Testing Heat Resistant Ropes
Sterling Solid Blog Apr 5th 2021- Rope access technicians perform an astonishing variety of work
- by Ben Erdman
Industrial rope access is a term used to describe a set of techniques for performing work at height. Generally speaking, rope access technicians perform their trade while suspended in a harness from a rope, with a second rope system in place as a backup safety arrangement in case the main line should become damaged. For more information about rope access, please visit www.sprat.org, or www.irata.org , both global trade associations for rope access.
Introduction
- Rope access technicians performing work
- Ben Erdman
Rope access technicians perform an astonishing variety of work, in just about every corner of the world, with an incredible record of safety. Their activities may range from inspecting pipelines on the North Slope of Alaska, to upgrading wind turbines in Tierra del Fuego, and maybe even washing the windows on your apartment building. A large amount of rope access work is done in the petroleum industry, performing inspections, making repairs, and upgrading infrastructure. The refinery environment presents an additional hazard to rope access techs, which is that much of the workings of a refinery require steam, which is piped at high temperatures ( approximately 700 F) all around the refinery.
"What would happen if a rope supporting a tech were to come in contact with a steam pipe? How long would it last?"
To answer this question, we first did some background investigation, to determine the factors involved. The following information was noted:?
- Almost all ropes used for rope access work are made of either polyester or nylon, also sometimes referred to as polyamide. Both of these fibers have a melting point of approximately 400F. However, its interesting to note, that they begin to experience significant strength loss well before that, around the 200 F mark. ( Interestingly, as they get colder, nylon ropes actually gain a bit of strength, down to about -40F)
- Average temperature of a steam tracing pipe is approximately 700F, and they are usually made of steel and are usually about 4 inches in diameter.
- Fibers do exist which have a higher resistance to heat, the ones suitable to making rope are in the family of aramids, which are commonly known by the tradenames of Technora or Kevlar.
- Rope access technicians come in a variety of sizes and weights, but for testing purposes 300 pounds is commonly used to represent a full sized worker and their equipment.
Simply by looking at the information above, we could be quite confident that a nylon or polyester rope that came in contact with a steam pipe would melt.
“How long will a weighted rope in contact with hot pipe take to melt through?”
To answer this, we created an electrically heated pipe which was capable of reaching the 700 degree mark, and could be mounted in our hydraulic tensile tester, and pulled to 300 pounds. We decided to test the following types of rope:
- Our standard polyester HTP, commonly used in rope access.
- Our Tech11, which has an aramid sheath braided over a nylon core.
- Our H3Tech11, which has an aramid sheath and core as well.
- Our newest 11mm Tech HTP, which has an aramid sheath and polyester core.
These ropes were tested using the described arrangement, with the following results
Sterling Rope Hot Pipe Results Summary
Test Temp (F): 700
Pipe Diameter (in): 4
Rope Contact (deg): 180
| Product Variant | H3Tech11 | Tech11 | H3Tech125 | Tech125 | 7/16HTP | 7/16HTP |
|---|---|---|---|---|---|---|
| Time(s) | 600 | 600 | 600 | 600 | 34 | 600 |
| Load Held (KN) | 2.0 | 2.0 | 2.0 | 2.0 | 0.31 | 2.0 |
| Residual ABS (KN) | 37.83 | 13.14 | 39.11 | 13.56 | 0 | 8.64 |
| Control ABS (KN) | 44.94 | 44.50 | 47.80 | 40.40 | 35.20 | 38.94 |
| Strength Retained | 84.2% | 29.5% | 81.8% | 33.6% | 0.0% | 22.2% |
HTP
This 100% polyester rope performed poorly. Essentially it melted through as fast as the tester could pull, like the proverbial “hot knife through butter.” If this rope were to come in contact with a hot pipe with a technician suspended from it, the failure would be almost instantaneous.
Tech 11
This rope exhibited an interesting behavior in the test. As it was heated over the pipe, the two tracer yarns, which are actually polyester, melted. The rest of the sheath is Technora and did not melt or fail during the 10 minutes of the test. However, the nylon core inside became liquefied where it was around the hot pipe and that liquid nylon came squirting out of the tiny holes in the sheath left by the two tracers which had melted away. The effect was a bit like squeezing toothpaste out of a tube. After the ten minute test, we pulled the rope to failure, which revealed a residual strength on average over several tests of about 13 kN, compared to the original strength when new of about 44 kN. While this represents a significant loss of strength, the residual number is enough to provide some safety to a technician.
H3Tech11
This 100% Technora (both sheath and core) rope was the least interesting test to watch. It simply pulled on the hot pipe with little to no effect, other than a slight color change, making it look a bit “toasted.” When tested for residual strength, it showed a residual strength of almost 38 kN, compared to an original strength of 44.5 kN.
Tech HTP
The Tech HTP performed somewhat similarly to the Tech 11, in that the core appeared to have melted while the sheath remained relatively intact. Though it should be noted that the sheath of the TechHTP is 100% aramid, including the tracers, unlike the Tech11. All of the specimens held the test load during the ten minute duration, with an average residual strength of about 8.6kN, compared to the original strength of 38kN. This is still more than enough to hold a technician’s weight until they can be safely rescued.
Conclusion
So, what conclusions can we draw from this testing? Well, we know that standard practice is to take all possible steps to avoid the rope coming in contact with a hot pipe. However, in the case where it accidentally may meet a pipe, these aramid fibers offer a significant advantage and level of protection to the worker. For more information, copies of test reports, or to discuss various options in rope, contact us any time.