First, find out before you start: Which kind of expansion joint is in your hand?
There is not only one type of flue expansion joint, metal, non-metal, rectangular and round, and the installation methods are different. You first look at the product list on our site- -for example, if you use "Non-metallic expansion joint (fabric fiber expansion joint)", then it is like"Metal rectangular expansion jointThe fixed way is different. The former is usually clamped by flanges, and the latter may also be welded. Alas, two days ago, I met a customer who installed non-metallic ones as metallic ones, and the bolts were screwed to death. As a result, the pressure plates were deformed. Do you think it was wrong?
Tips:If you use "Universal corrugated expansion joint"or"High temperature axial expansion joint", pay attention to check whether there is an arrow mark on the product-that arrow points in the direction of the guide tube, and it must be in the direction of the medium flow (don't install it backwards, otherwise the guide tube will be washed out). Think about it, the direction is reversed, the smoke is directly on the bellows, and it will leak in less than a few months.
2. Preparation before installation: tools, inspection and safety must be missed
Don't get started in a hurry. Do three things first, otherwise it will be more troublesome to disassemble if you find something wrong halfway through the installation:
- 1. Check the model number:Make sure that the size, pressure level and compensation amount of the expansion joint you got are consistent with the design drawings. Tsk, it is marked DN800 on the drawing. If you have a DN600 in your hand, it will definitely not work on hard mounting.
- 2. Check the appearance:Did the bellows bump? Are there any scratches on the flange face? Especially "Large diameter thick wall expansion joint", easily deformed during transportation. And guess what? Once at the scene, I found an oval one, which didn't match the flange at all, and I worked for half a day in vain.
- 3. Remove the transport fixtures:Some expansion joints are locked with screws or pull rods when they leave the factory to prevent shaking during transportation. Remember to remove these temporary fixtures before installation (unless "Direct buried (fully buried) type expansion joint"The kind that is not designed to allow disassembly). Is that the truth?
Note:Remember to wear a seat belt when working at high altitude. There may be residual smoke in the flue, so ventilate first. Safety first, don't try to save trouble.
3. Core steps: from positioning to fastening, step by step
Step 1: Find the right location.The flue expansion joint is typically mounted between two fixed brackets or near the outlet of the equipment. You hoist the expansion joint in place first, don't pull it hard, and slowly adjust it with an inverted chain or a gourd-this thing is delicate, and you will cry behind the bellows when it bumps.
Step 2: Counterpart.For flange connection, put the bolts in, don't screw them to death first, and leave some activity. For welding, fix it by spot welding first, and then full welding-pay attention to controlling the welding current, and don't burn out the bellows. You can try it on the ground before lifting it.
Step 3: Adjust the clearance.For "Compound hinge transverse expansion jointOr "Large tie rod expansion joint", the amount of pre-stretch or pre-compression may need to be allowed during installation. How to tune it? According to the compensation data in the product manual, it is generally enough to adjust the tie rod nut to the middle position at ambient temperature (for specific methods, refer to Q&A 12 "How to adjust the tie rod nut of expansion joint" on our site). What about that? Before installing, set the position on the ground, level it with a level ruler, and then lift it.
Step 4: Fasten.Tighten the flange bolts in diagonal order, and the torque should be uniform. Don't screw one end to death and then screw the other. The flange surface will tilt up and leak air.
4. Don't step on the high-frequency pit in the installation
- Pit 1: Forgot to remove the transport tie rod.Some workers try to save trouble and install it directly without removing the tie rod. As a result, the expansion joint can't move at all, and the thermal expansion and contraction are all stuck on the pipeline. And guess what? The pipeline is directly deformed and the expansion joint is scrapped.
- Pit 2: The pipe bracket next to the expansion joint is not adjusted properly.Remember, the expansion joint only absorbs displacement and does not bear pipe weight. You must set up guide brackets and fixed brackets on both sides. Is that the truth? The spacing of the brackets is wrong, and the expansion joint can't bear the weight, which will cause problems sooner or later.
- Pit 3: Tighten the bolts too hard when installing non-metallic expansion joints.The fabric fiber (non-metal expansion joint) pressure plate is easy to deform, and the flange gap is even after compression. Don't screw it to death. Two days ago, I met a customer. The non-metallic bolts were screwed and the pressure plate was bulging.
- Pit 4: The direction of multiple expansion joints is not aligned when connected in series.For example, "Compound straight pipe bypass pressure balanced expansion joint", it itself requires the two bellows to be coaxial, and if you install them crooked, additional bending moments will be generated. What about that? Before installing, set the position on the ground, level it with a level ruler, and then lift it.
5. Finishing work: inspection, pressure test and cleaning up the site
Don't leave in a hurry after installing, do three checks:
- 1. Visual inspection:Is the flange skewed? Are the bolts all screwed into place? Tsk, don't miss what you didn't screw.
- 2. Pressure test:If conditions permit, perform a hydraulic test with 1.5 times the design pressure (note "Non-metallic expansion joint"You can't do water pressure, you can use air pressure instead, and the pressure should not exceed 0.2MPa). What about that? Brush the weld with soapy water, if there are bubbles, it will leak.
- 3. Activity:For expansion joints with tie rods, push and pull them manually to see if they can expand and contract freely. If it gets stuck, quickly check that the tie rod nut is not properly adjusted.
You can't leave welding rod heads, bolts, gloves in the flue, because they will break the bellows when they run in with the smoke. Alas, I have said it many times, but some people still forget it.
Okay, follow this process, and there will be no big problems in the installation of flue expansion joints. If you are still unsure, look through other articles on our site, such as "The Specific Function of Expansion Joint Guide Tube" and "The Function of Expansion Joint Tie Rod", which are all very detailed.