Any Enerpac Experts or experience on the Forum?

[awemawson]

I'm re-building an EPCO 60 ton 'Garage Press' - I've replaced the double acting piston seal assembly as it was passing oil from one side to the other, but now that's all fixed a fault has developed in the Enerpac Hydraulic power pack.

It's an Enerpac BPE 14485 pump unit, with an Enerpac BVS 4 electrically operated change over valve. Pump will develop up to 10,000 PSI (yes TEN THOUSAND PSI not a typo!). The spool valve is operated by a remote pendant with an 'up' and a 'down' button. Both seem to work fine as I can hear the appropriate pilot valve click when the button is pressed.

When the Down button is operated, oil is fed to the top of the cylinder correctly, and if the press is squashing something pressure builds up and is held when the button is released - this is correct. However when the Up button is pressed it is supposed to release the pressure in the top of the cylinder and introduce oil into the bottom to raise the piston - this is not happening and the press continues to hold pressure for as long as you leave it, even without the pump.

I've been testing at 4000 psi to give my new seals a chance to bed in, and I've just had to release that pressure by cracking a fitting - wasn't too keen on that.

It all looks like the spool for the 'Up' isn't following the pilot but looking at it I'm not sure stripping it and rebuilding is in my competence. Hence seeking advice / contacts / sympathy / replacement.

Here are a few pictures and the details of the spool valve assembly:

[smiffy]

In the valve block there must be a pilot operated check valve and this is not getting a signal to open the valve . The  hole in the check valve for the signal is usually very small and become easily blocked .Is there a separate block underneath the operating valve as this is where a check valve should be  Mike

[awemawson]

Mike, if you open the .pdf file attached to my first post, there is a full drawing of it.

Some of the caveats in that document are what is making me think twice about opening it up, but I suspect you are right about something being blocked - the whole system has been disturbed so a bit of gunge could easily find it's way where it shouldn't 

[Lew_Merrick_PE]

Andrew -- The valve controlling the cylinder is a 4-Way/3-Position/Blocked Center valve.  The best thing (for you) would be that the Return Line from the "advance ram" plumbing has been clogged or blocked.  The next (as Smiffy wrote) is that the Pilot Actuator has been clogged or blocked.  Otherwise, it is going to me "bubble chasing Heaven."

[smiffy]

I had  similar problems on loading bridges at Heathrow ,Turned out that on assembly loctite had been used and as soon as any fittings were disturbed small bits of loctite entered the system and ended up blocking the  pilot valve holes which were only about 25thou in diameter
Parts 51 or 48 might be suspect . All I can see is a parts diagram not  a hydraulic diagram  Mike

[mexican jon]

Just a thought, where are you cracking the fitting to release pressure? are you doing it at the ram or the pump? the reason for asking is that the quick connects that you have on the end of the hoses sometimes don't open the check valve within the quick connect properly. It'll allow pressure to pass in 1 direction but will close and lock the pressure when you try to flow in the other direction.

[awemawson]

At the cylinder Jon. I had the same thought as you, and today's job is to turn up a pair of fittings to couple the quick release females unscrewed from the cylinder to a pair of 16000 psi gauges that I find I have on the shelf. That way I can put one on the end of each Enerpac flexible hose and see what's happening.

[mexican jon]

At the cylinder Jon. I had the same thought as you, and today's job is to turn up a pair of fittings to couple the quick release females unscrewed from the cylinder to a pair of 16000 psi gauges that I find I have on the shelf. That way I can put one on the end of each Enerpac flexible hose and see what's happening.

We use the same fittings for our enerpac's and also our BOP's and they are known to be an issue Hopefully it's just the fittings and you don't need to strip the pump down 

[awemawson]

Well the plot thickens 

With just the Enerpac flex hoses, sealed at their far ends by virtue of the male quick disconnect, I can pump either of them up to 9,000 psi, and they will release when the other direction is operated. You can tell that they release, as when at that pressure the hose is very stiff and tries to unwind.

With my test fittings made up this morning that allow me to fit 16,000 psi gauges on the ends via female quick disconnects that I have removed from the cylinder, exactly the same operation. Pump one up by pressing the button on the pendant, let the pendant button relax and the pressure is retained. Press the other pendant button, and after a short delay the original side is relaxed and the new side pressures up. Now I notice that the original side doesn't relax until the other one builds up a bit of pressure hence the delay.

So I removed the robbed female fitting from one gauge and fitted it to the top of the cylinder - inspecting it's mounting hole carefully - I was sure it WAS just a hole and no valve was lurking in there 

Now I can pressurise the cylinder such that it gets to my set point of 4,000 psi AND release the pressure, but remember the other hose is not connected and still blocked by it's q/d fitting.

Returning the other hose to the bottom of the cylinder I can no longer release the pressure.

My tentative conclusion at the moment is that in the 'UP' direction the hydraulic pressure isn't building up enough when connected to the cylinder to operate whatever it operates and I need to find out WHY.

...all very confusing, trouble is that a few years back when I rebuilt this press after it's disastrous fire, I don't think that the piston seals were correct - certainly it never would get to the pressure that it should have and I suspect was leaking across the piston - this may have been overcoming the issue that I am now seeing 

[awemawson]

  SORTED 

It was the lack of pressure in the lower portion of the cylinder 

It occurred to me that the cylinder still hadn't done a full stroke in both directions, so there must be air trapped at least in the lower portion. Now I had a bit of a large weep from the end cap of the cylinder (at the bottom as it sits). There is a  5" diameter male thread of 12 turns that screws into a female thread in the end of the cylinder bore, and there is a recess for a 1/4" x 5" diameter 'O' ring to squash between a shoulder and the end of the cylinder to do the sealing. I'd fitted a new 'O'ring but obviously things weren't quite right - what to do? Well it would be possible to replace the O ring without fully dismantling (starting that 5" thread is a b****r in situ) - so I unscrewed 10 turns, inspected the O ring which actually looked fine, but wound some thick PTFE tape round the exposed threads and screwed it firmly back together. I'd have liked to use Loctite hydraulic thread seal, but if the weep wasn't cured I'd never get it unscrewed again 

So I gingerly  drove the cylinder fully extended to minimise lower volume then re-assembled the hydraulic connection for the lower chamber and started to pump it back up to the top. It takes about 8 minutes and 20 seconds to fully extend, and due to the fat 4" rod, "only" 3 minutes to retract.

Hey presto - not only did it work in that the cylinder would reverse, the end cap leak was fixed 

So my conclusion is that the Enerpac pump needs to establish pressure in the 'opposite' direction in order to release pressure in the other, and because of the air in the cylinder and the low rate of pumping that pressure had never been established.

So now I'm a happy bunny and it works I'll post a thread about the state this press was in when I got it as I don't think I documented it here  When done I'll edit a link into this post.


Link to rebuild thread is here :


http://madmodder.net/index.php/topic,11437.msg133941.html#msg133941