10.1 - Safety nets
SMD safety net stock, in excess of 50,000m², is managed, repaired, maintained and tested by our fully trained stores teams located at our Logistic Centres in the Midlands (Nottingham) and Scotland (Coatbridge).
In addition to a unique visual ID tag attached to the net, all nets carry an RFID tag which is linked to our net management software ensuring net location, test date and required maintenance is logged and maintained in a central system. This ensures these safety critical nets are kept to the highest standard and ready for issue to site as required.
10.1.2 Safety net installation
When choosing a fall arrest system, the use of nets must be planned; consideration must be given to the following:
Safety nets are only suitable as a collective passive form of fall prevention where suitable fixing points with a proven load strength of 6kN are provided. Typically, this takes the form of a primary steel frame or anchored fixings into a concrete core or wall.
Where deck spans are designed such that pre-propping is required (temporary props in place prior to installation), a different method of fall arrest may be more appropriate due to the logistical issues for net installation and removal caused by the temporary props.
NOTE: Safety netting must not be fixed to secondary steelwork such as scaffold handrails or cladding rails.
Safety nets are usually only suitable for floor heights in excess of 3m. The floor below must be clear of all possible obstructions or protrusions. When planning safety netting, reference should be made to the deflection chart within FASET guidance. As a general rule the storey height in metres should be a minimum of: 2 + (shortest span of the nets in metres / 5)
Example: For a net with a shortest span of 6m: 2m + (6m/5) = 3.2m floor minimum storey height
There are a number of recognised methods for installing safety nets that are approved by FASET. The preferred method will depend on numerous factors such as storey height, ground condition, site-specific rules etc.
The recommended methods are:
- Storey heights 3.0 – 4.5m
- Net pole and claw with the occasional use of ladders
Storey height in excess of 4.5m
MEWP or rope access technique.
The use of a MEWP (mobile elevated working platform) is preferable, however there are instances where this may not be suitable (ie. where use of a MEWP would mean extending the boom through more than one floor of steel work or poor/restricted access for MEWP’s).
Rope access is a suitable method for safety net installation where storey heights exceed 4.5m and MEWP access is not possible. It should be noted that the Rope access technique is considerably more time consuming and will therefore impact on both programme and cost.
Note: In some circumstances MEWP’s may be required when working below 4.5m. Unless MEWP's have been specifically requested the standard Net pole and claw technique should be used.
Ground conditions and access using Plant (MEWP)
MEWPs rely on ground conditions for their stability. This applies equally to those which require the use of jacks or outriggers and those which operate free on wheels. Poor ground may well settle when subjected to the loads of MEWP's wheels or outriggers and this in turn will result in the machine being out of level and becoming unstable and unsafe.
A visual inspection is often adequate however, it is essential that the assessment is made by persons with relevant knowledge and experience to know when further expert advice and assessment is required.
Ground bearing capacity can also change throughout the project with weather & site conditions such as new excavations, a view of the conditions needs to be an on-going activity.
It is important to note if the ground conditions are unsuitable on our arrival to site, for Health and Safety reasons ours teams will not be able to carry out their works, which in turn could lead to additional delays and costs.
Nets can be de-rigged in the same ways in which they are rigged, dependent on the storey heights and the site requirements.
Nets must not be de-rigged until the decking sheets are 100% fixed into place and stitched together, or on to floors that have had studs welded as this creates multiple snagging points once the nets have been lowered.
Safety netting must be de-rigged prior to any welding operations as the weld splatter will burn through and damage nets.
10.1.3 Safety Nets Used in Isolation
The use of Personal Active Fall Protection (Harnesses) in Conjunction with Safety Nets.
Safety Nets, used in isolation, provide effective fall protection for the installation of metal decking at height and have become established decking industry best practice since the late 1990s.
Reliance exclusively on a safety netting system, that provides passive / collective protection, has resulted in zero recorded injuries from falls from height during the installation of decking in the last 10 years. Whilst there have been instances where decking operatives have fallen into a net these have all recovered unaided, without sustaining injury.
Nets are rigged as close as possible to the underside of the steel frame, which generally results in a maximum potential fall height of 500mm with minimal associated risk in the event of a fall.
When the BCSA Best Practice Guide for Metal Decking & Stud welding was written contributions were received from industry experts, safety professionals and Andrew East of the HSE. Whilst this document is not an ACOP, it can be held up as evidence of best practice which is particularly relevant given the HSE’s move away from prescriptive documentation. The BCSA Guide clearly states that reliance exclusively on safety netting is acceptable.
Reliance on safety netting in isolation is widely accepted on UKCG projects throughout the UK and HSE state a preference for collective, passive fall arrests (i.e. safety nets) over active personal solutions (i.e. harnesses)
FASET'S Three C’s of Safety Netting
Being a FASET member, all netting installed by SMD is 3C compliant as follows:
- Compliant Product - Nets manufactured to BS EN 1263-1
- Comprehensive Maintenance - SMD are a FASET member with comprehensive procedures and records
- Competent Riggers - SMD riggers are competent & certified to BS EN 1263-1
Personal fall arrest protection as an extra precaution
Issues surrounding the use of harnesses/lanyards/inertia reels etc in conjunction with nets are:
- Storey heights - are rarely sufficient for a personal fall arrest solution to work taking into account lanyard lengths, shock absorber tear out, operative’s body length, stored materials etc.
- Attachment points - suitable anchorages are rarely available in a suitable location and with sufficient structural capacity for fall loads which are dynamic & considerable.
- Inertia reels are a system that protects one edge may not protect from a fall over another, due to the “pendulum" effect.
- Increased risk of fall - operatives often experience snatch or snagging with running lines & inertia blocks which could cause a fall into the net.
- Added risk - the activity or installing/removing personal fall arrest devices at height may increase the overall risk of the decking activity when compared to the use of nets alone.
- Fall Injuries - in the event of a fall into the net, an operative attached to personal fall protection could be injured by the tether/lanyard/inertia line.
- Rescue Issues - in the event of a fall into the net, the very fact that operatives are attached would complicate any rescue / recovery.
Youngman staging / Span deck type systems have been considered & discounted due to the risk increase when the staging is being installed and moved. If a board is located on the leading edge they need to be manually moved to allow the next sheet to be installed. This creates a hole through which the operative could fall and also introduces a new manual handling consideration as the staging would need to be a minimum of 7m in length.
Airbags/Bean Bags provide passive / collective protection and are mainly used when decking is being installed to masonry structures. Increased fall heights, speed of installation, issues at perimeters adjacent handrail and handling concerns make this a less favourable solution than netting.
The installation of decking is very similar on numerous projects. Safety nets, used in isolation provide a suitable, sufficient and robust fall arrest solution that satisfies the requirements of legislation and the Health and Safety Risks would not be reduced by introducing active, personal protection and, to the contrary, would increase.
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