Sight Glass Gauge Lies

[cyberbadger]

Hey folks,

I also post on smokstak.com online forum, and this topic came up...

Has anyone had troubles with sight glass fittings with ASME code auto check ball fittings? The balls sticking and not letting the sight glass read true?

I'm a Vertical Fire Tube aficionado myself. I've learned on land to check with trycocks.

Have you practiced taking independent "readings" other then your sight glass? Have you seen your sight glass lie to you? What have you done about it?

-CB

[Lopez Mike]

Wouldn't this show up on your daily gauge blowdown?

[DetroiTug]

I've seen this issue come up more than once. The gauge glass assemblies with the excess flow check balls I think are intended for stationary boilers. Our boilers get rocked around a lot and the reading fluctuates - velocity in and out of the upper and lower fittings is faster than for the intended design and these balls check. With deposits in the boiler, they sometimes stay checked. Solution: Remove them.

A better solution is run with the valves just off seat enough to see some fluctuation in the gauge. If the level is changing, it's reading - open on both ends. With the valves just off seat, if the glass breaks, the discharge is going to be minimal. And of course blow the glass routinely.

-Ron

[Lopez Mike]

Yeah, on locomotives the fireman is supposed to be trained to notice if the water level isn't 'active' in the glass.

And I was being a little sarcastic with my comment about blowing the glass daily. I'm as bad as anyone. For some brain dead reason, my glass assembly needs a wrench to crack the drain instead of a handle of some sort so I get lazy. A good little Winter project for me to silver solder or press on some sort of handle so it isn't a pain to deal with.

A hard lesson in my dotage has been that anything that is awkward to do or needs a special tool or any such difficulty will just not get done.

I work on boats and I am often tempted to put the batteries either on the table or in bed so that the owner will maintain them. "There! Ignore that!." They always seem to get stuck away in the bilge somewhere to dry out and die at the worst possible time.

[fredrosse]

On the Margaret S. the gauge glass is mounted on the Starboard side of the boiler, so when I move to Port or Starboard, causing a list on the boat, I can immediately see a change in the indicated level. Understand that this may not be a workable proof of gauge function for a boat with a different orientation for the glass, but it works very well for me, I can often check the glass response while underway very easily. Also I keep the boiler full when not operating, and drain the upper part of the boiler into the feedwater tank before lighting a fire. The gauge glass also shows itself working with this operation.

Back in Nov 2011 there is a forum discussion "Gauge Glass Safety Issue" which created a potentially dangerous condition with the ERNST boiler water level gauge installed on my boat. I don't know if other gauge glass manufacturers have a similar potential for dangerous loss of the automatic shutoff feature, but it may be worth checking if you have automatic shutoff valves on your gauge glass setup.

[Lopez Mike]

That was a very timely article. The ball getting lodged out of place is something the designer should have guarded against.

I've never had my gauge completely apart. It might have such a feature for all I know. Hmm. I'm relocating the gauge vertically this Winter. Right now I carry the water within a couple of inches of the top of the glass. Having a fire tube boiler gives be a great deal of leeway in where I run the level. A good time to disassemble the beast to its constituent fragments.

[andym]

Hi - We teach steam to engineers who run our 2 steamships. You certainly require crew to watch for the water changing level as the vessel responds to wave action. We also require a cross test on the glass every watch (4 hours on - 8 hours off). Cross testing all gauge glasses was a requirement for engineers taking over a watch. This was with larger fittings with decent sized fittings.

[Dhutch]

We dont have try cocks, or a crew member watching full time, but we do have a two sight glasses and I do perform a daily blow down check every morning, as well as cracking the drain to confirm the level several times a day.

I have never had issues with the gauges miss reading, or the ball in the lower gauge body interfering.

This plant is installed on a 22ton 58ftx7ft narrowboat, so it is not static, but not on the high-sea either.


Daniel