The Impact of Damage to Harnesses due to Burning or Burnt-through Holes

On March 13, 2007, Singing Rock Ltd. carried out internal tests as a basis for monitoring the impact of burning and burnt-through holes on the solidity of a new sling. In practice, such phenomena may occur with welder's profession, for example.

Test No. 1

Burning through a circular section Ø 5 mm at one spot

Fmax = 18,34 kN

Test 1

Test No. 2

Burning through a circular section Ø 5 mm at two spots

Fmax = 16,12 kN

Test 2

Test No. 3

Burning through a circular section Ø 5 mm at three spots

Fmax = 14,05 kN

Test 3

Test No. 4

Burning through a circular section Ø 5 mm at four spots

Fmax = 13,17 kN

Test 4

Test No. 5

Burning through a circular section Ø 5 mm at one spot, combined with surface burning of the yarn about 70% wide

Fmax = 13,89 kN

Test 5

Test No. 6

Surface damage to the yarn at a number of spots, about 90% of the yarn, with part of thermal damage reaching the edge of the sling

Fmax = 14,57 kN

Test 6

Test No. 7

Point surface damage due to heat, Ø about 2 mm, at a number of spots

Fmax = 11,46 kN

Test 7

Test No. 8

Thermal damage to the edge of the sling

Fmax = 12,45 kN

Test 8

Test No. 9

Thermal damage due to heat with no direct contact, Ø 8mm

Fmax = 20,18 kN

Test 9

Test No. 10

Thermal damage due to heat with no direct contact, 35 x 5 mm

Fmax = 15,01 kN

Test 10

Test No. 11

Sling with no damage

Fmax = 22,44 kN

Test 11

Test No. 12

  • the age of the sling: 10 years
  • new strength sewing
  • point contact damage through heat
  • 4 samples out of 4 did not withstand at the point of the strength sewing stáří popruhu 10let

Fmax = 6,01 kN

Test 12

In case of the 10 “year-old” slings, we did not come to the study’s objective since all the five samples of various damage levels burst at the point of the new strength sewing, which made it impossible to monitor the relation between the solidity of an old sling and the level of damage.


As far as new slings are concerned, no heat damage may be considered safe. Some producers quote in their manuals for auditing technicians an option to label damages due to burnt-through section up to Ø 5mm as safe and convenient for further use in the way described in Test No.1 of this study.

According to the results, the slings have brought an interesting piece of information,i.e. that point thermal damage (Test No.7) is more dangerous than a burnt-through sling, (Tests No. 1 – 3), for example. The point damage belongs to the most frequent thermal damages that we encounter during auditing.
These damages occur mainly during the processes of cutting and grinding with angular grinders, or welding.

As for the old slings, this may be concluded – do not carry out any additional adjustments in the main construction of the harnesses owing to the decrease in solidity of slings due to new strength sewing down to a dangerous limit!The only exception may be seen in the repair of the end points of “tightening slings” and that is only owing to the prevention of running of the sling end through a buckle or clip.

Elaborated by:
Dalibor Plíšek
Customer Service Manager