Fall protection test tower

SATRA’s test tower is designed to assess the performance of fall protection systems that require a large test area.

The fall protection test tower installed in 2004 has proved to be a valuable resource to SATRA. The tower is 9 m high and fitted with a variety of rigging points and pulleys. Two test beams are fitted close to the top, the uppermost including a facility for an electric hoist. Two access ladders are provided and below the tower is an impact absorbing area to arrest the fall of any drop mass that is released due to the failure of a test sample. Adjacent to the tower is a 70m runway beam which can be used for the installation of cable-based anchor systems.

The tower has been used to carry out a test that replicates someone falling when his or her mobile anchor device is at the point of traversing an intermediate anchor bracket. The concern that led to this test is as follows. Because the intermediate anchor brackets generally consist of a tube (or sleeve) that encircles the vertical anchor cable, if the force of arresting the fall was sufficient to cause the intermediate anchor to release from its mounting bracket, there would be a possibility that the mobile anchor point would remain clamped onto the intermediate anchor tube. In this event the whole assembly would slide uncontrollably down the length of the anchor cable.

A second test that has been carried out to assess the performance of the system in a possible real life scenario, is to use an articulated anthropomorphic dummy to generate a backwards fall. Some guided type fall arresters use a cam which requires a downward force to lock onto the anchor cable and consequently there is a risk that a backwards fall would prevent an effective locking operation, again leading to an uncontrolled descent.

The test area incorporates a raised shipping container with floor to ceiling windows, which enables customers to watch their PPE products being tested from different angles.

Deadweight anchors

These are devices that are temporarily installed on roofs to provide an anchor point for anyone working in that area. The devices are not mechanically fixed in place so will not affect the integrity of the roof. Instead they rely on the friction with the roof surface to provide a reliable anchor point. The test involves building a test roof adjacent to the base of the test tower. The deadweight anchor device is then installed on the test roof, and connected to a 100 kg test mass via a steel cable that is routed via pulleys at the base and top of the test tower. The 100 kg mass is then raised 2.5 m and released. To pass the test the deadweight anchor must not move by more than 1 m during the arrest of the fall of the 100kg test mass. The SATRA test tower has been used to test many of these devices.

Temporary anchors

Other types of anchor, such as tripods, have been tested using the tower. These devices are subject to dynamic testing similar, but not identical, to that used for deadweight anchors, together with a static strength test.

Flexible horizontal anchor lines

These are used to cover large areas where workers need to be protected, such as on the roof of an industrial building. Unlike the deadweight anchor, which restricts the working area to a limited radius from the central anchor point, cable systems permit protection to be provided over a much larger area. The systems involve a cable (usually steel) being routed around the work area via a network of intermediate and end anchor points. A worker then attaches to the cable via a travelling device (or mobile anchor point), which is connected to his or her full body harness. When the worker moves across the roof the travelling device follows and maintains the connection to the horizontal anchor line.

To assess these cable systems using the SATRA tower involves building and testing configurations of cable systems that will be representative of typical installations. A 100kg test mass, connected to the horizontal anchor line, is dropped through the height needed to generate the required arrest force. During the arrest of the mass, the peak cable deflection and end load are recorded. To pass the test, these values must be within 20 per cent of the values predicted by the manufacturer. The height of the test tower has enabled SATRA to carry out tests with increased severity, including those to simulate several people falling at the same instant.

Electricity pylon tests

The tower was designed with universal mounting plates on two of its sides. These permit additional features to be installed to replicate conditions found in certain working environments. For instance, one side is currently fitted with a metal section designed to replicate the upper section of the leg from an electricity pylon tower. This has been used for a number of tests but of most interest are two tests that go beyond the scope of the current European standard (EN 353-1:2014 – 'Personal protective equipment against falls from a height. Guided type fall arresters including a rigid anchor line').

Temporary edge protection systems (guard rails)

The tower has also been used to apply horizontal test loads to scaffold structures fitted with edge protection systems to ensure that they can meet defined maximum loading and deflection criteria.

General strength testing

The test tower is fitted with an electric hoist and the horizontal runway beam can be fitted with anchor plates and a manual hoist. Hence by mounting a load cell on either structure it is possible to create a tensile test machine that can test components, either 8 m in length on the tower or 70 m in length on the runway beam.

---