Hot Water heating Boiler: ASME Section I PG 61.1 versus 61.4 1

[SNORGY]

Hypothetically...

I have a "boiler" (which started off in design as a "heat medium heater" until the heat medium conditions required it to become a "boiler") that supplies water/glycol as heat medium. It is classified as a high-temperature water boiler per ASME Section I: - no way around it.

PG-61.1 states, in part:

"Except as provided for in PG-61.3, PG-61.4 and PG-61.5, each source of feeding shall be capable of supplying water to the boiler at a pressure of 3% higher than the highest setting of any safety valve on the boiler."

PG-61.4 states:

"High-temperature water boilers shall be provided with means of adding water to the boiler or system while under pressure."

As fate would have it, PSVs on the *new* "boiler" are set at a setting significantly higher than the shut-off pressure that can be developed by the *existing* centrifugal feed pumps, so that in the present system, compliance with PG-61.4 is possibly achieved, but full compliance with PG-61.1 (wrt water supplied at 103% of SP) is certainly not achieved.

My question is, does PG-61.4 supersede and relax PG-61.1 for this particular issue in this instance, or is a modification required in one or the other of:

(1) Pump upgrade to achieve the 103% of SP on PSVs;
(2) Change boiler PSV settings to lower than existing feed pump shut-off pressure?

I am unclear as to the correct interpretation, and I would appreciate some input before taking it up with our Regulatory body.

Regards,

SNORGY.

 

[CodeRef]

It appears so according to the following interpretation ..... the question now is ...does the Reg. Body agree on the boiler classification as a high temp water boiler?

Interpretation: I-89-67
Subject: Section I, PG-61.1, Feedwater Pressure
Date Issued: January 21, 1991
File: BC90-782
Question: Does the feedwater pressure requirement of PG-61.1 apply to boilers with a single means of feeding water complying with PG-61.2?

Reply: Yes, with the exception of high-temperature water boilers and forced flow steam generators with no fixed steam and water line (see PG-61.4 and PG-61.5).


FAQ731-376

 

[SNORGY]

Thanks CodeJackal.

I was working from home and did not have access to the hard-copy library of all of the various interpretations; to be ruthlessly honest, I probably didn't search hard enough or look in the right places to find what you did.

I appreciate the effort you made in coming up with this.

The "boiler" was supposed to be an "API fired heater". However, when the vendor designed it, in following the data sheets and specifications, it was discovered that the surface area exceeded 500 ft^2 and the temperature exceeded 120 C. The Regulator's inspector made the discovery when the Vendor submitted the coil design for registration under B31.3.

Redundancy was, accordingly, put into the operating philosophy for the existing heat medium pumps and into the lines feeding the "boiler", and modifications were made to meet ASME Section I. The only thing that wasn't done (yet) was address the fit between the centrifugal pump characteristic cureve and the pressure requirement of PG-61.1.

Regards,

SNORGY.

 

[GenB]

I think that a buckup pump should do the job else pump replacement.
Unless the Jurisdiction gives you trouble, if the existing pumps push against operating pressure you amy be okay.
is the Jurisdiction call as to let you run the boiler.
In this case the 103 p.c will be a recomendation.
gen

 

[CodeRef]

SNORGY,
Hand searching through every interpretation can be very time consuming and leaves potential for missing key words/terms/phrases, but it is important to have the official hard copies in order to verify online searches performed on the web or other places.

See the following links for the tools I use:

http://www.authorizedinspector.com/Interpretations/Interpretations.htm

http://www.reedyeng.com/3b.htm

The interpretation I referenced indicated that there are exceptions to PG-61.1 found in 61.4 and 5. I understand that all you needed was reassurance that the exception was valid. I believe the interpretation cleared that up for you even though it did not answer your question directly. As GenB says, I agree it is probably good to have 103% as a recommendation but because your design is a HT water boiler and not a "steam boiler", the exception applies.

Now that you are comfortable with this exception, maybe you can help to answer a question of mine. PG-61.1 references PG-61.3 as well as 61.4 and 5 as an exception and this confuses me. How can PG-61.3 be an exception? I understand that PG-61.3 was revised in the 05 Edition to include small hobby boilers, and perhaps this is important based upon the small size, however, the first paragraph brings into the scope, ALL boilers does it not? and to state this as an exception? I don't see where this could be considered an exception? Your insight is appreciated...

FAQ731-376

 

[SNORGY]

Thanks CodeJackal.

Sorry my response is sporadic. I am in a hotel on the other side of the country for the next few days on "vacation" (well, away from work anyway...).

I will try to respond to this in the morning or as soon as I can.

Regards,

SNORGY.

 

[SNORGY]

CodeJackal:

I got back from vacation for a day or two. I leave again this week for about a month.

The decision taken on this "boiler", ultimately, was to lower the PSV set pressure to about 3% lower than pump shut-off. This was done because the feedwater (glycol circulation) system could easily be operated and controlled within those constraints.

Thank you for your valuable post and information.



Regards,

SNORGY.