Safety nets have become an essential part of the construction industry, specifically aimed at preventing the risk of material and human falls from heights.
Until a few years ago, safety nets in projects located in central locations of large cities were quite noticeable, but they have become increasingly widespread as time goes on.
Ropes
In TS 1263-1, ropes are classified into three categories based on their usage: edge ropes, tying ropes, and connecting ropes. "Edge ropes" surround the nets and are the components that evenly distribute the impact caused when the safety net is subjected to a load and support the final load. "Tying ropes" connect the nets to hook points, while "connecting ropes" are used to join multiple nets. The standards mention only ropes for connecting the nets to supporting structures or between each other, while in the industry, materials such as alloy or steel hooks are commonly used for these operations.
Nets
In TS 1263-1, the term "net" is defined as "the connection (union) of small net openings."
Nets are examined in four categories based on the maximum net opening size (IRmR) and the minimum energy the net must have (ER AR and ER BR). The choice between Q and D mesh-patterned nets in the market is generally determined by the requirement for edge rope usage. In S and V type safety nets, where the use of edge ropes is mandatory in the standards, D mesh-patterned nets are typically used.
SAFETY NET CLASSIFICATION
In TS EN 1263-1 Standard, safety nets are classified into 4 categories:
Class A and B define the minimum energy absorption capacity of the net, i.e., how much energy it can absorb. This capacity is expressed in kJ.
For example, Class A has an energy absorption capacity of 2.3 kJ, while Class B has a capacity of 4.4 kJ.
Class 1 and 2 define the maximum net opening sizes.
For example, the size for Class 1 is 60 mm, while the size for Class 2 is 100 mm.
NET OPENING ROPE
The net opening rope must be made of at least 3 separate threads, tightly braided together and must have been tested according to TS EN 1263-1 Standard, Section 7.3.
EDGE (BOUNDARY) ROPE
The boundary rope is the continuous rope that passes through each net opening around the perimeter of the S and V safety nets. The minimum tensile strength of the rope depends on its type.
For example, Type K rope should have a tensile strength of 30 kN. Edge ropes must be tested according to TS EN 1263-1 Standard, Section 7.5.
ATTACHMENT ROPE
Attachment ropes connect the safety net to the anchor points and/or structural elements of the structure where the net is installed. The minimum tensile strength required for the rope depends on its type. For example, the tensile strength for Type L or Type M rope is 30 kN, while for Type R rope, it is 15 kN. If Type F rope is used, the minimum tensile strength should be 20 kN. (For ropes, the types, minimum tensile strengths, and the safety net systems they are used for can be found in TS EN 1263-1, Section 4.3.)
Attachment ropes must be tested according to TS EN 1263-1 Standard, Section 7.5.
JOINING ROPE
The joining rope is used when multiple safety nets are required for an area to be protected. The minimum tensile strength for this rope must be 7.5 kN, and it must be tested according to TS EN 1263-1 Standard, Section 7.5.
SAFETY NET LABEL
Safety nets must have a label showing the following information:
The label must be permanently attached to the net and remain in place for the duration of the net's life.
USER INSTRUCTION MANUAL
For the use and application of safety nets, a (guide) instruction manual, according to TS EN 1263-1, Section 9, should be provided with each delivery of the net. This usage instruction must be in the user’s native language. The instruction manual should at least contain information on the following topics:
In addition to these instructions, special installation instructions related to the net’s specific applications should also be considered. According to TS EN 1263-1 Standard, Section 9, the following information must also be included in the instruction manual and provided with the safety net:
REMOVABLE TEST NET EYE
Safety nets must be tested at least every 12 months for deterioration due to UV rays. All safety nets should have at least three net eyes loosely woven for testing purposes. Each test net eye must have the same number, be made of the same material, and be from the same production batch as the attached net.
For all safety nets older than 12 months, there should be an existing test label indicating that the net was tested within the past 12 months and meets the manufacturer’s minimum test energy absorption capacity. Test labels are valid for 12 months, and the labels should not be expired when the net is installed. The net owner must keep the test results for the net.
DIMENSIONS OF SAFETY NETS
The TS EN 1263-2 Standard applies to system S safety nets, and system T, system U, and system V safety nets, which have an area of more than 35 m² and where the shortest side of the net is at least 5 meters long.
Considering the scope of the TS EN 1263-2 Standard, system S safety nets must meet the following criteria:
If a load falls on a net smaller than 35 m², compared to larger nets, due to the smaller net area, there will be less stretching and more limited energy absorption. When the net area is less than 35 m², a B-class net with a 4.4 kJ energy damping capacity may be preferred.
FALL HEIGHT
Fall height is the distance a person falls from the work platform to the safety net. The larger the fall height, the greater the impact when falling.
The fall height should be kept as minimal as possible by installing the safety net as close to the work platform as possible. If possible, safety nets should not exceed 2 meters from the work platform. The maximum fall height permitted by TS EN 1263-2 is 6 meters. (This corresponds to a nominal fall height of 7 meters considering the worker’s center of gravity.)
Within a 2-meter distance from the outer edge of the net, the fall height (Hr) between the work platform and the net should not exceed 3 meters. This is because safety nets do not stretch excessively at corners and edges. (TS EN 1263-2)
If the slope of the work platform is more than 20 degrees, the distance between the edge of the work platform and the lowest point of the outer edge of the safety net should not exceed 3 meters.
He: Fall height
b: Catch width
c: Lowest point of the outer edge of the safety net
t: Distance between the edge of the work platform and the lowest point of the outer edge of the safety net
CATCHING WIDTH
When a worker moves, if they get caught, they are subjected to a downward fall as well as a forward/falling movement. The distance of the forward fall is affected by the fall height. In other words, the higher the fall, the greater the forward movement. Safety nets that provide protection at the edge of the work platform should be wide enough to cover the forward movement of the falling person. The net width between the edge of the work platform and the outer edge of the safety net is referred to as the catching width.
The minimum catching widths for the maximum fall heights specified in the TS EN 1263-2 Standard are shown in the table below (Table 3).
GAP (CLEARANCE) DISTANCE
When a worker falls, there must be sufficient clearance under the safety net to allow for its deformation (stretching). The amount of deformation depends on the fall height and the width of the net.
NET SAGGING
Net sagging or initial sagging is the amount of deformation (stretching) caused by the net’s own weight. Net sagging should be between 5% and 10% of the shortest side of the net.
To achieve sufficient initial sag, the safety net should be at least 10% larger than the area it will cover (along both sides). Excess netting should be rolled up at the attachment point or attachment system to distribute the load evenly and prevent excessive stress on the net.
EXCESSIVE STRETCHING AND LOW STRETCHING
Safety nets should not be excessively stretched in order to allow for flexibility and absorb the energy created by the fall. An overly stretched net or one with too many attachment points may not stretch enough. In both cases, the impact on the person falling onto the net increases, and the load on the net and structure also increases.
A net that is too loosely stretched may stretch too much, and if there is not enough clearance beneath the net, the falling person may hit an obstacle or the ground.
APPLICATIONS
Safety nets should be installed according to the criteria specified in the TS EN 1263-2 Standard:
Safety nets are designed to absorb the energy from falls up to 6 meters, but they should be installed as close as possible to the working surface. The scope of the areas protected by safety nets should be clearly specified, and workers should be warned not to exceed the safety net boundaries.
When safety nets are the first level of fall protection, meaning that falls cannot be prevented by other means, the safety net should preferably be installed no further than 2 meters below the working level.
When safety nets are used within system T, they should generally be considered as the second level of fall protection, in addition to measures like the use of guardrails. System T safety nets should be placed horizontally or with a slight backward slope.
Safety nets used in class A and system S, if used for falls from heights greater than 2 meters, should have an area of no less than 35 m² and the shortest side should be at least 5 meters. If any of these two criteria are not met, a class B safety net should be used. Small area safety nets should be installed after consulting with the manufacturer.
When safety nets are installed to protect workers from falling from the edge of a working area, they must have sufficient catching width to accommodate the potential horizontal movement of the falling worker.
In practice, when selecting the net to be used, it should be noted that the energy absorption capacity of the net decreases with age, and the lifespan should be considered. If the nets will be in use for a year or more, checks should be conducted to ensure that aging has not reduced the net’s energy absorption capacity below the classified level during the usage period.