Corrosion challenges facing submersible pumps

Coated Pump Component

Pradhyumna Ingle explains that corrosion in pumps is the first sign of spoilage especially when one talks of submersible pumps; the concern for corrosion is manifold as it is used in heavy industries and deep well drilling. Corrosion affects efficiency of the pump and can even lead to pump failure.

 

Pradhyumna Ingle

Pradhyumna Ingle

A submersible pump is a pump which has a hermetically sealed motor close-coupled to pump body. The whole assembly is submerged in the fluid to be pumped. Submersible pumps are divided into two major parts – motor side and pump side. The motor side has two major components which are the stator and rotor which is made up of Silicone steel / CRNO (cold rolled non-oriented) stampings. The motor is filled with water or at times with water + glycol mixture which acts as a coolant. The filling is done prior to installing the pump for operation in field. Thus the rotor is always in contact with the water or water + glycol mixture.

In oil industry, drilling for oil is a difficult process especially when you are mining in tough conditions like in the cold sea, in ice-laden places and so many more.

A standard pump starts corroding within a year from purchase. Corrosion is the first sign of spoilage. When we talk of submersible pumps, the concern for corrosion is manifold as it is used in heavy industries and deep well drilling. The submersible pump casing which is a hermetically sealed casing can be composed of different kinds of metals, like chrome or stainless steel, or polymers. If any liquid were to leak into the casing due to corroded metal, the motor could short out easily and pose high repair costs. Even the rotor is susceptible to corrosion since it is always in contact with saline water or water + glycol mixture and runs at about 2800 rpm.

The corrosion of either the casing or the rotor affects efficiency of the pump and can even lead to pump failure. Cost of retrieving and reworking failed pumps can be significant.

To protect the rotors from corrosion most manufacturers use some kind of chemical coating. Usually epoxy paints, two component primers with a two component Polyurethane, Synthetic Enamel Paint with a Zinc Etch Primer, Chrome plating and Powder coating are used as anti corrosion solutions.

Ironically these current methods have their share of shortcomings such as short protection life, expensive and complicated process of machining rotor for application and inconsistent protection offered by differential film thickness due to thinner addition while mixing.

The experts in the industry have identified the need in the market for a solution that can overcome these shortcomings.

(The author is Business Director, General Industry, Henkel Adhesives Technologies India Pvt. Ltd. Henkel recently introduced an indigenously developed product Loctite® Safe Coat in the market. This product was specifically developed for protection of submersible components from corrosion. Henkel Adhesive Technologies India Private Limited is a subsidiary of Henkel AG & Co. KGaA, Germany. In India, Henkel is into adhesives, sealants and surface treatments for consumers, craftsmen and industrial applications.)

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