Oil hydraulic systems

A hydraulic system consists of

joined together by pipes and anciliary equipment.


Power Source

For agricultural machinery the usual power source will be a tractor, either directly from the tractor's own hydraulic system or from a pump connected to the tractor's PTO. Elsewhere, power is supplied by a pump usually driven by an electric motor.

An accumulator may be included in the system to reduce the required pump outlet power or to smooth out oil flow.




Hydraulic actuators are of two types: linear actuators - cylinder rams, or rotary actuators - motors. Rams can be push, pull or double acting. As the ram extension must be less than the barrel length, a greater extension can be achieved by using a telescoping action.



Pipes, pipe ends, filters and oil coolers.


Making a hydraulic pipe

Hydraulic pipes in service, particularly in agricultural machines, can get damaged and therefore need replacing. Damage can be caused by excess stress from pulling the pipe or knocking the fittings, and from rubbing away the outer rubber coating, exposing the inner wires resulting in fraying or corrosion.

Types of hydraulic pipe

crimped hydraulic pipe ends

There are two general types of hydraulic pipe. Those that have crimped ends and those that have re-usable screw-on ends. Each type uses a slightly different size hose so it is important to check hose and fittings match. Re-usable fittings will not grip crimp type hose properly and are likely to fly off when system is pressurised. When made up, either type can be used interchangeably.

The simplest way to make up a replacement hydraulic pipe is the use re-usable fittings as this does not require specialist equipment.

Making a hydraulic pipe using re-usable ends

re-usable hydraulic pipe fittings

The first step is to cut the hose to the required length. The cut should be straight and clean, with no fraying of either rubber or wire. This can be done with a hacksaw but is much better done using large cable cutters. Hold the hose in a bench vise and screw the ferrule on by hand, then tighten with a spanner or socket until the hose almost reaches the end of the thread inside. Grip the ferrule in the vise and push the pipe end fitting into the ferule, being sure not to tear the inner rubber edges. Tighten until about 5mm from the end to allow adjustment later. Before fitting, check there is a clear passage through the pipe by blowing through it.


hydraulic pipe ends a selection of hydraulic fittings