When assessing safety for gates, not only are the planned users of the gate to be considered, but also the passers-by and unanticipated visitors.
Children will casually run their hands over gates or railings as they walk past and readily reach into gaps, and it is not uncommon for elderly or disabled people to hold on to posts or rails for support.
Although it is not obvious to passers-by, there are a number of potential hazards that may be present on what is, in effect, an automated machine. This responsibility falls firmly with the installer and should be considered when risk assessing any existing or new gate installation.
Speaking about gate safety, IN2 Access and Control’s Director, Derek Foreman said: “As with any potential hazard, the most effective way of eliminating these would be to design them out, ensuring gaps are less than 100mm and hinge gaps do not reduce during operation of the gate, so that they no longer present a danger.”
“When this is not possible, there are several technologies available in today’s market which can reduce and eliminate these hazards, including mechanical guards, pressure sensitive safety edges and optical solutions; all of which have benefits and drawbacks.”
Gaps to prevent crushing are referenced as per EN 349, which gives distances between 25mm and 500mm for various parts of the body, but as we cannot predict which body part will be affected; anything that will fit in the wider gap could be at risk. Essentially, any reducing gap below 500mm must be protected.
The Door and Hardware Federation (DHF) have negotiated with Health and Safety Executive (HSE) to describe practical limits for safe (zero gap change) hinge areas as follows:
- Maximum post/stile gap of 100mm (BS 6180)
- Minimum post/stile gap of 25mm (to prevent finger draw in)
- Maximum gap change from open to close of 20% (because minor gap changes would not cause injury)
Anything else must be protected.
Mechanical Guarding
This method tends to be the lower cost solution of the three available technologies. Mechanical guarding physically shields the hinge gap and prevents people from getting hands or fingers trapped in a closing space. This is typically a wide strip of EPDM flexible rubber-like material which is clamped by two pieces of aluminium to the surface of the gate or piers.
There is no standard available for these devices; hence there is no referenceable “state of the art” as is the case with fixed rigid guards and safe edges. Anyone considering the use of a flexible guard must consider their use and suitability against the relevant Machinery Directive Essential Health and Safety Requirement 1.4.1:
- Must be of robust construction
- Must be securely held in place
- Must not be easy to bypass or render non-operational
There will need to be some form of verification of their performance as fitted to ensure that they remain effective under all foreseeable conditions. For instance, when someone falls against the guard. This does not mean that they should not be used, just that a machinery directive compliance assessment must be made on-site as installed.
This is a simple low cost and quick-to-install solution.
This solution is not, however, considered the most aesthetically pleasing of the three, as they are very visible at the gate pillars.
Pressure Sensitive Safety Edges
These are available in a variety of sizes from 8mm upwards – the most commonly used being resistive edges, which are monitored by either a separate CAT 2 or CAT 3 safety controller, or more increasingly, available 8K2 Ohm safety input directly on the control panel of the gate.
The safety edges are made from a durable rubber and are part of a fully monitored safety system which, should they be damaged or removed, would stop the operation of the gate until rectified.
The installation of this solution is typically more involved than the previous method and it is important that the correct profile size is selected and positioned correctly when fitting to the gate, or gate piers.
Optical Solutions
This tends to be the least cost effective solution of the three, but will generally replace other required safety devices on an automatic swing gate.
Typically, a laser scanner is used with time of flight technology offering alternatives to using rubber safety edge systems on the remainder of the gate hazards and is sometimes chosen for more ornate or prestige gates. Mounted on both sides of the gate, these devices detect any object entering the protected area and would typically stop the gate until the obstruction has been cleared.
Typically, these devices can be less reliable than previous solutions due to the method of detection and would require general housekeeping (i.e. cleaning, removal of leaf litter etc.) to ensure reliable operation is maintained.
For further impartial guidance on gate safety, you can find comprehensive information by downloading the DHF's “Guide to Gate Safety Legislation and Standards”. Or by visiting the HSE website here.
Image: AAC Service LLP
Copyright: The Crown Estate
