Kobelt 7012 Series, Owner'S Operation, Installation & Maintenance Manual

Page: 14 / 32

Helm pump-7012 Kobelt Manufacturing Co. Ltd.
Rev A MNL-7012 14 of 32
7 O
PERATION
The operation of a hand hydraulic steering system is very simple. A steering wheel is fitted
directly to the helm pump. Two hydraulic lines from the lock valve (or porting block) on the
rear of the helm pump connect to a double acting balanced displacement steering cylinder. A
tiller arm is clamped to the rudder shaft and the steering cylinder is bolted to the tiller arm.
Turning the steering wheel will pump hydraulic oil to one end of the steering cylinder. As the
cylinder moves, oil from other end of the steering cylinder is push backed up to the opposite
side of the helm pump. This called a two-line system.
When you stop turning the steering wheel, the hydraulic oil in both lines is “locked” by the
rudder lock valve (sometimes called a non-return valve). The rudder will stay in place and not
move until you start turn the steering wheel. Second function of the lock valve in a two or
more-station system, - steering wheels not in use do not turn.
If helm pump order with Porting Block instead of lock valve, then
the rudder will not stay in position and can move by water current.
Some sailing boat use porting block to feel rudder force on the
wheel.