Pressure Gauge Dead Weight Tester

I've been looking for an article on the above subject, which I seem to recall was in Model Engineer, probably in the '80s or '90s. I've gone through all the online indexes using all the search phrases I can think of with no luck. Does any one recall such an article? or am I dreaming (been known to happen! ).

John

There is one described in one of the Kozo Hirioka books sorry cannot remember which book as I no longer have them.

I just has a look through the kozo books. The imperial one is described in the Heisler book and the metric in the Climax book.

Stephen

Thanks Baz and Steven but I have never had any of his books so it can't be that I'm remembering. I do have the "Live Steam" mags that have a couple of his construction articles, so will have a look through those , but I don't think that is what I remember.

John

Hi John

I wonder if it might be worth searching under the name Roy Amesbury. I believe he wrote an article in ME on the construction of pressure gauges in the mid 70s, perhaps he talks about dead weight testing?

Stephen

I've had a look through the "Live Steam" mags and he describes a dead weight tester at the end of the Climax series in a section on making a pressure gauge. In those articles he mentions that there will be an imperial version in the forthcoming Heisler book but there is nothing in the Heisler build series in "Live Steam".
Looking at the one in the Climax series the diagrams don't fit with the images I have in my minds eye. Unless someone comes up with something I will have to go through the paper indexes for the 80's and 90's and see if anything pops out at me.

Steven: I've got photo copies of Roy Amesbury's articles on making pressure gauges but on testing , all he says is "Of course the gauge must be checked against a large accurate one".

John

Like John I'm sure I've seen an article on dead weight testing of pressure gaugues in either Model Engineer or Model Engineers Workshop.

After sleeping on it I'm inclined to think MEW in the 2002 to 2012 (ish) area is marginally more likely. Memory also says that the title wasn't what might have been expected.

Clive

I suppose you could just start with the Budenberg Gauge company depending on how much detail you want.

An article by E.W. Sheppard titled "A pressure-gauge tester" appeared in ME No 3546 Vol 142 October 1976. It described the design of a deadweight tester.
Bear in mind that in these days of health and safety in extremis, any gauge used for boiler testing should be calibrated by a tester that holds UKAS certification.

If it's in the Heisler book I'll scan it for you. Might take me a day or 2 to find the book. Send me your email via PM

Hiraoka’s book, Building the Heisler, goes into great detail in building a deadweight pressure gauge tester. He includes making the gauge, which I guess John does not require. The essential detail is that he suggests a ground or drawn 1/8” rod for the plunger (or piston), into a reamed hole in the cylinder. His drawing calls for a smooth sliding fit. There is no seal, as this would introduce friction, but he says that the small clearance causes very little leakage, due to the oil viscosity.

The deadweights sit on top of the pointed plunger, on a carrier that has a clearance to avoid contacting the cylinder. The weights have masses calculated to produce the required pressure, based on the cross-sectional area of the plunger. The carrier represents 25psi, plus three weights for 25 and two 50 psi weights. Maximum pressure is thus 150 psi. He allows the the miniscule mass of the plunger! I can quotes masses, if rquired.

The cylinder and adaptor to suit the gauge are made from hex brass, with suitable thread and cone to seal, and the two parts screw into a block or manifold with a 1/8” hole, with a plug to seal the end.

I haven't posted images as I'm not sure of the copyright; can a moderator comment. My copy published in 1986. I can provide further detailes if required.

Bill

I did make kozo’s dead weight tester many years ago when I had access to some very accurate weighing equipment. As drawn it works very well and has been used by many to check pressure gauges on locos, the only modification I have made is to include an oil reservoir, only needs to be a bit of brass with half inch reamed hole and a piston fitted with an o ring, the piston rod is threaded so piston can be wound in and out of cylinder. In use gauge to be tested is fitted, weights applied and piston turned inwards to force oil under piston to float the weights, sorry for long winded blurb , a pic would have been better, must try harder posting them.

Or, as Duncan suggests, PM me with your email.

Bill

A dead weight tester is something I had often thought of making - it seems so simple ? From the figures given, ie a piston of 0.125" dia would give a ratio of weight to pressure of approx 20.4 ? If this is so them yes an accurate weight is needed, if the ratio is dropped then the accuracy of the weight is less critical ? Then a piston of 0.65" dia would give a ration of 3 to 1 ? and a 56Lb weight would generate a pressure of 168 psi ? A good gauge would read to 5% or better ? NO allowance has been made for the weight of the piston or other devices used to hold or carry the weight ! This is the basics ? Noel.

The 1/8" plunger has a CSA of 0.01227 in^2. Therefore, 100 PSI requires 1.227 lb weight, a ratio of 81.5. Hiraoka provides the following weights:

Plunger: 0.11 oz

Carrier: 4.80 oz (plus plunger gives 4.91 oz, i.e., 25 PSI)

25 PSI weight: 4.91 oz

50 PSI weights (x2): 9.82 oz

The chapter title says inch version, so perhaps a metric version was published elsewhere. All dimensions in the Heisler book are in US Conventional/Customary Units, including threads.

Bill

The difficulty of making one with home facilities is that the piston and bore are superfinished with about 0.0003" clearance, the piston usually hard chromed.

With a silver steel plunger and the bore finished with a toolmakers reamer made from the same rod I reckon it will work. For our occasional use it doesn't natter if it weeps a bit,

I seem to have a recollection from many years ago when I worked in a lab of one which worked on air. If you have a restrictor in the feed line and a variable needle valve in the exhaust you can adjust it to get it to just float, then it really doesn't matter if it leaks a bit. However you then need a supply of air at significantly higher pressure, which I at least haven't got.

I've found Kozo's book

My club has a deadweight tester used to calibrate the master gauge used by our boiler testers. I believe that the key components they used - the piston and cylinder - were sold for a diesel injection pump and met the high finish/very close tolerance requirement. I guess that if it can handle diesel fuel without leakage, it can do this job! Working out the weights required is a straightforward job once you know the piston diameter.

I'm on holiday at the moment and without access to any more details but it might be something worth exploring.

Thanks everyone for your replies so far. The one Tony mentions in ME might be the one I'm thinking of. Mine don't go back quite that far (1979 ) but I may have seen it going through old copies in our club library (they go back to day one ). The one detailed in the Climax article and book is metric and with a bit of math the dims. could easily be modified to be imperial which is what I want as all my gauges are in PSI ( except the one on my German toy steam engine which is in bar! ). Thanks Bill and Duncan for your offers.
Here's the gauge I currently use for boiler testing.

It would be an interesting project, I used to carry out deadweight testing when I was an instrument mechanic, from 10 psi to 25000 psi, not using the same tester. And oxygen gauges which needed a barrier between the oil in the tester and the gauge which was run with trichloroethane iii. The lowest pressure gauges had their own special needs, as the weight of any fluid in the borden tube was enough to affect the readings. They were coupled to the deadweight tester with a low pressure air source. At that time we also had quantities of gauges to refurbish which had the "tru-lume" dials and pointers, radium, that is. The radioactive bits were removed in controlled conditions and after cleaning the dials and pointers were replaced with flourescent modern types. These work in the dark cockpits of aircraft with UV backlighting.