RE: Boiler commentary
Excellent commentary Harry. Much needed. If you would post (perhaps you already have) the the MLS and STIG sites, this would really get your words out. Whether or not they are heeded is another matter, but you got the word out and that is what is improtant. Noel Original Message Follows From: Harry Wade <[EMAIL PROTECTED]> Reply-To: sslivesteam@colegroup.com To: Multiple recipients of sslivesteam Subject: Boiler commentary Date: Mon, 14 Mar 2005 09:54:07 -0600 Since we're in a lull in the action, I've had some concerns about some things I've lately seen in print on boilers, specifically testing pressures, and my concern is that very misleading messages are being sent by this and those who don't know better will take this to be good practice, or worse yet "required" practice, and begin spreading misinformation, possibly causing someone else who doesn't know better and follows the misinformation to damage an otherwise perfectly good boiler. What has caused my concern is the recent article in SitG wherein it is stated that Torry Krutzke's Pikes Peak Loco K-loco retrofit boilers are hydro-tested to 220psi, with fittings in place no less, and along the same lines that Accucraft supposedly tests Ruby boilers to 160psi. It almost seems to me that in Ga1 live steam these days there are a few things, and a few people, who subscribe to the "If a little is good then a lot more is a lot better" school of thought. This is unecessary, and mis-guided. This should not be taken as a criticism of Pikes Peak or Accucraft, they are entitled to test to whatever pressures they see fit, and they may very well have good reason for doing what they do, although I can't think of a single one. The reason for my comments is to counteract any tendency there might be in the wake of this for people in Ga1 live steam to begin saying that hydro-testing to a high multiple (250% to 400%) of WP (working pressure) is now in some way a requirement or a good thing. It is not and should not be. The universally accepted, and in some cases regulated, test pressures for miniature copper boilers are 2 X WP (200%) for the initial (new) test and 1.5 X WP (150%) for all subsequent tests. Thus for a boiler intended to operate at a nominal 40psi, the new (1st time) test pressure should be done at 80psi and subsequent tests should be done to 60psi. These are neither minimum nor maximum pressures but are "target" pressures, but in any case there is no compelling reason to take test pressure substantially beyond this, certainly not to 300% or 400%. The other thing that I see, in ALL gauges of live steam, is the practice of hydro testing a boiler with the fittings in place. A hydro test is not intended to test fittings nor are fittings intended to withstand hydro-test pressures. One does a hydro test to determine the soundness of the boiler structural envelope and one weep or leak at a fitting renders any hydro test of the shell inconclusive, at least for the purpose of a hydro test in the first place. I know that this won't prevent people from hydro-testing with the fittings in place, because I know how much extra work is involved in stripping a boiler down and plugging the holes with solid threaded plugs for a test, but the record should show, and the general Ga1 population should know, what the correct procedure is in case they decide to use it. Regards, Harry Wade Nashville Tennessee
RE: Boiler commentary
At 12:09 PM 3/14/05 -0600, you wrote: >1) Users may have a tendency to raise the pressure setting on their pressure relief valves above what the factory intends. A bad habit to get into, but even so this cannot justify a test standard of 300% of WP. >2) Pressure gauges are not normally checked for accuracy in the US. So let's say a guage is out by 25% under-pressure, which in my experience would be an extreme case, producing a PSIG (gauge reading) of 40psi when in fact the actual pressure is 50psi . . . . for that we need to test to 160psi, 300%+ of actual WP? >3. CYA and government regulations. What "regulations" Accucraft or any other mfg must comply with, or chooses to comply with, are not my concern and are not the subject of my post. My concern is that that many rank & file Ga1 live steamers in the U.S., in particular newcomers to live steam, will see those test figures and get the notion that these are, or should be, recommended or standard practice when in fact they are just as likely to be harmful. Regards, Harry
RE: Boiler commentary
I think that there are possibly three reasons that the units are tested to such pressures that don't necessarily have any metallurgical bearing: 1) Users may have a tendency to raise the pressure setting on their pressure relief valves above what the factory intends. Since the majority of prv's are not staked or tagged like their full sized brethren, this is easy to do. A number of safety valves from Accucraft do not have an inherent adjustability like the small valves similar to the type that Aster uses. So people put shims in them to raise the spring pressure, or stretch the spring. In normal applications of pressure relief valves, if you pull the wire and tag off, your insurance is NULL. Since our units aren't directly subject to insurance or regulatory inspections. 2) Pressure gauges are not normally checked for accuracy in the US. I have not run across any mention of gauge checking being available at any steam meet. The cost of a master gauge traceable to NIST is about the cost of a Ruby. The cost of one of those calibrated piston pressure generators for gauge testing is much higher. (Don't reply about them being easy to make, I am talking about one that is NIST traceable). Also there would be the cost of recertification of the equipment every year, and liability insurance for providing the service. 3. CYA and government regulations. The latest Accucraft boilers are coming with a boiler certificate for satisfaction of European regulations. This requirement has been discussed somewhere in cyber space more than a few times. Mike Eorgoff
Re: Boiler commentary
Hi Harry I could not agree more. Even elastic will only stretch to a certain point to return to its original length one over stretched it is always "to slack". I remember the classic Cockenzie boiler test in Scotland a number of years ago I think the plate was 8 inch thick if my memory serves me right. The boiler had been tested if I recall 8 times!! The insurance officer did not believe Lloyds etc and insisted seeing the needle on the pin. This time the boiler blew. This was put down to "brittle fracture". It had been ultrasonic and radiographically examined but no significant defects had been found. The cockenzie report is of course classic literature. Back to our little kettles, the hydraulic tests are carried out cold, the boiler is run hot. It is usual to examine a vessel before and after the test. This is to ensure that any defects which the test possibly caused or brought to notice can be found before putting the device into service. Over high test pressures can cause considerable damage when the device is put into service. A silver soldered joint is not welded and stress relieved. Who carries out a radiographic examination before and after on our little kettles??. Who has proven gauges? who uses at least two of them for the test? etc etc. I agree fully with you Harry. test to sensible pressures. unless the state requires more. Bert - Bert & Edmunda [EMAIL PROTECTED]
