Pressure Gauge Repair

[Speedy Builder5Participant @speedybuilder5]

Oops, well I guess the axle driven water pump works OK.

I am starting to re-build my SPEEDY loco after painting the chassis, testing components as I go. So this morning, I rigged up a side tank, pump bypass valve, and a pressure gauge onto the pump outlet.

Bypass valve open, a bit of compressed air on the cylinders and round and round the wheels went, in and out the axle driven pump. Slowly closed the bypass valve and "Pop", the gauge was blown to bits! Well, I now know that the pump delivers more than 120psi !

Being a safety critical piece of equipment, I will have to replace the gauge, but would it be feasible to repair the gauge by removing the Bourden tube, flattening it and rolling it back into shape again. I have to say that the mechanism inside the gauge is incredibly crude and am surprised that is in any way accurate.

If I was able to repair it, it would not be used on any steam engine of mine !

Positive Comments please – Bob

[Speedy Builder5Participant @speedybuilder5]

[Robert ButlerParticipant @robertbutler92161]

So why repair it then?

Robert Butler

[GeorgineerParticipant @georgineer]

Rather like climbing mountains, I suspect: "Because it's there".

George B.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Speedy Builder5 on 14/11/2020 12:17:57:

[…]

Being a safety critical piece of equipment, I will have to replace the gauge, but would it be feasible to repair the gauge by removing the Bourden tube, flattening it and rolling it back into shape again. I have to say that the mechanism inside the gauge is incredibly crude and am surprised that is in any way accurate.

If I was able to repair it, it would not be used on any steam engine of mine !

Positive Comments please – Bob

.

Sorry, Bob … but the only positive thing I can think of to say is:

Glad you weren’t injured

MichaelG.

[duncan webster 1Participant @duncanwebster1]

There was an article in ME some time back by Henry Wood on how to make bourdon tubes, and it is explained in Kozo Hiraoka's book on the Heisler.

[Jeff DaymanParticipant @jeffdayman43397]

Hi Bob, the best instruction I have seen for building a pressure gauge for a small locomotive is in Kozo Hiraoka's "Building the Shay" book. I am sure you can find all the info you need there for making the new Bourdon tube and linkages you need. Kozo's instructions are step by step and very clear. The rest of the book is excellet reading as well, even if you never plan to build a Shay.

Kozo also details how to test the finished gauge, so if you follow his instructions and the gauge works an d tests OK  per text there is no reason you could not re-use the repaired gauge on a locomotive. 

Edited By Jeff Dayman on 14/11/2020 13:25:14

[SamsarandaParticipant @samsaranda]

The reason a pressure gauge is there is to accurately indicate the pressure that is present in the system, having destroyed the gauge if you rebuild it how will you calibrate the gauge to give sensible readings? Having in the past been responsible for checking and calibrating pressure gauges on a deadweight tester my advice would be scrap it, to replace it would cost very little, if however you have access to the correct equipment to recalibrate the gauge when repaired then try it.
Dave W

[old martParticipant @oldmart]

That bourden tube is kinked and will never be safe to use, just take my word for it. The gauge will not be hard to replace anyway.

[duncan webster 1Participant @duncanwebster1]

Posted by Samsaranda on 14/11/2020 13:42:35:

The reason a pressure gauge is there is to accurately indicate the pressure that is present in the system, having destroyed the gauge if you rebuild it how will you calibrate the gauge to give sensible readings? Having in the past been responsible for checking and calibrating pressure gauges on a deadweight tester my advice would be scrap it, to replace it would cost very little, if however you have access to the correct equipment to recalibrate the gauge when repaired then try it.
Dave W

If you do rebuild it just get your boiler tester to check it. He/she should have a decent gauge, our chap checks his against a deadweight tester

[Howard LewisParticipant @howardlewis46836]

The proper way to check a pressure gauge is using a deadweight tester

Our club uses a "Master" gauge that was calibrated on a deadweight tester, and was provided with a chart showing the gauge reading at various pressures.

Judged by the condition of that bourdon tube, it has been heavily stressed locally. And rolling and flattening bit will probably harden it, even if it is not much closer to failure..

Two likely destinations come to mind "The black museum" or the bin.

There we are, two non PC words in one post!

Howard

[Speedy Builder5Participant @speedybuilder5]

Thanks for the advice, probably just keep the threaded tail and make it into a blanking plug for doing the hydraulic test ! Have a little cry over it, and chuck the rest away.

Looking at the various vendors of gauges, they mostly look like they come from the same source although Reeves do say they are UK made.

[Author]

Posts