Horizontal Lifeline Systems
What are horizontal lifeline systems?
Horizontal lifelines are designed to offer protection, as their name suggests, for horizontal work in which there is a risk of a fall to a different level. Moreover, collective measures cannot sufficiently protect against this risk.
The regulations are clear with regard to the horizontal nature of the work. Lines of this type cannot deviate more than 15º from the horizontal plane.
What are the applicable standards?
Before the latest amendment made in 2012, horizontal lifeline fall protection systems were regulated by the EN 795/1996 standard, in sections C and D, flexible and rigid lines respectively. In addition to horizontal lifelines, this law also regulates the anchorage points, in their various forms.
EN 795 has always been a "controversial" product standard. As already explained above in (APUNTAR ARTÍCULO), it has never received the unanimous agreement required by the European Union.
With the updated EN 795:2012 standard, things have become even more complicated, as its scope of application is now limited to:
Systems to be used only by a single user. Most, if not all, the permanently-installed horizontal lines and almost all temporarily-installed lines on the market are for more than one user.
Systems that can be dismounted for inspection. Elements anchored to structures are expressly excluded from its scope of application.
The management of this situation is now complicated, given the fact that everything excluded from this standard is to be regulated in Technical Specification TS 16415.
What are horizontal lifelines used for?
Horizontal lifelines are primarily installed as fall arresters, although, in some cases, they can also be installed to prevent falls. This latter case is known as fall restraint.
When mounting a fall arrester lifeline, either an estimation (rigid lines) or a calculation (flexible lines) must be made to determine the minimum free fall distance required and the forces that will be generated by the fall.
On the other hand, a fall restraint system is installed when, regardless of whether or not the minimum fall clearance distance is achieved in the calculation, the fall arrest system is used in such a way as to prevent the fall from happening.
Classes?
Horizontal lifelines can be either flexible or rigid.
Flexible lifelines: EN 795-C
As its name suggests, a flexible anchor line is made with materials, metal cables or work ropes that deflect with the impact generated by the fall. On the other hand, it should be mentioned that flexible lifelines are not generally designed for suspension work.
The Calculation
Based on the type of fall and, consequently, on the resultant impact, the cable will perform differently, with regard to the amount of stretch and also the amount of force transferred to the end anchors.
Consequently, it is not possible to standardise the calculation for flexible lines and create a generic calculation that could be used in all cases, instead calculations needs to be made on a case by case basis.
On the contrary, as rigid lines have no deflection, it is possible to calculate beyond the minimum estimated loads of the standard (EN 795-D).
Thus the obligation to make a calculation for each flexible line established in standard EN 795-C makes sense. The main aims of the calculation are to determine:
The Minimum Free Fall Distance
The Load at the End points
The Load at the End points
The factors affecting cable stretch are:
- The fall factor The greater the factor, the greater the stretch.
- The number of users anchored to the line.
- The actual line layout:
- The longer the line, the greater the free space required.
- The longer the spans (distance between intermediate supports) the greater the braking distance.
On the other hand, account should be taken of the multiplying effect of the cable, meaning that the lifeline end anchors are critical.
If, moreover, the lifeline is attached to an existing structure, then the regulations require the end anchors to withstand double the load contemplated in the calculation.
Other Related Concepts
The fall factor
Based on the position of the lifeline in relation to the worker, the fall distance will either increase or decrease.
Swing falls
The prevention of swing falls is as important as the minimum free fall distance.
Rigid lifelines EN 795-D
Unlike flexible lines, a rigid lifeline, does not deflect with the fall arrest impact.
It could therefore be obviously concluded that rigid systems are better than flexible ones, given the fact that:
- As there is no deflection, the minimum free fall distance is smaller.
- This type of lifeline generates smaller loads;
- The anchor sections or rails do not generate a cable multiplier effect.
- Therefore, unlike the flexible lines, the end anchors do not have to sustain additional forces.
- Generally, more people can be simultaneously anchored to these systems.
- Moreover, with just a few changes, it is also possible to perform suspension work.
Another fairly important factor, when deciding on which type of system to install, is aesthetics.
In general, fall protection systems are not eye-catching, and those with cables are even less so. Many architects opt to install rigid systems in order to maintain the aesthetic principles of the building being constructed. On the contrary, the number of rigid protection systems is infinitely lower than flexible systems, due to the fact that:
- They are far more expensive
Rigid Lifeline System applications
Fall protection
systems for truck tanks
Fall protection Systems
for Rope Access Works
The work to open the tank covers generally requires the installation of rigid lifeline systems due to the fact that:
- There is an extremely limited free fall distance, from the tank cover to the ground (3.5M), requiring the installation of systems with a fall factor of 0, which also do not deflect or increase the fall clearance distance.
- Normally these operations are performed outdoors, requiring the erection of specific structures to support the lines.
Elytra can carry out the study, calculation, design and installation of the structures to support these rigid lifelines. We can even handle the procedure to obtain official project approval by the Official Association of Engineers, if the customer so requires.
Fall protection Systems
for Rope Access Works
Fall protection systems for work positioning, or what is commonly known as "suspension work” or “Rope access works” must permit both types of loads: dynamic and static.
Rigid fall protection systems are good at withstanding static loads of this type because, unlike flexible systems, they do not become progressively distorted.
