Use of Spectacle flanges 1

[johcatrac]

I plan to use spectacle flanges in a 1600 psig 320°C liquid application. My question is because this spectacle flange will be in a normally closed condition, will the thermal gradient across the flanges cause any distortion and hence leaks in the long term? On the other side of the flange is a drain line leading to an atmospheric tank.

 

[LittleInch]

Hmmm,

Would be interesting to see the P & Id, because you don't normally do this. Spectacle blinds are usually d/s of valves so that they are in a section which can be isolated so that they can be swung without loosing large amounts of product all over the floor.

If its metal there won't be a thermal gradient, the far side of the flange will be 319C, especially if the line is insulated which I would expect for personnel protection. This is no different to a blind flange so if its good enough for that then it's good enough for a spectacle blind.

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[racookpe1978]

What is properly pointed out above is the "removal" operation: How will you prevent all of the liquid upstream of the spectacle flange from draining out/spurting out onto the ground and into the workers' faces when you loosen the spec. flange to remove it?

Unless this is in a naturally drained point (up higher than the tank and ALL intermediate piping between the tank and the spec. flange position) so you can guarantee everybody and OSHA and the EPA that you will never, ever have liquid in the line when the bolts are to be loosened to be removed, you need an isolation valve, a vent/drain type of pressure control and bleed off rather than just a single spectacle flange.

This is the problem with wafer valves as well. Nice idea. Very cheap. But when you have to work on the line either upstream or downstream, you are removing the valve as well

 

[johcatrac]

Sorry, should have been clear - the spectacle flange is being installed downstream of an isolation valve. The line is 3/4" and the downstream stub of pipe from the valve will be around 3 ft. So, if the valve is leaking there will be fluid entrapped.
Also doesn't spectacle flange bolts need higher torques because of the double gaskets?

 

[Amir35]

If you select proper Material and rating,there will be nothing to worry about.For example ASTM A387 Gr11 Cl 2 is a good material for HP steam superheat ,Any way you may consult with your Process Engineering Discipline.

 

[LittleInch]

Your spectacle blind won't see the temperature on the other side of the valve. Even if there is a leak, this will be small and in a short time will pressurize the pipe and flow will cease. 3 feet away from a 3/4 " valve will be at ambient temperature.

~And no, just because there is another gasket, it doesn't affect the bolt torque / axial force on the bolt. It will affect the length of the bolt[tt][/tt] and hence the number of turns required to get the same torque, but not the torque itself.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.