Find out one thing before installation: Is the one you bought really high temperature resistant?
Don't be fooled by the manufacturer's "temperature resistance 800℃". The one in our siteNon-metallic expansion joint (fabric fiber expansion joint)AndHigh temperature axial expansion joint, material and structure are completely different things. The temperature resistance limit of a non-metallic compensator depends on the fiber layer and the sealing material-it is not just a number. Two days ago, I met a customer and bought a compensator with a temperature resistance of 1000℃. As a result, it burned out in less than a week after installing it. When I take it apart, the fiber layers are carbonized. Later, after checking the working conditions, it was found that the flue gas contained sulfur, and the actual temperature was only 700℃, but the medium was corrosive, and the fiber layer couldn't hold it at all.
First, check the working temperature, not only the peak value, but the continuous working temperature; Second, find out the composition of the medium. Is it flue gas, steam or dusty airflow? If it contains acidic gas, a non-metallic expansion joint with fluororubber coating should be selected. Otherwise? It burns out within a few days of installation, and the rework cost is several times more expensive than the equipment itself.
The first step of on-site installation: Take the "pull rod" as a decoration? Then you wait for the rework
Non-metallic compensators usually come out of the factory with a limit tie rod or screw-this thing is not an ornament. Many installation teams saw the pull rod and felt that it was in the way, so they dismantled it directly and threw it aside. As a result, as soon as the temperature rose, the compensator was forcibly cracked and creaked. Listen to me, check if the tie rod nut is loose and the compensator is crushed before installing. How to adjust the expansion joint tie rod nut? As mentioned in the previous question and answer, it should be tightened according to the actual compensation amount. In cold installation, the thermal displacement space must be reserved, which is generally pre-adjusted according to 50% ~70% of the design compensation amount. For example, if the thermal elongation of the pipe is 100mm, the tie rod should be adjusted to allow a compression or tensile margin of 50~70mm. Otherwise, once the temperature rises, the tie rod will not move, and the compensator will tear directly.
Some manufacturers tighten the tie rod very tightly for the convenience of transportation, and even flatten the non-metallic compensator. Be sure to loosen the nut when you go to the site to allow the fiber layer to return to its free state. Remember: the role of the tie rod is to limit excessive displacement, not to hold it dead.
Finding the right flange is more important than falling in love
The flange centering deviation should not exceed 2mm. The non-metallic compensator is a flexible connection, but the flange connection surface must be flat and centered. In many scenes, a hammer was knocked casually and welded to death. As a result, the compensator was tilted and stressed, and the fiber layer was fatigued and torn in advance. And guess what? Later, the customer removed it and saw that the flange surface was crooked by nearly 5mm, the bolts were twisted, and the sealing surface was directly crushed.
Also don't forget the deflector-aboutSpecific Function of Expansion Joint Guide TubeWe have a special explanation on our site. It protects the corrugated parts from high-speed airflow, especially high-temperature flue gas pipes containing dust. If there is no guide tube, the dust hits directly on the fiber layer and wears out in a few months. During installation, the direction of the guide tube must be consistent with the flow direction of the medium, and the direction of the arrow should be clearly marked. Don't install it backwards.
Pay attention to bolt tightening: don't believe "the tighter the better"
The flange bolts of the non-metallic compensator should be tightened symmetrically and multiple times, and the torque should be controlled by a torque wrench to prevent local crushing of the sealing surface. When the baffle doors and expansion joints in our station are installed, we often encounter customers who screw the bolts without knowing it. In high-temperature environment, the bolt material should be heat-resistant alloy steel, and ordinary carbon steel is not screwed after softening at high temperature. Two days ago, a project used ordinary 304 bolts. As a result, after three months of operation at 700℃, the bolts were all loose, and the flange surface leaked and smoked.
Screw it by hand until it is tight, then twist it three times in diagonal order with a torque wrench, increasing torque by 30% each time. The torque value refers to the parameters given by the manufacturer. Generally, the torque of M16 bolts is between 80~120N·m. Don't try to save trouble and screw it to the end at once, it will only make the seal gasket unevenly pressurized, and air leakage is a matter of time.
Don't rush to restart after installation-do cold check first
The pressure test should not be less, the pressure should be controlled within 1.5 times of the design pressure, and the pressure holding time should be at least 15 minutes. Then check for any abnormal noise and deformation. One day you hear a crunch, nine times out of ten the compensator has been forcibly stretched. Another way to do it is to shine a flashlight around the flange to see if there is any light leakage. Final controlNational Standard for Non-Metallic Expansion Joints JB/T 12235-2015Re-test it. Don't trouble, one accident is all for naught. We have counted that 80% of non-metallic compensator failures occur in the first month after installation-either the tie rod is not properly adjusted or the bolts are not evenly tightened.
Routine maintenance playing stupid is the deadliest: do you think everything will be fine if you put it on?
It is inevitable that the fiber layer will age under high temperature. Check the surface regularly for cracks, blisters, or discoloration. Especially the side close to the heat source is often the first to fail. You can install a temperature monitoring point, and stop it quickly if it is overheated. FollowCorrect installation method of expansion joint of large tie rodAs mentioned in, the tie rod nut should be checked for looseness every six months. Don't wait for the pipe to shake before you regret it.
Tsk, there was a customer who didn't care for it for a year, until one day the smoke came out and found that a hole had burned in the fiber layer. It won't cost much to replace a non-metallic expansion joint (fabric fiber expansion joint), but what about the loss of discontinuation? Therefore, don't go through the motions in daily inspection. Touch the surface temperature with your hands, sweep it with an infrared thermometer gun, and record it. If you find fine cracks on the surface, contact the manufacturer quickly to evaluate whether it can be repaired. Don't hold it hard.