Why do you have to have regular inspections? — Don't wait until you miss it to regret it
Two days ago, I met a brother from a power plant. Their desulfurization tower was exportedNon-metallic expansion joints (fabric fiber expansion joints)Suddenly it was torn, and the hot smoke was wrapped in slurry and directly leaked out. After the production line was stopped for 3 days, the light loss was a small million. You say it was wrong or not? In fact, this kind of accident can be completely avoided-as long as it is checked regularly, it will only take a few hours to replace one if the signs of aging of the fabric layer and corrosion of the metal frame are found in advance.
Non-metallic compensators (also called non-metallic expansion joints and fabric fiber expansion joints) are widely used in smoke and air ducts, desulfurization systems and cement production lines, because they are resistant to high temperatures, corrosion resistance and can absorb large displacements. However, its soft belt is tossed by high temperature, dust, acid and alkali gases all the year round, and its aging rate is much faster than that of metal parts. When you see air leakage, smoke leakage and abnormal noise before dealing with it, the internal structure is often hurt. SoHow to check a non-metallic compensator?This problem is actually one of the core lessons of pipeline maintenance.
Appearance inspection: Seeing, touching and listening, three steps to find out the big fault
Look-scan details with your eyes
Standing on the side of the compensator, first look at the surface of the fabric for bulging, scratches, fluffing, and whitening. Bulging usually means debonding between layers, and scratches deep may have damaged the inner PTFE or rubber film. Pay special attention to the corners of rectangular non-metallic expansion joints-that position has the most stress concentration and is most likely to crack first. Look at whether the metal flange is corroded and the weld is cracked.
Touch-to feel with your hands
Put on the gloves and touch the circle along the surface of the circle band. If it feels hard and sticky locally, it means that the material has degraded. Rubber compensator or rubber PTFE compensator is especially afraid of this-it will be brittle and cracked when it is hard, and it will be corroded by the medium when it is sticky. The normal feel should be uniform elasticity and smooth surface.
Listen-Find abnormalities with your ear
When the equipment is running, get closer and listen to whether there is a hissing air leak or a puff bulge. Experienced masters know where they leak as soon as they hear it-the hissing sound is mostly due to the fabric needle eye being enlarged, and the puff sound may be the displacement of the internal cushion.
After these three steps are completed, 70% to 80% of the surface problems can be found out. However, some internal injuries have to rely on these methods.
Dimension and displacement compensation ability check-measure to know whether there is failure
Nonmetallic compensators are not only soft connections, they absorb the thermal expansion and mechanical displacement of the pipe. Think about it, the pipe can stretch tens of millimeters when it is hot, and it all depends on this soft guy's deformation to digest it. If it loses its elasticity due to aging, or does not leave enough margin during installation, the consequence will be pipe stress hard top, flange crack, or even equipment.
How to check? Simple: Measure the actual length and width of the compensator under shutdown, and compare with the factory design dimensions. If the amount of compression has exceeded 80% of the design maximum, or the amount of stretch is almost to the end, then you have to consider replacing it. Common standards, such as JB/T 12235-2015 "Non-metallic Expansion Joints", specify the displacement limit and fatigue life.
In addition, don't forget to look at the guide tube (if any) -the specific function of the expansion joint guide tube is to protect the fabric from being washed by high-speed airflow. If it corrodes and collapses, the compensator life is directly discounted in half.
Sealability and airtightness test-a dozen pressures, all leaks appear
The front ones are all visual and feel, and the real tough battle is the airtightness test. Especially in the desulfurization flue gas baffle door, air-cooled island system and other occasions with high sealing requirements, the high air leakage rate not only increases the energy consumption, but also may lead to scaling and corrosion of peripheral equipment.
Close the valves on both sides of the non-metallic compensator, seal one end with a blind plate, and give 0.05~0.1MPa compressed air to the other end (don't overpressure, the fabric can't bear to rush), and then coat each seam, flange surface and bolt hole with soapy water. Where bubbles are the leakage spots.
Before the test, confirm that the compensator has no obvious bulge or tear, otherwise it will collapse directly when the wind takes a dozen, which will be dangerous. The pressure holding time should be at least 5 minutes, and the pressure should not drop before it is qualified. If there are not many leaks, you can try to plug them with special repair glue; But if the fabric leaks in a large area, or several leaks are strung together, don't toss it, just replace it with a new one.
Judgment and treatment of common faults-which can be repaired by themselves and which must be replaced
Come on, go straight to the dry goods:
- Small scratches and slight fluffing on the fabric surface: Apply a layer with silicone rubber or fluororubber repair agent, and it can top for a while when it dries. However, the premise is that the covering layer is not damaged, and the medium temperature does not exceed the temperature resistance range of the repair agent.
- Air leakage due to loose flange bolts: This can be tightened by itself, and the torque value is tightened 2~3 times in diagonal order. Don't screw to death at once, it will easily deform the flange.
- Local bulging and delamination of circular zone: It indicates that the fabric and inner layer have been detached. Don't fix it, just change it. Because the bulge will get bigger and bigger and break sooner or later.
- Metal frame corrosion perforation: Look at the corroded area. If it is only a small piece, you can apply anticorrosive paint after repair welding and polishing; If a large area is thinned, the whole frame has to be replaced.
- Fabric distortion due to displacement exceeding limit: First check whether the pipe support is displaced or the original selection is too small. If it is a bracket problem, adjust the bracket; If it is a type selection problem, the expansion joint with a larger compensation amount must be replaced.
At the end of the day,How to check a non-metallic compensator?Not going through the motions, but turning "examination" into "diagnosis". Each inspection records the appearance status, size data, and leakage, and compares the historical trend. For example, the compression amount in the last quarter was only 40%, and this time it reached 60%, which means that the aging has accelerated-the spare parts replacement plan can be arranged six months in advance.
Don't wait for the smoke to panic. Follow this list, and your non-metallic compensator (whether it is a rectangular non-metallic expansion joint, rubber compensator, or PTFE compensator) will last three or five more years, and it will be perfectly fine.