1. First understand: why is the insulation layer of the compensator easy to break, and what are the consequences of breaking it
The insulation layer of the compensator is damaged for two reasons, to put it bluntly: first, the environment is too bad, and second, the construction itself is not in place. Think about it, the pipe expands and contracts by heat, and the compensator itself expands and contracts there. If the insulation layer is too tightly wrapped, too hard, or the wrong material is chosen, and it shakes with the bellows, can it not crack?
What's even more ruthless is the high-temperature flue gas and steam pipeline-as soon as the temperature rises, if the insulation material is not temperature-resistant enough, it will directly burn and carbonize, losing the heat insulation effect. There are also those open-air pipes. When the rain soaks, the insulation cotton absorbs water and becomes heavier, which is crushed. The metal bellows are in a humid environment for a long time, and the corrosion is accelerated, and the life span is directly cut off by half.
Consequences? Three words: money for nothing. Once the insulation layer is broken, the waste of energy is a trivial matter. The key is that the compensator bellows or fabric fiber layer is directly exposed to high temperature and corrosive media, and the compensators bought by hundreds or thousands may be scrapped in a few months. What's more troublesome is that once the insulation layer falls off and blocks the pipeline, or the baffle door gets stuck, the whole system has to be shut down for emergency repair.
So,Compensator insulation repair？ It is not just a layer of cotton to finish the job, every step has to be taken seriously.
2. The "physical examination" before repair is indispensable-metal vs non-metal compensator, what is the difference between the key points of the examination
Everyone knows the principle of checking before repairing, but most people are planted in the "wrong direction of checking".
bump intoUniversal corrugated expansion jointOrHigh temperature axial expansion joint
This kind of metal compensator, after you peel off the insulation layer, focus on whether there are cracks, corrosion pits and scratches on the surface of the bellows. Especially the welding heat-affected zone and trough position, which is the stress concentration point, is most prone to problems. Shine it with a flashlight to see if there are any bright dots-that could be a sign of intergranular corrosion. Measure the wall thickness again. If the thinning exceeds 20% of the designed wall thickness, don't repair it and change it.
WhileNon-metallic expansion joints (fabric fiber expansion joints)Orrubber compensator, the main points of the inspection are completely different. This kind of compensator relies on fabric fiber layer or rubber layer to seal and displace. After you peel off the heat insulation, you should follow the direction of the fiber to see if there is delamination, fluffing and penetrating damage. The rubber compensator should also be touched to see if it is sticky and hardened-pinch it with your hand, and if it doesn't bounce back, it means that it is seriously aging, and it won't last long after repairing it.
Also, don't leak the deflector. Whether metallic or non-metallic, the role of the guide tube is to prevent the media from directly washing the bellows or fabric layer. If the guide tube deforms and falls off, no matter how well the insulation layer is repaired, the inside will still be blown out.
3. Practical points: How to avoid damaging the bellows or fabric fiber layer when dismantling the old insulation layer
In this link, on-site workers are most likely to overturn. The reason is simple: the old insulation layer is exposed to wind and sun, and it often sticks to the surface of the compensator-especially those insulation structures fixed with asphalt or resin glue. When disassembled, a layer of skin is accidentally taken off the surface of the bellows.
When dismantling the old insulation layer, only wooden or copper scrapers and plastic shovels can be used for tools. It is prohibited to directly use shovels and crowbars. RightMetal rectangular expansion jointOrRectangular non-metallic expansion jointFor this kind of special-shaped parts with many corners, it is necessary to use a soft brush with low-pressure compressed air to blow off the floating ash first, and then peel it off manually to avoid hard objects getting stuck in the trough.
Don't touch the tie rod nut when removing the insulation. Especially the tie rod nut of the expansion joint, which is used for preload adjustment. As soon as you move, the displacement of the compensator changes. Take a picture before disassembling and note down the location, and you can only restore it when you put it back.
ForRubber PTFE compensatorIts lining PTFE layer is extremely thin, and it is afraid of high temperature and scratches. When dismantling the insulation, shovel along the axial direction of the pipe, and don't pull it horizontally. If it is torn, then the compensator insulation layer repair is half in vain.
4. Choose the right insulation material and structure: High-temperature axial expansion joint and rubber compensator have different requirements for insulation layer
The thicker the insulation material is not the better, nor is it the more expensive. The key is to look at the compensator type.
Such asHigh temperature axial expansion jointThe working temperature is often above 500℃, and generally rock wool and glass wool are directly burned into ash. Ceramic fiber blanket or aerogel felt must be used, and there should be a layered structure: the inner layer is made of high-aluminum ceramic fiber (temperature resistance 1260℃), and the outer layer is made of ordinary ceramic fiber or aluminum silicate wool. How to calculate the thickness? The principle is to make the external surface temperature not exceed 50℃, and at the same time leave the expansion space of the bellows-don't plug it, and leave at least an annular gap of 10~15mm.
Whilerubber compensatorOrRubber PTFE compensatorFeeling the other way around. Rubber is afraid of high temperature, but the purpose of heat preservation is not to keep the rubber warm, but to prevent external heat sources (such as the high-temperature pipe next to it) from baking the rubber. In this case, the insulation layer should be wrapped outside the rubber compensator, but it must be made into a detachable structure and fixed with stainless steel cable ties or quick buckles, which is convenient to open and check the state of the rubber body during maintenance.
As forDirect buried (fully buried) type expansion jointOrSleeve type pipe expansion jointThe insulation layer directly contacts the soil and groundwater, and it should be waterproof in addition to insulation-the outer protective layer has to use three-layer PE anti-corrosion structure, otherwise once the water vapor penetrates, the insulation will become cold and accelerate corrosion.
5. Reassembly and sealing: How to wrap special-shaped parts such as baffle doors and rectangular expansion joints to prevent air leakage
Reassembling insulation layer is a technical work, especially for special-shaped parts. You're wrapped so tight that the compensator can't move; If you pack it too loosely, air and heat leakage outside equals a white pack.
Let's startFlue gas baffle doorOrDesulfurization flue gas baffle door。 This kind of equipment itself has flange connection and operation mechanism, and the insulation layer cannot cover the transmission connecting rod and flange bolt. The correct method is: only cover the valve body, and leave a bare area of 250mm at the connection between the operating mechanism and the flange, which is convenient for daily inspection and tightening. When wrapping, lay with aluminum silicate cotton felt in layers and staggered seams, the thickness of each layer does not exceed 50mm, and then fix it with stainless steel strip, and add 0.5mm thick aluminum skin as a rain cover on the outside-the joints of aluminum skin are tightly blocked with silicone sealant.
Metal rectangular expansion jointAndRectangular non-metallic expansion jointThe difficulty lies in the four corners. The right angle position can easily become an air leak point. I generally suggest using prefabricated special-shaped insulation modules, making the corners into R-angles, pressing and molding with molds, and directly stuck on them on the spot. If there is no prefabrication condition, fill the corner gap with high-temperature-resistant sealant (calcium silicate-based, temperature resistance above 1000℃), and then compress it with fiber blanket.
After reinstalling, do a thermal imaging test. After running for half an hour, scan it with an infrared thermal imaging camera, and find that the temperature is abnormally high, which means that the insulation is not tightly sealed, so make it up quickly.
6. Life management after repair: Don't wait for the next time it is broken before repairing, keep an eye on these three positions in daily inspection
After the insulation is repaired, it is not once and for all. If you keep an eye on three parts, you can eliminate the accident in the bud.
The joint between the insulation layer and the metal pipe or flange. Here, the temperature difference is the largest, the thermal stress is the most concentrated, and it is easiest to crack. Inspect once a month and press the seam with your hand to see if it feels loose. If the temperature gradient suddenly changes by infrared detection, local repair should be made immediately.
Drain hole (if any) at the bottom of the compensator. Especially for outdoor installationExternal pressure single axial expansion jointOrCompound hinge transverse expansion jointClogging of the bottom drainage hole may cause condensed water to accumulate and damage the insulation layer. During the inspection, poke the drainage hole with a thin wire to confirm that it is unblocked.
The exterior of the insulation layer at the crest of the bellows. This is the place that is most severely washed by displacement. Over time, the insulation cotton will be rubbed into balls like marshmallows. You gently press the wave crest with your palm. If it feels empty underneath (the insulation layer is separated from the bellows), it means that the fixed structure has failed and has to be tightened again.
Compensator Insulation Repair?It is not a one-time thing, but a system from inspection, material selection to construction and maintenance. Follow these six steps for each repair, which can prolong the life of the compensator by at least 3 times.