Section I Code Jurisdictional Limits
Section I Code Jurisdictional Limits
(OP)
Hi Everyone,
I was looking into Figure PG-58.3.1 (a) of the ASME code Section I and noticed interesting thing:
Why for surface & continious blowdown from steam drum, chemical feed, vent, soot blowers etc. boiler external piping ends in the first valve, but for drain, feed for integral economizer/superheater two or more boilers, blow-off from water/mud drum it extends to the second valve? Is there any reason for this?
Thank you,
Curtis
I was looking into Figure PG-58.3.1 (a) of the ASME code Section I and noticed interesting thing:
Why for surface & continious blowdown from steam drum, chemical feed, vent, soot blowers etc. boiler external piping ends in the first valve, but for drain, feed for integral economizer/superheater two or more boilers, blow-off from water/mud drum it extends to the second valve? Is there any reason for this?
Thank you,
Curtis





RE: Section I Code Jurisdictional Limits
RE: Section I Code Jurisdictional Limits
Thank you for your response.
How about surface and botom blowdowns? What is rationale behind having only one valve in steam drum/surface (continious) blowdown and two valves in mud drum (intermittent) blow-off?
Thank you,
Curtis
RE: Section I Code Jurisdictional Limits
The bottom blowoff has 2 valves since it needs a "root" block valve in case the operative blowoff valve leaks due to seat damage. Without such a backup valve, the drum water level could drain to lo-lo water level without a backup preventive measure. The fluid and junk that is removed thru the bottom blowoff is debris , cut rings ( from rolled tube ends), welding rods, and other things that tend to cut the seat on the operative valve. For this reason these valves need to be wye-pattern globe valves- to allow rod-out of debris and refacing teh seat while it is welded in the line. Refer to B31.1 par 122.1.4, 122.2, 122.1.7.C.
One particular problem is that the boiler dwgs which define the termination points do not always define the blowoff connections, and thus the EPC is unable to meet the B31.1 requirements ( or has an excus) iN the above defined paragraphs. So, if you are the end-user, your spec for the boiler/hrsg shoud require the boiler mfr to define whcih termination points are the blowoff connections. I had seen one case where the blowoff was not defined, and the construction contactor had run flexible pipe from the root valve to a drain pit- when the blowoff was opened,the flex piping failed and flayed about in a deadly manner. This is what was supposed to be avoided by the above paragraphs.
The surface blowdown is sourced from above lo-lo water level, so technically it cannot lead to a lo-lo water level if it leaks.
"Nobody expects the Spanish Inquisition! "