cylinder relief valves

[Garry ColesParticipant @garrycoles69390]

Hi, A question about cylinder relief valves. Do you set the pressure for these valves at boiler pressure or little bit higher in order to get rid of any water that has built up in the cylinder.

Thanks

Garry

[Brian Baker 2Participant @brianbaker2]

Hi Garry, don’t be tempted to set them too high, I set mine at Boiler Pressure or perhaps just a shade above.  You want them to open as soon as pressure in the cylinder, caused by hydraulic lock gets above safe levels.

Regards

Brian B

[noel shelleyParticipant @noelshelley55608]

I’m with Brian, just above the maximum steam pressure, but bear in mind any compression at the end of the stroke depending on timing. Noel.

[Garry ColesParticipant @garrycoles69390]

Thanks for the info, that’s what I thought. Just wanted confirmation.

Garry

[Nigel Graham 2Participant @nigelgraham2]

The cushioning pressure of steam is much lower then the admission pressure, because most of what was in the cylinder has expanded and been released before the valve closes to exhaust. It’s condensate that’s the problem, not the compressed steam.

I would think setting the relief valves to boiler-pressure ideal: the pressure of steam in the cylinder before cut-off is lower than that so won’t open the relief-valves.

Interesting question, that one. Are many miniature locomotives fitted with relief-valves?

[Garry ColesParticipant @garrycoles69390]

Hi Nigel Graham 2. I thought that I would ask that question because the first loco that I built was Martin Evans  2-6-2 William, which did not have these valves. I did not know about them until I started building Doug Hewsons BR Standard 2-6-4 Tank Loco. So they are a new string to my bow. When I first studied them, I thought about the pressure, and came to the conclussion that the setting pressure must be around the boiler working pressure. I asked the question to make sure that what I thought was right.

Garry

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