28 March, 2024

Apex manufactures specialist cylinder with integral linear transducer

25 August, 2020

One of Apex Hydraulics’ clients recently requested a replacement cylinder for a large application in the Republic of Ireland. The project was a linkspan for a ferry port, with the cylinder being required for a Roll On, Roll Off Road. This allows a road to extend out to the car ferry when it docks at a port, rather than extending a ferry door down onto the port. The linkspan utilises two cylinders, working as a pair, although only one needed replacing.


Positional readout

A vital feature of this type of cylinder is a transducer (also known as positional readout, electronic feedback or a potentiometer) which allows a PLC or control system to control the speed and distance of the cylinder extension. Without this, the two paired cylinders could act at different speeds, with damaging and even dangerous effects. As these cylinders could be moving a number of passenger-carrying vehicles on board a heavy section of steel road, there can’t be any discrepancies. The only way to control this accurately is with electronic feedback from both cylinders, allowing each cylinder to be independently controlled. The transducer needs to be accurate to less than a millimetre, allowing both cylinders to be extended by exactly the same distance, same time and same speed.

Valves and software

Apex used existing drawings of the cylinders to produce an identical cylinder replacement for the linkspan. A solenoid valve was used to control the volume and speed of oil, with the transducer being the electronic read-out of the position within the hydraulic cylinder, accurate to within half a millimetre.

The system is controlled by computer and is therefore far more complex than the simple mechanical aspects of the cylinder. The software uses the transducer to pinpoint the exact cylinder location, then commands the solenoid valve to allow oil in or out to advance or retract the cylinder. It also controls the speed of the process. The transducer can give a complete read out of the cylinder position from open to closed and is able to tell the system to advance to any position required, dictating to the valve when to slow down and when to close.

Swift delivery

In spite of the complexity of the project, Apex Hydraulics turned the entire cylinder manufacture around within 9 weeks. This was an especially swift turnaround because the project was completed over the Christmas period, in order to meet the customer’s deadline.

As with all cylinders for applications in and around the sea, there were a number of important considerations, particularly around preventing corrosion. The stainless-steel rod was chrome plated to ensure longevity in spite of the salt air and water and strong winds that can be expected at a harbour.

The outer cylinder was coated with three coats of specialist dockside paint. This level of specialist paint was required to protect against the wind and elements. The cylinder was relatively large, with a 280mm bore x 150mm rod x 4500mm stroke. A trunnion mount was required, to take into account the varying height of the ferry, as it goes up and down according to the tide. The result was a top spec, highly robust, specialist cylinder complete with internal linear transducer. The client received a full Manufacturing Record Book (MRB) from Apex Hydraulics.

www.apexhydraulics.co.uk




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