Main steam gauge calibration.

[asal0312]

Does anyone have any recommendations where I can send my 2 main steam gauges for testing/repair/calibration within the U.S.? They do not read the same and I would rather send them out to be checked since the boat is new to me and has been in use for 30 years. What does everyone else in the hobby do when a gauge is in question?

[cyberbadger]

How far are they off?

If they differ by only 5-7 PSI at times I wouldn't worry about it too much -- Especially if the range of the gauges differs.

Mechanical Pressure gauges are not generally meant to be very accurate over their full range.

http://www.dascosales.com/pressure-gauge-accuracy.php

-CB

Post Scriptum:

I like to have 2 pressure gauges on my boiler. One modern, one old/antique - as much for double checking and failure also useful if you have them at different locations/angles on the launch.

Ultimately your functioning safety/relief valve is the backup you need to trust for pressure.

I recently bought two antique gauges - I tested them on my current boiler under steam with siphons and ball valves to isolate them. The one was true, the other totally wrong. Luckily the one I wanted to work for my new boiler read true!

If your gauges are reading very far off - I'd consider replacing them instead of calibrating them unless they are an important fixture/element of your launch.

-CB

[Mike Rometer]

Re-setting Bourden type dial gauges is extremely simple, I used to do them daily. The only difficulty is having a known pressure to set them against i.e. another, correctly calibrated gauge, or a dead-weight tester.

The two main enemies are wear, and impact (dropping them).

If the gauge is badly worn then best replace it, re-building it is more a clock-makers task and probably would cost more than the new gauge.

They are not expected to be accurate throughout the full range, only in the middle third - half, which is why you should always choose a gauge with your S.W.P. in that section.

[ccdewitt]

I should very much like to recommend Gauge Repair Service in Los Angeles. They are found at http://www.grsusa.com/.
I have had very satisfactory results with them, I have sent them old worn out gauges and they have worked to put them back in service. I haven't sent them any work in the last five years but I hope they are still with us.

[Oilking]

I had Branom Insturments in Portland, OR do a calibration check on two test gaged 0-150psi & 0-600psi for $70. The gages were given dated calibration tags, it would have been double the price if you wanted a calibration certificate. No work or adjustments needed to be done.

Dave

[Lopez Mike]

Yellow pages for steam supplies. Seattle has Steam Supply and Rubber.

A dead weight tester is a simple and rewarding project. I've built two over the years and the accuracy is totally set by how accurate you know the diameter of the ram and the weight. A home built unit can be as good as any commercial one.

The diameter you can measure with your micrometer. I use drill rod which is very accurate. Measuring the weight takes some looking around for an accurate set of scales.

Remember that the weight of moving part includes the piston and the weight. The rest is arithmetic.

In case the instructions you find don't mention it, you give the piston and weight a gentle spin when pumping the piston off its lower stop to minimize static friction.

[fredrosse]

I was lucky and got a deadweight tester on e-bay for $27, they usually cost in the thousands when new. The one I bought came without weights, so I had to make them.

I got a set of laboratory weights, 16 weights ranging from 1 gram to 5000 grams, and compared their stamped weights to a $20 Harbor Freight Digital Scale. The Harbor Freight scale was dead on for all of the weights but one, the 5000 gram laboratory weight indicated 4999 grams on the Harbor Freight Scale! Since then I have bought several more Harbor Freight scales, and they are always close to perfect all the way from 1 gram to 5000 grams. I cannot vouch for all Harbor Freight scales, but I have compared their readings to the laboratory weights on at least 6 of them, and never an error bigger than 1 gram in 5000, very very good.

With the deadweight tester I bough (piston 0.1 square inch area, 0.3568 inches diameter) I was able to make test weights that fit onto the stage of the deadweight tester. I machined a large piece of brass to 7.000 pounds, with concentric indents to take the additional load of added laboratory weights. The 5000 gram (11.02 pounds) laboratory weight stacked on top of the 7 pound weight gives 180 PSIG maximum testing, plenty good for my purposes.

If you make your own, 23/64 drill rod has an area of 0.1014 square inches, so a 10 pound deadweight would equal 101.4 PSIG. A 3/8 drill rod equals 0.110 square inches, and 11.04 pounds deadweight would be required to register 100 PSIG. My deadweight tester uses 20w motor oil, and a common grease gun (loaded with motor oil) can be used to provide the pressure to lift the test piston (and weights) up before giving them a spin.

[artemis]

I have used:
Scaler Sales
12119 NE 99th Street, Suite 2000
Vancouver, WA
360-993-1222
It's been a couple of years, but they're still in business. Recalibrate/rebuild steam guages including antiques. Also rework antique gauges for different pressures including new gauge faces.

I realize that most of us in hobby steamboating tend to try to save money but avoiding "professionals" is more expensive as it could result in funeral expenses for a number of nearby persons. The steam gauge is one step ahead of the pressure relief valve. It informs you when you are getting close to the working pressure. If your pressure relief valve is set for 150 psi and your pressure gauge reads 155 psi (and it has been calibrated by a professional firm) then draw your fire and shut the boiler down. The money you'd save in funeral costs would pay to have your main steam gauge (as well as safety valve) properly checked/set for many years. Both should be checked yearly. Most NBIC (National Board Inspection Code) authorized shops can do both AND most jurisdictions require this.

[Lopez Mike]

So here's one to ponder.

My safety valve is stamped 150. When I got the boat it popped around 145. Never any higher. This measurement and all of the following ones have been duplicated with two different gauges both of which have been checked with a dead weight tester.

Also it would groan and carry on just before popping.

Over three years the pop point has crept down to around 138-140. The pop is crisper. It is very reliable. It had only a couple of hours service when I acquired the boat.

I'm guessing that the pop getting crisper as a result of the seat or some moving part wearing in or some small bit of grit working its way out. The downwards drift in pressure might be from the same issue.

At least it seems to be drifting in a safe direction. I keep an eye on it. As a result of sloppy firing I test the valve many times a day.