HPS Troubleshooting Tactics: Common Hydraulic Valve ...

This is final article in our &#;Problem Solving Series,&#; where we will discuss approaches to identifying & resolving different issues that can plague a hydraulic system.

Huade Hydraulic contains other products and information you need, so please check it out.

Diagnosing and fixing valve issues may take a little bit of troubleshooting, and we&#;re here to help.

Once a problem arises, it&#;s always better to systematically solve it by looking at the most common problems first, and avoid simply changing random parts, which can cost downtime, be disorganized, and result in a misdiagnosis.

The Fail-Safe Condition of an improperly functioning valve is important. Knowing what happens on the machine when a valve failure occurs may make the difference between somebody getting hurt or not. ISO standards such as : provide general rules and safety requirements.

Hydraulic Valve Failure Modes typically result in the actuator or pump not performing correctly. A hydraulic valve typically has either a mechanical or electrical failure mode. Let's take a look at some common issues in each mode, and then let's look at some common problems and issues that caused them according to valve type.

Top Issues to Look For in Mechanical Valve Failure Mode

The Fail-Safe Condition of an improperly functioning valve is important. Knowing what happens on the machine when a valve failure occurs may make the difference between somebody getting hurt or not. ISO standards such as : provide general rules and safety requirements.Hydraulic Valve Failure Modes typically result in the actuator or pump not performing correctly. A hydraulic valve typically has either a mechanical or electrical failure mode. Let's take a look at some common issues in each mode, and then let's look at some common problems and issues that caused them according to valve type.

The most common source of mechanical hydraulic valve failure is due to extended hydraulic fluid contamination, resulting in the hydraulic fluid and filters being replaced. Often, the pressure-reducing valve will not reach the appropriate pressure or the directional control valve will not operate the actuator or motor properly. 

Other issues include:

• Spool stiction: The spool does not completely shift, and the actuator or motor does not fully actuate to the open or closed position. In the case of a directional control valve, the downstream motor or actuator does not operate properly.

• I

  nadequate flow to the valve:

  Often caused by issues with pump cavitation, plumbing restrictions, or the hydraulic tank fluid level not being full enough for the suction side of the pump.

• Incorrect sizing: Typically caused when the flow requirements are greater than the valve flow rating. An undersized valve will not operate an actuator or motor at the proper speed. An oversized valve will likely operate fine but could result in a larger pressure drop out of the A&B ports to the actuator or motor.
• Seal wear: Sometimes a valve seal wears and causes a leak, reducing or stopping the performance of the valve.

Top Issues to Look For in Electrical Valve Failure Mode

The most common electrical failure mode issue is caused by not meeting the minimum voltage requirement at the valve solenoid to always shift the valve. Check the voltage at your power supply and at the solenoid valve when shifting to fully know your voltage drop.

The next most likely issue resides with intermittent performance due to poor electrical connector or wiring. Loose connections or worn terminations at electrical connectors may cause the valve solenoid to not always actuate.

Improper voltage going to the solenoid is a third issue that can lead to failure. Solenoids are rated as either Alternating Current (AC) or Direct Current (DC). If the incorrect voltage type or rating is applied, the solenoid will likely fail.

Possible Causes to Common Problems By Valve Type

There are many different types of hydraulic valves, and many ways in which each can malfunction.

There are many different types of hydraulic valves, and many ways in which each can malfunction.

Complexities for each valve do not make troubleshooting easy, so let&#;s start by considering how each type of valve should be evaluated for common problems.

Although there are dozens of varieties that all serve different purposes, we will focus on issues and common causes that lead to them among

Pressure Control Valves (Pressure relief valves, pressure-reducing valves, and sequence valves, 

Directional Control Valves and 

Flow Control Valves.

1. Pressure Control Valves

Pressure Relief Valves

Common IssuesPossible CausesLow or erratic pressure
Adjustment off, contamination, wear and tear, sticking, spring damage
Low or no pressure
Valve is loose, poppet is off, orifice or balance hole is plugged, spring is broken, debris holding valve open
Excessive noise 
High oil viscosity, worn poppets, excessive line pressure return, pressure settings off
Excessive system pressure when adjusting
Broken or worn spring, improper spring, drain line restricted
System overheating
Relief setting is off, high viscosity, leaking valve seat

Pressure-reducing Valves

Common Issues     Possible CausesErratic pressure
Oil contaminants, restricted orifices, valve spool binding, improper spring, worn poppet or seat

Sequence Valves 

Common Issues                Possible CausesNot functioning
Broken spring, contaminants in plunger seat or orifices, leaky or blown gasket, plugged drain line, worn plunger, oil impurities, overheating
Premature movement to secondary operation
Excessive or high inertia load on a primary cylinder, valve setting is low
Slow or no movement
to secondary operation
Relief valve setting is too close to sequence valve setting, spool binding, valve setting is high

2. Directional Control Valves

Common IssuesPossible CausesIncomplete shifting
Centering spring defective, spool adjustment, worn or binding linkage, low pilot pressure
Actuator shifting
Spool is worn, shifted, or not centering; cylinder or valve seat leakage
Cylinder load dropped
Loose lines in valve housing, broken spring, leaking relief valves or O-rings, spool valve position is off

3. Flow Control Valves

Common IssuesPossible CausesVariations in flow
Spool binding, leaks in cylinder, oil is dirty or has a high viscosity, low pressure
Erratic pressureWorn poppet or seat, oil is dirty
Slow flowPiston travel or orifices restricted, leaky relief valves, oil too hot, valve piston is cocked

For more on the common causes and problems of hydraulic valves, visit the

Adjusting and Verifying

After figuring out any valve issues and causes of those issues, it&#;s time for action. 

For more on the common causes and problems of hydraulic valves, visit the Caterpillar manual After figuring out any valve issues and causes of those issues, it&#;s time for action.

Depending on what problem was identified, you may need to:

• Set the relief valve
• Install pressure gauges and adjust to the correct pressure
• Repair or replace damaged or worn parts
• Fix any functional issues
• Clean and replace hydraulic fluids

After making any adjustments, complete any essential checks and run the system. Monitor for pressure, temperature, and sound changes. 

After making any adjustments, complete any essential checks and run the system. Monitor for pressure, temperature, and sound changes.

If all seems to be running smoothly, do a final verification by checking the pressure sensor for potential failure.

Planning Ahead

With all systems a go, you may want to include the problem in a scheduled preventative maintenance program.

A preventive program may include:

• Investigation of fluid health and appropriate lubrication
• A strategy for adding critical filter locations to trap more particles
• A schedule for fluid and filter changes
• Filter change-out according to pressure differential, adding a pressure gauge or indicator
• Installation of electrical monitoring devices of filter differential pressure or analog transducers to log trends
• Automatic supply re-orders

Any preventive maintenance program should be clearly defined with well-documented maintenance activities, and the plan should be regularly reviewed and adjusted if necessary.

Any preventive maintenance program should be clearly defined with well-documented maintenance activities, and the plan should be regularly reviewed and adjusted if necessary.

Hydraulic Parts Source is a leading fluid power remanufacturer, and we&#;re ready to serve you. Contact us today to discuss forming an alliance by calling (888) 477- or get a quote by emailing .

bshannon

Posted 6/2/ 08:01 (#)
Subject: Open Center/Closed center hydraulics questions

.

What is the difference? I know my red tractors have open center hydraulic systems, and the Oliver I used to have and the have closed hydraulics. My son went out and bought a John Deere (i think) VRT planter this spring. From what I can tell the John Deere is the only one he can use on this planter due to the closed center hydraulic system. Is there any kind of get around to use on open center systems like a PTO pump? I am thinking of purchasing another tractor and it will probably not be a John Deere, but I would like it to be capable of being the planter tractor.
jdbob

Posted 6/2/ 08:10 (# - in reply to #)
Subject: RE: Open Center/Closed center hydraulics questions

ND

The JD pto pump will run one Vac but with an old style open center tractor if you placed an orbit motor on planter for Liq Fert the open center tractor would lose its hyd pump in short order. All orbit motors used by farm tractors need closed center-if your against JD buy a MF or or or a White 2-105,,or a 135 or 155 or 180 or a Case or larger Case tractors in this series. thorfarms

Posted 6/2/ 08:19 (# - in reply to #)
Subject: RE: Open Center/Closed center hydraulics questions

Lincoln, North Dakota

If you are looking for more details, kindly visit hydraulic directional valve.

Open center hydraulic system used a fixed displacement pump like a gear pump and are protected by a relief valve. They have constant flow. Any valves used with open center have to have an open path back to return while in neutral. Closed center hydrualic systems use pumps that are variable displacement or on demand. In closed center hydraulic systems there is no open path back to return untill a valve is moved. When the hydraulic valves are in neutral and there is no demand for flow the hydraulic pump operates in a standby mode untill there is a request for oil flow.

Edited by thorfarms 6/2/ 08:22

wht one

Posted 6/2/ 08:39 (# - in reply to #)
Subject: RE: Open Center/Closed center hydraulics questions

E. CO, exactly half way between NE and OK

I think my White 135 is open center hydraulic and my Case IH is closed center. Pat H

Posted 6/2/ 09:10 (# - in reply to #)
Subject: RE:Further simplification

cropsey, il

Open center (Simple) - think of a gear pump - to gears meshing together pushing fluid through. The valves in open center systems allow flow to go through them all the time. When you use a valve it redirects the flow to the outlet. If the flow dead heads, a relief valve will open and allow flow to go through. Usually this makes a high pitch whine noise when the relief is open. Without the relief valve something would break.

Closed center - the pump is a version of the hydro pump on a combine where it controls how much it pumps (on a combine, the hydro lever controls flow and pressure usually determines flow on a closed center tractor pump). The valves in a closed center shut completely off when flow isn't needed and direct flow to the cylinder etc. when you use the valve. The pump senses the drop in pressure (or other factor) and starts pumping more fluid (takes milliseconds). When you shut the valve the pump senses the rise in pressure and shuts down. Closed centers have a relief as well in case of an over pressure situation (something broke or ?).

Older tractor used open center systems because it's simple and cheap. The drawback is fluid is always chasing through the system and that takes power and creates heat. The closed center system is more efficient. Most of the time, planters, etc. don't care which system supplies hydraulic pressure. You can get into situations where you need to reduce the flow to a fan or similar and if it's enough, the pump will see the port as closed and shut down. A lot of times fans use a bypass line to allow a little more flow and to allow the fan to coast to a stop when the hydraulic valve is closed.

GM Guy

Posted 6/2/ 09:22 (# - in reply to #)
Subject: RE: Open Center/Closed center hydraulics questions

NW KS/ SC ID

wht one - 6/2/ 07:39

I think my White 135 is open center hydraulic and my Case IH is closed center.

Your White 2-135 has a Flow Compensating Closed Center hydraulic system. Similar to JD. Allis was the first and the only for a while, with a PFC (Pressure and Flow Compensating) Closed Center system.

Oliver came out with closed center on the 55 series, so All White products (over 100 hp at least) will be closed center.
wht one

Posted 6/2/ 12:09 (# - in reply to #)
Subject: RE: Open Center/Closed center hydraulics questions

E. CO, exactly half way between NE and OK

Bill, I didn't know that, how do I adjust the flow rate on the White? wht one

Posted 6/2/ 12:19 (# - in reply to #)
Subject: RE: Open Center/Closed center hydraulics questions

E. CO, exactly half way between NE and OK

jdbob - 6/2/ 07:10

The JD pto pump will run one Vac but with an old style open center tractor if you placed an orbit motor on planter for Liq Fert the open center tractor would lose its hyd pump in short order. All orbit motors used by farm tractors need closed center-if your against JD buy a MF or or or a White 2-105,,or a 135 or 155 or 180 or a Case or larger Case tractors in this series.

I think you can use an open center hyd system on a hydraulic motor if you use all the oil it pumps. We ran a hyd fan on a Flexicoil air seeder with a Steiger tractor that had open hyd system. We mounted a belt driven hyd motor to drive the fan. We put a flow valve on it to by pass part of the oil so we could regulate the speed. newag1

Posted 6/2/ 14:22 (# - in reply to #)
Subject: RE:Further simplification

WNW Illinois, Henry Co

WNW Illinois, Henry Co

Pat,

very good explanation,

Starting with the 81 year model IH 86 series, they are all PFC, closed center, as were Case tractors of same vintage.

i remember going to a sales meeting in , intoducing them to the dealers, and they were bragging how good the system was, and oh yeah case also had it. then a few years later Case had IH too.

so most any, (Certainly not every) model had closed center since in the red series. dont know about any others except the JD ones as there were hardly any dealers of others around after the 80s

good luck

Edited by newag1 6/2/ 14:23

rancherman

Posted 6/2/ 14:28 (# - in reply to #)
Subject: RE: Open Center/Closed center hydraulics questions

I ran our  JD vac planter for the first time this year with my MF tractor.   Used to pull it with the  ,  and  even the in the early years of the planters' life.  Worked fine with the  open center.

 

Both JD's are closed center,   but my MF is  open.    Oil temp is going to be higher with the open center. It's just a  fact of physics.    It's going be important to  make sure to route the discharge  the return flow directly to sump.  If you just  hook the discharge back to the service valve outlet,   some of this extremely hot oil is going to  be recycled back into the charge circuit.  A fairly large portion is routed  directly back to the  intake side of the  Hyd pump,  without the benefit of cooling in the sump.   Dumping 100% of return  to sump  at least  ensures  some cooling before  starting over again.

a  open center  in neutral makes very little pressure in the  circuit.  Very little heat, very little drag. 

  When you  pull the lever, ALL the oil in the circuit is  forced  down the work path,  and if  the work  is less than  what is being supplied,  then the relief valve  dumps the excess  back to  sump.   Oil flowing over  either   the work, or  the relief is going to  make pressure (system rating)  and  this is where the heat comes from.    Neat thing about  the closed center, is  that they only supply  the exact amount of  volume as  what the work requires.  No gobs of  excess flowing over a  relief valve making  even  more heat! 

Even  on our  ,  we  were told to dump the return directly to sump.   My   8 row planter uses a tiny orbit motor, and the   was able to keep up.  Apparently,  by the time the 50 series  came about,  it's ok to just use the service coupler for  return.  It had higher capacity pump.   

Closed center also relies on  a certain amount of  return to  supply the intake side of the pump.

Ever notice  when you lift a  single action cylinder  dump wagon,   how an  early JD  will chatter  after lifting  about  halfway up?    It needs  time  to recharge its  internal  reservoir..  and  can  continue  after waiting  just a couple seconds.   It's  'starved'  because a  single  action  cylinder doesn't send  return back to the intake side of the pump.

ronm

Posted 6/2/ 18:29 (# - in reply to #)
Subject: RE:Further further simplification

Fruita CO

The water system in your house is like a closed center system. Pressure is there all the time but no flow until a valve is opened. The irrigation ditch in front of my place is like an open center system...it runs all the time until I throw a dam in & open a headgate to divert water. GM Guy

Posted 6/3/ 09:44 (# - in reply to #)
Subject: RE: Open Center/Closed center hydraulics questions

NW KS/ SC ID

wht one - 6/2/ 11:09

Bill, I didn't know that, how do I adjust the flow rate on the White?

Bill is my dad, and That is an excellent question that hopefully Robert Greif or Kooiker know the answer too. :)

On the allis there is a little half turn valve with an indicator that comes through the cab floor on the 2wds and you can adjust it in the cab.

The White, all we have done is lower the system pressure with the screw under the cab so the pump doesnt have to work so hard.

After reading here on NAT, we became aware of a pressure relief valve, and I hope we were not adjusting it, as that would cause system overheat since its always in bypass.

Since all we seem to do with the White's is tillage (its what that big ol long frame does best! :) ) we like lowering the PSI so it will still lift the blade plow, but not much more. GM Guy

Posted 6/3/ 09:52 (# - in reply to #)
Subject: RE:Further simplification

NW KS/ SC ID

So they were PFC, not just PC? So that just left JD and White with PC and everyone else was running PFC?

Allis debuted PFC with the series in 73. Amazingly it works great. We never havy hyd. problems on our old allis', but the Whites seem to give fits. jdbob

Posted 6/3/ 12:00 (# - in reply to #)
Subject: RE:Further simplification

ND

Everyone complains on JD that its all about their marketing but on the 30 series you can adjust flow right on the remote & that has nothing to do with marketing people but Design People. Thinking the late 20 series had this design as well. The rabbit & theturtle flow lever. Really no other company had this remote valve but correct me if I'm wrong. GM Guy

Posted 6/3/ 15:47 (# - in reply to #)
Subject: RE:Further simplification

NW KS/ SC ID

allis had in cab control. a feature not found on JD till the series? :)

In all seriousness, it seemed to accomplish the same thing the JD flow rate control did, but it was done with a little arm in the cab under the seat. Allis only came standard with one control rod, but the others could easily be added.