1. Check the model, material and direction of the guide tube after unpacking
When the goods arrive, don't rush to unpack and go up. Two days ago, I met a customer. When I unpacked the box, I saw that the model was right and the material was fine. As a result, the direction of the deflector was reversed-the smoke directly washed the fabric layer, and it leaked in half a month. This is not a bad manufacturer. The arrow on the packaging box is clearly marked, but the installer didn't look at it.
Confirm the model, material (such as fabric fiber or rubber compensator) and nominal diameter of the non-metallic expansion joint by comparing the invoice and drawings. Pay special attention to the direction of the arrow on the guide tube-it must point to the direction of the medium flow, in the same direction as the smoke or hot air in the pipe. Our station hasNon-metallic expansion joint (fabric fiber expansion joint)Andrubber compensatorThere are two categories, the former is high temperature resistant and the latter is corrosion resistant, but the installation logic of the deflector is the same: wherever the arrow goes, the medium goes. If the direction is wrong, the guide tube becomes a "blocking tube", which not only fails to protect, but also accelerates the wear of the ring belt.
2. How to arrange the fixed bracket and the guide bracket? Don't let the compensator take extra thrust
For the layout of the bracket, many on-site diagrams save trouble, and both ends of the expansion joint are directly welded to the pipeline. As a result, as soon as the pipe heats up, the full thrust is pressed on the non-metallic expansion joint-it is originally only responsible for absorbing displacement, not as a force point for you. The fixing bracket must be arranged on one or both sides of the expansion joint to lock the pipeline in sections, so that the expansion joint only compensates for the displacement between the two fixed points. The guide bracket should ensure that the pipe expands and contracts in the predetermined direction, and don't let it tilt and twist.
A 30-meter-long flue with a middleRectangular non-metallic expansion jointThe fixed brackets are arranged at 5 meters at both ends of the expansion joint, and the guide brackets are arranged at 6 meters intervals. In this way, when the flue is thermally expanded, the expansion joint only absorbs the displacement between the two fixed brackets, and the thrust on both sides is carried by the fixed brackets. If the spacing between the fixing brackets is too large, the expansion joint will be forcibly elongated, and the fibers of the fabric layer will break sooner or later.
3. Is the screw disassembled or not during installation? Something big will happen if you demolish it early
This question is repeatedly asked in our Q&A (Do you need to remove the screw of the expansion joint), the answer is clear: transporting a screw and installing a screw are two different things. When the non-metallic expansion joint leaves the factory, there are usually transport screws (also called positioning screws) at both ends, which compress the compensator to the installation length and prevent deformation during transportation. Once installed in place,Definitely don't rush to dismantle— — First, adjust the tie rod and the guide device, wait until all the pipeline systems are connected and fixed, and finally loosen the transport screw.
Why? Because the non-metallic expansion joint itself has low stiffness, as soon as you remove the screw before it is fixed, it rebounds immediately, the flange surface is misaligned, and the bolt hole is not aligned. More seriously, if the pipeline still has cold tightening or pre-tensioning requirements, removing the screw in advance is in vain. Correct practice: After the flange bolts are tightened, remove the transport screws one by one-note that they are "one by one", not completely disassembled. Remove one, see how the flange fits, no problem remove another one.
4. How to adjust the tie rod nut? The amount of pre-stretch is not casually screwed
The adjustment of the tie rod nut directly determines that the expansion energy saving cannot be compensated in place. We also talked about it in our Q&AHow to adjust the tie rod nut of expansion jointThe core is one sentence: the nut position determines the initial compression or tension amount of the compensator. For example, if the design displacement of the pipeline is 50mm, the installation environment temperature is 20℃, and the operating temperature of the pipeline is 200℃, then the pre-stretching amount is usually about half of the design displacement-25mm. When adjusting the nut, screw the nut on the tie rod outward so that the compensator is stretched to a pre-stretched state of 25mm.
The tie rod nut doesn't stop moving after being screwed down. Early in operation, as the pipe temperature increases, the nut automatically displaces inward until the compensator completely absorbs the displacement. If the pre-stretching amount is increased, for example, it is pulled directly to 50mm, the compensator will be over-compressed after operation, and the fabric layer will be folded and stacked, which will reduce the service life. When adjusting, measure the flange spacing with a caliper. Don't twist it by hand.
5. Pay special attention to these points for non-metallic expansion joints for high-temperature flue gas pipelines
High-temperature flue gas pipelines (such as power station boilers and cement kiln tails) are the main battlefields of non-metallic expansion joints, but when the temperature exceeds 300℃, ordinary fabric fibers can't bear it. You have to use it at this timeHigh temperature axial expansion jointOr specially coatedNon-metallic expansion joint (fabric fiber expansion joint)With thermal insulation and multi-layer sealing structure inside. Note also when installing: the gap of the guide tube should not be less than 10mm, otherwise it will be stuck after thermal expansion; The insulation must be wrapped in place so that the bare fibers cannot be exposed to smoke.
In addition, high temperature pipes often have drainage requirements. If the humidity content of the flue gas is large, a drainage pipe or a reserved drainage hole should be installed at the bottom of the non-metallic expansion joint to prevent condensed water from accumulating and corroding the flange. Don't ask why you know-I've seen too many cases of ring belt rot due to poor drainage. In addition, heat-resistant steel should be selected for the fixed bracket in high temperature conditions, instead of ordinary carbon steel, because the strength will drop by half at high temperature.
6. What to check after installation? Don't miss the guide tube clearance and tightness
Don't rush to seal and insulate after installation. Take a flashlight to illuminate the gap between the guide tube and the inner wall of the pipe-if the gap is too large, the airflow will directly impact the fabric layer; If the gap is too small, the guide tube will push against the pipe wall after expansion in the hot state, resulting in abnormal noise or even damage. The standard gap is usually 5~15mm, depending on the design. We talked about it in detail in our Q&ASpecific Function of Expansion Joint Guide TubeIf you can't remember, go back and look through it.
When doing the airtightness test, fill the inside of the non-metallic expansion joint with low-pressure air (0.05~0.1MPa), and check the surface of the flange joint and ring band with soapy water. Is there any bubbling? If so, either the flange bolts are not evenly tightened, or the loop belt itself has needle holes. If the band is broken, don't think about gluing it-replace it with a new one quickly. Anyway, the modular design of the non-metallic expansion joint makes it easy to disassemble and assemble. Finally, don't forget to review the torque of all bolts, especially in high-temperature areas. The bolts will loosen in hot state, and they should be tightened twice after 24 hours of operation.