Pressure Relief Block, Curtis plow

[J_J]

SpudHauler, Are you using SA cyl, and if you did, did the B port go to tank? Do you have pic of your cyl?

 

[glastron23]

RickB totally agree, this circuit needs protection from induced pressures (fetching the blade on a big rock) some thing has to give, he got lucky and it was the bolts and not something REALLY expensive. JJ a relief to protect a cylinder needs to be higher, it's only function is to protect the cylinder/arms/hoses/valve body etc from induced load shocks and not to relieve the system pressures when in use.

 

[AKKAMAAN]

When do you ever set a downstream relief valve higher than system pressure?

This is for work port pressure relief valves....

When you want to prevent a function from "folding" from external force that creates higher pressure than pump pressure....

Example:

1>Knuckle boom crane, boom cylinder will drop when stick extends the length of the entire arm

2> steering cylinder on logging equipment, cant allow "folding" when you drive into a stump etc...that would jack knife the machine...


edit!
System PRV and work port PRV are protecting two separate parts of the system....separated by the spool valve (CV)....

I was once taught that the system PRV was a PUMP PROTECTION and the work port prv was a MOTOR/CYLINDER PROTECTION....I still like to express it that way...

Sometimes the structure can hold higher forces than pump can create, and a plow blade could eventually be a perfect example of that....

 

[RickB]

SpudHauler, Are you using SA cyl, and if you did, did the B port go to tank? Do you have pic of your cyl?

Snowplow angle cylinders don't have 'B' ports. The posted photo shows two cylinders with a single hose each. The butt end of the rod is the effective piston area. The rod seal is the only sealing element.

 

[J_J]

Every single time that the RV is protecting a work circuit from shock loading when the spool is centered and the work ports are isolated. Backhoes, snowplows, whatever. If nominal system pressure is 2500 psi or so, circuit relief valves are typically 2750 -3000 psi.

If the work ports are blocked, then you could set the relief pressure anywhere. What if the cyl are 2500 psi cyl?

 

[kennyd]

Thanks Rick, at least we understand how they work-hopefully Spud does now also:thumbsup:

 

[Duffster]

SpudHauler, Are you using SA cyl, ?

Did you look at the pics?

 

[J_J]

I do understand work port relief, and shock load. I am still looking at the selector valve, and the number of hoses attached.

 

[J_J]

Did you look at the pics?

Apparently I did not see that pic. Was it there at the start of the post?

Getting old sucks.

 

[RickB]

If the work ports are blocked, then you could set the relief pressure anywhere. What if the cyl are 2500 psi cyl?

If the system relief is 2500 PSI and the circuit relief is 2000 PSi, no more than 2000 psi can be applied to the cylinder in question. Components are supposed to be designed to withstand maximum system pressures. If the design calls for circuit relief @ 3000 psi those components better be chosen to handle it.

Give it up. You are wrong on this. I'm not going to sit here all night and debate with you. Guys from Jacksonville, FL need to be careful handing out snowplow advise. Some of us know a little more about the subject.