1. Where are non-metallic compensators used? Don't use it in the wrong place.
Non-metallic compensator (also called non-metallic expansion joint/fabric fiber expansion joint) is mainly used to deal with low-pressure and high-temperature pipeline systems such as flue gas, hot air and dust. To put it bluntly, where the metal expansion joint can't withstand high-temperature corrosion or large displacement, it should play. For example, the desulfurization flue gas pipeline of the power station, the kiln tail waste gas pipeline of the cement industry, the blast furnace gas pipeline of the steel plant, and even the flue gas purification system of the waste incineration plant-the temperature in these occasions is always five or six hundred degrees, and some instantaneous peaks can rush above 1000℃, and the metal parts are soft for a long time.
Unlike metal compensator, it relies on fiber fabric and rubber composite layer to absorb displacement, and does not generate thrust itself, which can save a lot of trouble in bracket design. But you have to put it on a high-pressure steam pipe? That is wrong-if the pressure exceeds 0.1MPa, you have to choose the type carefully, and don't use it as a high-pressure part. A customer in our station once wanted to use a rectangular non-metallic expansion joint on a 2MPa compressed air pipe, but before it even ran, the fabric layer bulged.
2. Find out these 4 parameters before installation, otherwise it will be in vain.
The first is the displacement-you have to calculate how many millimeters the thermal expansion and contraction of the pipe are offset, and calculate the axial, transverse and angular directions separately. Many on-site pictures save trouble, and they say "come to a 200mm one" when they open their mouths. As a result, the actual displacement is only 30mm, a small horse pulls a big cart, and the fabric folds age quickly. The second is the temperature-the highest temperature and instantaneous peak temperature of the medium directly determine which layer of fabric to choose: silicone cloth can withstand the temperature of about 200℃, fluorine cloth can reach 300℃, and ceramic fiber will be required if it is higher.
The third is the media composition. Have strong acids and bases? That has to be lined with PTFE, which is the "rubber PTFE compensator" or "PTFE compensator" on our station. The fourth is the installation space-rectangular non-metallic expansion joints for square pipes and rounds for round pipes, don't get confused. Two days ago, a customer welded a round one to a rectangular air duct. As a result, the seal was not tight and it took half a month to rework. You say it was wrong or not?
3. Installation steps and the details of the easiest rollover.
Hoist in place → Adjust bolt pre-tension → Weld or flange connection → Remove transport screw. But the worst thing about the rollover is-when will the transport screw be removed? Many people dismantle it as soon as it is installed, and as a result, the compensator is pulled out before the pipe is hot. Correct practice: Wait until the pipeline is installed, the bracket is fixed, and then disassemble it before trial operation. The FAQ of our station specifically mentioned "Does the screw of the expansion joint need to be disassembled?" That's what it said.
In addition, the direction of the guide tube must follow the flow direction of the medium, and the direction of the arrow should not be reversed. And guess what? A cement factory installed the guide tube backwards, and the high-temperature airflow directly washed the fabric layer, which was perforated in three days. We also talked in detail in the FAQ of our station that "the arrow direction of the expansion joint" is for this purpose.
4. In daily use, the three most easily overlooked pits.
Pit 1: Let the compensator bear the load.The non-metallic compensator only absorbs displacement and does not bear weight. The weight of the pipeline depends on the bracket. Even an elbow should be supported separately. Don't let it hang. Some site drawings save trouble, hang the valve directly on the compensator, and the flange leaks within a month.
Pit 2: Neglect insulation.The outer insulation layer not only insulates heat, but also prevents condensed water from corroding the fabric layer. However, many people think that "it can withstand high temperatures anyway" and don't pack it. As a result, the outside condenses and water seeps into the fabric, accelerating aging. Especially noticeable in winter.
Pit 3: Large compensator for small displacement.Some people choose oversized specifications for "insurance", which leads to wrinkles and accelerated aging of fabrics under low displacement. According to JB/T 12235-2015 standard, the working displacement of the compensator is preferably controlled between 60% and 80% of the rated displacement. You say that using a 200mm compensator to absorb a 20mm displacement, isn't that a waste of things?
5. When should I change? Don't wait until it leaks to dismantle it.
The life of a non-metallic compensator is usually 3-5 years, but depends on the operating conditions. If you find that the surface of the fabric layer is cracked, hardened, delaminated, or the flange bolt can't be tightened after it is loose (indicating that the sealing layer has collapsed), then you have to change it quickly. Another signal-the vibration of the pipe suddenly becomes louder, or there is an abnormal noise around it, which may be that the internal guide tube has fallen off. Usually check the appearance quarterly, focusing on welds and fabric overlaps.
If you want to save trouble, rubber compensators are cheaper than fabric compensators, but the temperature resistance is only about 100℃, so don't get confused. When encountering high-temperature flue gas, nonmetallic expansion joints (fabric fiber expansion joints) or rectangular nonmetallic expansion joints have to be used. In the final analysis, with the right selection, the right installation, and the maintenance keeping up, it is not a problem to use a compensator for five years.