Hydraulic pressure relief valve stopped holding
 

We are installing a "PTO wet kit" on our truck.

The kit, that I bought at a truck parts store, consists of a Muncie
PTO, 13 GPM gear pump, and a pressure relief valve with a cartridge
similar to Sun RPGC-LAN. I say "similar to" because the actual model
is a fixed pressure RPGC-L2500N, but it is hard to find anything in
google about that model number. RPGC-LAN is a number that is easier to
find.

I had a tank that I put to use.

Anyway, we did a first test of the system, with the output and return
hoses connected directly to each other. No problem.

Then we left the hoses disconnected, so that there was no circuit, and
proceeded to run the pump to test the relief valve at full pressure
and to warm up the oil quicker.

At first everything was great, pressure held at 2500 PSI, everything
was flowing. After a while, though, something happened and pressure
dropped to 500 psi, then more.

I started looking. The pump pumps with good flow, I know this because
I pumped some oil into a bucket.

Took out the pressure relief cartridge. I found out, to my surprise,
that it is very easy to puch the piston in with a plastic pen. If it
is a 2500 PSI valve, it should have taken a force of several hundred
pounds. Instead I can easily do it by hand.

The picture is he

http://www.sunhydraulics.com/model/RPGC

I do not really understand what could have happened and why this valve
could fail and become so easy to open.

Would anyone have any idea? What could it be?

Thanks

i

i

Hydraulic pressure relief valve stopped holding
 

I do not really understand what could have happened and why this valve
could fail and become so easy to open.

Would anyone have any idea? What could it be?

The spring inside it broke
i

Hydraulic pressure relief valve stopped holding
 

On 2015-03-06, Karl Townsend wrote:

I do not really understand what could have happened and why this valve
could fail and become so easy to open.

Would anyone have any idea? What could it be?

The spring inside it broke
i

That is what I think too -- but I wonder, how could that happen?

i

Hydraulic pressure relief valve stopped holding
 

"Ignoramus21464" wrote in
message ...
On 2015-03-06, Karl Townsend
wrote:

I do not really understand what could have happened and why this
valve
could fail and become so easy to open.

Would anyone have any idea? What could it be?

The spring inside it broke
i

That is what I think too -- but I wonder, how could that happen?

i

My Husqvarna chain saw eats expensive made-in-Germany clutch and
recoil starter springs.

-jsw

Hydraulic pressure relief valve stopped holding
 

On Thu, 05 Mar 2015 20:50:12 -0600, Ignoramus21464
wrote:

On 2015-03-06, Karl Townsend wrote:

I do not really understand what could have happened and why this valve
could fail and become so easy to open.

Would anyone have any idea? What could it be?

The spring inside it broke
i

That is what I think too -- but I wonder, how could that happen?

Material or procedural defect in the manufacture of the spring.

--
Stain and poly are their own punishment.

Hydraulic pressure relief valve stopped holding
 

Karl Townsend fired this volley in
:

The spring inside it broke

That's the most likely scenario. How many decades has it been running at
near top pressure in a "full-singing chatter mode?" G

When they squawk (and of course they inevitably do), they're wearing out
ball, seat, and spring.

Lloyd