mechanical seals for the high-pressure pumps, and head seals and bearing plates for the pressure vessels. On islands and remote sites, replenishment time justifies holding that stock.

Question 21

If I buy desalination spares from a distributor in Europe, are they European-origin?

Accepted Answer

No. Origin is set by where a product was made: a Toray membrane is still Japanese and an ERI PX still US-origin even when bought in Spain. Tariff preferences under EU trade agreements apply only to EU-origin goods.

Technical questions on SWRO spare parts

ERI PX pressure exchangers