Anchorage Guide for Work At Height

Categories: Working At Height Tags: Anchorage

There are many types of fall arrest anchorage equipment including chemical, expansion, ground, temporary and permanent, but which one would you choose and on what basis would you make that choice? It can be a daunting task especially if there are external pressures from clients, principal contractors, designers and even your employees to get the project completed on time. There are a few simple rules that should make life easier when choosing the correct type of fall arrest anchor; the first thing you have to do is consider the intermediate attachment equipment you will be using. Intermediate attachment is an all encompassing phrase used to describe the fall arrest equipment that connects the user and their harness to the anchorage point. Take this into account, as certain intermediate attachments require a higher standard of anchorage testing and certification and subsequently your method statements and risk assessments will need to be more detailed and complex. Lets take a closer look at the different types of anchorage equipment.

1. FALL ARREST TEMPORARY ANCHORS & LOCATIONS

This is a type of anchor that is used with Fall Arrest equipment, for example shock absorbing lanyards and inertia reels. “Temporary” means you can use it for that moment in time, it is temporary for you to use but it may be permanent to the structure. The most important aspect in choosing this type is that it has to withstand a dynamic force of 12kN which gives an appropriate safety factor, as fall arrest equipment has to limit the arrest forces to 6kN. This type of anchor might include the steel structure of a building, such as a structural column or a girder. Selecting the appropriate suitability of anchors is usually a decision which is made based on experience and competence. However if there is any doubt you should consult your architects, chartered engineers, or other such competent person ensuring that you have written documentation to support this decision. Anchor points should be chosen in consideration of the free fall distance required should the user fall. Where possible the fall arrest anchor should be above head height to minimise the fall distance required. Consideration should also be given when choosing the anchor location as to avoid the possibility of creating a pendulum swing fall.

2. FALL ARREST PERMANENT ANCHORS & LOCATIONS

This type of anchor is used with Fall Arrest equipment, as mentioned above. “Permanent” means an anchor that is designed to be nothing else but an anchor for fall arrest equipment; this includes any elements or components which are incorporated into the anchor point. For example, eye bolts, permanently installed wire or rail systems and dead weight anchors. The most important aspect of permanent anchors is that they must be installed, tested and certified to BS EN 795 by trained and competent people. That certificate must be attached to the permanent anchor and be legible. It is recommended that  A1 anchors (e.g. eye bolts) are installed by a qualified competent person. Further advice on installation and periodic proof loading of class A1 anchor devices conforming to BS EN 795 (which includes anchor devices designed to be secured to vertical, horizontal and inclined surfaces such as walls, columns, and lintels) can be found in BS7883.

3. DEADWEIGHT AND COUNTERBALANCE ANCHOR SYSTEMS

It is important that attention is given to wet or icy conditions as this can significantly affect the frictional performance of the anchor. BS 8437:2005 recommends that the anchor should be checked ensuring that it does not move when subjected to a load of four times that which will be applied in a work positioning situation, it further says that users should also consider the possibility of rescue, which might involve the weight of two persons.

4. PERMANENT HORIZONTAL FLEXIBLE ANCHOR LIFELINE

When installing a horizontal flexible anchor lifeline special consideration needs to be given to the deflection of the line when under fall arrest load, and particular attention needs to be given to the position of the anchor line supports when assessing the required free space below the user in case of a fall. Maximum distance between anchors, and the number of operatives attached to the anchor line must be strictly in accordance with the manufacturer’s instructions.

5. ANCHOR SLINGS

Anchor slings can be made of textiles, steel wire rope, or chain. Textile anchor slings should have a minimum breaking strength of 22kN and the minimum strength of anchor slings made from wire rope or chain should be 15kN. Due to the weakening effect of looping anchor slings or lanyards through themselves – a miss configuration known as larks footing or choking – should be avoided, unless they are specifically designed to allow this, for example by provision of special loops along their length, or designed to a higher rating to make an allowance for the miss configuration e.g. wire slings rated to 24 kN or higher.

6. ADJUSTABLE RESTRAINT ANCHORS

Restraint is a system of working that allows an operative to reach the leading edge or fall hazard and no further – if used correctly, thus preventing them from falling. Adjustable restraint allows the operative to set the restraint system to suit the task at that moment in time. This is done by setting the distance from the anchor point to the fall hazard using a rope grab cam device which fixes the correct length of rope taking into account the length of connectors etc. This prevents the user going beyond the point at which they could fall. It’s an ideal way of working for the roofing industry as the fall hazard changes almost on a minute by minute basis. The anchor point for adjustable restraint must be able to with stand a dynamic force of 12kN because adjustable restraints must have a fall arrest back-up (EN353-2), in the event of the system being misused. To reduce the likelihood of this type of system being misused it is recommended that all personnel who use adjustable restraint systems receive competent training and certification.

7. FIXED LENGTH RESTRAINT ANCHORS

Just as for adjustable restraint systems, a fixed length restraint lanyard allows the operative to reach the edge of a fall hazard but no further and so prevents them from falling. The system is a fixed length and therefore the anchor only has to be able to withstand 3 times the body weight of the user, this is in case the operative trips – or for some reason runs at the open edge!! Where several users are connected to the same anchor point it’s recommended that at least three times the combined body weight of the users is used. Working in fixed restraint prevents the operative falling and so removes some of the fall related issues, such as suspension trauma, fall height clearance etc. If misused in such away as to allow a user to fall the consequences can result in serious injury or death.

CONCLUSION

The selection and positioning of anchors is a critical element of working at height. Life and death hangs on the choice, and it goes without question that they should be utterly reliable and have an adequate margin of strength to be able to withstand the dynamic and static forces that could be applied to them in service. Choosing the correct anchor should be done on a risk assessment matrix basis and be selected using the experience and knowledge of a competent person; if there is any doubt, a suitably qualified person should be used to certify the integrity of the anchor selection.