Machinery, and the duty that comes with it
Put an operator on a gate and the gate and its automation together become
machinery. A new powered gate installation falls under the
Supply of Machinery (Safety) Regulations: it has to be designed
and built so that it is safe in normal use, it has to be assessed and marked as
conforming, and it has to be handed over with the documentation that records what
was done and what was proved. That paperwork is not a formality. It is the only
written account of how the gate was set up and what it was measured at on the day
it was left running.
From then on the duty of care moves with the building. Whoever is responsible for
the premises is responsible for the gate: keeping it maintained, keeping its
safety devices working, and being able to show that somebody competent has checked
it. We cannot take that duty off you and neither can anybody else. What we can do
is install a gate that meets the standard, set the forces properly at
commissioning, write the readings down, and come back and check them.
BS EN 12453, and what a compliant gate does on contact
BS EN 12453 is the standard for the safe use of power operated
gates, and most of it comes down to one idea: force limitation. A
gate set up to it does not simply stop when it meets an obstruction. It stops
within a limited force, within a limited time, and then backs off. The forces are
measured with a force tester at the points the standard specifies — the
leading edge, the closing edge, the places where a gate can trap something
— and the readings have to fall inside the limits the standard sets. They
are measured, not judged by eye.
Force limitation is only one of the ways of protecting an edge.
Photocells across the opening, safety edges on
the moving parts, and how the gate is guarded all do their share, and which of
them a gate needs depends on where it is, who uses it and whether those people
have been trained. A gate on a private drive and a gate on a communal entrance
used by residents, visitors and delivery drivers are not the same problem, and
they should not get the same answer.
A gate that has been set up properly
Stops within the forces the standard allows and then backs off. Photocells
and safety edges that have been proved to work. Readings taken with a force
tester, written down and dated, so somebody can tell you when it was last
known to be safe.
A gate that has not
Closes with whatever force the motor can produce. Relies on people getting
out of the way in time. Has a photocell nobody has tested, an edge nobody has
pressed, and no record of a single reading — so nobody can say whether
it is safe or not.
Why an unserviced gate becomes dangerous
Gates rarely fail all at once. They drift, and the drift is invisible, because a
gate with a dead safety device opens and closes exactly as it did the day before.
Four things go wrong quietly:
Photocells fail or fall out of alignment. A knock from a
vehicle, a loose bracket, a lens full of dirt or a wet terminal, and the beam that
was protecting the opening is no longer protecting anything. Nothing about the
way the gate behaves tells you.
Safety edges wear or seize. The strip along a moving edge is
rubber and it lives outside. It splits, it fills with water, the sensing element
inside corrodes, and the edge that was meant to feel contact stops feeling it.
Force settings drift out of limit. Hinges wear, a leaf sags, a
post moves, the ground shifts, and the gate starts to bind — and the usual
response is to turn the force up until it closes again. Every one of those
adjustments pushes the gate further outside the limit it was commissioned at.
And the trapping points are always there. There are crush points
where a swing gate closes on its hinge post and where a sliding gate meets its end
frame, and shear points along the run of a sliding gate where it passes a fixed
structure closely enough to trap a hand or an arm. Those points exist on a
properly guarded gate too. The difference is that on a properly guarded gate they
are protected, the forces are limited, and somebody has checked recently that they
still are.
The words on your quote
- Force limitation
- How hard the gate is allowed to push. The
gate is set so that when it meets something it stops within a defined force and
time, then reverses. Measured with a force tester, not set by feel.
- Photocell
- A beam across the opening. Break the beam and the
gate stops or reverses. It protects the line it crosses and nothing else, which
is why one pair is rarely enough on a busy entrance.
- Safety edge
- A pressure-sensitive strip on a moving edge.
Something presses on it, the gate stops. Fitted where the risk is contact with
the gate itself rather than something crossing its path.
- Crush point
- Where a moving part closes on a fixed one. A
swing leaf on its hinge post; a sliding gate meeting its end frame. The gap
closes to nothing, so it has to be guarded or the force has to be limited.
- Shear point
- Where a moving part passes a fixed one. Along
the run of a sliding gate in particular, close enough to trap a hand or an arm
between the two.
- Force tester
- The instrument that gives you a number. It
measures the forces at the points BS EN 12453 specifies, so the result can be
recorded, compared to the limits and compared to last year.
- Manual release
- How you move the gate with the power off. A
key or lever that disengages the motor — for a power cut, for getting a
vehicle out, and for leaving a gate safe while it waits for a repair.
- Operator
- The motor that moves the gate. Underground, ram
or arm on a swing gate; a rack-driven unit on a sliding gate. We use CAME
automation.
What you get at the end
A new gate is handed over with the documentation that goes with a piece of
machinery: what was installed, what the safety devices are and where they are, the
force readings taken at commissioning, the operating and manual release
instructions, and the recommended service interval. The electrical installation
feeding the gate is certified separately under BS 7671 — that side is
covered on our
electrical
and data installations page. Keep all of it. It is what an insurer, an
inspector or the next contractor will ask to see, and on a gate somebody else
fitted it is almost always the thing that is missing.