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Spare parts and lifecycle support

Prewash coalescer spare parts

Prewash coalescer spare parts are the electrical components of the electrostatic coalescer, often called an electrostatic precipitator, that removes entrained caustic from kerosene after the caustic prewash of a sweetening unit: the entrance bushing, electrode insulators, the direct current (DC) power unit and its bushings. Axsia Howmar supplies them for its own designs and for units built by others.

Entrance bushings, electrode insulators, DC power units and power unit bushings
4 part families
For the electrostatic prewash coalescers and precipitators of jet fuel and kerosene treating units
Kerosene sweetening
Our own designs and units built by others, including makers that no longer trade
Any make

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Where the parts sit

A DC field in clean kerosene, and the parts that carry it

A power unit beside the vessel steps a low-voltage supply up and rectifies it to direct current. The output passes through a power unit bushing, along a conduit and through the entrance bushing to the electrode grid hung on insulators inside. Everything on that path sees caustic-wetted kerosene and, during an upset, a conductive dispersion. Those are the parts that track, trip or fail, and they are the parts listed on this page.

How the prewash coalescer works

Skid-mounted horizontal electrostatic coalescer package at the fabricator: vessel, top-mounted power unit, control panel and skid piping assembled for testing.
Skid-mounted horizontal electrostatic coalescer package at the fabricator: vessel, top-mounted power unit, control panel and skid piping assembled for testing.

Where these parts are used

The prewash coalescer sits between the caustic prewash contactor and the sweetening reactor of a kerosene or jet fuel treating unit, including UOP Merox units. UOP Merox is named only to identify the process; the trademark belongs to its owner. The unit applies a high-voltage DC field to a clean, low-conductivity product, so its parts differ in rating and detail from those of a crude oil desalter even though the principle is the same. See electrostatic coalescer prewash for how the unit works.

Parts most often replaced on prewash coalescers

Prewash coalescer spare parts: what each part does and why it is replaced
PartWhat it doesWhy it is replaced
Entrance bushingCarries the high-voltage DC supply through the vessel wall to the electrode grid while holding vessel pressureSurface tracking or breakdown after caustic, water or deposits reach the insulation; seal deterioration; damage at maintenance
Electrode insulatorSuspends the energised grid from the vessel and isolates it from earthTracking across a caustic-wetted surface, cracking, or deposits that cannot be cleaned
Power unitSteps up a three-phase low-voltage supply and rectifies it to a steady, controllable DC output for the gridRectifier or transformer failure, obsolete controls, repeated trips, or an upgrade to voltage control and current limiting
Power unit bushingCarries the DC output out of the power unit and into the conduit to the entrance bushingOil leaks, insulation breakdown, damage; replacement during power unit overhaul
Gaskets and sealsSeal bushing flanges, manways and nozzlesReplaced at every opening; material matched to caustic and aromatics exposure

Prewash coalescer parts in the catalogue

The entrance bushings, electrode insulators and power unit bushings below are listed in the open catalogue and suit both duties. Use the part finder to filter by category, or search by an old part number or drawing reference. Power units are made to order and quoted from the nameplate of the existing unit. For a desalter or dehydrator, see electrostatic coalescer spare parts.

When a part failure is really a process problem

Repeated bushing or insulator failures on a prewash coalescer usually trace to caustic reaching the grid zone: a high interface, a caustic draw-off that is not keeping up, or a distributor that is letting caustic short-circuit the field. Low field voltage and power unit trips have the same causes more often than not. If parts are failing again within months, read troubleshooting and performance diagnostics before ordering again.

What we need to identify the right part

  • A photo of the vessel nameplate and the power unit nameplate, with the power unit rating and output voltage.
  • The part’s drawing number or old part number, even partial, if you have it.
  • A photo of the part with a dimension for scale, where no reference exists.
  • Operating temperature and pressure (say whether barg or bara), caustic strength and the hazardous area classification of the unit.
  • Documentation required: EN 10204 3.1 material test certificate, certificate of conformity, high-voltage test certificates.

Need parts for a desalter, dehydrator or prewash coalescer?

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