View Full Version : Yet another Denford triac at fault!

21-02-2018, 11:07 AM
My Triac has developed another fault on the ATC..

When tool changing the carousel comes in to the spindle really slowly,then gets stuck just pressing against the spindle,I can hear lots of air exhausting from somewhere,which drains my compressor below 100psi, then the compressor charges up and this usually gives it the extra push against the spring to bring the tool to the spindle. Sometimes the tool changer times out.

The cylinder retracts fine,and there are no problems with the up/down or tool release.

When I switch over the pipes to the in/out cylinder,the problem is reversed and the carousel goes into position at the spindle no problems and retracts slowly.

The cylinder was replaced when I bought the machine a couple of years ago, so is fairly new, could this problem be a stcky solenoid valve or is the cylinder likely shot?

21-02-2018, 12:56 PM
Yep sounds like the cylinder is at fault

21-02-2018, 08:20 PM
The fact the problem reverses, makes me think it's more likely to be the solenoid failing.

When the air is exhausting, remove the hose from the non-pressurised side of the cylinder (i.e if it's pressured into the spindle, remove the hose at the spindle end). If it's the cylinder that's leaking, then the air will escaping from the cylinder. If it's coming out the hose, or there's no change, then it's likely to be either the solenoid, or something lose/broken near the solenoid (I have seen the pressfit couplings simply fall apart and start leaking with age).
I'm not sure what machine you've got, but if it's a separate control box, the solenoids are all mounted in a box on the rear of the machine. I think if it's a machine with built in control box, then they're in the main control box.

If you do need a cylinder, I should still have a new one kicking around.

Ade taplin
22-02-2018, 05:40 AM
Hi I had a similar fault on my triac this week where the carousel would only travel 1 way when it should of retracted the solenoid just exhausted air out. I stripped the solenoid and found it was traveling further one way than the other, I figured it to be the internal clear seal was damaged, these have been discontinued so I just fitted a similar sized O ring now all is fine. I figured that the 2 clear seals are there to limit the solenoid piston travel. The cost of a replacement solenoid is getting on for 100. Hope this helps


22-02-2018, 09:14 AM
I thought it probably would be the solenoid as the cylinder is fairly new. If I take off the pipe at the spindle end, no air escapes from the cylinder and carousel is pushed firmly up to spindle.

I have the machine with the built in control cabinet, solenoids are top right.

Is it this part that would need replacing?

https://uk.rs-online.com/web/p/products/0722851/?grossPrice=Y&cm_mmc=UK-PPC-DS3A-_-google-_-3_Pneumatic+Solenoid%2FPilot-Operated+Control+Valves_Crouzet_Exact-_-Crouzet+-+Pneumatic+Solenoid%2FPilot-Operated+Control+Valves+-+0722851-_-crouzet+81513200&matchtype=e&gclid=CjwKCAiA8bnUBRA-EiwAc0hZk8V_e1k5a1TY00YO94wZ5rvruXUDUCXIobGQ2Sux3W sbXiXJdO63aRoCtP4QAvD_BwE&gclsrc=aw.ds

Or this bit...

https://uk.rs-online.com/web/p/products/0722924/?grossPrice=Y&cm_mmc=UK-PLA-DS3A-_-google-_-PLA_UK_EN_Pneumatics_And_Hydraulics_And_Power_Tran smission-_-Pneumatic_Valves_And_Manifolds%7CPneumatic_Solenoi d%2FPilot-Operated_Control_Valves-_-PRODUCT+GROUP&matchtype=&gclid=CjwKCAiA8bnUBRA-EiwAc0hZkwvNyPq8A41__7J_fJdY-NFHpoIOKFnpgKEDczbw3OGsRHDrKD9RDxoCmTIQAvD_BwE&gclsrc=aw.ds

22-02-2018, 03:54 PM
Good question. I never realised these used pilot operated valves, so it could be either part causing the problem.

I'd try swapping the pilot valves (...378 part) around first, as it could be a seal between the pilot valve and 4/2 valve body causing the problem. If the seals are ok, then you can see if the fault moves or stays.

Ade taplin
22-02-2018, 04:03 PM
Hi again the rs parts you have suggested are a lot newer than the ones in mine. I have the UNIVER E-0170 solenoids which are around 100 to replace. have you tried swapping the solenoids around as all 3 of mine are identical. I've tried to attach a jpg but struggling

22-02-2018, 04:34 PM
And having looked at the datasheet, it could even be seals underneath the 4/2 valve leaking, as they mount onto a base which the hoses connect to.

I'd still start by swapping the pilot valves, and checking those seals. Then if the problem doesn't move, swap the valve bodies, and check the next layer of seals.

23-02-2018, 01:01 PM
Swapped pilot valves, still same issue. Opened up the valve body and found a tiny square section o-ring that was creased, turned it upside down and now works. Can't seem to find a replacement seal set so will order a new valve body. Thanks for the help.

23-02-2018, 03:43 PM
Sounds like a Quad ring, or x-ring, but by the time you find the right size, and somebody to supply them, a new valve body isn't that expensive. Plus the new valve should be guaranteed to work.