What should the minimum safety factor be for a cartridge valve in a load holding application?
Ed Danzer
Ed Danzer
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Safety factor for a cartridge valve?
- Thread starter EdDanzer
- Start date
I would say at least 2:1, but it depends upon the application. That is 2 times the maximum working pressure not 2 times the cracking pressure.
If the application is well guarded and there is minimal possibility of a burst valve causing serious damage or harm, then 3:1 would be adequate.
A load holding valve on a theme park ride should be at least 5:1 as there is an obvious risk if the valve fails.
This is where risk assessments work best.
Also...it is more often the case that the failure mode is a split or crack in the manifold, especially with aluminium or brass alloy manifolds.
Adrian
If the application is well guarded and there is minimal possibility of a burst valve causing serious damage or harm, then 3:1 would be adequate.
A load holding valve on a theme park ride should be at least 5:1 as there is an obvious risk if the valve fails.
This is where risk assessments work best.
Also...it is more often the case that the failure mode is a split or crack in the manifold, especially with aluminium or brass alloy manifolds.
Adrian
As high as you can get. Just check all the manufacturers catalog ratings. You can even look at the "Minimum Burst Pressure" in some catalogs to see how much it takes to destroy a valve.
You must have a reason for asking a wide open question like that Ed.
I have found pressure ratings mean nothing when a poorly designed circuit sees Pressure Spikes 3-6 times Relief Valve or Pressure Compensator setting and 3,000 PSI equipment blows or cracks and the Gauge says 2,500 PSI at rest.
I've often had a Pressure Gauge installed on a system that I suspected had a Pressure Spike problem. However, I put a Check Valve, Free Flow into that gauge so I could see how hih Pressure was getting after the circut ran for a few shifts. It's surprisng to see a gauge on a 1,500 PSI circuit reading 4,200 PSI the next day after installing that setup. No need to wonder why the components are failing in such a short time.
Pressure Spikes cause more damage to hydraulic Plumbing and Components than a lot of people imagine.
Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING
You must have a reason for asking a wide open question like that Ed.
I have found pressure ratings mean nothing when a poorly designed circuit sees Pressure Spikes 3-6 times Relief Valve or Pressure Compensator setting and 3,000 PSI equipment blows or cracks and the Gauge says 2,500 PSI at rest.
I've often had a Pressure Gauge installed on a system that I suspected had a Pressure Spike problem. However, I put a Check Valve, Free Flow into that gauge so I could see how hih Pressure was getting after the circut ran for a few shifts. It's surprisng to see a gauge on a 1,500 PSI circuit reading 4,200 PSI the next day after installing that setup. No need to wonder why the components are failing in such a short time.
Pressure Spikes cause more damage to hydraulic Plumbing and Components than a lot of people imagine.
Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING
MikeHalloran
Mechanical
That's a damn sneaky (and most excellent) diagnostic tool, Bud.
Thanks.
Mike Halloran
Pembroke Pines, FL, USA
Thanks.
Mike Halloran
Pembroke Pines, FL, USA
I am not so sure that valve manufacturers would publish data that states the pressure at which their valves would fail.
Cartridge valves are obviously a good fit in a machined cavity. The material of the manifold supports the valve when it is exposed to the forces created by the internal pressures. The valve manufacturers would have to test all materials and publish the lowest failure pressure.
What if they test a low grade aluminium block and get a failure pressure of 7500 PSI? Someone could pickup a valve and make their own manifold from an even lower grade of aluminium and the failure could be at 3000PSI. This would lead to lots of questions being asked.
It is more likely that valve suppliers would offer a machined manifold of a known quality and they would state the maximum working pressure. Also slight differences in material and machining tolerances can make the burst pressure vary quite widely.
In my time I have seen many low pressure 'devices' working at pressure well over 10 times their rated pressure. It's really down to the application on how long things will last before they break.
Where a pressure gauge reads say 4500 PSI, a picoscope or similar high frequency transducer will see at least 50% more. where a gauge reads 4500 PSI, the pressure will have actually reached about 6500-7000 PSI, but only for a mateer of milliseconds per spike.
Adrian
Cartridge valves are obviously a good fit in a machined cavity. The material of the manifold supports the valve when it is exposed to the forces created by the internal pressures. The valve manufacturers would have to test all materials and publish the lowest failure pressure.
What if they test a low grade aluminium block and get a failure pressure of 7500 PSI? Someone could pickup a valve and make their own manifold from an even lower grade of aluminium and the failure could be at 3000PSI. This would lead to lots of questions being asked.
It is more likely that valve suppliers would offer a machined manifold of a known quality and they would state the maximum working pressure. Also slight differences in material and machining tolerances can make the burst pressure vary quite widely.
In my time I have seen many low pressure 'devices' working at pressure well over 10 times their rated pressure. It's really down to the application on how long things will last before they break.
Where a pressure gauge reads say 4500 PSI, a picoscope or similar high frequency transducer will see at least 50% more. where a gauge reads 4500 PSI, the pressure will have actually reached about 6500-7000 PSI, but only for a mateer of milliseconds per spike.
Adrian
stroupaloop
Mechanical
After reading the responses here, from my experience, you will or can find out the maximum operating pressure as well as the burst pressure of valves. Perhaps not all vendors will initially supply the information, but any well-respected company will have test data on their valves performance, one specifically being the burst failure, requiring them to take the valve up to "failure" pressure. On a sidenote, its quite fun to watch this happen behind a nice thick piece of plexi-glass as they destroy a valve.
Additionally, Bud makes a very good point. His method of measuring the "highest" pressure seen within a system is a great way to initially identify dynamic changes within the hydraulic system. For instance, most pressure gauges, under a DAQ system, will not carry enough response time to record some of the natural pressure spikes generated from operation. Although perhaps sometimes it may not be as important to note some of these being that they only occur for milliseconds, it is still nonetheless important to recognize they do exist and can cause potential harm to the system.
Additionally, Bud makes a very good point. His method of measuring the "highest" pressure seen within a system is a great way to initially identify dynamic changes within the hydraulic system. For instance, most pressure gauges, under a DAQ system, will not carry enough response time to record some of the natural pressure spikes generated from operation. Although perhaps sometimes it may not be as important to note some of these being that they only occur for milliseconds, it is still nonetheless important to recognize they do exist and can cause potential harm to the system.
- Thread starter
- #7
Thanks for the responses. The cartridge valve manufacture rates the valve a 5,000 psi maximum working pressure and has a fail pressure of about 17,000 psi. I think it starts to fail at just over 5,000 psi.
We will be sending a new valve to a testing lab to test my theory.
Ed Danzer
We will be sending a new valve to a testing lab to test my theory.
Ed Danzer
Hi, Pl see below technical information you can see from Sun hydraulics:-
Counterbalance valves should be set at least 1.3 times the maximum load induced pressure.
These valves have load holding function, pilot to open the valve with a additional function of relief valve. This setting of relief valve is also called as setting of counterbalance valve which should be at least 1.3 times load induced pressure.
I hope, it is clear.
Rajan Bedi
FLUID POWER CONSULTANT
Rajan Bedi
THE TECHNICAL ASSOCIATES
Counterbalance valves should be set at least 1.3 times the maximum load induced pressure.
These valves have load holding function, pilot to open the valve with a additional function of relief valve. This setting of relief valve is also called as setting of counterbalance valve which should be at least 1.3 times load induced pressure.
I hope, it is clear.
Rajan Bedi
FLUID POWER CONSULTANT
Rajan Bedi
THE TECHNICAL ASSOCIATES
- Thread starter
- #10
The valve is a Sun CKGB-XEN and the threaded body material starts to yield at 6200 psi according to a test done by Bodycoat in Portland Oregon.
We have contacted Sun about fixing the problem with no positive results yet.
The way to know if you are having this failure you will see o-ring failure on the nose piece, a piece break off the threaded body where the lock ring is inserted, or just excessive axial movement of the nose piece.
If you are having problems with Sun Pilot operated check valve visit for contact information and call Ed Danzer.
Ed Danzer
We have contacted Sun about fixing the problem with no positive results yet.
The way to know if you are having this failure you will see o-ring failure on the nose piece, a piece break off the threaded body where the lock ring is inserted, or just excessive axial movement of the nose piece.
If you are having problems with Sun Pilot operated check valve visit for contact information and call Ed Danzer.
Ed Danzer
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