Surface Blowdown Connection

[macmet]

I have a scotch marine boiler that has a 1 1/4" surface blowdown connection. Can anyone tell me if I can step down and use a 3/4" metering valve on this connection or does it have to be 1 1/4"?

 

[786392]

Dear,
In all Fairness,I understand this should not be reduced as it must be the design requirements of certain%age blowdown;
that may not be achievable with reduced dimensions
of lesser Cross-sectional area available for flow actually(almost half or even lesser).

Best Regards
Qalander(Chem)

 

[NickDubya]

Please note that boiler surface blow down is used to trim the TDS which regular bottom blow down does not remove. TDS in the make up water to the boiler is the limiting factor and is location i.e. local water quality and condensate return dependent. If you have calculated that the valve you intend to fit will pass sufficient fluid to maintain the tds level you require for your application then you can go ahead and reduce the outlet size. I would however maintain the bottom blow down valve size as this may be sized to a code. If you have trouble maintaining TDS in practice you can always increase the frequency of bottom blow down to keep TDS in line - get an actuated valve and put it on a timer if you want. If you're not sure about TDS control, speak to your water treatment contractor, you'll be paying through the nose for your chemicals so get your pound of flesh and his advice on valve sizing and settings ;-)