A leading energy supplier requested the manufacture and corrosion protection, against pitting and cavitation, of 2 1600mm NB butterfly valves to extend their service life. In service at a nuclear power station, the CW valves would be subject to constant exposure to seawater.
The body and blade of the butterfly valves were cast using BS3100: Grade A1 cast steel. The shafts were manufactured using BS970-431-S29 high strength stainless steel.
Newly cast butterfly valve body and blades.
Following suitable surface preparation (abrasive blasting), the blades were coated with Corroglass 600 to a minimum DFT of 1500µm and when cured were thickness and spark tested.
Body and blades post abrasive blasting
The shafts were also protected against corrosion using Corrocoat Armagel. This was to prevent any pitting corrosion in service. Armagel is suitable for immersed environments where good resistance to chemical attack combined with resistance to abrasion, is required – such as pipes, chutes, process tanks, valves, etc
The bodies of the valve were also suitably prepared before being coated with multiple coats of Plasmet HTE. This was done to a minimum DFT of 1500µm and used in areas requiring abrasion (and chemical) resistance. A top coat of Corroglass EB was then applied, to reach a total DFT of 2500µm.
Corrocoat EB is ideally suited for brush application to areas subjected to sea-water, or other aqueous immersion. The coating also provides good cavitation resistance.
In order to provide all round protection, the external surfaces were coated with Plasmet ZF, a surface tolerant coating. A final coat of Corrothane AP1 was then applied.
Spray coating of blades Hand application of Corrocoat EB to valve body
After curing, the valve body and blade were thickness and spark tested to identify any holidays, and ensure the processional quality of the coating work.
Completed valve body and valve blade
Coating the valve with our specialist protective Corrocoat coatings will significantly increase the expected service life and protect the valves against the exposure to seawater – from pitting and cavitation corrosion in particular.
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