1. What is an angular non-metallic compensator? Find out where its "horns" are
To put it bluntly, angular non-metallic compensators are specially used to absorb the angular displacement of pipes. Imagine that when the pipe turns, thermal expansion and contraction or the foundation sinks, the pipe will produce an angular displacement like a person twisting his waist-ordinary compensators can't bear this force, and it is common for the flange to crack and the weld to tear if it is carried hard. The angular non-metallic compensator has a set of hinges or tie rod structures at its upper and lower ends, so that the bellows can only rotate around a certain center point in a plane. This "angle" refers to angular displacement. It is different from pure axial compensators such as "non-metallic expansion joints (fabric fiber expansion joints)", which are only responsible for longitudinal expansion and contraction, but can't control turning.
A belt of fabric fibers (that is, the main body of the non-metallic expansion joint), plus metal flanges at both ends and a set of angle limiters. This set of limiting devices is the soul-it limits the bellows to only swing angularly while withstanding the blind plate force of the pipe (that is, the thrust generated by the internal pressure of the pipe). If there was no such thing, the bellows would bulge and be scrapped as soon as the pressure went up. To put it bluntly, it just gives the pipe a "joint" to make the pipe bend safely.
2. What is the difference between it and ordinary non-metallic expansion joint? A key difference in structure
Ordinary non-metallic expansion joints, such as "non-metallic expansion joints (fabric fiber expansion joints)" or "rubber compensators" in this station, generally rely on multiple layers of fabric and rubber to absorb axial displacement or a small amount of lateral displacement. Structurally, it is a soft connection, with flanges at both ends clamped, bellows in the middle, and no extra tie rods or hinges. And the angular non-metallic compensator, you look at the side of it, will have two or four tie rods, or a pair of hinge plates that are perpendicular to each other. The function of these tie rods is also mentioned in our common questions and answers-the function of the expansion joint tie rod is to bear the internal pressure thrust and prevent the bellows from being stretched and damaged.
A customer installed an ordinary non-metallic expansion joint next to a 90-degree elbow. As a result, after three months of operation, the flange surface was directly misaligned by 5mm, and the seal failed and smoked. After changing to the angular type, the pull rod eats the thrust and absorbs the angular displacement cleanly. The difference is so obvious – one is "passive absorption" and the other is "directed guidance". So don't blindly save money and save trouble. The first step in selection is to ask clearly: Is there any angular displacement at this position of the pipeline?
3. Which working conditions must use angular type? Old mages in power plants and cement plants all know
In the flue duct systems of power plants and cement plants, angular non-metallic compensators are almost standard. Guess why? Because the flue gas pipeline has high temperature and large span, the angular displacement accounts for a large proportion of the displacement caused by thermal expansion and contraction. Especially the flue between the boiler outlet and the dust collector. When the temperature difference of several hundred degrees comes, the pipe twists and turns like it is drunk. At this time, the "Corrugated Expansion Joint for Power Station Industry" or "Metal Corrugated Expansion Joint for Cement Industry" of this station can also carry a part of it. However, if you encounter right-angle turning and Z-shaped trend, the metal corrugated pipe can't turn at all, so it must be angled non-metallic.
There are also desulfurization systems, such as the connecting sections before and after the "desulfurization flue gas baffle door". The medium is highly corrosive and can't touch the metal bellows, and non-metallic materials are more acid-resistant. Moreover, the pipeline at the inlet and outlet of the desulfurization tower usually has a large angular displacement, and the ordinary axial compensator is looking for death. Old mages usually arrange a pair of angular types at each inflection point, or use the "compound hinge transverse expansion joint" in combination to decompose the multi-directional displacement.
In addition, for vacuum pipeline systems like air-cooled island, this station has "double hinge expansion joint of air-cooled island vacuum pipeline", which is actually a variant of angular compensator. The vacuum environment requires extremely high sealing. The fabric layer and sealing layer in the angular non-metallic compensator must be specially designed to avoid air leakage, otherwise the vacuum degree cannot be kept.
4. The three easiest pits to step on during model selection: size, angle and flange matching
Choose size large over small. Many buyers think that the bigger the compensator, the safer it is. As a result, the flange bolt holes don't match, and the holes have to be expanded on the spot. The length of angular non-metallic compensator is strictly calculated. If it is long, the stroke of the tie rod will be insufficient, and if it is short, the compensator will have no room to swing. The correct way is to let the manufacturer set the length according to the actual angular displacement and diameter of the pipe, and don't pat your head.
The angle parameter is wrong. The nominal "angular displacement" of an angular compensator is the maximum swing angle on one side, such as ±5°. But if you understand this angle as the total displacement, you're screwed. The actual angular displacement required by the pipeline is the rotation angle of the centerline of the pipeline in the hot state, which needs to be calculated by drawing. Many small factories directly give a 3° goods, and as a result, the pipe will die as soon as it is hot.
Flange matching confusion. We have products such as "metal hose" and "PTFE-lined metal hose" in our station, and there are various flange standards (national standard, American standard and Japanese standard). The flange of angular non-metallic compensator is usually matched with the pipe flange, but many people buy the universal flange cheaply. As a result, the distribution circle of bolt holes does not match, or the width of the sealing surface is not enough. Remember that the force of the angular type is more complicated than that of the axial type, so the flange strength must be checked. Don't make do with ordinary flanges.
5. Installation and routine maintenance: Installing the wrong angular compensator is equivalent to wasting money
What are the most common mistakes made when installing? The angular compensator is installed as axial, and the limit nut of the tie rod is not adjusted to the correct position. Our FAQ "How to adjust the expansion joint tie rod nut" makes it very clear-the nut must be loosened to the designed stroke position before installation, otherwise the tie rod will break as soon as the pipe moves. The angular type is more troublesome. Its tie rod must be parallel to the direction of the pipe, and the hinge axis must be perpendicular to the displacement plane. If you install it backwards, it not only can't compensate for the displacement, but also will react the force on the pipe rack, which may pull the pipe rack askew for you.
Regularly check the fabric bands for cracks, ageing, especially near heat sources. Pay attention to whether the tie rod and hinge are corroded and stuck. If the rust dies, the angular function will be lost. Also, some old factories like to wrap the insulation layer outside the compensator. Remember not to wrap it too thick to press the movement space of the tie rod, otherwise it will be white. I once saw a cement factory, and the insulation cotton was stuffed. As a result, the tie rod couldn't move at all, and the pipe blew up. The scene was miserable.
Don't wait for the pipe to collapse before you regret it. Angular non-metallic compensator is not a high-end black technology, but it is used in the wrong place or the wrong parameters are selected, and the cost is much higher than repairing pipes. If there is really an uncertain working condition, ask the manufacturer's technology directly, throw the pipeline layout, medium, temperature and pressure, and let them count. Save that consulting fee, and then one repair will be enough to buy ten compensators.