Hydraulic pressure dial replacement?

[Chris152]

We picked up a used 10 ton Clark Strongarm hydraulic bench-top press yesterday, works fine but the pressure dial is on 10/ 11 ton when it's not under pressure. It moves up from there when under pressure, but we want it to start at 0. I'm assuming it's not repairable as the rim holding the glass on is crimped. Sealey sell what looks like the same press and they have the gauge for £50
https://www.ccw-tools.com/Sealey-YK10B.V3-01---PRESSURE-GAUGE__p-43173.aspxbut I wonder if a generic one that costs less would do.
Thanks for any thoughts.

 

[Sideways]

Wika is a well established reputable brand of pressure gauges.
You will need to match the screw fitting of which there are a few permutations, max pressure, etc.
I'd start on ebay.

 

[ChaiLatte]

Wika is a well established reputable brand of pressure gauges.

But are they a well-established brand of FORCE gauges, which is what his picture shows?

The thread on the gauge is the easy part - you can adapt anything to anything.

The gauge reads directly in tonnes and thus is made specifically for the diameter of ram on the machine.

As long as the Sealey press has the same size ram as the Clarke (and being generic far-east imports, that is a good bet), that would be the most painless way to go.

It is slightly unclear from the picture, but the line at the top of the gauge suggests it is glycerin-filled. The glycerin acts as a damper and stops the gauge self-destructing when the pressure changes rapidly. For example, if you are pressing on something and it suddenly lets go, without the glycerin, the needle would bounce off the stop and lilkely damage the gauge.

 

[Chris152]

Aha, I get the idea that the force relates to the size of ram, I'd been looking to just find a dial that went to 10 tons but see it's more complex. Hmmm, maybe we're going to end up with a £50 surcharge on the gauge.
Will it just screw off/ new one screw on, or does it need priming?

ps Before we do anything else, given that it's still 'working', do you think there's any way to fix it - ie, get the indicator back to naught?

 

[Sideways]

But are they a well-established brand of FORCE gauges, which is what his picture shows?

That's an excellent point, but force = pressure x area so the conversion is trivial.
@Chris152 would have to estimate the piston diameter from the OD of the cylinder and the diameter of the ram where it exits the cylinder.

In use, I expect the gauge is mostly useful for getting an impression of how close to full force you are using the press. Many hydraulic and mechanical presses have no gauge at all and are perfectly useable for pressing parts together and apart. You get used to the feel of the press.

The cheap option is to simply ignore the gauge or remove it and cap off the thread.

 

[Chris152]

That's an excellent point, but force = pressure x area so the conversion is trivial.
@Chris152 would have to estimate the piston diameter from the OD of the cylinder and the diameter of the ram where it exits the cylinder.

In use, I expect the gauge is mostly useful for getting an impression of how close to full force you are using the press. Many hydraulic and mechanical presses have no gauge at all and are perfectly useable for pressing parts together and apart. You get used to the feel of the press.

The cheap option is to simply ignore the gauge or remove it and cap off the thread.

We were wondering if maybe we don't need it, except when it's at the top end of what it/ the frame can handle. As it reads from 11 through to 18 tons, we could use that as an indication for now and see how we go. The chances of us doing anything above 7 tons is perhaps low, we're using it for bearings, bushes and that sort of thing on a car. Clarke want £69 for a replacement, which is well over half the cost we paid for the press - if we do find ourselves needing a gauge at any point, we'll come back to it and I'll try to get my head around how to calculate the force from a gauge that measures just bars (they're pretty cheap on ebay) - at the moment, I'm failing in that!

Thanks Sideways.

 

[clogs]

my press has a 25ton Tangye hyd jack with no gauge.....
after u use it a few times as Sideway say's u'll get the feel for it......
if u fit a new gauge it'll give some idea of pressure to use as a comparison say when fitting bearings or bushings....
dont worry to much......
remember to use decent press tools, stuff with good clean straight /level ends.....I have a set of old sockets that do very well when selective fit is needed....if u dont it can go wrong very quickly.....
only a couple of times have I maxed out this press.....serious pressure.....
we had a 100tonner at work...it was in an armoured room.....lol.......

 

[Chris152]

remember to use decent press tools, stuff with good clean straight /level ends.....I have a set of old sockets that do very well when selective fit is needed....if u dont it can go wrong very quickly.....

Thanks Clogs - I'll spend some time looking at how to use the thing before we go ahead, esp the safety stuff.

 

[Duncan A]

You don't need to do any calculations - just copy the ton scale from the old gauge across to the new one using the kgf scale as a reference. Write the numbers with a paint pen or permanent marker, or engrave the casing and fill the engraving with a suitable colour for clarity.
Damped gauges are about £10 on ebay

 

[Chris152]

Thanks Duncan. I see them on the bay but I'm struggling to figure out what psi/ bar I would need to get.
The piston diameter is approx 42mm/ 1.65". Any idea what psi/ bar would be equivalent to 10 tons?
I found this guide but the maths isn't working for me...
https://www.sensorsone.com/load-measure-hydraulic-press-gauge/The example is for a 1.75" piston, so not far off our 1.65".

 

[Sideways]

1 bar = 100,000 pascals
= 100,000 Newtons / m2
= 10,000 Kg force / m2
(the force of 1 Kg is nearer 9.8N but lets keep the maths easy)
= 10 tonnes / m2

Area of your piston is = pi x (Diameter)squared /4
= 3.142 × (0.042)^2 /4
= 0.001385 m2

So multiplying,
1 bar pressure on your piston will create
0.01385 tonnes of force (about 14kg)

And taking the reciprocal, you will need
72 bar pressure to make 1 tonne

If your press is rated at 10 tons, the hydraulic pump must be able to make 720 bar
With 1 bar = 14.5 psi, that's 10,440 psi

A totally different league to air pressure gauges.
I hadn't done this math before and wondered if I had slipped a zero somewhere as the pressures are high, but I can't spot a mistake and hydraulic gauges are readily available in 400, 600, 1,000 bar ratings so I'll go with it.

Also a good point to mention that "hydraulic injection" is a hazard. Hydraulic oils don't mix with human anatomy and at these crazy high pressures, fluid can be squirted straight through skin and into muscle. The injuries that result are horrific and can lead to amputation or worse. Don't put your hands anywhere near hydraulics to feel for leaks !

 

[Chris152]

I just switched the computer on and hey presto, you'd just posted a reply - I did wonder if I was asking too much. That's brilliant Sideways, thank you. I did send the link I found to my lad last night and asked him to see if he could make any sense of it, so if he uses that we'll see how the result compares.
Hydraulic injection certainly sounds terrible, there doesn't seem to be any leakage and I checked the dipstick last night and there's still plenty of fluid (it's been stood over a year, the previous owner died, sadly), but we'll be very aware of what you've written.
Thanks again, C.

 

[Fergie 307]

With sideways on feel. I have a hydraulic press but my go to is still a 1960's Cromwell floor standing mechanical press. Basically a large square threaded rod you wind down via a big cast iron wheel, operated by a ball end ratchet lever like a fly press. You can feel exactly what is going on through the lever.
The picture on the left is a later version with a hydraulic ram, but otherwise the same design. The picture on the right shows a similar mechanism to mine, although on the Churchill the wheel.sits above the top beam rather than between the legs. Marvellous machine, saved from being scrapped by a local garage who had upgraded to a hydraulic one.

 

[Duncan A]

Apologies for my slightly muddled post earlier. It is not the old gauge that has dual scales, it is the new one that Chris152 posted a picture of.
On that (metric) gauge the inner scale is kgf/cm2 and the outer scale is Metric Tons, (American for Tonne) - which are slightly smaller than UK long tons and fair bit larger than USA short tons.
For comparison, 1 long ton = 2240lbs; 1 tonne/metric ton = 2204lbs; 1 short ton = 2000 lbs
1 tonne = 1.1 short tons approx.
Looking at the scales on the gauge, 10 tonnes need about 610kgf/cm2; with other weights proportional.
If you prefer to revert to using tons, then 10 tons = 9.1 tonnes; about 560 kgf/cm2 on the new gauge.
1 kgf/cm2 = 1 bar near as dammit, so a gauge calibrated in bar would do just as well.

 

[Duncan A]

Aaaargh! I wasn't ready to post that!
Anyway, I don't know why the numbers from the gauge come out so different to Sideways calculations. It's almost as if the "Metric tons" are actually USA short tons (2000 lbs) not tonnes (2204 lbs) or UK long tons (2240 lbs).
I'll shut up now before I confuse myself even more!

 

[Chris152]

So, on that basis, comparing to the one I linked to above
https://www.ccw-tools.com/Sealey-YK10B.V3-01---PRESSURE-GAUGE__p-43173.aspxthe one below would give a pretty accurate account of the pressure being exerted by the press up to about 11 tonnes? I've not yet checked the thread so just selected 3/8BSP.
(Forgive me for not engaging the maths, it really is way beyond me.)



Fergie - I'd imagine feel comes with experience but as we don't really have any, if we can get a cheap gauge that'll do the job I'd be happier.

ps Just checked, it's 1/2" BSP on ours.

 

[Sideways]

Apologies for my slightly muddled post earlier. It is not the old gauge that has dual scales, it is the new one that Chris152 posted a picture of.
On that (metric) gauge the inner scale is kgf/cm2 and the outer scale is Metric Tons, (American for Tonne) - which are slightly smaller than UK long tons and fair bit larger than USA short tons.
For comparison, 1 long ton = 2240lbs; 1 tonne/metric ton = 2204lbs; 1 short ton = 2000 lbs
1 tonne = 1.1 short tons approx.
Looking at the scales on the gauge, 10 tonnes need about 610kgf/cm2; with other weights proportional.
If you prefer to revert to using tons, then 10 tons = 9.1 tonnes; about 560 kgf/cm2 on the new gauge.
1 kgf/cm2 = 1 bar near as dammit, so a gauge calibrated in bar would do just as well.

That conversion scale from the link with the example digital gauge Chris152 posted (post #10) as an example states that it assumes a piston with a cross sectional area of 2.405 sq inches. That's an entirely random number as far as we're concerned. Presumably there is a piston with that Cross Sectional Area for which the gauge will correctly read the force exerted.

Chris estimated his piston dia as 4.2cm, that is approx 2.15 square inches. A bit more than 10% different from the area assumed by that other conversion scale.

But
Looking at the Sealey replacement gauge that Chris posted back at the beginning and in post #16, the gauge says on the face that they are calibrated for a 45mm dia piston.

If the Clarke and the Sealey 10 ton presses happen to be made using the same dimension cylinders (sometimes copying and convention leads to some defacto standardisation) , then 45mm not 42 could be the correct diameter taking account of the O rings in the cylinder, etc. If so, my maths would change slightly and come out at 15.9kg per bar pressure and 629 bar needed to make 10 tons.

Either way I'd buy a minimum 700 bar gauge.
800 or even 1000 will allow a bigger safety margin and be fine too but will be a little less precise as it won't be reading so far up on the scale.
100mm diameter is a nice big gauge for easy reading

 

[Duncan A]

Complicated innit?!

 

[Chris152]

Complicated innit?!

 

[Chris152]

That conversion scale from the link with the example digital gauge Chris152 posted (post #10) as an example states that it assumes a piston with a cross sectional area of 2.405 sq inches. That's an entirely random number as far as we're concerned. Presumably there is a piston with that Cross Sectional Area for which the gauge will correctly read the force exerted.

Chris estimated his piston dia as 4.2cm, that is approx 2.15 square inches. A bit more than 10% different from the area assumed by that other conversion scale.

But
Looking at the Sealey replacement gauge that Chris posted back at the beginning and in post #16, the gauge says on the face that they are calibrated for a 45mm dia piston.

If the Clarke and the Sealey 10 ton presses happen to be made using the same dimension cylinders (sometimes copying and convention leads to some defacto standardisation) , then 45mm not 42 could be the correct diameter taking account of the O rings in the cylinder, etc. If so, my maths would change slightly and come out at 15.9kg per bar pressure and 629 bar needed to make 10 tons.

Either way I'd buy a minimum 700 bar gauge.
800 or even 1000 will allow a bigger safety margin and be fine too but will be a little less precise as it won't be reading so far up on the scale.
100mm diameter is a nice big gauge for easy reading

Thanks Sideways, the piston is definitely 42mm, I'd not noticed the 45mm inscription on the Sealey dial. I'd just assumed the press was exactly the same in all details apart from the label. I'm currently waiting on an answer from the sellers of a couple of 1000 bar gauges - one has the wrong photo for the item description and one doesn't state connection size.

I really appreciate the effort you've both put into helping us - thanks again.