On Friday, May 27, 2016 at 5:44:32 AM UTC-4, Gunner Asch wrote:
On Thu, 26 May 2016 21:52:02 -0500, Jon Elson
wrote:

rangerssuck wrote:


The electrician, who really knows his stuff, pointed out that the controls
stop the motor, but it's really a hydraulic motor that drives the system,
and maybe it coasts a little when the electric motor is shut off. Also, he
pointed out, that the offset changes during the day, maybe as a result of
the fluid heating up. So, my not-at-all educated in hydraulic motors mind
started thinking, what if, instead of shutting of the pump, what if we
installed, right at the motor, the hydraulic equivalent of a DPDT relay
that would disconnect the motor from the pump and put a short across the
motor?
So, they have a single-purpose motor that runs a pump, that runs the
hydraulic motor? Geez, what idiots, of COURSE it will coast with all that
inertia.

Yes, you want a solenoid valve that relieves the pump and blocks the motor.
It may need to have some kind of shock absorber to prevent a hydraulic
hammer from wrecking the hoses. I'd check with a local hydraulic provider
for recommended parts, this is a fairly common job to do. it ought to work
quite well and index the pallets much more accurately.

Jon

Typically the relief valve will take the shock of the motor shutting
down, and as the shuttle valve closes..the hydraulics are taken off
the motor. Any changes are due to sudden pressure change as the
system bleeds off through the relief valve and any leakage through the
motor

Thanks. I have instructed the plant manager to discuss the need for protection devices with their hydraulics supplier. I'm (pretty) sure they'll get it right.