John Procter, Managing Director of Procter Sliding Gates, explains what architects and specifiers should consider when specifying sliding gates. This will help to ensure that the gates perform as intended, are safe to use and are economical to purchase and maintain.
Sliding gates are becoming increasingly popular, particularly powered and automated types, due to their security, space-efficiency and the wide variety of styles and infills available. Today sliding gates can be found in applications as diverse as houses, schools, hospitals, factories, warehouses, public utilities, airports, docks and ports, police stations and military bases. However, specifying sliding gates is a complex process, with many different factors to consider. This White Paper explains what to do and will help architects and specifiers to decide what they need prior to discussing their requirements in detail with potential suppliers.
Sliding Gates Advantages:
High security – They are difficult to force open, it is harder to access the more vulnerable points, and their more secure appearance acts as a deterrent.
Compact installation – Sliding gates normally require minimal space alongside a boundary whereas swing gates sweep a large area when opening – especially
for wide entrances.
More suitable for wide openings – One space-efficient sliding gate can often be used where a pair of swing gates would be needed – this also saves cost due to the number of mechanical and safety components being almost halved.
More suitable where the access roadway surface rises – Sliding gates are sometimes the only option here.
Uneven roadway surfaces – Can be passed over easily by cantilevered sliding gates.
Sliding Gates Disadvantages:
A run-back area is required – for each gate leaf (this is sometimes not available, depending on the site layout).
A guide track – is necessary for very wide openings (which means that periodic cleaning is required, depending on the volume of traffic, the nature of the site, etc)
Marginally less costly – Due to simpler construction.
More vulnerable to attack – than sliding gates.
Unsuitable for rising roadways – because they can foul the roadway surface.
If in doubt about whether sliding or hinged gates are the best option for a particular project, it is recommended that unbiased advice is sought from a supplier that offers both types (NB Procter Sliding Gates is a division of Procter Bros Ltd, of which the Procter Fencing Systems division manufactures hinged gates and fencing).
Sliding gates will most probably be one element of a perimeter security system that includes fencing and other features such as access controls, CCTV and electronic security/surveillance measures. It is important that the gates are not the weak point in the perimeter security, so care needs to be taken to ensure that the sliding gates are no less secure than the fencing. This has implications for the height, infill material and the fixings and fasteners used in the gate’s construction. Not only must the infill be difficult to cut, but it must also be climb-resistant (as must the support posts and leaf framework, of course). If appropriate, sliding gates can be equipped with anti-climb toppings as is often seen on high-security fencing.
It is also advisable to locate the gate so that it is clearly visible, and/or monitor it with CCTV. However, it is important to undertake a risk assessment before finalising the specification of the sliding gate and any associated security measures.
Size and Layout
In most cases the width of the opening is fixed, so it is a matter of specifying the gates to suit. The simplest option is to use a single leaf because, generally speaking, twin leaves require twice as many components. Most sliding gates are powered rather than manually operated, hence two leaves will also require twice as many components for the operating mechanism and twice as many safety components. However, if there is only a restricted amount of space for the runback area (the clear zone into which the leaf protrudes when it opens), then double leaves might be the only option. Furthermore, there is a limit to the size of a single-leaf gate, so very large openings may require a double-leaf gate (NB Procter Sliding Gates manufactures single-leaf cantilevered gates up to 8m wide and single-leaf tracked gates up to 16m wide).
Pedestrian traffic should be kept away from vehicular traffic for safety reasons, though site access requirements often mean that a hinged personnel gate needs to be installed adjacent to the sliding gate used for vehicular access. If a single-leaf sliding gate is installed, then the personnel access gate can be installed next to the pillar that accepts the gate leaf when it is closed. If double leaves are used in a bi-parting arrangement, however, then the hinged personnel access gate will need to be located outboard of the run-back area for the sliding gate leaf. An alternative would be to have a central gatehouse and personnel gate in the middle between the bi-parting gate leaves.
If double-leaf, bi-parting gates are installed it is normal to have both leaves the same width. However, for unusual site layouts it is acceptable to use leaves of different sizes.
Tracked Sliding Gates or Cantilevered Sliding Gates?
As with the question of whether to use sliding or swing gates, there is no simple ‘right’ answer to whether tracked or cantilevered sliding gates are best; it depends on the project requirements. In some cases the choice will be obvious (for example, if the ground is uneven then it will be better to use a cantilevered gate than one requiring a track to be laid) but, for projects when either type might be appropriate, the following table shows the main advantages and disadvantages for each.
Very wide openings – can be catered for (Procter Sliding Gates offer double-leaf tracked sliding gates for openings up to 32m wide).
Less expensive to manufacture – than equivalent cantilevered gates, though the cost of installing the track can outweigh the saving.
Mechanically simpler – than an equivalent cantilevered gate.
A guide track – must be laid in the surface of the access roadway, which requires a level roadway and more installation time.
Periodic maintenance of the track is required to keep it clear of debris (the cleaning frequency depends on the nature of the traffic, site, adjacent roadway, etc).
Uneven ground – is not a problem.
Simpler installation – No groundwork required for installing a track.
Simpler housekeeping – as there is no need to keep the area beneath the gate clear of debris.
A larger run-back area – is required, as the counterbalanced gate leaf is wider than the opening.
If there is no clear reason for using one type of gate or the other, Procter Sliding Gates usually recommends a cantilevered gate due to the advantages listed above.
Sliding gates can be used for a wide variety of applications, so it is important that the aesthetics are suitable for all types of project. Project Sliding Gates, for example, offers three series of sliding gates, one of which gives architects the freedom to design the gate leaves and support pillars (within reason). This means unique ornament designs can be created for private residences or prestigious commercial premises. Alternatively, on another series of gates the infill, colour and other details may be specified in order to customise the standard design.
Infill, for example, can be palisade, profiled welded wire mesh, railings or solid sheet metal. If the latter option is selected, laser cutting can be used to incorporate special designs – such as logos, numbers or text. Similarly, laser-cut profiles can be added to other types of infill. Note, however, that laser-cut features should always be assessed in terms of the impact they have on the gate’s climb-resistance.
In terms of finish, sliding gates for industrial premises are sometimes supplied in corrosion-resistant galvanising, though most gates today have a tough polyester powder coat applied on top to improve the aesthetics. Typically the supplier will offer a standard range of colours, with custom shades available to special order.
If installed at a workplace, powered gates also fall within the scope of the following:
- Provision & Use of Work Equipment Regulations 1998 (PUWER 98)
- The Health and Safety at Work etc Act 1974
- The Management of Health and Safety at Work Regulations 1990
Mechanical hazards presented by sliding (or hinged) gates are: crushing, cutting, shearing, entanglement, drawing-in and trapping. There could also be electrical, hydraulic and other hazards, depending on the design of the gate and its operating mechanism. Note that the accepted principle when addressing hazards is to design them out where practicable, then provide guards (eg physical guards around hazardous parts of machinery, and safety light barriers and safe-edges to detect the presence of personnel in potentially hazardous areas) and, finally, use warnings to reduce any residual hazards to an acceptable level.
Various British and European standards cover the design, use and testing of sliding gates. But note that the standards do not necessarily address every hazard. For example, if the run-back area is adjacent to a boundary fence, that fence may not be adequate to safeguard the area in which the gate moves; this fence must prevent moving parts from being reached through or over the fence, which will be a function of the size of the fence mesh apertures, the distance from the fence to the moving parts and the height of the fence. Although safety distances are laid down in the European standard BS EN ISO 13857, Safety of machinery. Safety distances to prevent hazard zones being reached by upper and lower limbs, this standard’s scope excludes children under the age of 14. In practice, the gate designer should assume that children will have access to the gates and misuse them (by attempting to ride on them while they are in motion, for example).
A new awareness of the need to CE mark powered gates is emerging, and many suppliers now state that their products are CE marked. However, a CE mark is only a claim of compliance; architects and specifies should therefore satisfy themselves that the gates do, in fact, comply with the Essential Health and Safety Requirements of the Machinery Directive 2006/42/EC and are, indeed, safe.
Because the safety of powered sliding gates is such a complex area, Procter Sliding Gates has published a White Paper, Safety requirements for powered sliding gates, which is available as a free PDF download.
Automation and Access Control
The vast majority of sliding gates today are automated by means of a powered actuator and a set of controls, with only small, infrequently used gates likely to be operated manually. Automation offers advantages in terms of security, health and safety and operational efficiency – especially where the gate is frequently used. If a gate is installed without automation, it is straightforward to retrofit an appropriate system in the event of circumstances changing and automation becoming desirable.
Over the last twenty years sliding gate manufacturers have used various means by which to transmit drive from the electric or hydraulic motor to the gate leaf. Chains are seldom used now, and some suppliers persist with friction drives, but Procter Sliding Gates uses a positive-driving rack-and-pinion that will not fail in the event of changes to the coefficient of friction resulting from grease that has leaked from bearings, wet leaves, sand or other contaminants. Because site requirements vary widely, automation systems are seldom the same from one site to the next. This is largely because of the role that access control plays within the automation system, and there are many different access control systems available, ranging from keypads, swipe cards and intercoms, through to induction loops and vehicle number plate recognition systems. In some cases, a combination of systems will be required so that, for example, company staff can freely access the site but visitors need to use an intercom. If a site has an existing access control system, it is important that the sliding gate is integrated within this rather than operating as a standalone access point.
For advice on the best type of automation and access control system, contact the gate supplier to discuss the site requirements and the options available.
As well as the main characteristics discussed above, there are other issues to address when specifying sliding gates; these range from fencing adjacent to the gate(s), lighting, and features such as flashing lights to warn when the gates are moving and other ways to increase visibility at night.
Remember, also, that planning consent may be required, depending on local requirements.
In general, the manufacturer will install the gate, as it is only during installation that the gate becomes fully assembled and can, therefore, be checked and CE marked (assuming the gate is powered and must comply with the Machinery Directive). It is vital that the gate is installed correctly if it is to perform as intended and with the required level of safety; this includes both the mechanical and electrical aspects, together with any associated access control system.
When a new gate is being installed in an existing entrance it is important to minimise disruption. This is why Procter Sliding Gates has designed its latest gates to be largely factory-assembled so that on-site work can generally be completed within one day. If installation time is important, architects and specifiers should check with the supplier for how long possession of the entrance will be required.
Architects and specifiers are also strongly advised to use installers that are accredited by organisations and schemes such as CHAS (Contractors Health & Safety Scheme), Construction Line, Safe Contractor, Secured by Design, and that adhere to an ISO 9001-2008 quality management system.
As with any machinery, powered sliding gates require periodic maintenance. Today’s gates are designed for a long, trouble-free life, but Procter Sliding Gates recommends that its gates are serviced annually or, if heavily used, every six months. This servicing not only maintains the operating mechanism and guides in good condition but also checks the operation of the safety features. If the site owner/operator does not wish to undertake this work, facilities management companies can sometimes undertake the work or the gate manufacturer can often provide a maintenance service.