McElroy Discussion Forums

Hello All,

It's been so long since I had a question which I suppose is a good thing.

I currently have two machines with the same problem; a Rolling 618 HF and T900 HF. The issue I am having can only be noticed when hooked up to a Datalogger since you need to be able to see the exact pressure. I know it is not a DL problem because I tried three different DL's and each machine displayed the same problem.

The problem is I can not get my static "Heating Pressure" below 60-65psi. This is the same on both the 618 and T900. This just happened to the 618 machine today while I was welding, and during the "heat soak" time no less. My "front end plot" showed the proper shift sequence with the pressure dropping to drag (29psi) and then trickling down to 0psi once the carriage was in neutral. After two minutes of soak the pressure steadily rose to 60-65psi and stayed there the rest of the soak time. I did not move the selector valve or directional valve at all. After I cancelled the weld I was trying to figure out what happened but with pressure applied I can not get static pressure below 60-65psi now. I know it's not having the wrong Sun Valve (Fusion Pressure) because it was working correctly all day plus it would be down at 50psi.

My only thought is that "Selector Valve" blew a seal and is allowing other pressure to bleed into the heating pressure. I plan to replace both the directional and selector valves to see if that will remedy the problem but won't be able to until Monday.

Does anybody have any thoughts? Thank you.

I believe you may be right on its tail at this point. The DL system is a really good thing other than sometimes it shows some information that you would have been happy just not to know. All joking aside, its better to see these little issues before they can manifest into a larger problem. One other item you may want to think about but I need to line this one up in the sights for you first. When dealing with heavy wall pipe and medium force units but sometimes even HF units you will see a rise of pressure over the first part of heat soak. This is due to the thermal expansion of the material. As I can best describe it, the HDPE as it starts to heat has to go from a cold ridged state to a flowing heated state. The area between these two states is where the issue is. In this area the material is expanding creating pressure on the heater/ opposite pipe and because the directional valve is by this point in an isolated “neutral” position (neutral meaning the cylinders are hydraulically locked) the pressure is seen on the DL. Once the pipe reaches the “flowing state” the pressure will bleed back to 0. let us know what you find out please.
DR.

We have the same issue with three of our DL5's. Its very time consuming waiting for the pressure to fall below drag. And sometimes it never does so the technicians have to bump the carriage valve to relieve the pressure before they can begin their soak. Definitely a problem for us.

So......good times : (

We replaced both the directional and selector valves with no change. Both the Facing and Heating pressures when dialed down to "zero" would show 80psi with pressure applied and 50psi with Directional in neutral. We took these readings with two different DL4s. I figured it wasn't the Sun Valves since both the Facing and Heating were showing the same pressures.

We swapped the entire manifold block that already included directional, selector, and sun valves from a spare 28 carriage we have lying around. Everything worked as it is supposed to on the 618 Rolling. For kicks we then swapped out each Sun Valve from the defective block one at a time just to cure our curiosity of what could be the problem. Nothing showed us signs of the old problem.

Looks like we will be ordering a new manifold block.

I'm glad you guys got the machine up and running again. I'm a little surprised that the manifold block seems to have fixed it. That shouldn't have much to do with issues like that.

At any rate you have it fixed now. Let us know if you have any other issues and we'll do what we can to help you troubleshoot.

Thanks.

Also wanted to mention,

The negative pressure issue isn't really an issue. It is a real event that the newer DataLogger's can actually see. There will be a tech bulletin at some point to help eliminate the confusion.