Latest boiler regs?

Hi all,

I'm new on here and would like to pick a more experienced brain or two.

A mate is building a PYRTE traction engine and has been told by an inspector that the steam piping needs to be 5/16" (8mm) to get by the latest boiler regs as it has not been certified so far.

The original runs nicely on 1/4" piping, so is there really any need to upgrade this piping and the necessary fittings, after all, it is around the 1.5" scale? Or is this just an over zealous inspector who's used to larger models having a hissy fit?

Many thanks in advance,

George

Not looked at the green book in a while but pretty sure there is nothing akin to this in it. Indeed why would there be? So long as the boiler is safe and to spec what you do with the steam is your business...ah, it drives me mad!!

George, what the inspector told your mate is a load of rubbish. The steam piping is external to the boiler and not covered by the regs.

John

now I have looked - ask your inspector to show you where he thinks this is a requirement. Whilst I fully support strict adherence to the regulations it drives me mad when inspectors add their own, unfounded preferences and insist you make the boiler to them. I recently calculated the minimum wall thickness required for a loco boiler to safely meet all current requirements, needless to say that the inspector was utterly dismayed at the very suggestion of using anything less than (what turned out to be) three times this thickness. Why make it that thick I asked, the answer was that it had always been that way. I ask you...?

George - In a previous life I was a pressure vessel surveyor. The boiler regs for grown up boilers applied just to the boiler - I cannot believe it should be any different for model boilers but the world has got a whole lot madder since then. I agree with fizzy - the boiler regs apply to the boiler (IMHO) and what you do with the steam thereafter is your business. Sound like your mate's inspector is a bit officious, bit of a jobsworth. Ditto's fizzy's jobsowrth "it's always been done like that" inspector, what's the point of specifying calcs in the regs if jobsworth then ups them by three times? Ask him to show you exactly where it states in the regs what the pipe size should be, bet he can't.

Chris

Without knowing why he wants the piping changed its a bit hard to say.

A couple of possibilities. I think the PYRTE uses a pipe from the boiler to a manifold (which is called the steam pipe) onto which the safety valve fits so this would be covered by the regs.

1. May be that he feels this pipe is too small a dia to allow full steam to exit the boiler if it were to blow the safety valve. You say the engine is 1.5" size, by comparrison the 1.5" alchin has two 1/4" holes for steam to get from boiler to safety valve so at least double the area of your 1/4" pipe

2. What wall thickness is the 1/4" pipe. It may be he feels your friend has used too thing a gauge and wants it increasing so to prevent the bore from getting too small the outside dia will have to increase.

J

Edited By JasonB on 05/01/2015 07:36:56

For those that don't know how the PYRTE is plumbed the two photos either side of the top row show the rather unusual way steam gets from the boiler. Its not like other traction engines

here

This video shows the plumbing better. Boiler takeoff is the top of the water gauge, then into the left of teh manifold, from there out the right of the manifold and into the cyllinder block, then the regulator. So all pipework under pressure and would be included in the steam test.

Edited By JasonB on 05/01/2015 07:55:50

Edited By JasonB on 05/01/2015 08:18:04

Hi Jason, Now you mention the external piping being live it makes me a little more doubtful about calling this inspector chappie over zealous.

Many thanks for that! Very much appreciated.

George

There's still nothing in the regs that covers an external steam pipe, even if the safety valve is fed from that pipe. The inspector presumably assumes that a 1/4" pipe is not adequate to relieve the pressure via the safety valve. That can easily be determined by the steam test. If the inside diameter of the pipe is equal to or greater than the diameter of the seat in the safety valve then it should be fine. If the boiler passes the accumulation test and the pressure doesn't rise above 10% of the working pressure (50psi?) with the burner on full then there shouldn't be a problem.

At the end of the day though you have to satisfy the inspector (even if he is wrong!) if you want the boiler tested. I'm sure it's no big deal to increase the diameter of the pipe if that will make him happy.

John

It's not just the boiler being tested under the PSS2000 its a system test. Green book 1.2

Green Book clause. 3.13a states that system is "boiler shell including fittings and pipework"

Fittings are defined in 3.3 and include saftey valves and regulators etc.

In essence the whole system has to satisfy the inspector not just the boiler she'll, at the end of the day it's the inspectors nuts on the line.

Steve

If the safety valves, main boiler stop valve and any other boiler fittings are attached to a pipe from the boiler then it is my understanding that that pipe forms part of the boiler and is governed by the same requirement specifications.

The main boiler stop valve should form the last bit of the boiler, as it were, as there should be no boiler fittings after (downstream of) the main stop valve.

In other words, if the main stop valve is disconnected from all other downstream pipework and or equipment the boiler should form a self-contained unit complete in itself with respect to the boiler shell and all it's required fittings.

Chris

and what justification is there anywhere for an inspector to dictate this dimension - none what so ever! It either passes the test or fails! Soon there will be no model engineers as modern youth simply cant fathom such unfounded stipulations!

As I said without knowing why he wants the pipe changed its all justy speculation. He should have issued a written notice to say why he failed the boiler, find out from your friend why he wants it changed then we cangive a more educated answer

Could also be the fact the feed comes off the water gauge is affecting how that recovers or reads.

We are assuming it is a 1/4" pipe on the drawing and the same wall thickness as the drawing, if it were 5/16 he would have every right to ask for it to be changed.

George is your friend called Alan? if not then someone else on the Pyrte group was also being told to go to 8mm pipe and a number of other things that are needed before their boiler will be passed.

**LINK**

J

I hope the following tit bits of advice will help newcomers to steam models : There are three parts to a test on a new, modified, or repaired boiler. The first one is bare boiler hydraulic test at twice working pressure for which external fittings would be removed and the resulting holes plugged with suitable blanking screws or plates. A new superheater should also be tested to twice working pressure. The second test, also hydraulic, is at one and a half times working pressure and includes all boiler fittings and their pipes so the pressure gauge needs to read to one and a half times working pressure. The water level gauge must be positioned so the lowest level is above the firebox crown and should be independent of any other fitting or manifold; It is blown down during the steam test so fit a drain pipe to the lower cock. It is not a good idea to scald the inspector......So pipes are tested during all steam tests..... for full details you should read the advice given in the green book (2012) Colin

Hello All,

Well, I have stirred up a hornets nest here, haven't I?

First of all, it is not Alan, but I am sure he is keeping an eye on things with great interest.

Secondly, the original piping was 1/4 inch o/d and 6mm has been used as the 1/4" is not readily available nowadays.

Thirdly, on the original design there was no way to isolate the boiler from the piping (the feed to the steam take-off tube, meaning the pressure gauge, safety valve and ultimately the engine) meaning that this part from Colin's reply - The water level gauge must be positioned so the lowest level is above the firebox crown and should be independent of any other fitting or manifold - is not met, but this still doesn't explain about the 5/16" (8mm) tubing.

Regarding the lowest level of water showing being above the top of the firebox crown, this doesn't seem to apply as the firebox is simply a box containing a simple pot boiler with the exhaust vent at the top, because of the unconventional design, but the sight gauge shows an at least 1/3rd filled boiler at its lowest level. It is essentially a simple horizontal, single water-tube boiler with a gas fire under the back end which should have the water level with the centre of the boiler in normal use.

Perhaps Jason's suggestion about the safety valve being restricted by the pipe diameter could be the problem?

The head scratching continues...

George

George, 1/4" OD is readily available in a number of different wall thicknesses, I could list ten suppliers off the top of my head.

If substituting materials it is always best to be on the cautious side and take the next size/spec up rather than down.

You don't say what the wall thickness of the pipe is on the drawing, if your friend went off spec on the dia did he also go off spec with the wall thickness? Maybe use plumbing or brake line tube?

As its not to drawing the inspector would be in his right to ask for the tube to be changed and could either have said while you are at it I would prefer it changed to 8mm for XYZ reason. Or if your friend said he could not get the 1/4" to change it to then he may have been told to go to the next available (to him) size up.

Also the boiler on the PYRTE is a bit out of the norm. A boiler inspector is not a trained or qualified person, they get the position based on experience. Now that is likely to be mostly on loco boilers or the usual design for traction engine boilers where they can use there expecience to make a judgement. Not having been presented with a boiler of this type before can you really blame them if the want to cover their backs and ask for it to be as drawn or better?

J

Edited By JasonB on 06/01/2015 12:07:07

George,

My knowledge of the specific subject is limited to what I have learned from this thread. ... But; it does seem to me entirely reasonable for the inspector to require that the pipe size be increased to the next size up, rather than decreased to the next size down.

MichaelG.

.

Edit: my post was delayed by 'brunch' ... I think Jason is of like mind.

Edited By Michael Gilligan on 06/01/2015 12:21:08

Hi Guys.

the main reason for him wanting the size changed was, in his opinion too small to run the engine at a reasonable speed. He said , that the existing pipe would run it, but there would be no oomph to it. And you would get nowhere soon. He also wanted another means off getting water into the boiler. As in another entry point. This was I case the first pump failed. I can understand this on a coal fired engine as you can't just switch the heat off. But this one is gas fired, so any. Such problem. You would just turn the gas off. But a mechanical pump has also now been made and fitted to keep him happy. Now, it's just a case of waiting until mid march to take it back for pressure test part 1.

regards

dave

Hi all, I'm the Alan mentioned by Jason a few posts back. he's right I was talking about Dave Greenham's experiences with his boiler inspector and it spooked me a bit.

Now Dave's inspector had made him put another bush into the boiler so that he has two entry points for water feed to the boiler.

2012 regs 6.6 States

" Boiler water arrangements shall be by at least two independent means ( two of each, or a combination of , hand pump, injector, mechanical pump etc) a single boiler inlet with two check valves is acceptable"

I think this speaks for itself!!!

I am nowhere near as far along as Dave with my Pyrte and I plan to have a sit on trailer with gas cylinder and water tank in it. I will then run a gas pipe to the burner and a single water feed to two hand pumps in the tender ( with check valves).

I want to use hand pumps as , if I use an injector or axle/crankshaft pump I will need to arrange for a return feed to the tank in the trailer, yet another pipe!! At least with hand pumps there is no need for a return.

For those that are not familiar with the layout of PYRTE, It is a very simple pot boiler as George has explained, with no need for boiler tubes and fancy fireboxes a' la locos. It's just a piece of 4" tube with a plate at each end and a PB stay through the middle.

On the back end are 3 bushes.2 for the sight tube and one for a blowdown valve at the bottom. The steam feed is taken from the top fitting on the sight tube . The boiler water feed is also on there. My question is this, as the top sight tube is getting pretty busy , would it be ok to feed my boiler , from the hand pumps, utilising a T peice for the feed and blowdown valve?

Regards

Alan M