Alfa Laval JWP
Freshwater Generator Parts
JWP-16 and JWP-26 · Titanium plate packs · Two-stage ejector
What the letters and the figure on a JWP plate actually tell you
The JWP is Alfa Laval's single-stage freshwater generator, a titanium plate unit that distils seawater under vacuum, built in two series, JWP-16 and JWP-26; generators from other makers sit under engine room equipment. This page is about one family and one habit worth breaking: reading a capacity out of the type designation, which is the one thing this designation does not carry.
It is a flange size, not an output
The maker states it at the foot of its own data sheets: the figure in the type designation indicates the diameter of the inlet and outlet flanges — for the jacket water on the smaller series, and for the jacket water and seawater connections on the larger one. Two units with different figures may be doing similar work through differently sized connections, and a figure copied as a capacity has been misread.
The one number not in the name
The same data sheets say the quantity of freshwater produced can be altered within each size by varying the number of plates in the heat exchanger assemblies. That is why a plate pack cannot be ordered from a type designation alone: within one size, units left the works with different stacks.
The electrical package differs by series
Both are listed with the pump and the electrics as additional equipment necessary for operation rather than as part of the unit, and the item is not the same one: the smaller series is listed with a manual starter box carrying motor starters and a salinometer, the larger with a control panel doing that job, and an extended panel as an option.
Names no longer in the programme
Units still in service can carry names the current programme does not show: older plates may read Nirex, and the maker's JWP-26 dimension table carries JWSP and SP designations beside JWP. Alfa Laval's later AQUA generators are a different build: one pack of a single titanium plate type does the evaporating, separating and condensing, and the process and utility plates differ only in gasket layout. A JWP plate, gasket or plate count therefore does not carry over to an AQUA unit.
Desalt DPU · DPU-2 · DPU-36-C
A separate Alfa Laval plate distiller line. The maker's own plate-pack exchange scope lists DPU 36 packs apart from JWP-16 and JWP-26 packs, so a DPU pack is not quoted from a JWP book. The Desalt name does not tell the two apart, because the maker titles its JWP-16 and JWP-26 data sheets with it too. Replacement plate packs, gaskets, ejector and pump parts are the usual scope, and the designation from the plate is what identifies which line an enquiry belongs to.
What the unit is, and what was ordered around it
The maker's data sheets split this machine into three tiers, and the split explains most of the confusion that arrives with a freshwater generator enquiry.
The unit itself, listed as basic equipment, is a set of titanium plate heat exchangers for the evaporator and the condenser, a generator shell, a two-stage brine and air ejector, a freshwater pump, a freshwater control sensor and a frame. Then comes a tier the data sheets call additional equipment necessary for operation: a combined cooling and ejector water pump with its electric motor, the starter box or control panel with motor starters and salinometer, and a feed-water anti-scale dosing unit, listed as necessary once the heating medium runs above a stated temperature. A third tier is optional — a hot water loop module for steam boosting, an extended control panel, a rehardening filter, disinfection equipment. Read that as a purchasing map: several of the things most likely to fail sit outside the basic unit, and may carry another manufacturer's plate even though the generator is Alfa Laval.
The ejector is worth understanding before writing a symptom into a request, because it does two jobs at once: it draws the surplus seawater out of the shell as brine and it makes the vacuum by exhausting the non-condensable gases. Behind it the ejector pump is separately installed with its own suction from the sea, and it supplies three things — coolant to the condenser, feed water for the evaporator, and the driving water for the ejector. One worn wet end therefore presents as three symptoms at once. The steam saturation calculator gives the boiling temperature for the absolute pressure in the shell, so a vacuum reading can be checked against the shell temperature.
Materials decide which generic fault lists apply. The maker describes this family as titanium heat exchanger plates and other seawater resistant materials, non-coated, so items from a general freshwater-generator fault list such as breakdown of internal coatings or plugged tubes belong to other designs, not to a JWP as built. What is left to look at on a JWP is scale on the evaporator plates, the state of the gaskets and the ejector circuit, and the maker's data sheets tie the first of these to the feed-water anti-scale dosing unit.
What is ordered against a JWP, tier by tier
Listed the way the data sheets divide the machine: the shell and its two plate assemblies, the ejector and the pumps, the control and monitoring items, then the consumables.
- Evaporator plate packs complete, and individual titanium plates
- Condenser plate packs complete, and individual titanium plates
- Plate gaskets, quoted per assembly rather than per machine
- Clamping bolts, tie bolts and pressure plate items
- Generator shell gaskets, cover joints and sight glass parts
- Demister elements and retaining parts
- Two-stage brine and air ejector nozzles and diffusers
- Ejector body joints and connection gaskets
- Ejector water pump impellers, shafts and wear rings
- Mechanical seals and seal kits for the ejector pump
- Freshwater pump wet-end components and seals
- Freshwater control sensor and its fittings
- Salinometer cells and electrodes
- Solenoid dump valve internals and coils
- Motor starters and control panel components read from the panel
- Zinc anodes for the shell and water boxes
- Feed and vacuum-line valve internals
- Anti-scale dosing unit pump and line parts
- Rehardening filter and disinfection consumables where fitted
- Descaling and cleaning chemicals for plate work
- Service kits made up per assembly and interval
The plate and gasket lines go wrong most often, and always in the same way: a quantity quoted for the machine when it was needed for one assembly, or a pack quoted when a partial renewal was intended. State the assembly, the plate quantity you counted and whether gaskets are wanted loose or bonded. Neighbouring sealing items sit on the filters, gaskets and seals page.
What has to be counted, not just copied
This is the rare machine where the most important figure in the request is one you have to go and count. Everything else is a photograph.
- Complete type as marked, letters ahead of the size included, and the figure after the C
- Serial or works number from the unit's plate, photographed, and the item numbers from the spare parts drawings in the unit's instruction manual if it is still on board
- Plate quantity in the evaporator assembly, counted rather than looked up
- Plate quantity in the condenser assembly, counted separately
- Whether plates on board are gasketed or glued, and the gasket material if recorded
- Whether the electrics are a manual starter box or a control panel
- Heating medium: engine jacket cooling water, or a closed circuit heated by steam
- Whether a hot water loop module is fitted for steam boosting
- Whether an anti-scale dosing unit is fitted and in service
- Whether a rehardening filter or disinfection equipment sits downstream
- Ejector pump make and type from the pump's own plate, as it was a separate order line
- The symptom observed: salinity rising, production falling, vacuum not holding, leakage on opening
- Whether the plates have been chemically cleaned or reconditioned before, and when
- Photographs of the unit plate, the open frame with the pack visible, and the pump and panel
On this machine the first question is whether the plates are still plates
Plate work is the whole economics of a freshwater generator, and it is unusually decidable. The maker's reconditioning practice for plate heat exchangers describes what happens to a pack that comes off: gaskets and scaling are taken off with dedicated tools and chemicals, plates are cleaned in heated and agitated chemical tanks, every plate is dye penetrant inspected for cracks and pinholes because that is what establishes whether the regasketed plates are reusable, and new gaskets are bonded with a two-part epoxy and cured under compression. The useful part for a buyer is the inspection: reusable or not is a test result, not an opinion, and it turns the choice between a new pack and a refurbished one into a question with an answer. It also explains why a machine descaled in place — the maker offers a cleaning-in-place route that removes scale without dismantling — can still need plate work later.
What follows is a three-way split rather than the usual two. Consumables and elastomers — plate gaskets, shell and cover joints, O-rings, pump mechanical seals, zinc anodes, dosing and rehardening consumables, filter items — are ordinary supply questions where a verified alternative can be reviewed against your approval requirements, with material records and dimensional evidence attached to the offer. Titanium plates and complete packs sit differently: plate geometry, thickness and material grade are what make a pack work, and the realistic comparison is between a new pack, a reconditioned one from the removed plates, and a reconditioned exchange pack, which the maker offers for JWP-16 and JWP-26 from its own workshop; for the removed plates the crack-detection result decides. Anything carrying instrumentation or control — the freshwater control sensor, the salinometer, the solenoid dump valve, the panel — goes to an OEM-route review, and the panel is identified from its own plate, because at build it was a separate order line. Which of the three we propose is stated on every line before a price is attached.
JWP freshwater generator parts — common questions
Can you quote a plate pack from the type designation on the plate?
Not on its own, and the maker's own data sheet is the reason. It states that the quantity of freshwater produced can be altered within each size by varying the number of plates in the heat exchanger assemblies, so two units carrying the same type may have left the works with different packs. The type designation gets us to the right family and plate geometry; the count off the opened frame gets us to the right pack. Send both, evaporator and condenser counted separately.
What does the figure after the C mean?
The connection size. The maker states at the foot of its data sheets that the figure in the type designation indicates the diameter of the inlet and outlet flanges, for jacket water on one series and for jacket water and seawater on the other. It is not an output and it is not a plate count — though it is the answer when the request is for flange gaskets or pipework items.
Distillate salinity is climbing. Is that the salinometer or the plates?
It can be neither. The ejector both draws the brine off and makes the vacuum, and the pump feeding it also supplies condenser coolant and evaporator feed water, so a worn ejector pump wet end or a scaled ejector shows up as a quality fault before a pumping fault. Report what production and vacuum are doing alongside the salinity reading, and whether it was checked against an independent sample.
Is this the same product line as your separator page?
No. The Alfa Laval separator parts page covers centrifugal purifiers and clarifiers — bowls, disc stacks and interface control. A freshwater generator shares a maker name and nothing else mechanically: it is a plate heat exchanger assembly under vacuum with an ejector, a shell and a distillate circuit. Both can travel in one request, identified from two separate plates and quoted from two separate books.
Is Vessel Core connected to Alfa Laval?
No, and there is no agreement of any kind. Vessel Core holds no dealership, distribution, representation or partnership agreement with Alfa Laval, and quoting a component against one of its designations implies no approval by the maker and no claim of interchangeability.
Submit your RFQ now.
Send the type designation as stamped on the unit (JWP, JWSP, SP or Desalt DPU), the connection flange size, and the component description — plate pack, gasket set, ejector or pump wear item. Vessel Core checks the designation against the current and superseded naming before a quotation is prepared.
