What exactly is a socket type metal expansion joint? How is it different from ordinary corrugated expansion joint?
Let's start with the structure. Socket-type metal expansion joint, to put it bluntly, is a section of pipe with socket, which is sleeved into another section of pipe with socket, sealed with a sealing ring in the middle, and absorbs the thermal expansion and contraction of the pipe by sliding. Compared with our common corrugated expansion joints-such as our site'sUniversal corrugated expansion joint— Completely different things. The corrugated expansion joint is compensated by the elastic deformation of the corrugation, and the socket type relies on the relative sliding of the sleeve, so it is essentially a sleeve structure. Yeah, that's the one on this siteSleeve type pipe expansion jointRelatives, but the socket type emphasizes the matching sealing mode of the socket and the socket.
The pipe is hot, and the inner pipe extends outward; Cold, retract. What does the seal rely on? Pressed between the socket ports by one or more layers of sealing rings (usually rubber or PTFE). This is completely different from corrugated expansion joints that rely on metal corrugations to bear fatigue stress. So ah, what the socket type does best is axial compensation, and the radial yaw capacity is almost zero. Someone asked: What is the difference between that and the ordinary "sleeve-type pipe expansion joint"? To put it bluntly, the socket type is a concrete implementation form of the sleeve type, but the sleeve type usually refers to flanges or welding connections at both ends, while the socket type is directly inserted into it, and the installation is rougher.
What's good about socket connection? What is the short board?
Biggest advantage – no welding. Think about it, how troublesome is it to start a fire in a chemical plant or a steam pipeline? It is expensive and time-consuming to get a fire certificate and pull a cordon. Insert the socket directly, tighten the flange or clamp, and you're done. It is also quick to disassemble and assemble. Just pull it out and change the sealing ring during maintenance. The seal relies on a rubber ring or PTFE ring, such as this station'sPTFE-lined hoseThere is also a similar sealing concept in. Suitable for steam, hot water, chemical media, especially those lines that require frequent overhaul.
However, the shortcomings are equally obvious: the pressure level can't go up. The corrugated expansion joint can withstand tens of MPa, and the socket type generally achieves 2.5MPa, which is almost the same. It is easy to extrude the high sealing ring. In addition, the temperature is also limited. Ordinary rubber rings can't bear 150℃, so PTFE or graphite rings have to be used, but the cost will go up. Also, it cannot withstand large lateral or angular displacements, and if the pipe support is not properly made, the socket can easily come out.
Don't just look at the picture in the selection: a parameter is incorrectly calculated and completely completed
Alas, two days ago, a customer from a cement factory complained to me: They wanted to use the originalMetal Corrugated Expansion Joints in Cement IndustrySwitch to socket type, I think it's cheap and easy to install. And the result? The caliber is right, the pressure is right, but forget the amount of compensation. The thermal displacement of the cement pipeline is large, and the socket sliding section is only 200mm. As a result, the temperature rises, it will be directly pushed through. You say it was wrong or not?
Caliber, pressure, temperature, compensation amount。 The diameter and pressure depend on the working condition of the medium, and the temperature determines the material of the sealing ring. The amount of compensation is most critical-you have to calculate how much the pipe elongates from cold to hot, and leave another 20% margin. For example, the steam pipeline is 50 meters long, the temperature difference is 200℃, the linear expansion coefficient of carbon steel is calculated as 0.012mm/m·℃, and the elongation is 120mm. You have to choose the model with a compensation amount of at least 150mm for socket type, and it is best to have a tie rod limit to prevent accidental prolapse.
In addition, don't be fooled by the picture given by the manufacturer. Some products have a nominal compensation amount of 200mm, but that is the limit value under no pressure. When pressurized, the friction of the seal ring will eat a part of the stroke. Therefore, when selecting the model, you should ask the manufacturer for "effective compensation amount", which is the same asModel and size of expansion jointIt is labeled differently in.
3 Most Common Mistakes to Make When Installing
Insufficient socket depth. Many people tried to save trouble, so they inserted half of it and it was over. As a result, as soon as the pipe was hot, it came out directly, and the steam sprayed on the spot was like a fountain. Standard practice is to plug in place and check the marking line on the socket. Second: the guide bracket is not in place. The socket compensator needs the pipes on both sides to be strictly coaxial, otherwise the socket will be stuck, the sealing ring will be worn, and it will leak in a few days. refer toCorrect installation method of expansion joint of large tie rodAccording to the requirements in, the distance between the guide bracket and the expansion joint should be within 4 times the diameter of the pipe. Third: the tie rod nut is adjusted randomly. Some socket types have pull rod limits, and some people screw the nut to death, thinking it can increase the seal. In fact, the role of the tie rod is to limit the excessive tensile displacement, see this articleHow to adjust the tie rod nut of expansion joint- -There must be a gap after the nut is adjusted, so that the expansion joint can slide freely during operation. Otherwise, if you pull hard, the sealing ring will collapse directly.
It leaked, stuck or rang when it was used. How to fix it?
The failure of the socket metal expansion joint is 90% due to the seal. Seal ring aging-the rubber used for two or three years, hardened, cracked and leaked. Medium corrosion-chemical medium has swollen the seal ring and stuck. Installation eccentricity-the pipe is misaligned, the socket is crooked, the seal ring is worn, and the abnormal noise comes. In contrast,Universal corrugated expansion jointThe life of the corrugated sheet is usually longer, and the fatigue life of the corrugated sheet is made of stainless steel, which can reach thousands of times, while the socket seal ring is a consumable part, which has to be replaced in 2-3 years. However, the corrugated expansion joint is afraid of water hammer and chloride ion corrosion. Once the corrugation breaks, the whole has to be scrapped. The socket type can be revived by changing the circle at least.
There is also a special occasion-underground directly buried pipelines, such as this station'sDirect buried (fully buried) type expansion jointUsing a corrugated structure plus an external pressure sleeve. Compared with the socket type, the direct buried type is not afraid of soil corrosion, but the installation is complicated. However, if the socket type is buried in the soil, the damaged seal ring can't be replaced at all. So, above-ground pipelines can be used, but underground pipelines can be used with caution.
Check the state of the sealing ring once a year. If the medium temperature exceeds 100℃, try to use PTFE sealing ring. 100% coaxiality is guaranteed during installation, and centering tire fixtures are used if necessary. Also, the tie rod nut should leave a gap according to the stroke given by the manufacturer, and don't lock it.
Should I choose socket type or corrugated type? A table makes it clear
| Contrast dimension | Socket type metal expansion joint | Corrugated expansion joint (e.g. general type) |
|---|---|---|
| Pressure rating | ≤2.5MPa, mainly low pressure | Up to 10MPa + |
| Temperature range | -40~350℃ (sealing ring limited) | -196~800℃ (depending on the material) |
| Installation space | Short axial length, but requires sliding space | Long axial length but no sliding clearance required |
| Maintenance costs | Low, just change the sealing ring | High, leakage needs to be replaced as a whole |
Seeing this, you may ask: When exactly is the socket type used? I'll give you three scenarios: low-pressure steam, hot water circulation, chemical non-highly toxic media and require frequent disassembly and assembly. High pressure, high temperature, large displacement, underground pipeline-honestly choose corrugated type, such as this station'sExternal pressure single axial expansion jointWith better stability. In addition, if it is a place where the dust is heavy and the temperature fluctuates violently in the cement industry, the socket type is easy to get dust stuck and the sealing ring wears fast, so it is not as good as the specially designed oneDouble three-way expansion joint in cement industry。
Socket type is a good tool, but you need to know its boundaries-when the pressure exceeds 2.5MPa, the temperature exceeds 350℃, or the compensation amount needs to be with lateral displacement at the same time, don't hesitate to change to corrugated type. On the contrary, it saves worry, money and welders, and the socket type is really fragrant. Did you pick the right one?