Gate Safety Hazards and Controls

Hazards And Controls

When identifying hazards and danger zones associated with powered gates, you should consider, among other things, the following:

  • Any points where persons may be injured by being crushed or becoming trapped, for example:
      • meeting point between swing gates when closing,
      • sliding gate at “end of travel” positions,
      • trapping of feet between lower edge of gate and ground,
      • space between a moving gate and a fixed object, and
      • contact with moving parts at the drive unit
  • Hazards from being caught or hooked by sharp edges or projections;
  • The impact forces produced by a gate when it strikes a person or an obstacle;
  • Hazards associated with the gates being activated automatically, or by another person (for example, by a sensor under the road surface activating a gate when a car drives over it, a remote button, a key fob pressed by a third party or a gate operated by dialling a mobile phone);
  • Possible ways in which safe operating systems (such as key-pad or key-fob systems) could be defeated, bypassed or inappropriately operated, thereby placing any person at risk. (This is particularly relevant where children, members of the public, or persons not familiar with a location have access to powered gates and may not recognise a risk to their safety);
  • The possibility of gates becoming detached from their supports and falling over;
  • All danger zones up to a height of 2.5m should be identified; and
  • Electrical hazards, such as electric shock or erratic behavior due to ingress of moisture on electrical circuits.

Increased risk

Factors that can give rise to an increased risk include:

  • use by children,
  • use by infirm or elderly people,
  • unrestricted access or other instances when it is not possible to instruct, train or supervise the gate users,
  • high frequency of use or large number of people passing by, or
  • a high degree of automation.

Generally, a perimeter gate, where the public may be present as users or passing by, will require the highest level of safety provision.

Powered gates: Specific Hazards and Control Measures

This guidance will address in detail two types of powered gates: sliding gates and hinged gates.

Sliding Gates

Figure 1 shows a plan and elevation view of a cantilever sliding gate. Figure 1(a) shows a sliding gate on tracks.
Areas A to H show the areas where injury could potentially be caused.
The bullet points A to H describe these hazards and the type of measures needed to control the risk from each
hazard. Figure 2 shows how safe edges can be installed to prevent crush and entrapment injuries.

Sliding Gate Hazards

 A - Main closing edge: crush and impact hazards controlled by either inherent force control, safety edges, light/radar curtaining or by having the gate hold-to-run.
Inherent force-control can be provided by intelligent drive units that cause the gate to reverse when an obstruction is sensed.
Safe edges are sensitive rubber switching strips which, when contact is detected, send a signal to the gate controller to reverse the movement of the gate.
Light/radar curtaining means placing a curtain of light or radar in front of the danger areas. If the curtain is breached while the gate is operating, the gate will reverse its direction. This may be installed to give protection to vehicles primarily but it will also prevent inadvertent contact with pedestrians.
Hold-to-run means that the gate can only be opened or closed by a person positioned in a safe area, consciously placing continuous pressure on a controller.

B -  Main opening edge: crush and impact hazards (crush hazard exists whenever a leaf closes to within 500mm of a fixed object, impact hazards are present throughout movement) controlled by either

  • Guarding
  • Safety distances - see Figure 4
  • Inherent or safety edge derived limitation of forces
  • Hold-to-run or light/radar curtaining

C - Entrance portal support frame: shear or draw in hazards controlled by either:

  • Safety distances
  • Safety edges – See Figure 2
  • Hold-to-run or light/radar curtaining

D - All other support frame, leaf or perimeter: shear and draw in hazards controlled by either:

  • Guarding
  • Safety edges
  • Hold-to-run or light/radar curtaining

E - Upper guide/roller draw in hazards controlled by either:

  • Guarding
  • Hold-to-run or light/radar curtaining
F - Lower cantilever gate rolling gear hazards (see Figure 1) controlled by either:
  • Lower edge slot for internal rollers
  • Guarding for external or exposed rollers

G - Lower tracked gate rolling gear hazards - see Figure 1(a) controlled by:

  • Guard to within 8mm of ground

H - Drive unit draw in hazards controlled by:

  • Guard

Please Note:
The preferred method of protecting risks B, D, E and H is to guard off the entire run-back area of the gate and provide a maintenance hatch for drive unit access.
List A to H is not exhaustive, other examples may exist depending on design detail. 

Gate Hazards

Hinged Power Gates

Hinged gates have some similar hazards to sliding gates. However, the fact that the gates swing open and closed presents some other hazards that must also be considered.

Swing gate hazards

A - Main closing edge crush and impact hazards controlled by either:

  • Photo-electric beams on the closed face in combination with inherent or safety edges or limitation of forces
  • Hold-to-run or light/radar curtaining

B - Opening crush and impact hazards controlled by either:

(Opening crush hazards exist wherever a leaf opens to within 500mm of a fixed object, impact hazards are present throughout movement)

  • Safety distances, for the crush element only - see Figures 6 and 7
  • Inherent or safety edge limitation of forces
  • Hold-to-run or light/radar curtaining

C - Hinge area crush, draw in or shear hazards controlled by:
  • Safe design hinges - see Figure 7
  • Guards
  • Safety edge
  • Hold-to-run or light/radar curtaining

Hinge Hazards

D - Lower edge shear and crush hazards controlled by either:

  • Safe distances in combination with inherent limitation of force - see Figure 8
  • Safety edges on both sides of lower opening edge
  • Hold-to-run or light/radar curtaining

 Swing Gate Hazards

Please Note:
This list is not exhaustive, other examples may exist dependent on design detail. Nonetheless, all hazards must be revealed by assessment and controlled.

Overview of safety measures

An overview of the measures which may help to reduce risk:

  • controlling separation distances between fixed and moving parts to reduce hazards from crushing, shearing and drawing-in points;
  • Ensuring adequate separation distances between the control panel and the nearest danger point on the gate so that the user is not in a dangerous position and people cannot reach through a gate to operate a control panel on the other side;
  • installing guards, for example a fixed guard to cover mechanical trap points such as guide rollers or sprocket drives;
  • providing leaf surfaces that are smooth and free of parts that protrude which could catch people’s clothing;
  • operating the gate in hold-to-run mode;
  • limiting the forces, for example protection built into the drive system; and
  • installing sensitive protective equipment such as pressure sensitive strips (safety edges), safety sensor flooring, light/radar curtains or similar protective systems.

 Sliding gate hazard

 

It may be necessary to combine the above approaches to achieve an acceptable level of safety, as indicated in table 1 of EN 12453:2001.

ISO EN 13857 provides information on safety distances to prevent hazard zones being reached.

The use of European standards (ENs) covering safety requirements, test methods and safety distances will assist the risk assessment.

EN 12453 specifies minimum levels of safeguarding of the main edge for different types of users. It also specifies a maximum crushing force of 1400N for gaps greater than 500mm, a maximum allowable crushing force of 400N for gaps between 50 and 500mm, and that the force exerted on contact must have reduced to no greater than 150N within 750 milliseconds.

The gates should also reverse if they inadvertently hit someone or something, and the gates should have an emergency release mechanism in case someone gets trapped.
Methods for testing forces are specified in EN 12445.

EN 12978:2003 + A1:2009 deals with electro-sensitive protective equipment (ESPE) (for example, light curtain) and pressure sensitive protective equipment (PSPE) (for example, safety edge). However, it does not cover other currently available technologies such as inherent force limitation or programmable systems (see section below on Standards).

Further information on the Powered gates and the Machinery Regulations 2008 can be found HERE