Budenberg Dead Weight Pressure Tester

Our Clubs had a Budenberg Dead Weight Pressure Tester donated to it. Its Complete with all the weights and reference pressure gauge, I contacted Budenberg in the UK and they were very helpful they identified the model and year of manufacture (1965) and sent me the operation instruction. I've had it working and tested the reference gauge and its bob on, I've also tested a few other pressure gauges large and small.

I know that the small gauges you get to fit on Locos are not that accurate so I'm aware that you have to be careful just how you interpret the results.

I'm still unsure just how we can get the best out of it so I'd welcome some comments. Photos below

Stew

I served my time as an instrument technician at ICI, the apprentices got all the pressure gauges to calibrate, spent numerous hours working on the exact piece of test equipment. Happy Days.

As you say the small gauges are by nature only an indicator, the range between index marks being guessed by the user.

Start by getting a decent gauge and calibrate it with your new toy.

Make a test manifold to hold your new 'test' gauge and any other gauges to be tested. This way you tested is mobile and its accuracy can be traced back to the dead weight tester.

A simple air pressure pump can be made, or purchased, to go with the test manifold.

Well it could be used as your 'master' gauge Stewart - and only used to calibrate/check your other boiler test gauges, thus helping to keep it in accurate condition. e.g. not used by all and sundry - day to day.

I believe it would still need to be 'certified' from time to time - as you will need to have a back-reference to quote when it is used to check other test gauges. My Society is thinking of having a single 'master' gauge that is used to check our boiler test rigs - as this reduces the cost of sending off multiple gauges for testing.

Regards,

IanT

Readings should be corrected for local gravity and temperature for the highest accuracy. The weights are normally stamped with the standard gravity (normally 9.80665 m/S^2) and the piston is normally stamped fro the standard temperature (20°C typically).

Many 'happy' hours spent in power stations around the world with Budenberg dead weight testers (for calibrating transducers) and dead weight gauges (what we used for high pressure readings before transducers got reliable enough).

A dead weight tester is sufficiently quick and rugged to use that there is no benefit in using a bourdon tube gauge as a working master.

Edited By Mark Rand on 24/01/2018 23:05:28

The difference in local gravity between the highest and lowest anomalies on Earth is 0.7%.

No doubt here are plenty of applications where such small changes are critical, but can anyone actually read a model-sized pressure gauge to a precision of 1%...

Neil

I worked in an engineering establishment and was responsible for checking and calibrating our test house pressure gauges using a budenberg deadweight tester identical to the one featured, the only parameter that we worried about was temperature, made sure the gauges to be tested stabilised to the same temperature as the test rig. For a model engineering set up I wouldn’t worry about any of the parameters except extremes of temperature difference between test rig and gauges being tested. Have fun.

Dave W

I've always wondered why I feel much heavier when I get back from holidays in Canada Neil - this might explain it (my wife thinks it's all down to Tim Hortons though).

The 'allowable' variation on a gauge is (in theory) +/-2% - but the practical test is that the 'red' line should be at (or slightly below) the stated working pressure of the boiler - and if marked on the gauge glass & bezel, be such that it cannot be moved by accident (or on purpose...)

Regards,

IanT

Even the posh gauge on the tester only reads in 2 psi steps and it looks to be about 4" in diameter.

If anyone on the planet can read a 1/2" or even a 3/4" diameter gauge to an accuracy of 2%, I take my hat off to them

At a scale length of 0.2" = 100psi that's 4 thou...

Neil

Surely miniature pressure gauges can only be used as simple indicators.

Looking at a picture of a 0-80psi gauge the gauge needle appears to have a width covering about 6psi.

Can that tester be used to test pressure relief valve settings? If so then that should be the way to go.

Brian said "Surely miniature pressure gauges can only be used as simple indicators."

Not if you have FSD miniature pressure gauges!

These were all individually calibrated on Freddie Dinnis's dead weight tester.

Freddie also re-calibrated a number of commercial gauges on the club locos, painting out the old dial and re-doing them.

Cheers,

Julian

Yes Neil, sorry I wasn't very clear (probably distracted by thoughts of Boston Creams? ) - 2% is the desirable 'accuracy' of the test gauge I believe - mine are 4" Budenburgs and I understand that they are made to that kind of quality.

Smaller gauges (as fitted to the boiler) can vary in design (and their % accuracy) but the key thing is that they can be 'red-lined' to show the boilers working pressure (Pw) reliably. As far as I'm aware, that's all that's required when testing them (e.g. no other markings or graduations)

Brian, safety valves can be set using a test rig but where 'inspection' is required, they are also tested as part of the 'Steam' (and accumulation) test. Basically, the valves have to open at (or slightly below) the working pressure and also be shown to release enough pressure to keep the boiler below Pw + 10% under maximum firing conditions.

Regards,

IanT

Thanks for the info Ian.

Thanks for your input and debate Chaps

Some useful information and insight to take account of.

Cheers

Stew

We have one at work, I've used it to drive pressure sensors in simulations. The one bit of advice I was given was to spin the weight to make sure the piston didn't stick, but I do wonder how much that is really required!

It's one of those things that has now become habit whenever I use the machine, so can't make an objective assessment!

+1 for spinning to make sure that the weight is floating.

Should be calibrated regularly, but unless you fail to take care of the rig and its weights, and chew lumps off them, should be very little variation in accuracy.

A very useful piece of kit.

Howard