Maybe it's ‘A matter of correction'?

First of all, let me nail my colours to the mast. I'm involved with electro-mechanical systems although, as an access control design engineer of many years standing, I am well versed in the merits of both end user solutions. Indeed, it is my company's experience that good quality automation systems of both types are extremely reliable. However, cheaper equipment of either variety - if badly installed - can be unpredictable. Alas, our engineers are frequently called to repair both types of system where corners have been cut to reduce costs.

There is little doubt that hydraulic systems are prone to leakage and are, therefore, somewhat environmentally unfriendly. The viscosity of hydraulic fluid may vary with temperature and contamination, etc, giving rise to performance inconsistencies. Also, if they're not properly maintained, hydraulic systems can run low on fluid which may then render the gates inoperable and cause lasting component damage. At one point in the article, Robert Lane - managing director of installer Domsat - states that: "We just top up the fluid from time to time...", but then Paul suggests: "Electro-hydraulic systems are virtually maintenance free"!

None of the above is an issue with high quality electro-mechanical systems which are simpler, involve fewer parts - and, thus, are inherently more reliable - and require minimum routine maintenance.

Hydraulic gate systems use small (and much cheaper) high speed motors because the fluid acts as a ‘gearing' medium. The motors employed in electro-mechanical systems are necessarily more substantial, but mass production - largely driven by high demand - has rendered mechanical systems less expensive. Sensing circuits used in the latest electro-mechanical systems are more reliable and faster acting than hydraulic relief valves.

Paul's article also claims that recycled oil provides a "cushioning effect". Technically, that is incorrect. Fluid is incompressible! I would also dispute the claim that: "Hydraulic systems are much quieter". It can be demonstrated that mechanical systems are quieter than their hydraulic equivalents.

There is no doubt in my mind that electro-mechanical systems are simpler in both design and function, and are generally easier to install. And, in response to the suggestion that they have an "innate weakness" in the drive gear, our records show that not only have we never replaced a drive gear in over 20 years of working with Ceda electro-mechanical systems, we have also installed systems that haven't needed any major attention over the same time frame.

As I suggested at the beginning of my response to Paul's article, I believe it is far too heavily biased towards electro-hydraulic systems. Any customer buying a hydraulic system on the basis of certain comments made within ‘A matter of perception?' could, sadly, find that it doesn't live up to expectations.

Joe Baker Managing Director Atlas Group