Metal expansion joint is not a "universal patch". First, find out what problems it solves
Those thermal expansion and contraction, vibration displacement and installation errors in the pipeline system are all minor problems, but any one that is not handled properly can make you rework until you cry. Metal expansion joints are essentially elastic joints on pipes-specially used to "suck displacement". It doesn't carry hard like a flange or pass stress on to the bracket like an elbow. To put it bluntly, it is the "shock absorber" equipped with the pipe itself. In the past two days, I met a customer. The steam pipeline was not equipped with expansion joints, and the valve well was directly cracked after three months of operation. Tsk, save a little money and lose a lot of money.
Dazzling product line: choosing the wrong type is loading a time bomb
High temperature axial expansion jointSpecially serving power station boilers, the straight pipe section absorbs axial displacement;Metal Corrugated Expansion Joints in Cement IndustryIt is resistant to high temperature dust, and the material and thickness of corrugated pipe are different;Desulfurization flue gas baffle doorSupporting flue gas system, corrosion resistance is a hard index. AndUniversal corrugated expansion joint、Direct buried (fully buried) type expansion joint、Compound hinge transverse expansion joint…There were dozens of categories alone. How to choose? Look at the working conditions: medium temperature, pressure, displacement direction, space limitation. For example, the air-cooled island vacuum pipe has to be usedDouble hinge expansion joint for air-cooled island vacuum pipeline, you take the general-purpose type to install it, and the vacuum degree will be directly deflated.
Don't just look at the caliber when selecting the model, but the stiffness, guide tube and tie rod are the real details
Many people only focus on the caliber and compensation amount when they get the parameter table. As a result, the bellows cracks after three months of installation. What's the problem? The stiffness is not counted right. We have them in our stationStiffness and Calculation Formula of BellowsIt must be checked when designing. The stiffness is too large to absorb the displacement, and it is too small to bear the pressure. Againguide tube— — That thing is installed in the opposite direction, and the medium directly washes the bellows, doubling the corrosion rate. And guess what? In many projects, the bellows are perforated for half a year because the direction of the arrow of the guide tube is not aligned with the flow direction of the medium. Andtie rod：How to adjust the tie rod nut of expansion joint？ Instead of casually tightening, you have to set the preload force according to the calculated value. As we specifically mentioned in our Q&A, the function of the tie rod is to limit the over-stretching of the bellows, but the nut locking pressure is wrong, which will either fail or damage the pipe.
The easiest pit to step on at the installation site: Do you remove the tie rod nut? Where does the arrow go?
The most common problems at the installation site —Does the screw of the expansion joint need to be removed?The transport screw is fixed and must be loosened or removed after installation, otherwise the expansion joint cannot be expanded or contracted at all. I've seen someone test the pressure directly without dismantling it. The bellows was forcibly cracked, and it would cost tens of thousands of dollars to replace it. And there's a pit:The direction of the arrow of the expansion joint refers toThe flow direction of media, when installed backwards, will generate vortex erosion, especially for media containing particles, such as pneumatic conveying pipelines in cement plants. Pretending backwards is chronic suicide. In addition, when installing the expansion joint of the large tie rod, it is necessary to ensure that the tie rod is parallel to the axis of the pipeline, and do not tilt, otherwise it will be stuck during lateral displacement.
Three things for daily maintenance: see cracks, record displacements, and replace them on schedule
First, whether there are cracks, corrosion spots or depressions on the surface of the bellows. On steam pipelines, it is the norm to change them every five years, but the high-temperature dust environment in the cement industry has to be changed in two years. Second, the actual displacement amount is recorded. Each expansion joint has a permissible displacement range. Take a ruler to measure it. If it exceeds it, it will be an alarm signal. Third, pressService life of expansion jointCycle replacement. Life is affected by the number of temperature cycles, and the greater the temperature fluctuation, the earlier the fatigue. If it isGas bellows, replaced every few years? Household use is usually 8 years, and industrial use is calculated per time. There are also instructions for Q&A in our station.
It is not difficult to make good use of metal expansion joint by selecting three parts and packing seven parts
To put it bluntly, the selection parameters are thoroughly understood-stiffness, guide tube and tie rod can't be leaked; The installation specifications are in place-the direction of the arrow, the removal of the screw and the preloading of the tie rod must be according to the standard; Regular inspection is not lazy-surface inspection, displacement recording, periodic replacement. The stable operation of the plumbing system depends on these easy-to-be-underestimated details. If you have any on handMetal expansion joint tool— — Whether it is the selection calculation table or the installation of torque wrench, using the right place can save half of the return fee. Really unsure, flipping through the product information and frequently asked questions and answers of our site is more reliable than guessing.