How are ropes tested?
TESTING OF MOUNTAINEERING ROPES ACCORDING TO EN 892
This parameter is measured after applying a load of 10 kg to single ropes, 6 kg to half ropes and 5 kg to twin ropes. This means that it might be very difficult to accurately test the diameter of your rope in domestic conditions.
The parameter is expressed as the weight of the rope per 1 m of its length. The weight of single ropes free of any finishes ranges from 52 to 88 grams, half ropes weigh approx. 50 grams, and twin ropes approx. 42 grams per metre. The rope core must account for at least 50% of its total weight.
Number of standard falls
It is the number of falls (drops) the tested rope has to withstand under conditions specified in EN 892. This standard requires at least 5 falls for single ropes loaded with a falling mass of 80 kg. Half ropes are tested with a 55 kg load applied. With twin ropes, the two ropes are loaded with an 80-kg weight at all times and the minimum number of falls is 12. The number of falls arrested in the course of testing is a direct measure of the safety (strength) of the rope. New ropes cannot practically get ruptured at shock loading provided that the rope is in satisfactory condition and well handled. The safety of the rope will gradually decrease as a function of the material aging and wear, i.e. as a result of the factors detrimental to its strength. Also humidity which often attacks the polyamide fibres of which the rope is produced decreases its strength.
Maximum impact force
Impact force is the force generated on the first fall under defined conditions (weight of load, fall factor, ...) and absorbed by the rope. During the testing, each fall increases the impact force in the rope and the final number of arrested standard falls is dependent on the rate at which it increases. The higher the number of standard falls, the longer the rope life. Practical usage of the ropes on the rocks or training walls differs from that under laboratory conditions. During standard rope tests, the rope end is tightly fixed, yet in field operation the belaying devices and systems allow for certain rope slippage, in which case the fall is arrested dynamically. As a result of the dynamic belaying, a proportion of the fall energy is dissipated and the impact force diminished. For this reason, it is essential to control and use appropriate dynamic belaying devices.
CAUTION! The so-called fall factor is also important for the magnitude of the impact force – practically it is not important how long the fall is, but what is the magnitude of the fall factor. A fall of 5 metres with a fall factor of f=1 will give rise to a considerably lower impact force than a fall of the same length with a fall factor of f=2. The energy of the climber’s fall is absorbed by the so-called “active rope length” (shown red in the figures). CAUTION! The so-called fall factor is also important for the magnitude of the impact force – practically it is not important how long the fall is, but what is the magnitude of the fall factor. A fall of 5 metres with a fall factor of f=1 will give rise to a considerably lower impact force than a fall of the same length with a fall factor of f=2. The energy of the climber’s fall is absorbed by the so-called “active rope length” (shown red in the figures).
The useful static elongation is tested by applying a load of 80 kg to the rope and shall not exceed 10% for single ropes (single-strand ropes) and twin ropes (two strands tested at the same time) and 12% for half ropes (single strand).
The test performed in a special apparatus seeks to quantify the slippage of the sheath relative to the core when the rope surface is loaded. The test sample having a length of 2230 (± 10) mm is drawn through this apparatus. EN 892 specifies that the sheath-to-core slippage or the core-to-sheath slippage shall not exceed 20 mm. If, in real practice, the core slips relative to the sheath, swelling or so-called “stockings” may occur. If the ends of the rope have been poorly sealed, the core at the rope end may slip out of the sheath or the sheath may slip outside the core. The ends of our ropes are ultrasonically sealed into a single indivisible unit and if the sheath slippage requirements are complied with, the above condition will not occur.
Dynamic elongation during the first fall
This parameter gives information on the elongation of the rope during the first standard fall. The maximum allowable dynamic elongation is 40% during the first fall and it reflects the properties of the rope more efficiently that the static value of working elongation.
Excellent flexibility is one of the most important requirements imposed on climbing ropes. How is this parameter quantified? A simple knot is made on the tested rope and a 10 kg load is subsequently applied (in case of single ropes). Then, the internal diameter of the knot is measured and the knotability ratio is calculated. Its value shall not exceed 1.1 times the rope diameter.
CAUTION! Poor flexibility essentially impedes both the tying of knots and the rope's passage through the karabiners of the belaying system. The effects of the weather and insufficient care of the rope are also detrimental to the rope flexibility. Our company has built an in-house test laboratory for testing the performance of TENDON ropes, including a drop tower. Therefore, when newly developed ropes are shipped to European test laboratories for certification, they are fully prepared and their technical parameters are known.
REQUIREMENTS OF EN 892 – DYNAMIC MOUNTAINEERING ROPES
Testing of static ropes according to EN 1891
This parameter is measured after applying a load of 10 kg to the rope. The ropes may have a minimum diameter of 8.5 mm and a maximum diameter of 16 mm.
The useful static elongation is tested by applying a load of 150 kg to the rope (previous prestress 50 kg). It shall not exceed 5%.
It is always specified on the rope tag and depends on the rope diameter and the rope material. EN 1891 requires the minimum static strength to be 22 kN for type A ropes without terminations and 18 kN for type B ropes. CAUTION! The maximum recommended loading of the rope shall be 1/10 of the nominal strength as specified on the product tag.
Requirements for material properties
According to EN 1891, static ropes shall be made of a material the melting point of which exceeds 195 °C. It means that polyethylene and polypropylene cannot be used for their production.
Canyoning ropes made of those materials do not fall under the scope of this standard, even if they are in conformity with the standard in terms of static strength and other parameters.
This parameter is important mainly for rapelling on static ropes – if not met, the accumulation of the sheath on the core before the rapelling brake would endanger the safe descent. The sheath slippage for type A ropes shall not exceed approx. 40 mm on a length of 2 m (for ropes up to 12 mm diameter) and for type B ropes shall not exceed 15 mm.
The test apparatus is similar to that used for testing of mountaineering ropes, only the rope is about 2 m long. It has figure-of-eight knots on its ends and is tested with falls having a fall factor of 1. The rope shall withstand five falls. Type A ropes are tested with a load of 100 kg, type B ropes with a load of 80 kg. The minimum number of falls without releasing the mass is five.
A simple knot is made on the tested rope and a 10 kg load is subsequently applied. Then, the internal diameter of the knot is measured and the knotability ratio is calculated. Its value shall not exceed 1.2 times the rope diameter.
Testing of accessory cords according to EN 564
According to EN 564, accessory cords should have diameters of 4, 5, 6, 7 and 8 mm. Diameters 2 mm – avalanche cord, 3 mm – hammer cord and 9 mm – force cord do not comply with the standard.