bonnets 1

[raygsmm]

I have read that " Pressure seal bonnet valves shall be used only in steam or other clean non-corrosive services", anybody knows the technical behind that please???


2nd question:

Screwed bonnet shoul be tack welded to the secrewed body or provided with lockin pin,
Could any body please explain what is the mechanism of locking pin and why we use it??


Thanks all

 

[hsbcn]

Hi!

This link might help:

http://www.wermac.org/valves/valves_pressure_seal.html

Good luck!

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[reverman]

My company has manufactured stainless pressure seal valves used in corrosive environments without any known problems. so I'm not sure where that came from. Pressure seal bonnet is just a method of creating a gasket seal. Just like a bolted bonnet as long as the materials in contact with the corrosive fluid are resistant there is no technical reason a pressure seal will not work.

Now I will grant you it's pretty rare but mostly because it's rare that a plant will have a pipeline with a corrosive dangerous fluid at pressures high enough to require a pressure seal (Class 900 and up). Just as a matter of safety corrosive fluids don't need additional help at being dangerous by also putting them at very high pressures.

Item 2.

The tack weld or locking pin is used to prevent the bonnet from backing out. Pipelines can see a lot of vibration and thermal expansion and contraction. All these things can make threads unscrew themselves. This would be bad in the case of a bonnet so you need to either tack weld it or lock pin it to stop this possibility.

 

[raygsmm]

thanks alot guys fore these valuable responses.