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.
Applications for Engineered Horizontal Lifelines
Lifelines on roofs
Flexible lifelines are primarily installed on roofs due to their lower cost in relation to a rigid system.
Solutions vary, depending on the type of roof and anchorage in question.
Structural anchorage
As already indicated above, cable lines transfer the loads to the end anchor points, multiplying the loads generated at the point of the fall. This is known as the cable multiplier effect.
Moreover, for structural anchorage, the standard establishes that they should be made for double the load calculated.
If the loads sustained at the end points are already going to be high, and given the fall factor 2 used for anchorages of this type, it goes without saying that particular care should be taken over the anchorage place of installation.
- Decking; for roofs with conventional tiles.
- Truss structure for lightweight roofs; sheet metal, panels, etc.
- Beams; for roofs with hollow bricks.
Load Reducing Anchors (ARC)
When seeking an anchor point to secure a fall protection system, it can be complicated to find the best structural member and difficult to value its cost.
To avoid having to find structural members, someone came up with the idea of Load Reducing Anchors (ARC).
The great advantage of this fixing system is that these anchors reduce the loads to under the load that can be sustained by lightweight roofs. Moreover, they considerably simplify the installation work and the cost can be calculated more accurately.
- Sheet metal or sandwich panel roofing.
- Kalzip, standing seam roofing.
- Inverted or deck type roofing
Lifelines on Travelling Cranes and Runway Tracks
Cranes are one of the most common applications for the certified horizontal lines.
Travelling cranes
Running Rails
Movements along travelling crane beams for crane maintenance and repair work can only be protected with flexible horizontal fall protection systems. Let's explain:
Running rails
Access to the cranes from their running rails is also a high risk area for different level falls. Access to cranes often involves moving along the running rails. Unless the gangways are extremely wide, these movements are difficult to protect with collective protection systems.
Other fall protection system applications
Fall Protection Systems for Train and Bus Roofs
Fall Protection Systems for cleaning curtain walls and windows
The free fall distance between the roof and ground tends to be very low. In order to minimize the free fall distance, a fall factor 0 system shall be installed above the operator's head.
- Reducing the catenary of the lifeline spans.
- Using more rigid cables.
- Making the lifeline tauter at its ends.
Fall Protection Systems for cleaning curtain walls and windows
The installation of fall protection systems of this type is not a problem unless the fixing to the structure is complicated.
The necessary free fall distance is not such an important requirement as it was in the application above, unless dealing with windows on the first floor, close to the ground. In this case, the fall protection system shall be mounted with a fall factor of 0.
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.
- 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.
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.
