Sight glass tube?

[Rik ShawParticipant @rikshaw]

Can this material be safely used to make a model boiler sight glass? (I'm thinking small boiler at 80 psi)

Rik

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[Rik ShawParticipant @rikshaw]

[Brian GParticipant @briang]

Checking online, 80 psi = 162 Centigrade and the melting point of acrylic is 160 Centigrade, so I would say no. Even though the melting point can be modified, it would probably have become softened well before that.

Glass tube isn't that hard to snap to length if you first score it with a diamond file.

Brian

[michael howarth 1Participant @michaelhowarth1]

What Brian says is absolutely correct. I have considered using that stuff for sight gauges as well because of the propensity of thin wall glass tubing to fracture at the slightest excuse. I have measured the temperature of a glass sight gauge on a loco at 60 psi as best I can using an infra red thermometer and it was around the 80C mark. It is obviously cooler than the boiler temperature because it stands out and is air cooled. I am not totally happy with the infra red and would like some corroboration if possible. Any ideas?

Mick

[mark smith 20Participant @marksmith20]

What about polycarbonate such as this.

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[Jeff DaymanParticipant @jeffdayman43397]

Polycarbonate is not suitable for steam or hot water service under pressure. It is not safe for use in pressure vessels. It starts to soften about 140 deg C and flows freely at about 150 deg C. Other clear plastics are similar – don't use them in steam service. JD

[Boiler BriParticipant @boilerbri]

GLASS tube bought from a reputable dealer only please. We don't want you loosing an eye 😢

[MWParticipant @mw27036]

Posted by Boiler Bri on 08/10/2016 15:27:17:

GLASS tube bought from a reputable dealer only please. We don't want you loosing an eye 😢

And if you lost an i you'd only be boiler br

I'd agree, polycarbonate…ever try to drill the stuff? gets molten pretty quickly.

Michael W

Edited By Michael Walters on 08/10/2016 16:43:03

[John OlsenParticipant @johnolsen79199]

My own opinion is that you should assume that the gauge glass is at the saturation temperature of the steam at that pressure. If it was actually cooler, then steam would condense in it, raising its temperature. The outside layer might be cooled by the air but the inside has to be at steam temperature. In large sizes you can sometimes see drips of water running down the inside of the glass.

If you can arrange a shield it is a good idea. A guy here in NZ had a quarter inch glass go on a 7.25 loco once, and a piece of the glass struck him on the cheek, causing a small cut.

John

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