Marine Wiki Forum

This query is raised based on one inspection of the Hydraulic Power Unit (HPU) of the deck machineries (anchor windlass and winches). It was noted that even when there is no load, the motors were drawing high current - close to the maximum current.

System description
* There are two HPUs in the ship (320,000 TDW VLOO). The fwd unit drives the windlass and winches. It can run either one windlass or three winches simultaneously. The aft unit can run three winches simultaneously.
* Windlass: nominal pull (65T), nominal speed (9m/min), max. pull (103.8T), Oil consumption (607 lpm)
* Winch: nominal speed (15 m/min), Oil consumption (261 lpm)
* HPU - Hydraulic pump: Three numbers, Oil delivery per pump (256-317 lpm), Input shaft power per pump (130 KW), Pressure (250-217 bar), Peak pressure (315 bar)
* HPU - Electric motor: Type (Squirrel cage induction motor, 4 pole), Three numbers, Output per motor (135 KW), Power factor (cos phi 0.87), Running current (215 A), Starting current (415A), Starting method (Star-delta)
* HPU Pressure settings - three settings are there. Standby low pressure (30 bar), Standby high pressure (130 bar while anchor lowering, auto-tension operation), Working pressure (250 bar at anchor hauling, mooring operation)

When one winch was running at no load, with two motors in HPU operating, the current in the motor was about 210 A. This is close to the working current of 215 A. I guess that at no load in the winch, the flow required is less and hence there is less load in the HPU motor and therefore should show low current. Is that the case or is there some other explanation to this?

Hello Sandith
It is difficult to comment without more info about the hydraulic circuit and the construction of the pumps. Following queries spring to mind:
- How is the HPU pressure regulated (ref the three settings below)
- How is the return path of the hydraulic oil - high amperage indicates nearly rated flow of hydraulic oil at rated pressure
- The pumps seem to be fixed delivery pumps, is it correct?

Regards,
Venkat

Dear venkat..

Myself B.Anil kumar ref to sandith query am sending the information which ever you asked .. sry for the late reply due to lack of information...reagrding your comments..

According to my knowledge::

1) HPU regulated from pressure selection switch..
2) return path is rated flow of hydraulic oil...
3) you asked that are fixed delivery pumps : yes

Further if any information regarding this please ask me i will forward to you as per my knowledgee