Pressure gauges

giubu · Sep 16, 2019

Hello all,
I want to install pressure gauges for this old Mitsubishi MS40 I have.
I am thinking to use T connection between the 3 pump outlets and the control valves bank, and I will be installing 3 pressure gauges, one for each pump.
My question is what range of pressure should the gauges be for this kind of machine?
Would it be possible to install flow meters too, or is that irrelevant?
thanks

ITW · Sep 16, 2019

On my terex the i have 1 pressure gauge and it's installed on the relief valve you adjust max pressure on so you have control on how much pressure you are letting out on the system.
I think that is more important than how much pressure ech pump is delivering

My terex have max preasure at 250 bar so my gauge goes to 300 and something

giubu · Sep 16, 2019

So in your case it is installed after the relief valve?
Would it not serve the same function if it was installed between the pump and the relief valve? I mean the relief settings will still determine how much pressure goes into the system, or am I wrong?
Is there any way to know what max pressure my machine should be set to?

ITW · Sep 16, 2019

You want to make sure that you are not sending to much pressure to the system, that's why its better to have the gauge after the relief valve, so you have the possibility to adjust for the correct pressure.
But if you want there is nothing wrong with having one before also, it's only for knowing how much raw pressure you have than?

giubu · Sep 16, 2019

Hmmm, maybe my machine is older, therefore different in design, but if I follow the logic of the valves, it shouldn't make a difference whether I put the T before or after the relief, when that valve opens that is the maximum pressure in the system relative to that pump.
So you think 400 bar gauge should be adequate for my machine?

Vetech63 · Sep 16, 2019

You need to know what pressure the machine is supposedly operating/relieving at. Use a gauge that is 500-1000 psi over that rating. It is the most accurate at the upper end of the pressure scale.

giubu · Sep 16, 2019

thanks for the replies,
is there a ball park figure for a 4 ton machine, my problem is that information on this ancient beast is really scarce and I am pretty sure the controls have been messed around with in the past, so I don't know how reliable the actual reading would be.
on a related subject, the bucket curls in much slower than it curls out, is it a matter of mechanical linkage adjustment or something else?
thanks a lot

uffex · Sep 17, 2019

Good day
You may like to consider a quick connector as used on many later machines you can hook up a pressure measuring device very quickly once installed, another worth thinking about is the modern pressure sensors such as Wika you could calibrate such a sensor for use with a multimeter making pressure testing safe and remote. Food for thought.
Kind regards
Uffex

uffex · Sep 17, 2019

Regarding bucket curl the volume of fluid that is displaced by the cylinder going in is much geater than that when the cylinder extends, hope that explains.

giubu · Sep 17, 2019

uffex said:
Good day
You may like to consider a quick connector as used on many later machines you can hook up a pressure measuring device very quickly once installed, another worth thinking about is the modern pressure sensors such as Wika you could calibrate such a sensor for use with a multimeter making pressure testing safe and remote. Food for thought.
Kind regards
UffexView attachment 201966 View attachment 201967 View attachment 201968

Yes, a quick coupler is exactly what i was thinking of, only in a T configuration.
I have to admit I thought about digital gauges, but then I don't know if they will fit the look of my banged up ancient dinosaur over here, I guess steam punk is more adequate for it, and for my wallet too...
I understand the point about the bucket motion, I guess the volume of the rod takes up space inside the cylinder that oil doesn't have to fill up when retracting, while when extending it has to fill the whole inside volume of the cylinder, but I guess it can also apply more force because there is more surface area to push on. Learning something new every day...
thanks

John C. · Sep 17, 2019

Do you have any idea of what kind of pumps are installed in your machine. Gear pumps usually run up to around 2,500 PSI and sometimes higher depending on the manufacturer and application. Vane pumps can run up to around 3,200 PSI. Piston pumps are the high pressure work horses possibly going up into the 5,000 PSI range. If you can post a photo of the pumps, maybe someone here can identify what they are.
When checking pressures, you tee in between the pumps and the main valves. Steam punk is the only way to go in your part of the world. Manual gauges are the best.
The difference between open and close speeds on the bucket shouldn't be much. Does your machine have manual linkages operating the main control valve spools or is it pilot controlled? You might also check the piping between the main control valve and the bucket cylinder. Sometimes other types of controls are installed that can cause problems.

giubu · Sep 17, 2019

Hi John, thanks for the reply.

The pump is a Nabco ph82518 I don't know if that rings any bell. I have 3 of them mounted in series one after the other, and they are all very compact, my guess they are gear pumps, but I cannot be sure.
for the bucket, all the links are mechanical, that's why I thought maybe the spool was not moving all the way in. The difference in speed is quite noticeable, I would say almost half as fast. The only thing between the spool and the bucket is one relief valve, other controls have two. I was thinking to mess around a bit with the linkages to see if I notice any difference.
thanks

John C. · Sep 17, 2019

They could be either gear of vane pumps. I think 5,000 PSI gauges should be plenty. The manual linkages do get bent or debris gets stuck up in places that prevent full movement of the linkage. If you have a helper, you could put them in the cab and have them pull the levers with the machine shut down while you watch the movement of the spools.

giubu · Sep 19, 2019

All right,
I'll get to work on it and report back, thanks for the inputs.
all the best

giubu · Oct 12, 2019

Hi there, I've been away for a while, got back and started working on the machine.
so I have inspected all the linkages for the bucket, took them apart, cleaned them and checked for interference, they are all good... what I have noticed is that the spool will travel out about 1mm less then it's neighbors, even with all the linkages disconnected.
So I took off the cup to reveal the spring, see if anything in there was blocking the travel motion. Nothing as far as I can see. I thought maybe there is a way to adjust the end travel on these spools. The spring is retained by a swiveling plate held on by some kind of round bolt with a notch on it to accept a flat screwdriver. I tried to undo it and it wouldn't come loose, so I thought I ask first to see if anybody has any experience with these kind of spools.

uffex · Oct 12, 2019

Good day G
I have not a good picture of your actual spool but most have the spring retaaining bolt Loc-tite bonded in as a safety measure, without a. spool clamp these can be a challenge to remove, in the field I have used a sheet of canvas backed emery - rap the spool into the sheet canvas side - nip the bundle into a vice provided you have rapped it in the correct direction the spool lands will bite into the canvas and give enough. grip to loosen the bolt. Remember to clean and re Loc-tite on assembly.
Kind regards
Uffex

giubu · Oct 12, 2019

So you suggest I remove the actual spool from the control bank? wouldn't that cause lots of fluid to come out? I guess I could jam some clean cloth in there to stop it.
I would also like to replace the spring on another spool as it is totally bent and the lever will not come back to neutral position. Is it possible to remove the bolt with the spool in place with the aid of a spool clamp tool? I tried to search for this tool to get an idea of what it looks like, maybe it's worth buying it or trying to fabricate it, but I couldn't find anything on the net. I can hold the spool tight with a wrench on the linkage on the other side of the valve, the problem is I cannot get a good grip on the spring side, and for sure I don't want to go in there with any kind of flame to melt the Loctite away...

uffex · Oct 12, 2019

Good day G
Yes you are likely to have a lot of fluid on your floor, most outfits that attempt this kind of process have a vacuum pump that they attach to the the tank it can induce air into the system which may require bleeding out, another precaution is to lift the suction filter from the tank and enclose it it a plastic bag however this will only prevent fluid from the pump direction it will still syphon. The spool clamp is a. simple device that you can make if you look at the tube clamps those which two bolts that are no doubt on the machine use this principle for the spool clamp plus a handle to hold it tight. I am not sure how much space you have to do this in situ but you appear enthusiastic.
Good luck

giubu · Oct 12, 2019

hmmm, if I understand you correctly, I can use the threaded holes where the bolts of the cup fit to screw in a plate with a hole in the middle to compress the spring and then somehow get a grip on the head of the bolt to undo it?
Even imagining that I can get so far, will screwing this bolt further in give me the possibility to change the travel of the spool?
your insights are always greatly appreciated

uffex · Oct 12, 2019

I guess illustrations always work best
Kind regards
Uffex

Pressure gauges

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