Blast and Coat Oilfield Submersible Pumps

Incoming Pumps

Internal Pump Parts

Coat Exterior

Wash Exterior

Degreasers

Blast Clean

Monel Spray
Monel Coating
To protect the submersible pump housing from corrosive down hole conditions, the housing is coated with Monel or stainless steel and a chemical sealer. In the two step coating process, the stainless coating mechanically protects the sealer which has soaked into and dried in the stainless coating. Metallic coatings can vary from 3 mil to currently 16 mil. Proper surface preparation is essential for good adherence of the metallic coating to the pump housing.

 

Step # 1 - Remove all oils - Degrease and Plug Holes -

from the manufacturing or repair processes from the pump housing surface. Make sure all plugs will not leak when the housing heats up during the blast and thermal metal spray. Tape exposed machined threads and areas that may trap abrasive which can be released later when assembled to the down hole equipment.

 

Step # 2 - Blast Clean -

to remove surface contaminants, previous coatings, and modify the pump surface to provide an "Anchor Pattern".

 

 

Housing before blast cleaning Houzsing after blasting
Steel abrasive is the most typically used because of its long life and its ability to be used in a blast wheel. Aluminum oxide can also be used but has a short life and can't be used in high production blast wheels. G-25 to G-14 steel grit is more aggressive than steel shot and is used to remove previous coatings quicker and provide a deeper anchor pattern. Steel grit come is at least 3 hardness ranges with the 50-58 Rc range being most typical.

 

Skewroll Blaster

Skewroll Conveyor

Skew Roll Blaster

A skewroll blaster is used to rotate the work as it travels forward under the blast wheel(s). Two blast wheels are used for 6" diameter work and above to avoid "barber poling" blast coverage. Blast wheel horsepower varies with the production rate required. Durable replaceable cabinet lining is required for the aggressive abrasive. The extra-hard abrasive has shorter life and may require an automatic abrasive adder to maintain a consistent abrasive operating mix and a classifier to avoid excessive fines build-up.

 

Step # 3 - Thermal Arc Spray Coating - Monel Spray Coating

4 Spray Guns

Spray Gun Console

Two Wire Spray Coating

The thermal arc spray melts wire like a MIG welder but uses two wires shorted against each other and a jet of compressed air to blow the molten metal against the work. Each gun may use up to a 400 amp. power supply.

 

400 amp gun Dun Diagram

The concentrated molten spray pattern of the gun on the work is around 1-1/2" in diameter. Since the spray must be overlapped for a continuous coating, the work must be only advanced around 5/8" forward per revolution.

A wheel blast pattern is around 24" to 36" long, and uses skewrolls on its work conveyor. The metal spray process uses "Skewed Wheels" or a work cart conveyor instead of skewrolls. The metal spray gun travel must be mechanized for consistent coating thickness. The fumes from the process must be contained in the cabinet and removed by the dust collector which is vented outside.

 

Thermal Arc Spray Work Conveyors -

skew wheel conveyor

Skew Wheel Conveyor

work cart conveyor

Work Cart Conveyor

The skew wheel work conveyor is a basic system that conforms to the arc spray pattern requirements and is used frequently for in-line systems where blast cleaning, wheel or airblast, and coating are on a single line. The rear wheels power the work rotation and the front wheels are on a slight angle to the work to produce a small amount of travel forward for each revolution of the work.

The work cart style places the submersible pump on carts which have two sets of wheels - one set on tip to rotate the work, and the second set for the cart travel. The carts are moved by a chain and a gear motor. The rpm of the rotation and the speed of the chain are independently controlled to produce the exact pattern spacing required to match the spray pattern overlap and the coating thickness desired. (see below)

The coating thickness is typically measured using a magnetic coating thickness indicator (shown below) or a micrometer.

 

 

 

spray pattern

Spray pattern overlap

Coating gauge

Coating thickness indicator

Inline Coating Systems

In-line Coating Cabinet

Traveling Coating Cabinet

Traveling Coating Cabinet

Thermal Arc Spray

Automatic Monel Spray System

Dust Collector

The dust collector ventilating the coating process is also important. The coating dust consists of a very light powder, smoke, plus heavy particulate. The cabinet has access areas for the spray guns and open area for the work to pass through. Smoke must not escape into the operator's area.

Dust CollectorDust Collector

Step # 4 - Apply Sealer -

Sealers are applied to the exterior of the submersible pumps over the thermal arc spray coating to provide a chemical barrier to down hole corrosive fluids. The sealer has to also withstand elevated temperatures. It also has to be fluid enough to soak into the spray coating and still dry quickly as to not delay shipping.

Two part epoxy is typical but new well technology may change the sealer requirements. Paint application follows state and federal rules, but generally paint spraying necessitates a proper booth while brushing or rolling may only require extra ventilation.

 

open painting paint spray booth

 

Additional information on blast and coat at www.cleanproducts.com or call 405-382-1441

Clean Products Inc.

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