Plate Evaporator

medium 99 models total

A plate evaporator uses stacked titanium plates to flash seawater into freshwater vapour under vacuum, run on jacket cooling water from the main engine, trading the shell-and-tube evaporator's robustness for a smaller footprint and faster response to load changes.

Read more — Plate Evaporator explained ▾

What defines a plate evaporator

A plate-type freshwater generator produces distilled water from seawater by flash evaporation under vacuum, using low-grade heat -- typically 70 to 85°C jacket cooling water drawn from the main engine -- rather than dedicated steam. The vacuum, held by an ejector or a vacuum pump, lowers the boiling point of seawater so evaporation happens at engine cooling water temperature instead of 100°C. What sets the plate type apart from the shell-and-tube evaporator is the heat exchange surface: gasketed or brazed plates instead of a tube bundle. Plates give more heat transfer area per unit volume, respond faster when engine load and cooling water temperature change, and are easier to open up and inspect for scale, but the gasketed versions carry more seals that can leak and the plate pack is less tolerant of thermal shock than a tube bundle.

Plate evaporator flow scheme — Flow scheme of a plate-type freshwater evaporator: seawater feed flashes to vapour across the plate pack heated by engine jacket water, the vapour is demisted and condensed by cooling seawater, leaving as distillate while brine and the vacuum ejector complete the circuit.

Main components

Plate heat exchanger sections

Usually two plate packs in one shell: an evaporator section heated by jacket water, and a condenser section cooled by seawater, arranged so vapour rising off the evaporator plates condenses on the condenser plates without further pumping.

Vacuum system

A steam or seawater-driven ejector, or an electric vacuum pump on newer units, holds the shell at the vacuum needed for the jacket water temperature available -- the lower the heat source temperature, the deeper the vacuum required.

Salinometer and dump valve

A conductivity sensor on the distillate outlet continuously checks salinity; if it rises above the set point an automatic three-way valve dumps the batch to bilge instead of the potable water tank.

Brine and distillate pumps

The brine pump removes concentrated, unevaporated seawater from the shell; the distillate pump draws off the condensed freshwater. Both run under vacuum conditions, which makes their seals and NPSH margin more demanding than a normal centrifugal pump duty.

Selection and sizing

Daily freshwater output required against crew and technical water demand, plus a margin for reduced engine load in port.
Available jacket water temperature and flow at the lowest engine load the vessel regularly operates at, since output falls sharply below a minimum temperature.
Seawater temperature range for the trading area -- warm seawater reduces the achievable vacuum and therefore output.
Materials of construction: titanium plates for seawater and vapour-side corrosion resistance, versus lower-cost alloys accepted only in benign trades.
Space and headroom for opening the plate pack for cleaning without lifting it out of the engine room.

Regulations and class

Potable water produced aboard falls under flag state and port health requirements for drinking water quality, and class rules require the freshwater generator's salinity alarm and automatic dump to potable tank be demonstrated at survey. Where the evaporator draws from the same jacket water circuit as the main engine, class also checks that a fault in the evaporator cannot compromise main engine cooling -- an isolating arrangement or a dedicated heat exchanger loop is required on many designs for exactly this reason.

Typical faults

Fault	Cause	Consequence
Falling freshwater output	Scale build-up on the evaporator plates, worse in warm or hard seawater	Reduced heat transfer, eventually output too low to meet demand, requiring plate pack acid cleaning
Repeated automatic dump to bilge	Salinometer drift, or brine level too high carrying droplets into the distillate	Loss of produced water, and if the alarm is disabled or ignored, a real high-salinity batch reaching the potable tank
Loss of vacuum	Worn ejector nozzle, air leak at a plate gasket, or vacuum pump seal wear	Evaporation stops or output collapses even with normal jacket water temperature
Gasket leak between plates	Gasket age-hardening or incorrect tightening torque after cleaning	Cross-contamination between brine and distillate sides, or external leak into the bilge

What to look for in a supplier

Plate material certificate (titanium grade) matching the seawater corrosivity expected on the trading route.
Guaranteed output curve against jacket water temperature and seawater temperature, not just a single nominal figure.
Gasket spares in the exact plate profile, since gaskets are not universally interchangeable between makers.
Documented cleaning procedure and access arrangement for opening the plate pack in place.

Output drops noticeably in port whenever the main engine idles at low load -- that is the jacket water temperature falling, not a fault, and running the auxiliary boiler or an electric heater to supplement heat is the normal workaround rather than something to trace as a defect.

Inspector Mode Show All 99 total

9 manufacturers · 99 models

Alfa Laval

26 ✓ 7 verified

AQUA D-type

5-40 t/day FW · Seawater → Freshwater · Plate evaporator freshwater generator

Medium

Seawater → Freshwater

Type

Plate Evaporator

Technical Specifications

Kapazität JWP-16: 0.5-10 m³/24h je nach Heiz- und Kühlwassertemperaturen
Kapazität JWP-26: 4-35 m³/24h, optional bis 100 m³/24h
Plattentyp: Titanium Grade 1, 0.5 mm Plattendicke, korrosionsbeständig
Betriebsvakuum: 85-95% (ca. 4-10 mmHgA absolute)
Ejektor-eingangsdruck: Minimum 3 bar Meerwasserdruck erforderlich
Ejektor-ausgangsdruck: Maximum 0.8 bar
Gewichtsbereich: 600-955 kg (JWP-26 Varianten)
Jacket-wassertemperatur: 55-95°C flexibel einstellbar

Product Lines

JWP-16 (0.5-10 m³/24h)
JWP-26 (4-35 m³/24h)
DOLPHIN (single/double effect)
DPU-36 (10-55 m³/24h)

Common Failures & Inspection Points

Area: Plattenverkalkung und Korrosion (Calciumcarbonat, Magnesiumhydroxid, Calciumsulfat-Ablagerungen)
Check: Alle 6 Monate: Plattenpakete sichtprüfen, mit milder Säurelösung (z.B. Descalex) einweichen, weiche Bürste zur schonenden Reinigung nutzen, auf Pinholes/Risse prüfen, Ringflächenschäden (Pitting, Kratzer, Erosion) kontrollieren
Area: Gasket-Verschleiß und Dichtungslecks (Neoprene-Beschichtungsabblätterung, Gasket-Beschädigungen)
Check: Alle 12 Monate: Gasket-Oberflächenschäden (Verschleiß, Verformung, Spuren von Salzkristallisation) sichtprüfen, bei Drucktest Leckstellen markieren, verschlissene Gaskets ersetzen, Abdichtflächen reinigen und trocknen vor Neubefestigung
Area: Ejektor-Vakuumverlust und Luftlecks (Verschleiß Ejektor-Düse, schlechte Vakuumhaltung, Dichtungsverschleiß)
Check: Wöchentlich Vakuummeter prüfen (soll 85-95% halten); bei Schwierigkeit: Luftdruckverlusttest (falls Vakuum >2% in 8h fällt = Leck vorhanden). Inspektionsstöpsel entfernen, Ejektor-Hals mit Taschenlampe prüfen, Ablagerungen mit Abreißer entfernen, Ejektor-Pummen-Eingangsdruck muss ≥3 bar sein
Area: Demisters-Verschmutzung und Salzübertrag (Demister blockiert durch Salzablagerung → hohe Salinität)
Check: Alle 6 Monate: Demister-Element sichtprüfen (Blockaden, Salzaufbau), Kondensator auf Rohre-Lecks testen (Drucktest), bei hohem Salzgehalt: Kondensator und Demister chemisch reinigen oder ersetzen. Brine-Level über Sichtrohr kontrollieren
Area: Salinometer-Sensorverschmutzung und fehlerhafte Qualitätsmessung (Salzgehalt-Sensor verschmutzt, kalibriert falsch, Elektrodenablagerung)
Check: Täglich: Salinometer-Wert prüfen (soll <10 ppm sein); bei Messfehler: Sensor mit trockener Bürste reinigen, NIE mit bloßen Händen anfassen, Elektroden auf Verschmutzung prüfen, ggf. mit Lösungsmittel entkalken. Zielwert: Salzgehalt des Destillats <10 ppm
Area: Hygiene und Biofilm-Bildung in Rohrleitungen/Tank (Legionellenrisiko, mikrobielle Kontamination bei Lagerung)
Check: Alle 3 Monate Tankwasserqualität prüfen (mikrobiologische Keimzahl); monatliche CIP-Reinigung (Cleaning-in-Place) durchführen, Rohrleitungen mit Biozid/Chlor spülen, Tankdeckel auf Lichteinfall/Verschmutzung prüfen, Temperatur des Frischwassers ≥55°C halten um Legionellenvermehrung zu verhindern

Typ-universelle Inspektions-/Wartungspunkte fuer Freshwater Generators (Alfa Laval, Mega-Schwarm 2026-06). Per-Modell-Specs nicht auto-gefuellt.

Service: Operate below 2 ppm salinity. Chemical cleaning every 3-6 months. Do NOT operate in coastal waters (pollution).

Spare Parts: Alfa Laval: Einspritzdüsen und Ölfilter an Bord vorhalten. Lead time: 1-4 Wochen.

Strengths

Titanium Grade 1 plates give excellent corrosion resistance and long service life
Wide capacity range (0.5–100 m³/24 h) via modular JWP‑16, JWP‑26 and optional series
Low vacuum operation (85‑95 % of ambient) reduces steam consumption
Flexible jacket‑water temperature control (55‑95 °C) allows optimisation with ship waste heat
Compact weight for its output (600‑955 kg for the larger JWP‑26) compared with multi‑effect units

Weaknesses

Requires a minimum seawater inlet pressure of 3 bar, limiting installation on low‑pressure pump systems
Titanium plates and ejector hardware raise capital cost relative to aluminium or stainless‑steel exchangers
Scaling (calcium carbonate, magnesium hydroxide) must be managed with regular chemical cleaning every 3–6 months
Maximum ejector outlet pressure of only 0.8 bar restricts integration with high‑pressure condensate systems
Weight may still be significant for small vessels where space and displacement are at a premium

Typical Vessels: Container shipsCrude oil & product tankersBulk carriersCruise linersOffshore supply vesselsLNG carriersNaval auxiliary ships

Certifications: IMO Type ApprovalDNV GL Classification

Decision Guide: Choose if the vessel needs reliable, high‑purity freshwater at capacities up to 100 m³/24 h, has adequate seawater pressure (≥3 bar) and can supply waste heat for jacket water. Avoid on small craft with limited power or low seawater pressure, or when upfront budget is a primary constraint.

Use Cases: Installed as the main desalination plant on long‑range merchant vessels to supply crew galley water, boiler feedwater pre‑treatment and HVAC systems; also used on offshore platforms where high‑quality water is required for process and living quarters.

Plate Evaporator

What defines a plate evaporator

Main components

Plate heat exchanger sections

Vacuum system

Salinometer and dump valve

Brine and distillate pumps

Selection and sizing

Regulations and class

Typical faults

What to look for in a supplier

9 manufacturers · 99 models

Alfa Laval

Sasakura

Atlas Danmark

GEA (Condorchem Enviro Solutions)

Serck Como (Wärtsilä Water & Waste)

GEA (GEA Westfalia Separator)

RWO Water Technologies (RWO GmbH)

DongHwa Entec

Wärtsilä