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Pressure Gauge feed

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George Sword18/01/2021 11:30:31
14 forum posts

I was wondering if there is a right or wrong way to plumb in the pressure gauge on my Garrett.

The drawings indicated that I just tee into the steam supply from the block on the top of the boiler to the manifold that supplies the water feed valves.

Someone told me (a good while ago) that this would result in an inaccurate readings depending upon the usage of the aforementioned valves.

I suppose I could just tap into the boiler but I am unsure if this is wise and I am concerned how I would get a steam tight seal on a curved surface. The boiler is steel.

Any guidance would be much appreciated.


Martin Connelly18/01/2021 13:16:17
1664 forum posts
180 photos

The measured pressure can be affected by the flow of fluid (gas or liquid) past the tapping point. It may be this that was being referred to. You need a tapping point where there is either no flow or constant flow past it to avoid this issue. Without knowing the system you are looking at I don't know if this is a valid reason to consider.

Martin C

JasonB18/01/2021 13:19:28
19973 forum posts
2179 photos
1 articles

See item 6.6 of the test code, many older designs will need to be altered to allow this, best speak to whoever is going to be testing the boiler.

Nick Clarke 318/01/2021 13:26:42
1096 forum posts
42 photos
Posted by JasonB on 18/01/2021 13:19:28:

See item 6.6 of the test code, many older designs will need to be altered to allow this, best speak to whoever is going to be testing the boiler.

That section of the test code refers to water gauges, not pressure gauges. AFAIK there is no issue fitting a pressure gauge to a manifold. It is frequently done that way.

noel shelley18/01/2021 14:02:45
390 forum posts
11 photos

6:10 states that it must have a working gauge but makes no memtion of where it should be fitted. Provided that there was no throttleing of the steam to the manifold due to insufficient size of passage way from the boiler this would seem a good place to connect the pressure gauge.

Dante Portas work showed the results of unwanted thottleing between the boiler and cylinders, and properly gas flowed locos. Only at the end of steam were valve chest pressure gauges fitted. Noel.

Edited By noel shelley on 18/01/2021 14:03:24

MichaelR18/01/2021 15:06:19
409 forum posts
80 photos

On the 3" scale Marshall traction engine the Pressure gauge feed is taken from the manifold on boiler top that supplies the injector and water lifter valves as in picture.



pressure gauge steam feed..jpg

Edited By MichaelR on 18/01/2021 15:10:13

George Sword19/01/2021 10:19:15
14 forum posts

Many thanks to everyone for your comments.

I am going to plumb it into the manifold on the boiler top.

Paul Lousick19/01/2021 11:13:37
1693 forum posts
625 photos

The Australian code has a similar requirement for water columns (water level gauge), where it has to be independent of steam take off connections.

If the steam port of the column is connected to the same outlet as a steam take off point, the pressure will drop as steam is used while the pressure in the water port of the column remains at full boiler pressure. The water level in the glass will rise because of the difference in pressures, giving an incorrect water level in the boiler.

The pressure gauge is important but not a vital piece of equipment like the level gauge. If the pressure drops, the engine stops. If it gets too high, the safety release valve operates. On my engine the pressure gauge is connected to the manifold for the steam port of the water gauge. It will not cause a false water level reading as it does not use steam, just the pressure in the pipe. Only connected to this point was convenient.


Edited By Paul Lousick on 19/01/2021 11:18:57

br19/01/2021 11:51:34
461 forum posts
3 photos

Station Road Steam -- Archive traction engine section.

Worth a look as plenty of models. / pictures. plus full screen and blow up facilities.


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