Flue expansion joint fixing bracket, so that it can be installed without accident

Why do flue expansion joints have to be equipped with fixed brackets? Let's make it clear what the hell this thing is for

As soon as the flue heated up, the pipes clicked and the expansion joints were pulled like rubber bands. Hey, don't just blame the expansion joint for poor quality-many times it's the fixing bracket that isn't fitted correctly, or at all.

Simply put, the fixed bracket is to "paddle the runway" for the expansion joint. The expansion joint itself can only absorb displacement, but the direction depends on the bracket. If there is no fixed bracket, as soon as the pipe expands, it will scurry everywhere, ranging from the adjacent equipment to the crook, or the whole flue will collapse. Two days ago, I met a customer. The flue at the inlet and outlet of the desulfurization tower used corrugated expansion joints. As a result, no fixed bracket was installed. As soon as the temperature rose, the expansion joints were directly torn. Do you think it's a loss or not?

Therefore, the fixed bracket is not "optional", but "standard". It divides the pipeline into independent compensation sections, so that each expansion joint is only responsible for the displacement of its own section. Is that the truth?

Look at the working conditions before selecting the bracket: high temperature, corrosion, large displacement? First take a seat from the product library of this site

Don't buy a general-purpose expansion joint as soon as you come up. The working conditions are different, and the selection is far different.

• High temperature condition (> 400℃): For example, the flue of a power station boiler must be usedHigh temperature axial expansion joint。 This expansion joint is heat-resistant, and the thrust of the fixed bracket should be accurately calculated, otherwise the bracket will deform.
• Corrosive media (desulfurization flue gas): RecommendedDesulfurization flue gas baffle doorMatchingPTFE-lined hoseOrNon-metallic expansion joint (fabric fiber expansion joint)。 The material of the fixed bracket must also be corrosion-proof, don't use ordinary carbon steel.
• Large displacement (> 100mm): Do not use single axial type, useCompound hinge transverse expansion jointOrCurved tube pressure balance expansion joint。 At this time, the fixed bracket needs to bear greater horizontal thrust, and the legs have to be thickened.

When you are not sure, directly turn through the product information in our station. Each model has a working condition table and installation requirements. Such asUniversal corrugated expansion jointSuitable for conventional temperature and pressure,Direct buried (fully buried) type expansion jointSuitable for underground pipes. Take your seat.

3 checks before installation: whether the expansion joint model is correct, whether the bracket position is calculated, and whether the reserved space is enough

Don't rush to do it. Do three things first-just like checking the weather before you go out, and save yourself getting drenched halfway.

First, check the expansion joint model.Is the nameplate on the box consistent with the design drawing? Especially the length, number of corrugations, flange diameter. Many accidents just take the wrong size, stuff it hard, and finally leak air.

Second, does the bracket position count?The fixing bracket should be attached to the fixed point of the pipe, such as the midpoint position between the two expansion joints, or near the equipment interface. You can refer toCompound straight pipe bypass pressure balanced expansion jointIt requires pairs of fixed brackets to balance the thrust. Generally, the design institute will give the spacing of the brackets. If not, remember a formula: the spacing of the fixed brackets should not exceed the pipeline length corresponding to the compensation amount of the expansion joint, and the spacing of the guide brackets should be determined according to the pipeline stiffness.

Third, is the reserved space enough?Especially in the pre-stretch direction. Many expansion joints have been pre-stretched when they leave the factory (the tie rod is marked), and they must be installed with a gap for thermal expansion in the cold state. You measure the distance between the flanges at both ends of the expansion joint and the fixed bracket to ensure that the pipe will not be pushed to death when it is hot.

Hands-on installation: 5 steps to complete the welding, bolt tightening and pre-tension adjustment of the fixed bracket

All right, check it out. Let's go. Remember, if you install it in the wrong order, there are endless consequences.

1. Step 1: Clean the welded area.Use an angle grinder to polish the rust and paint on the base of the bracket and the surface of the pipe clean, exposing the metallic luster. Don't try to save trouble, otherwise the weld will not be firm.
2. Step 2: Position the welding bracket.First, spot weld the bracket on the pipeline, and then calibrate the verticality with a horizontal ruler, and the error is controlled within ±3mm. After confirming that it is correct, weld fully. The height of the weld shall not be lower than the thickness of the base metal. After welding, knock off the coating and check whether there are any cracks.
3. Step 3: Install the expansion joint.Hoist the expansion joint in place with flange surfaces parallel, and tighten the bolt by hand after it is inserted. attentionArrow direction of expansion joint— — Refers to the flow direction of the medium, don't install it backwards (reverse will cause the bellows to be washed by the medium).
4. Step 4: Bolt tightening.Use a torque wrench to tighten in three passes in diagonal order, and refer to the expansion joint instructions for the torque value. Don't screw too hard at once to prevent the flange from deforming.
5. Step 5: Pre-stretch adjustment.This is the most critical thing. Refer to the FAQ "How to adjust the tie rod nut of the expansion joint" on our station: loosen the support limit nut, and use the tie rod to adjust the compression or stretching amount of the expansion joint to make it meet the design cold tightness value. After adjustment, lock the back cap to prevent loosening.

When pre-stretching, it is best to monitor the displacement with a dial indicator to ensure that both sides are synchronized. Otherwise it will skew.

The 4 most common mistakes after installation: the bracket is dead, the direction is reversed, the thrust piece is missed, and the tie rod nut is forgotten

• Stent Top Dead:Is there a sliding gap between the base of the holding bracket and the pipe? Some masters weld to death directly, and the expansion joint is equal to white installation. Correct practice: There should be a 2~3mm gap between the base of the bracket and the pipe, or a PTFE gasket should be added to allow the pipe to slide freely.
• Reverse orientation installation:The arrows on the expansion joints are not decorations! It represents the medium flow direction. If installed backwards, the bellows lining guide tube will be washed out and cause vibration. We stood on the FAQ "What is the direction of the arrow of the expansion joint" and explained it very clearly, so we went and turned it over.
• Missing thrust:ForExternal pressure single axial expansion jointOrStraight pipe pressure balanced expansion jointThe thrust is the safety that prevents the bellows from being overstretched. Many people don't install it because it's troublesome, and as a result, the expansion joint is straightened and scrapped.
• Forgot to adjust tie rod nut:The tie rod nuts are usually in a pre-tensioned state when they leave the factory, with the aim of preventing transport bumps. Must be loosened or adjusted to design values after installation. Many customers use it directly according to the factory state, and the expansion joint has no stroke available, and it will deform as soon as it heats up.

And guess what? As long as these 4 pits are avoided, 90% of expansion joint failures can be avoided in advance.

After installation, everything is not fine: keep an eye on these three indicators during acceptance, and run less to the site in later maintenance

After installing, don't rush to turn it on. Accept according to these three indicators, so you can worry less later.

• Displacement Amount:Use a marker to mark a starting point on the bellows of the expansion joint. After the medium is introduced to heat up, measure how much the bellows has actually expanded and contracted. If the deviation from the design value is more than 10%, it means that there is a problem with the mounting or pre-stretching of the bracket and it needs to be re-adjusted.
• Sealability:Check flange joints, bracket welds with soapy water or leak detector. If there is any leakage, deal with it immediately. Don't wait for the leakage to soak the insulation cotton.
• Stent Stability:Shake the pipe by hand, and the fixed bracket should not move at all. If shaking occurs, it means that the bracket is not stiff enough or the weld strength is insufficient.

What about post-maintenance? Check once every six months whether the tie rod nut is loose and whether the anti-corrosion paint of the bracket falls off. EspeciallyNon-metallic expansion jointThe fabric layer is easy to age, and cracks are found to be replaced in time. Do this, and you can go from "firefighter" to "hands-off shopkeeper"-right?