1. What exactly is the non-metallic compensator ring belt? What does it have to do with non-metallic expansion joints?
When many customers hear the term "non-metallic compensator band" for the first time, their first reaction is: Isn't this the layer of cloth on the non-metallic expansion joint (fabric fiber expansion joint)? Yeah, not entirely. The ring belt is the core functional part of the non-metallic compensator, you can understand it as the "skin" of the entire compensator-responsible for sealing, temperature resistance, and absorption of displacement. And the whole non-metallic expansion joint, in addition to the ring belt, also has a metal frame (flange), insulation layer, fasteners, and guide tube (if matched).
The ring band is the "core" and the expansion joint is the "shell". When you buy non-metallic expansion joints, you essentially buy a "loop band + frame" combination. However, many small factories that supply non-metallic compensator ring belts will sell the ring belts, because the profit of frame processing is thin, and the ring belt material is the majority of the profit. Two days ago, I met a purchaser of a cement production line. He bought a ring belt directly from a small factory for a cheap price and changed it himself. As a result, the flange aperture difference was 3mm, and it was forced into it on the spot, and it leaked after two months-this is the relationship between the ring belt and the whole compensator.
Second, there are all kinds of belt materials, such as silicone cloth, fluorine tape, ceramic fiber... Which one should I use?
The most pitful thing about material selection is that manufacturers recommend materials according to the "highest working conditions". For example, if you are just smoke at 150℃, he directly gives ceramic fiber + silicone cloth, saying that it is "more durable". As a result, the price doubles, and the life of silicone cloth at 150℃ is not as long as that of nitrile rubber cloth-because although the temperature resistance of silicone cloth is high (200~300℃), its elastic recovery is poor at this temperature and it is easy to shape and deform.
You directly tell him the temperature of the medium, whether there are corrosive gases (SO₂, HCl, etc.), and whether there are dust particles. In my experience:
- Ordinary hot air (≤150℃, no corrosion): Nitrile rubber cloth or neoprene rubber cloth, the most cost-effective.
- High temperature flue gas (150~300℃): Silicone cloth or fluorine tape. Fluorine tape is better in acid and alkali resistance, but the price is 2~3 times that of silicone tape. Don't be fooled into "fluorine tape must be used".
- Ultra-high temperature (> 300℃): It must be reinforced with ceramic fiber cloth + stainless steel wire mesh, and be equipped with heat insulation layer.
In addition, many manufacturers who supply non-metallic compensator bands will take "multi-layer composite" as a selling point. Three layers of silicone cloth sounds better than two layers of cow, but the key is whether there is a high temperature resistant adhesive between the layers? If not, use it for half a year and foam in layers. If you ask him to produce an interlayer peel strength test report, you can sift out 80% of the workshops.
Third, the design of ring belt structure affects the life: single layer, multi-layer, with heat insulation layer, don't just look at the thickness
Some customers ask "How thick is the loop" as soon as they come up? Thickness is important, of course, but structure is more critical than thickness. Take a real case: the non-metallic expansion joint used in desulfurization pipeline of a steel mill, with a nominal band of 8mm, was worn out in 3 months. Changed to a different factory, the same 8mm, but the inner layer was reinforced with wire mesh, the outer layer was used with fluorine tape, and the middle was sandwiched with insulation cotton. It took two years to use it without any problem.
- Single-layer ring belt: Only applicable to low pressure, low temperature and small displacement scenarios (such as indoor ventilation ducts).
- Multilayer belt
(The multi-layer here is not simply stacking a few layers of cloth, but functional layers: temperature-resistant layer + reinforcing layer + sealing layer). For example, a typical flue gas ring belt: inner ceramic fiber cloth (temperature resistance + heat insulation) → middle stainless steel wire mesh (tensile resistance) → outer fluorine tape (sealing + corrosion resistance).
4. Supply non-metallic compensator ring belt, the easiest pit for you to step on-dimensional tolerance and flange matching
Circle belts are soft bodies, and the dimensional tolerance tends to be larger than that of metal pieces. However, some factories that supply non-metallic compensator belts control the tolerance within ±5mm, which is said to be an "industry standard". In fact, JB/T 12235-2015 allows a deviation of ±1.5% (and not less than ±3mm) for the length and width of the loop. If you think about it, a 1m wide loop band, ±5mm deviation means that the flange bolt holes may be misaligned.Two days ago, a buddy who was doing desulfurization in a power plant ordered four loop belts. When he came back, he found that one side grew 15mm, and he broke it hard. As a result, after running for a month, the loop belts were torn from the bolt holes-this is the fault of dimensional tolerance.
V. Installation and routine maintenance: What should I do if the ring belt is loose, leaky or broken?
The ring belt is actually not difficult to install, but 80% of the leakage is due to the wrong order of bolt tightening. Remember:Pre-tighten diagonally from the middle to both sidesScrew to the specified torque in 3 times. Don't screw to death at once, otherwise the force on the ring belt will be uneven and the local stress will be concentrated.- air leakage: First check whether the bolts are loose, and then check whether there are needle holes in the belt body (often caused by small particle erosion). The needle eye can be temporarily repaired with silicone rubber, but it is recommended to replace it within half a year.
- Loose: The relaxation of the band is mostly due to the material creep at high temperature. If the slack amount does not exceed 5% of the original length, you can adjust the tie rod nut (this site has a common question and answer "How to adjust the tie rod nut of the expansion joint"). If it exceeds 5%, you have to replace it with a new one. Don't hold on.
- Broken: If the break is in the corner, it can be repaired by hot vulcanization of patch of the same material + high-temperature resistant glue. If it is broken in the middle area, directly change the whole circle belt, and it won't last long if it is repaired.
6. Selection process + manufacturer screening: it takes 5 minutes to get it done, saving tens of thousands of after-sales costs
- Define operating condition parameters: Medium, temperature, pressure, pipe displacement (axial, transverse, angular).
- Determining Band Material: Look at the second verse.
- Determine the number of structural layers: Look at the third verse.
- Confirm flange interface dimensions: Note that the sealing face width, bolt bore diameter and spacing of the ring belt must match your flange exactly.
- Require manufacturers to provide factory inspection reports: Including pressure test, airtightness test and dimensional inspection.