messing with things you shouldn't

[phil d]

Just before Christmas, I was mad busy and got a call to one of the farms I do a bit for," the electric gate won't open or close", as  I said I was mad busy and the farm in question was 50 miles away. I set off at some ungodly hour and arrived there around 7am, the idea being to fix the problem then head to my original job. I quickly diagnosed the problem as being a faulty photocell, and not having a spare decided to link it out until  I could obtain another, (yes I know I shouldn't but needs must and it had other safety devices), Anyway I went back yesterday as the farmer had got a new sensor and fitted it. The farmer was there and he asked why I had wrapped a cable tie around one of the rubber safety edge switches, these are designed to stop the gate dead if the rubber edge hits anything. Inside them there is a thin wire rope that keeps a microswitch in the closed position, if the rubber deflects it the switch goes open circuit, likewise if the rope snaps it goes open circuit, either way the gate stops. This cable tie would cause the device to go open circuit so I was mystified as to how come the gate was operating, I opened the control panel to find the 2 wires from the edge switches had been cut and linked out!

What the hell is going on here I wondered, the problem is that this farmer owns 2 farms, the distant one and one near me, he lives at the one near me and staff go down to the other farm to carry out work, the only person permanently down there is a bloke who lives in the farmhouse, naturally he denies opening the panel. Now I've met the "seal" fairies on several occasions but am now wondering if the same fairies have moved on to tampering with safety devices.

I have shown the farmer the gate operating properly, I.E all safety devices working and wrote on the panel that safety devices must not be tampered with, what else can I do? Ok, I temporarily defeated the photocells, that was my decision and I stand by it, after all there were other devices operating. What concerns me now is that should anyone else tamper with it again and there is an incident I can see me being right in the firing line.

I just wish people would stop messing with things that they know nothing about, the edge strips were functioning correctly so why did someone decide to link them out?  

 

[Andy™]

electric gates have their own specific requirements. bypassing a photocell is not something i would ever do, even as a temporary measure (but then i keep spare photocells & safety edges). most edges are not switches either - push them and they short at around 3-500 ohms. the end of line has an 8K2 resistor so the panel knows if its bypassed, unless its programmed as an NC safety edge (this is usually used on external edge controls). safety edges are not always required either - todays gate didnt need one due to forces low enough, although most sliding gate & almost all industrial gates do need them

also, edges do not stop the gate dead - they must reverse slightly before stopping

there must also be a risk assessment for the gate (its also covered by machinery requirements)

the correct action if you cant make it fix the photocell or safety edge would be to isolate it and take it out of gear so it could be moved manually or change settings so it only works deadman. especially if it has any automatic functions (like closing after a specific time

and this is what happens when you dont install the required safety equipment (bypassing would also have the same effect)

http://www.dailymail.co.uk/news/article-3341421/Get-brother-Dying-words-six-year-old-girl-crushed-sliding-car-park-gate-desperate-family-tried-vain-pull-out.html