Any hydraulic guys out here?

[Snaggletooth]

Got a question. The company I work for has a hydraulic lift on our dock. The tank and pump for it is inside in a cabinet next to my work area. The other day smoke came rolling out of the cabinet so I killed the power and opened it up.

 

On the pump assembly there is a shaft that sticks out and there is a coil on it. That was fried and the cause of the smoke. The lift will still work but it will drop back down to ground level when you release the button on the control.

 

They had a company repair guy (shade tree) come in and he spent three days working on it. This morning the lift was working but when I inspected the pump I saw he had removed the coil and not replaced it. He did some rewiring (hack job) and left it at that. The "repair" work he did it sloppy and left bare wires.

 

So with that info can anybody tell me what this coil does? It's a Delta Power Company DOL25 24 VAC. Fits a 1/2 shaft. I have some safety concerns about this repair and want to know how this works and what it does.

[spingley]

It looks to me like an electromagnetic coil on a solenoid valve, the shaft it sits on would be the armature. There are all different kinds, I cannot give you any particulers as to it's exact function. I know that is not much help.

[RandyR]

Yep, sounds like a solenoid. Probably a sensor of some kind. (I'm not a hydraulic guy).

 

I'd try to find the name & type of lift and call the company that made it, or do a web search.

[ctraylor]

When voltage is applied to the coil it magnetizes the center pole and closes a valve. This is probably the valve the stops the cylinder from coming back down. Just replace the coil. This is a magnetically controlled valve.

[Dano]

[bryan52577]

Michael

I would say it is possibly a "DCL" 24V 1.2 amp, look here at the Schematics of it. Wire colors are right for your pictures.

You could order a new one from them and install it after repairing what the "shade tree" screwed up?

 

Hope this helps.

Bryan

[SilvrT]

I dunno about "hydraulic" but I'm somewhat of an "electric" personality....

[Snaggletooth]

Thanks for the imput guys. Gettin the ID on the lift is a no go. Been there since the building went up 20 some years ago and all the tags, labels or ID plate are long gone. We took over the building 5 years ago so no way to find any records.

 

The lift is working as is and stays up in the raised position after the er....repair and don't bleed down. I'm looking at the coil as maybe a safety lock that holds the armature in place when the controls are not being used or in case of a failure it won't drop down unexpectedly.

 

I had a delivery driver come in today and asked if the the lift was repaired yet. I answered "I hope so" and handed him my helmet, gloves and the first aide kit. He broke the load down and carried it up the stairs on a two wheeler. Oh those of little faith. LOL!

 

But we shall see.

 

Thanks again

 

Mike

[ctraylor]

Just take the coil to an electrical supply and they can probably match it. It is a simple magnetic coil.

[bull463]

Hi

Most tractor supply stores have them also used on hyd, mowers

Bull463

[autopilot]

Based on your descriptions, it is a solenoid operated valve (probably an open/close 2-way). The "shaft" that the solenoid slides onto is the spool piece. Apply voltage and the spool shifts internally in response to the magnetic field to open or close a port in the wet system hydraulic circuit, hence the term "valve". This response to the magnetic field is also why it is vital to get the exact replacement or approved equal; to assure proper movement of the spool and achieve full opening or closing. These spools are usually spring loaded to one position or the other and energizing the coil causes the spool shift and consequent opening or closing of the wet circuit. Thinking through it, it appears, your valve is probably a hydraulic vent, electrically energized to hold closed while the platform is in the raised position. (When "down" is commanded or on failure of the electrical solenoid, the SV opens & vents fluid to the tank to release pressure). I assume the normal condition for the platform is "down", because the failure mode as you described the operation, permits the platform to lower in a relatively slow "bleed-down". Also, the normal condition for the solenoid valve "should" be de-energized. That would also allow the wet system to be de-pressurized at rest.

 

Replacing the solenoid with the manufacturers part or an exact electrical equivalent, will restore proper operation of that valve. [i agree with Bryan that it is likely the DCL version of the coil] Looking at the coil spec sheets reinforces the likelyhood that the valve is a 2 way vent. The 24VAC coil has integral rectifiers to convert the AC to DC and there would be no way to send a reversing voltage to the solenoid (you can't reverse the polarity of AC) However, the solenoid should not be placed into an active circuit, on the spool piece unless and until the other changes made in the "fix" are reversed! There's no telling what he did to force the system to hold pressure and if the faulty solenoid is replaced in the circuit and on the spool with those changes still in place, there's no telling what the hydraulics would do.

 

That's probably a whole lot more than you wanted to know........but you did ask, after all!

[Snaggletooth]

Hey Autopilot.

 

No such thing as too much information. And that is why I asked. I have some basic background on hydraulic systems from my youth while working as a mechanic for MF on construction equipment but this is a different animal.

 

I have been looking this thing over in my spare time the last couple of days and found some more parts he chopped off. Looks like a relay mounting board that was fried and the wires were just cut off. No new relay was installed. Just eliminated the old one. So I know the coil melted and a relay burned to a crisp. As to what caused it......only a wild guess would do at this point. I know for a fact the lift had not been used for over an hour as the pump has a distinct whine when it is running and it didn't make a sound before the smoke rolled.

 

We are on the same track as far as the function and the purpose but the guy that did the work removed so much of the wiring I'm having a hard time backtracking the cause of the problem.

 

My best guess at this point is the internal rectifier in the coil failed and caused the melt down and that shorted the relay. I'm going to disect the coil to take a look at the guts.

 

It's more than a safety issue at this point.......curiosity kicked in and that always screws up my spare time.

[wes0778]

My first thought is the fried solenoid may be the result of another problem. Most solenoids I have worked with have two sets of coils within them. A powerful "pull-in" set and a weaker "hold" set. The pull in set draw a lot higher current and are designed to operate for a very short period of time to move the core, usually against a spring, before turning the job over to the weaker coils that hold the core in place. If this transition does not take place and the power is applied to the "pull-in" coil, for an extended period, this will let smoke out and we know when that happens the solenoid is no good any more.

 

So I bet if you find the cause of the new whine, you'll find what ever is the movable core for the burned up solenod is, is stuck or seized.

 

I could be wrong:confused07:, I have been at least once before:innocent:, but my

Edited August 28, 2009 by wes0778
correct spelling