Removing Temperature/Pressure Valve

[abraxus]

I'm trying to replace the temp/pressure valve on my calorifier and it doesn't seem to want to budge. I'm concerned about using too much brute force as, whilst the tank's almost 25 years old, it still works very well, and so I don't want to break anything.

Any suggestions beyond brute force to try and get it to shift, or how to avoid breaking the fitting if I have at it?

 

[David2452]

Assuming you mean the PRV, I have had this problem a few of times, if you are trying to replace it because it is blowing off prematurely they often have a 3/8" or 1/2" BSP thread in the outlet, I have sometimes used a couple of BSP to 12mm hosetails and a short length of hose to couple a new one in line if I am unable to remove after using normal methods like plus gas, a bit of heat etc and am unwilling to risk damage.

 

[nigelmercier]

Alternate heat and PlusGas http://www.amazon.co.uk/exec/obidos/ASIN/B0001P02RK/dolcetto-21

 

[abraxus]

Thanks chaps, I'll get myself some PlusGas and give it a go.

 

[superheat6k]

Assuming you mean the PRV, I have had this problem a few of times, if you are trying to replace it because it is blowing off prematurely they often have a 3/8" or 1/2" BSP thread in the outlet, I have sometimes used a couple of BSP to 12mm hosetails and a short length of hose to couple a new one in line if I am unable to remove after using normal methods like plus gas, a bit of heat etc and am unwilling to risk damage.

Unless you can remove the valve lifter and spring you should never 'stack' relief valves. Each valve works by the differential pressure across it, so if the original is set for 4 bar and you add another of 4 bar the total stack pressure becomes 8 Bar. Even with one weeping, the stack pressure will be considerably higher.

Explained further here ...

http://henrytech.com/Tips/HT-TT11.pdf

 

[David2452]

I open the first one with a wedge