Rob Williams is Gate Safe’s Technical and Training Manager. Having spent 17 years working in the gate automation sector, he has a wealth of industry experience and his role with Gate Safe means that he is constantly tasked with undertaking independent risk assessments on automated gates – either directly in the field or via the numerous enquiries to the Gate Safe help line. As one of our trainers, Rob also regularly meets other installers and the interactive nature of the Gate Safe Aware training often throws up intense debates in relation to various technical issues and these can often be translated into valuable advice.
Rob’s safety tips are designed to deliver practical, effective guidance to ensure no detail is missed to ensure the safety of an automated gate or barrier.
I’m often asked if it’s ok to use mechanical safety edges rather than resistive ones. This normally happens when a member of Gate Safe is taking over an existing site where mechanical edges have previously been installed.
Mechanical edges work by having either an internal cable or lever running through the rubber profile which is attached to a switch at one end. When the edge is activated the cable or lever will pull the switch open. Resistive edges work by the controller looking for a resistor at the end of the edge. When the edge is activated the contact strip running through the edge changes the resistance seen by the controller.
My main concern with mechanical edges is that they cannot be monitored by the control circuit properly. The Standards do say that all electronic safety items should be a minimum of cat2. Unfortunately, this cannot be achieved with a mechanical edge, as the actual edge itself is not electronic. This means that there is potential for the edge to sustain damage and for the system to remain oblivious, consequentially leaving the gate operating in an unprotected and possibly dangerous mode.
While we are talking about self-testing, don’t forget that when possible use the test input on the logic board to monitor the photocells to verify that the relays aren’t stuck or welded together.
There is also the issue of coverage on mechanical edges. Often these have a large area at each end of the edge which is not active, sometimes up to 100mm, preventing coverage of the full height or length of a gate or barrier. This is likely to result in , leaving areas such as towards the hinges on swing gates unprotected - the very area on the gate with the most force!
If you do come across gates with mechanical safety edges fitted, please make sure you carry out a comprehensive risk assessment and test the edges thoroughly to make sure that they are in good condition and cover the areas of risk effectively. Inform the owner of the gates of the need to perform tests weekly to ensure that they are still working effectively and advise of the requirement to report any damage.
Whether you are dealing with mechanical or resistive edges it is important to remember that temperature, especially freezing conditions can have a massive impact on the sensitivity of the actuation with ice build-up possibly preventing the edge from switching at all. In these conditions I would carry out more regular and stringent tests on the system to ensure the system is safe to be used.
If you have any doubts, I would thoroughly recommend replacing the edges with monitored resistive types.
When wooden posts are used to hang gates, it is important to regularly check their condition as part of the maintenance schedule. Overlooking this important structural requirement can result in a catastrophic failure and a potentially serious accident.
A quick and easy way to check for rot is to use a sharp pointed knife. Push the knife into the post at ground level, and if it stays there and grips the blade when you pull it out, then the post is sound. However, if the blade falls out, then the post is possibly rotten, and further investigations should be carried out.
The same test can also be applied to wooden gate leaves - the condition of the wood is especially important near joints, hinge bands etc.
Remember that anyone involved in servicing and maintenance has a responsibility to leave the gate system in a safe condition. This isn’t just associated with mitigating impact and crushing risks arising from the automation, but also relates to the structural integrity of the gate supports and overall installation.
#maintenancematters #woodengates #makinggatessafe
At Gate Safe we have always been painfully aware that a single point failure, e.g. the failure of a hinge, can lead to serious injury or far worse, as demonstrated by numerous accidents. Given the fact that the British Standard BS EN 12604 has been updated to state that all swing gates should be fitted with three hinges, it remains baffling to note that gate manufacturers continue to fail to address this issue – and run the risk of putting themselves in the firing line in the event of an accident and any associated claims. This is clearly a matter which needs to be taken more seriously within the gate industry.
It should also be noted that, just because the standard was updated, this does not infer that gates fitted prior to that date should be deemed safe. It just means that the danger had not previously been recognised. Installers should protect their business and their reputation by fitting a third hinge or at the very least a tether on any swing gates installed before the new guidance, to prevent the risk of a catastrophic gate fail.
There also appears to be view circulating in the field that fitting a third hinge with an underground operator does not represent good practice, due to the difficulties associated with accurately aligning the hinges. Remember, the purpose of the additional hinge is to stop the gate leaf falling should there be a failure of one of the other two hinges, but it does not need to be offering support all the time. The solution to this problem is to position the third hinge with a little clearance between the pin and the eye, a 19mm pin in a 25mm eye. This is sufficient to stop the gate from toppling over in the event of a hinge breaking.
Recently one of my colleagues excitedly rang me to say that they had found a gate with three hinges and had the photos to prove it. However, upon closer inspection it appeared that two of the hinges were inverted, meaning that all of the weight was being placed on the bottom hinge alone, rendering the gate even less safe than a conventionally supported gate!
As Gate Safe installers we would ask you to always consider the following three steps:
One of the often-overlooked risks that Gate Safe comes across is that of ‘single point failure’ with swing gates, or put more simply, hinges failing.
In my previous life as an automation engineer with a busy schedule I know it is all too easy to focus purely on the electronic repair you’ve been sent to carry out and not pay attention to the gate and its supporting structure. In reality, all engineers should conduct a risk assessment before carrying out any works. Unfortunately, we see too many reports of gates falling, often with disastrous consequences, sometimes because the engineer didn’t look at the bigger picture.
Not that the industry has taken this on board but BS EN 12604:2017 now states that all new swing gates should have three hinges. And, what about the thousands of gates that are already in existence? Just because the standard has changed it doesn’t mean that all existing gates featuring just two hinges are deemed safe. The risk of single point failure has always been there, it is just that now it has been more formally identified. Also, remember that if you come across gates with inverted hinges these can pose even greater risks. Installations featuring inverted hinges mean that all the weight of the gate leaf is being supported by one hinge, therefore significantly increasing the possibility of failure.
The solution to the above is a simple gate tether. Fixed between the hang post and the gate leaf, the tether will deliver peace of mind that should the worst happen and one of the hinges fail, at least the gate cannot fall.
We understand that adding a third hinge would be the ultimate answer but on many gates this could be very complicated and time consuming to carry out. It would also represent an unacceptably high cost to the customer. A gate tether provides an effective and inexpensive response to a potentially dangerous problem.
At Gate Safe, we often come across swing gates with no safety edges fitted to the bottom of the gate. When we talk to the installer, the excuse often given is that the motors are fitted with obstacle detection and therefore will be incapable of crushing someone. THIS IS INCORRECT!
On swing gates, the way the force is exerted along the gate differs to when it is applied ‘end on’ as per a sliding gate. Swing gates act like a giant pair of nutcrackers, with the strength of the force increasing the closer you get to the hinge. So, this means that when you are setting up the obstacle detection to ensure that the gate has very little force at the slam stile, as prescribed by the standards, by the time you get anywhere near the hinge the force will have increased substantially. If you then try to reduce the force applied by the motor and increase the sensitivity on the obstacle detection, the end result will be the gate has insufficient power to move. The temptation then of course, is to leave the power turned up which creates an unsafe gate with an increasingly dangerous force the nearer you approach the hinge. However, the installer will advise the client that the gate is compliant with the standards … Gate Safe argues that may be the case but it is not safe!
Remember that in addition to the obvious risks of impact and crushing, there is also the potential risk of drawing in and being dragged under the gate leaf as it moves. These are very difficult dangers to protect against if relying solely on obstacle detection. However, it is absolutely essential that these risks are mitigated and for that reason, Gate Safe recommends fitting full length safety edges at the very bottom of both sides of the gates leaves, on all automated swing gates.
Tidy wiring results in safer gates!
How many times have you come across a control cabinet or box that when opened, deposits a large ball of wires into your lap? Not exactly the best start for helping you fault find or carry out a maintenance task!
Ensuring tidy and labelled wiring can play a part in leading to a more reliable and safe system overall. If the cable routing and connections are clearly marked, then any subsequent visits will be less stressful and time consuming. It’s definitely worth creating a simple wiring diagram and the time spent on this will reap dividends in the long run. Of course, it is important to remember to revise this every time the wiring is adapted, for example, because you’ve had to change a cable core due to damage. It’s also good practice to take a photo of the wiring after every visit to keep a log of the system. This way it is possible to evidence if other people have been working on it in your absence.
I think it’s a good idea to make sure you have spare cores available when you first pull cables through at the installation stage and always leave draw cords in ducts. This will provide the flexibility further down the line to add additional equipment or replace damaged cables, should the need arise. When the installation is complete, always seal the ducts to avoid the ingress of water and unwanted visitors.
If possible, try to standardise the core colours for your installations as this makes wiring up and fault finding so much more straightforward – and don’t forget to record any changes.
Tidy wiring really comes into its own when you are carrying out maintenance and will result in a more seamless checking of safety circuits, including switching relays and verifying the resistance of safety edges – and ultimately ensuring the gates are left in a safe and compliant state.
Very Untidy Wiring
Wiring Done Right
Non-contact safety for gates and barriers
Gate Safe has long advocated that non-contact safety should always be the priority for gates and barriers however, before discussing the various options let’s first consider the basics.
Swing gates: have the hinges been designed in such a way as to eliminate reducing gap? Can the gates be positioned to avoid crush hazards?
Sliding gates: has the run back been fenced off? Are the support posts clad with welded mesh?
Anything that can be done to eliminate a risk by effectively designing it out will always be more cost effective than fitting electronic safety measures which will require maintenance and which may at some point fail. Ultimately, an inherently safe physical structure is vital.
When you reach the decision making process in terms of identifying the most appropriate non-contact safety, the choice will be guided by the risk assessment. For sites which feature children or the vulnerable, the safety measures requirements will naturally be greater than for a remote site with a deadman, hold to run operation.
Photocells are the most commonly used device and they are a valuable tool in the gate installer armoury. For low risk sites they should be installed on both sides of the gate as a minimum, fitted as close to the gate as possible. They can also be used if a gate is closing against a wall to protect a crush hazard, especially where an edge Is impractical, for example where a ram is close to a wall in the opening phase. It is important to make sure that photocells are wired into the correct circuit on the logic board to revert the gate in the desired direction. It should also be remembered that these safety devices can fitted in tandem to provide added protection, it is perceived that people straddling a single beam may limit their effectiveness.
Light curtains are the next level up of safety and in principle operate in the same way as photocells. The difference is that they have multiple beams that are spaced approximately 100mm apart and can be up to 2.5m high, protecting the full height of most gates, up to 10m width. The main advantage of these safety devices is that they are less susceptible to false activation due to snow, rain etc. In common with photocells they leave the arc of a swing gate unprotected but for sliding gates they offer a cost effective solution if they are positioned close to the gate, eliminating any ‘dead’ zones.
Laser scanners potentially offer the highest level of safety, providing the opportunity to be fitted onto the gate and actually move with the gate. However, four scanners would be required for a double leaf gate. This would provide the optimum solution for high risk sites, delivering four laser scanners projected forward from the scanner covering the full height and width of the gates, up to a span of 10m. Initially, the programming will - like all things new - be hard to get to grips with, but the more times you do it the easier it will become. Training is available from the manufacturers which we would recommend prior to installation. There are limitations, hinge protection will still need to be considered if the risk has not been designed out and the laser can only work in a ‘line of sight’. Therefore, a ram may block the laser’s sight so it may be necessary to fit the ram at the top of the gate with the laser fitted below it to offer the maximum protection. Similarly, with sliding gates there may be a dead zone between the curtains either side of the gate.
Lasers can also be used with barriers offering safety for pedestrians and cars and can additionally activate the barrier. In the picture below, the red area is the safety zone and the green area represents a virtual push button which opens the barrier when vehicles approach. Pedestrians are not ‘seen’ in the green zone, thereby eliminating the chance of false activation. The only additional risk that would need consideration is the pivot point for the barrier arm.
To conclude, designing out risks by mechanical means is the first step to achieving a safe installation. This should be combined with using the most cost effective non-contact safety devices that mitigate the risks associated with the specific site, taking into consideration the regular users, as well as people who may accidentally come into contact with the gate or barrier.
Every automated gate system has - or should have - a means of releasing the drive unit to allow the gate to move in manual operation should the need arise. This could either be by use of a key, a lever or a hydraulic valve, depending on the type of gate and motor used.
The requirement for a manual release is to not only enable the opening of gates in the event of a breakdown, but more importantly, to free a person should they become trapped by the machine – clearly a much more serious scenario. This then means that the keys / lever / tool to disengage the manual release MUST be readily available and close at hand. It is also good practice to ensure the current users are familiar with the release procedures as part of the regular maintenance regime. We recommend using a key safe installed in close proximity to the gates, obviously ensuring that the correct access code is issued to residents or duty holders. There is no point holding the keys in an office 20 miles away!
This leads me on to maintenance. It is very important not to overlook the manual release mechanism in any maintenance schedule. It is not unusual for the mechanism to seize up over a period of time because it is generally not used in the day to day operation of the gates. Underground operators with a detachable shoe release can be especially prone to this and therefore need regular inspection and lubrication to keep the release working. Wear and tear in this load bearing area can also take its toll.
Electro-mechanical rams often have the manual release as part of the gearbox, which can also jam or seize without the correct maintenance. We’ve seen many cases where this has occurred, which can lead to users forcing keys into the locks and snapping them off, rendering the whole unit useless.
Hydraulic operators generally have their manual release under a cover on the motor or separately sited on the pump. These can sometimes be more complicated to use compared to a simple key release, so it is vital to have the correct operation instructions clearly visible so gates can be released easily and quickly should an emergency arise.
At Gate Safe we view the manual release as a critical part of the system. Of course, we all hope that there will never be cause to use it, but if a scenario does present itself, there must be confidence that it will be working properly
Safety edges on the closing phase of swing gates
Gate Safe recently carried out a survey on some swing gates following a serious incident.
The gates in question were double leaf swing gates, featuring an open infill tube and rail construction, standing at about 2.1m high and 4m wide. They were automated using 24v rams in fully automatic operation, and photocells had been fitted inside and out. Safety edges had been installed horizontally to the bottom rails on the inside of site to cover the opening. A vertical edge was fitted to cover the reducing gap as the gates closed. Two further edges had been fitted to the walls that the leaves opened up towards, to prevent any crushing risk from the motors. Anti-finger trap guards were installed to cover the reducing gap at the hinges. All sounds great.
But think about it. NO SAFETY EDGES HAD BEEN FITTED TO THE OUTSIDE OF THE GATES.
As a result of this omission the following occurred. An elderly lady in her 80s was waving goodbye to her friend as she departed in her car. The lady was standing in the gate way, between the two pairs of photocells as the leaves started to close. The lady noticed the gates moving but could not move out of the way quickly enough. The leaf struck her and knocked her to the ground and then carried on trying to close. Eventually the gate’s obstacle detection system kicked in as she was being drawn underneath and the leaf retracted, but then tried to re-close, hitting her again. She was positioned approximately half-way along the gate leaf, so the force would roughly be twice that of the force at the slam stile of the gate. It was only the quick reactions of a passing neighbour who picked the lady up and moved her, that prevented a catastrophe. The victim suffered severe bruising and cuts and required a hospital visit.
Sadly, this is not a one-off incident. All too often we witness installers adopting the cavalier attitude that safety edges are not required on the outside of swing gates. But remember gates move in two directions! The risk of impact and drawing in exists just as much in the closing direction as it does in opening phase, as the above accident testifies. The force towards the hinge is much greater than at the slam stile and inherent force limitation does not remove the risks.
In the case of the gates detailed above, subsequent to the event, full length safety edges have now been fitted to the bottom of the leaves on the outside of site, creating a much safer system.
Check out the extensive guidance and risk assessment documents in the Gate Safe members area www.gate-safe/members to ensure you are up to speed with the correct placement of photocells and safety edges – and ALL essential protocols to ensure a safe and compliant installation.
126.96.36.199. Emergency stopMachinery must be fitted with one or more emergency stop devices to enable actual or impending danger to be averted.The following exceptions apply:— machinery in which an emergency stop device would not lessen the risk, either because it would not reduce the stopping time or because it would not enablethe special measures required to deal with the risk to be taken,
Kent. CT4 6YE
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