PC60 Komatsu Swing Brake Locks up

[WallenEngineering]

My PC60 started locking the brake while swinging. Seems to do it when swinging slowly at this time anyway. Stops the swing instantly so need to fix the issue. it doesnt do it all the time, nor in any particular spot, or particular direction. When it locks, i can usually reverse the swing, then return and it goes smoothly past the lock point. Seems to happen after the machine is running for a while, not when cold. Does the electric switch normally send power to the brake when it is off, or no power when off? I hope it is an electrical short and not hydraulic. Any help troubleshooting the brake hydro would be appreciated as well. have a service manual on the way but they tell me it will take a couple weeks. Thanks for the help.

 

[Cbrunner]

Without more detail your question is difficult to answer (and not knowing the machine). Out of curiosity though, do you have the maintenance records?

Following the problem down the line I would suspect one of two things;
1. Problem with the valve itself, the signal operating the valve, or the device driving the valve signal.
2. Problem in the fluid circuit - e.g. trash in the lines causing the valve to jam/clog/lock up.

When was the last time the filters in the machine were checked/changed, and the machine fully serviced?

You will probably find that the swing circuit is driven by a computer controller of some kind. The controller probably receives a signal from the joystick, and depending on the sensor type or joystick type it could be many different types of signal.

 

[kcj]

I don't know the machine or application at all, but basic troubleshooting is first:
-Manual or schematics available, on paper or online?

-Is it electrically controlled, or pilot operated from the swing motor?

-If electrically controlled or activated, put a recording device, or a 12 or 24 vdc light bulb, on the valve or device and find out if the electrical signal goes away when thge brake locks up or if electrical stays. That fork in the road will define your next diagnostic attack. Chase electrical signal or chase hydraulic issue.

-If electrical, could be anywhere, but just start tracing backward and finding out where the electrical disappears.

-If hydraulic operated, the brake shuttle valve may be failing or leaking. Hydraulic brakes are typically spring set, hydraulically released. If the pilot signal degrades in any way, the spring set brake applies.


Vague and general, but without a schematic that is where you have to start.

kcj