Boiler External Piping and Boiler Proper Connections
PG-58

PG-58.3.1 The steam piping connected to the boiler drum or the superheater outlet header shall extend up to and including the first stop valve in each connection, (except as required by PG-58.3.2. Not applicable) In the case of a single boiler and prime mover installation, the stop valve required herein may be omitted provided the prime mover throttle valve is equipped with an indicator to show whether the valve is open or closed and is designed to withstand the required hydrostatic pressure test of the boiler.

1. A locomotive is a single boiler and prime mover installation.
2. In a dome throttle installation the throttle lever indicates open or closed.
3. In a front end throttle installation the throttle lever indicates open or closed.
4. In a dome throttle, the throttle valve and dry pipe must be designed to withstand the required hydrostatic pressure test of the boiler.
5. In a front end throttle installation, the throttle valve must be designed to withstand the required hydrostatic pressure test of the boiler.

Not that I'm an expert on any of this, but just as a point of information, didn't some of the 1920s-era early Superpower outside dry pipe locomotives have a stop valve on the outside dry pipe, at the front-end throttle header inlet?

Howard P.

Howard;
That may have been, as perhaps the new front end throttles were experimental, and the manufactuer wanted a "Plan B" in the event of failure. However, multiple poppet throttle valves appear to have been reliable, and the practice was discontinued.

What seems to be part of the issue here is A.S.M.E. Section I is a NEW CONSTRUCTION code, and may not be totally relevant to repairs to existing boilers. "R Stamp" repairs can be made using the current code, or if there appears to be a conflict, the boiler can be repaired using the "Code of Construction" in effect at the time the boiler was built.

Another aspect to the boiler questions of late is that while an "R Stamp" shop may repair an existing locomotive boiler, if the boiler is "Non Code", an "R" stamp may not be applied. This is the reason for the "FRA Form 4" certification of existing boilers.

Regards, Nathan

In the case of a new boiler utilizing the locomotive's original spool valve throttle...under the current code would this be acceptable? Does the term "must be designed" infer that someone at some point designed it, or does it have to possess current ASME certification, leading us once again down the path that Linn took with his certification attempt re: safety valves at Strasburg?

ASME BPV Code, Section I, paragraph PG-58.3.1 addresses the use of a throttle valve without the application of a stop valve within the ASME Code jurisdictional limits for piping. The preceding paragraph, PG-58.3 directs the designer or manufacturer to ASME B31.1, "Power Piping" for the requirements of the components used in boiler external piping, "The following defines the Code Jurisdictional Limits of the boiler external piping systems, including general requirements, valves, and inspection. The limits are also shown in Figs. PG-58.3.1, PG-58.3.2, and PG-58.3.3. The materials, Design, fabrication, installation, and testing shall be in accordance with ASME B31.1, 'Power Piping'."

ASME Section I, 2007 edition, 2009 addenda references ASME B31.1, 2007 edition. Paragraph 107.1(B) reads, "Valves not complying with (A) above [valves meeting the requirements of the standards and specifications listed in Table 126.1, i.e. B16.34, 'Valves'] shall be of a design, or equal to the design, which the manufacturer recommends for the service as stipulated in paragraph 102.2.2."

The bottom line is the Code does not limit the use of a locomotive style poppet valve (or any other style of valve) as a throttle. This does not relieve the manufacturer of the responsibility to design and construct the valve to the applicable requirements of the Code considering pressure, temperature, materials and other factors the manufacturer and owner deem relevant.

.

If you get right down to it, I don't think the Code specifically addresses any internal piping. There are some rules regarding the projection of fittings into the boiler (i.e. level gauges), but I can't recall anything about things like surface blow-down piping or sparge pipes (I am going from recollection here, I may have this wrong). A designer must consider that the throttle valve and dry pipe would be under external pressure when the valve is closed and the other design considerations discussed in previous posts, but I would take the position that for new construction, an internal valve designed and constructed specifically for that purpose and built to the appropriate requirements of Section I and B31.1 is acceptable. What I would take issue with is the use of an original valve in a new boiler. A manufacturer could cut material from the valve to determine the metal's chemical and physical properties then determine if the material and design are adequate for the edition/addenda of the Code being used, but that would destroy the valve.

S.O.

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In this case you are discussing an existing, not newly constructed boiler that is permitted to operate because it meets the requirements for certification under the FRA rules. Whether the boiler is new or not, my position is the throttle valve is within the boundries of the boiler proper. Given that, as long as the throttle valve for the boiler in your example passes an evaluation by a qualified individual based on some kind of thickness testing and maybe some form of nondestructive examination (dye penetrant would be my choice) then absolutely.

A new boiler is just that and if you want one with an ASME Code Stamp on it then every part that falls within the jurisdictional limits of the Code must meet the Code requirements as well. I imagine the reality is that there are original valves being used in ASME Code stampped boilers. It's one of those things that the FRA or Jurisdictions can choose to decide to enforce or not.

Hello Matt:

While your post may be informative to those readers who are not familiar with the ASME B&PV Code, I am curious as to what you are trying to accomplish.

As an AI, what is your interpretation on compliance with ASME B&PV for a locomotive style boiler equipped with a steam dome throttle?

If a locomotive style boiler was under your jurisdiction, would you accept or reject a steam dome throttle on an existing boiler that is being repaired? Would you accept or reject a steam dome throttle on a newly constructed locomotive style boiler?

If your jurisdiction allows a "special" license for a previously unstamped boiler, what would your jurisdiction require with respect to a steam dome throttle?

These are important questions for designers.

Sincerely;

pkurilecz

PS: In my experience flues are considered to be internal to the boiler and are treated as piping subjected to external pressure.

I believe that the dry pipe is treated the same way when the boiler is equipped with a dome throttle.

It is my opinion that the dome throttle and dry pipe are extremely critical items in the overhaul of an existing boiler.

The consequences of failure of these components is just as severe, if not worse, than a boiler shell failure.