snorkel TB60 / TBA60 low hydraulic pressure compensator or pump?

[archibaldtuttle]

I have a compensator that is bolted directly to the pump on this boom lift and I'm trying to figure out if it is maladjusted, worn spring, etc. or I have a bad pump.

the adjustment described as the pump main is already bottomed. Been that way since I before I bought it in 2014 and been running we the people for 4 years modest hours. Functions across board slowed or have been erratic last couple months and the deadheaded main pressures is only showing 1400 PSI which is half of desired.

manufacturer says it is probably pump but tach i know who is remote so can't come look says he always suspects compensator first. this is a 2006 unit with less than 2000 hours on it. I have no reason to suspect it was run low on oil or clogged filter or compromised in anyway although i have only had it for 4 of its 12 year life.

It appears although i don't have an internal schematic that the compensator design diverts flow that does not pass through the compensator orifice to return piping to the hydraulic tank. There are two adjustments on the assembly, one that manufacturer claims adjusts operating pressure and that is already bottomed. The other is the 'compensator' adjustment and i haven't cracked the cap off that yet as i'm trying to better understand what i'm dealing with.

The pump itself is a proprietary eaton made for snorkel. its possible i could take it off of there and spec it and see what is available that could replace it but don't want to replace it unnecessarily and i've got excavators with 25 year old pumps going strong so I'm hesitant to indict the pump with better diagnosis.

Any help anyone who has worked on one of these can offer much appreciated. And/or experience, if i just pull the pump and compensator off can i take them to bench tested?

thanks,

brian

 

[TVA]

I’m not familiar with Snorkel, Genie usually have two pumps: hydrostatic for drive and gear for functions.
Speaking of terms - “compensator” in open loop pumps play the role of pressure regulator, and others - just too many control options.
Can you sent me a picture? I will try to guess what type of control that is.

 

[TVA]

And the first thing I would do - usual maintenance checks, especially suction strainer and suction hose for the pump! Look for clogs, deterioration of the hose and possible places of sucking air!
I know you said you have no reason to suspect these things, but “never assume” !!! Instead of assuming - verify!!!

 

[TVA]

On the other hand - if you talking fixed displacement pump, then the other control could be pressure compensated priority valve! Which depending on pressure gives more or less flow to the system, and the rest of the flow goes back to the tank!
In this case you can run machine hard for a while and then with IR thermometer or thermal imager try too see what’s hotter - pumps body or the controls, the down side of it is the controls bolted to the pump and can transmit heat to the pumps body. If you confident in your mechanical ability, you can try to take controls apart and see if something didn’t get stuck or have some dirt in it. Just be careful, and take pictures as you go tohave an idea how to assemble it back.

 

[TVA]

I had problem with HIGHLY proprietary fixed displacement pump with integrated in to rear cover pressure relief valve and priority valve before, on Hyster forklift! Beside integrated components it had none standart shaft - mount combination, the pump was absolete and I couldn’t find it anywhere! And something THIS proprietary will cost you arm, leg and kidney anyway, even if you can find it.

The solution to this problem was to go to local Chelsey PTO dealer ( who sell stuff for tow and dump trucks ) and ask him to sell me Parker P16 pump, matched displacement, with shaft/mount combination I needed. Then buying Brand brand priority valve and plumb it to pump externally.
In my case priority valve didn’t dump oil back to tank - the steering and transmission ( in Series ) had the priority, and rest of the flow went to functions, as each circuit had its own relief valves I decided not to install one at the pump - but you can by in line one and install it.

That’s in case your pump is bad and it’s gonna cost you dearly!

 

[Knepptune]

I don’t believe a compensating valve is that expensive. The adjustment that’s bottomed out is most likely your standby pressure. The one that’s sealed is most likely your working pressure. Should be 600psi roughly at standby and 2700 psi working.

The only time the pump puts out 2700 is when you call for a function. Just deadheading the pump while not calling for a function you shouldn’t even have 1400 psi.

I’d bet the machine had an issue with not upstroking and someone figured out that if they bottom out the standby pressure the machine would work with 1400psi standby pressure. (Yes they’ll work for awhile like that.)

I’d buy the compensating valve from snorkel unless you feel confident adjusting it. Just so you know if you bottom that spring out on the working pressure it will build 10,000 psi in half a second, bust steel lines or split the pump in half. Play with it at your own risk.

Really the first step is to verify it’s getting the signal to upstroke.

 

[archibaldtuttle]

thanks for all the replies. my email is screwy so didn't realize i had them . its 50 deg. in RI today so i'm going out to work on this.

I don’t believe a compensating valve is that expensive. The adjustment that’s bottomed out is most likely your standby pressure. The one that’s sealed is most likely your working pressure. Should be 600psi roughly at standby and 2700 psi working.

according to attached adjustment pic that snorkel sent me it's the opposite.

The only time the pump puts out 2700 is when you call for a function. Just deadheading the pump while not calling for a function you shouldn’t even have 1400 psi.

i didn't fully explain. i deadheaded it by calling the retraction function when it was already fully retracted. that is the recommendation by snorkel.

I’d bet the machine had an issue with not upstroking and someone figured out that if they bottom out the standby pressure the machine would work with 1400psi standby pressure. (Yes they’ll work for awhile like that.)

I’d buy the compensating valve from snorkel unless you feel confident adjusting it. Just so you know if you bottom that spring out on the working pressure it will build 10,000 psi in half a second, bust steel lines or split the pump in half. Play with it at your own risk.

Really the first step is to verify it’s getting the signal to upstroke.

theres a stoke limit adjustment but nobody at snorkel mentioned checking or adjusting it. i'm not really physically understanding the concept of upstroke or stroke limit. help me out here. my plan, in any event since it doesn't look too hard (famous last words) is to drain the tank and check the suction screen per TVA and take off the pump with the compensator assembly and the accumulator and have them benched at a local shop. film at 11.

 

[TVA]

Your plan sounds like too much work at this point!
First thing I would do is to try readjust the pump - you never know!
I’m not familiar with machine, but I think there’s supposed to be provisionto get to suction strainer without draining the oil! Also check if there’s in line high pressure filter.

 

[archibaldtuttle]

Your plan sounds like too much work at this point!
First thing I would do is to try readjust the pump - you never know!
I’m not familiar with machine, but I think there’s supposed to be provisionto get to suction strainer without draining the oil! Also check if there’s in line high pressure filter.

according to snorkel my main pump adjustment is already bottomed. the hydraulic filter is on the return. I don't see how i could get to the suction filter without draining the oil. there is no high pressure filter. i would never mind taking the easy way out but i have a petcock on the drain and can easily position 5 gal buckets and shut off the drain to change buckets. its got a bout 20 gallon capacity. it has to be drained in order to pull the pump anyway. at this juncture, it being the middle of the winter when i'm not planning to work it for a couple months and knowing that the main adjustment is bottomed, i would kind of like to know a little better what i'm dealing with so i'm kind of committed to taking the thing in to a hydraulic shop.

 

[TVA]

OK, I hear you! Yeah just check suction strainer and if it’s good them take it to the test bench to check the efficiency and controllability!