Two days ago, I met a customer and called him in a hurry: "The expansion joint leaked a few days after it was installed, and the tie rod was also broken. Is there something wrong with your quality?" I asked him to take a photo and send it over. When I saw it-good guy, the direction of the arrow was installed backwards, the transport tie rod was not disassembled, and the bolts were all screwed to death. Yeah, we're not gonna take the blame.
To be honest,How to install flue expansion jointThis matter looks simple, but there are quite a few people who flip over in practice. Especially non-metallic and metallic, the structure is different, and the installation details are far from the same. Today, I will shake out all the 7-step installation process at the bottom of the box for you. If you follow it, there will basically be no moths.
Find out which flue expansion joint you have in hand before installation
Don't screw the screws as soon as you get up. Take a look at the nameplate on the package first, or the appearance of the product:
- Metal corrugated expansion joint(e.g.Universal corrugated expansion joint、Corrugated expansion joint for power station industry) - -The main body is stainless steel bellows with guide tube, which is resistant to high temperature and high pressure.
- Non-metallic expansion joints (fabric fiber expansion joints)— Also calledRectangular non-metallic expansion jointThe ring belt is fiber fabric plus rubber, which is afraid of knocking and scratching, but the compensation amount is large.
- Rectangular expansion joint— — Used on square flues, mostly metal frames + non-metal bands.
Different kinds, the way of pretending is far different. For example, non-metallic ones must not be dragged when hoisting. Once the fabric layer is broken, the whole will be wasted. And the metal, the direction of the guide tube has to be figured out.
Step 1: Check the equipment and piping to confirm the direction of the arrow
When each expansion joint leaves the factory, there will be an arrow on the housing, which refers to the direction of media flow. And guess what? At least two out of ten played backwards. The arrow must point in the direction of the flue gas outlet, and the small mouth end of the guide tube is facing the incoming flow direction-install it in reverse, and the guide tube will hold the ash, which will wear through the bellows over time.
Tips: What should I do if the pipeline on site has been welded and can't adjust the direction? Then you have to make clear the flow direction when ordering, so that the manufacturer can customize it according to your direction. Don't wait until the scene to be dumbfounded.
Step 2: Lift in place and handle lightly
This step is the easiest to overlook. EspeciallyNon-metallic expansion joint (fabric fiber expansion joint)Its circle belt is a layer of cloth + rubber. Take a steel rope to strangle it, and it will directly strangle the mark. Correct practice: Use a sling or flexible sling to lift from the flange hole or special lifting lug.
Don't be careless with the metal ones either. Such asLarge diameter thick wall expansion jointThe weight is not small, and the lifting point should be symmetrical to prevent the bellows from twisting and deforming. Anyway, remember one thing:Don't knock, don't touch, don't drag。 It's broken, and that's not something you can fix with some paint.
Step 3: Flange connection or welding-do not screw the bolts at once
For flanged connections, thread the bolts in first, but don't tighten them in a hurry. You have toDiagonal alternating preload— — First tighten 1 point, then tighten 2 points diagonally, and then 3 points apart... Like screwing a car tire, step-by-step force in two to three passes. Finally, hit it again with a torque wrench, and ask the manufacturer for the torque value (generally in the product description).
If it is welding, it is more particular. Such asMetal rectangular expansion jointWhen welding, cool while welding to prevent thermal deformation. Remember to knock out the weld slag after welding and check for pores. Don't finish welding, and then repair welding if the follow-up pressure test leaks, which will trouble you to death.
Step 4: Adjust the tie rod and nut
This is the hardest hit by rollovers.
When the expansion joint leaves the factory, in order to prevent the bellows from shaking during transportation, it is usually installedtransport tie rod(Also called temporary pull rod). This thingMust be removed！ If it is not dismantled, the expansion joint cannot move when the pipeline expands and contracts, the tie rod is directly bent, and the bellows is easy to tear.
But there is one kind of tie rod that can't be completely removed- -adjustment rod(Also called limit tie rod). Such asLarge tie rod expansion jointOrCompound hinge transverse expansion jointThe tie rod is used to control the displacement of the bellows. The adjustment method is: first loosen the nut to a little shorter than the installation length (see the design drawings for details), leaving a thermal expansion gap. Generally, the product instructions will state "cold state pre-stretch or pre-compression amount". Just do it.
attention: Never screw the tie rod to death and use it as a support frame! The expansion joint is not a pipe support, it only compensates for displacement and does not bear weight.
Step 5: Pressure Test and Acceptance
Don't run in a hurry after installation. Do a hydraulic or air pressure test first. Before the pressure test, check whether the guide tube has been displaced-sometimes the guide tube will be crooked during hoisting or welding, which will cause the medium to flush the bellows and greatly reduce the life.
The pressure test pressure is usually 1.5 times the design pressure, and the pressure can be kept for 10 minutes without leakage. But if you pretend to beNon-metallic expansion jointNote that the water pressure should not be too high (generally not more than 0.15MPa), otherwise the ring belt may bulge and rupture.
After the flue system heats up (for example, 24 hours after the boiler is ignited), tighten the flange bolts again. Because thermal expansion and contraction will make the bolts loose, if they are not tight, the flange surface is easy to leak. This is calledThermal settingDon't be lazy.
Just a few words at last
Actually,How to install flue expansion jointThe core of this matter is four words:Operate according to the rules。 Don't fool around with experience, don't skip steps to save trouble. Do you want to install it at once and leave it alone for three or five years, or do you want to stop it every three days for maintenance? Weigh it yourself.
In addition, if you encounter uncertain models, such asStraight pipe pressure balanced expansion jointOrCurved tube pressure balance expansion jointThese with pressure balance function, the installation requirements are stricter, it is best to let the manufacturer issue the installation instruction. Don't blame me for not reminding you if something happens.