Correct sizing of Deaerator's safety valve - fatal failure of boiler check valve

[Rspain]

Dear All,

When looking at the safety valve of a pressurised deaerator (with low MAWP - i.e. 10-15psi) feeding a boiler, often face the following doubt:

Must a fatal failure of check valve between deaerator and boiler be considered (thus possibility of boiler condensate backflowing into deaerator) during sizing stage of the safety valve?

If so, the safety valve size would result huge, since the amount of potential condensate flashing would be very big.
If not, I don't quite find the sizing very orthodox....

What is your feelings/knowledge on this?

Is there any normative on how this possibility is to be considered, if at all?

Thanks for your help,

Rto

 

[racookpe1978]

Hmmmn. The condensate would be a cooled liquid (cooled below its saturated state in the condenser), then pumped at low pressure by the condensate pump towards the boiler feed pump, right?

Are you thinking of its flashing after being pressurized from the main feed pump?

 

[crshears]

Howdy Rspain,

Boiler feed check valves are often, but not always, duplicated to reduce this risk to highly improbable; an internal visual inspection of both valves should be performed during maintenance shutdowns. Supersizing of deaerator safeties for this particular reason is thus avoided.

You can guess my recommendation if you are still in the design phase...

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[Rspain]

Thank you