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ASME 1 rules for overpressure protection in HRSG

ASME 1 rules for overpressure protection in HRSG

ASME 1 rules for overpressure protection in HRSG

(OP)

Dear Sirs,
Can someone explain  where to find, within ASME 1 Code (or additional rules to ASME), the requirements  about the necessity of safety valves and their capacity  with a view to protect against overpressure :
  a) Steam Turbine Side ;
  b) Cold Reheat Side  ?
We guess that the existence of an isolation valve is of importance.
Please confirm the same and consider all known cases .


Sincerely,

A. TSAMPALAS
 

RE: ASME 1 rules for overpressure protection in HRSG

Yes, you can review the following paragraphs in Section I (2004 Edition) - steam tubine side is superheater outlet;

PG-67
PG-68

Cold reheat is reheater inlet to the boiler from the HP turbine, and this would not be addressed in the Code.

RE: ASME 1 rules for overpressure protection in HRSG

(OP)
Dear Mr Metengr,
Thanks for your reply.

Sincerely,

ATsampalas

RE: ASME 1 rules for overpressure protection in HRSG

An interesting historical summary of why reheater components are not covered by section I is found in "Power Boilers" by MD Bernstein and L. Yoder, p3, - they claim that the 2 major US turbine vendors have successfuly prevented the inclusion of that piping in section I, although neither of those vendors have  supplied that piping system since the 1950's.

RE: ASME 1 rules for overpressure protection in HRSG

Regarding the max capacity of the reheater relief valves, some unusual scenarios can arise for the case of multiple HRSG's on a header system:

a) If the STG has tripped and the HRSG is on a bypass system , the max steam flow to the reheater may need to include the add'l steam flow from the HP bypass spary attemporator

b) Such a  reheater  could be considered as  a "separately fired superheater" in that it has isolation valves at both inlet and outlet ( since it is downstream of the IP boiler bank on a HRSG, it cannot avoid code inclusion). The code clause that proportions the relief valve capacity to the "separately fired superheater" surface area has been interpreted to mean all the steam the reheater can generate if it is blocked,  and there may be a code case or interpretation that formalizes this.

c) some plants have included an "overload valve", bypassing some HP main steam directly to the hot reheater, to avoid overpressuring the GE STG that has a low throttle pressure limit.  This design must add add'l releif capactiy in the hot reheater piping near the intercept valve to account for the max casualty flow thru the overload valve.

RE: ASME 1 rules for overpressure protection in HRSG

Hi,

Sorry to add a question to this thread, but what does ASME 1 cover exactly?

Thanks.

RE: ASME 1 rules for overpressure protection in HRSG

(OP)
Dear Mr Metengr,
Following your reply dated 30 March 2006 and due to an inappropriate answer, my message had been truncated.
To see our problem, please have a look at the link hereafter:

http://users.skynet.be/fb248691/03042006_1.pdf
Sincerely,

A_Tsampalas

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