At about three o'clock that afternoon, just after the second step of the pipeline inspection in the chemical plant, there was a piercing noise in my ears — a clanging, clanging, like someone beating a drum on the wall of the pipe with an iron bar. My heart skipped a beat, and I ran over to follow the sound, and found that it came from the one I just installed yesterdayUniversal corrugated expansion joint。 The whole equipment shook like a screen of chaff, and the surface of the bellows was trembling visible to the naked eye. The welder next to him turned pale, and the wrench in his hand almost fell to the ground. He hesitated and squeezed out a few words, "It seems…it's backwards?"
I squatted down and saw that the direction of the guide tube was indeed marked opposite to the direction of the medium flow, and the arrow pointed opposite. Tsk, this is a lot of trouble. The chemical pipeline is running either steam or high-temperature medium. ThisChemical Metal Expansion Joint Added BackwardsThat's the same as torturing a bellows.
The expansion joint is a "joint". Installing it backwards is equivalent to making people walk backwards
Many masters think that the expansion joint is the same at both ends, so just screw it on casually. But look at the one we use in our factoryHigh temperature axial expansion jointThe function of the guide tube is to guide the medium through smoothly and protect the bellows from being washed at high speed. The small mouth of the guide tube flows towards the medium, so that the medium can slip along the wall of the guide tube, and the bellows basically does not contact the fluid. Once installed backwards, the big mouth faces the entrance, and the medium hits the ripples directly like a high-pressure water gun-not to mention loud noise and fierce vibration, the bellows is washed so badly, and the fatigue cracking speed doubles.
Previously, a customer found it troublesome to install it, so he started it himselfUniversal corrugated expansion jointInstall backwards. In less than a month, the bellows leaked, and the steam came out like fireworks. He was so angry that he called us overnight to scold the quality of our products. I asked him to take a picture and see that the welds of the deflector were all worn out by the medium. Therefore, the arrow on the device is really not for fun, it is life-saving.
How can you tell at a glance that you are acting backwards? Three tricks to teach you not to waste money
The easiest way – look at the deflector. You stand on the side of the pipeline and take a look along the direction of the medium flow: the small mouth of the guide tube is facing upstream (the direction of the medium flow). If you find that the big mouth of the guide tube is facing upstream again, it is the reverse, so don't hesitate.
In addition, if you find the following situations after driving, 80% of them are in the wrong direction:
- Abnormal vibration: Shaking like a tractor, you can even see the bellows swaying back and forth.
- Local overheating: Touch the corrugated sidewall with your hands. Normally, it is warm. If you install it backwards, it will make you shrink your hands. If you don't believe me, try it (remember to wear gloves).
- The tie rod nut is inexplicably loose: AboutHow to adjust the tie rod nut of expansion jointWe have specifically said before that the preload torque should be consistent according to the specification. However, after reverse installation, the impact force of the medium will be transmitted to the tie rod through the bellows, and the torque is abnormal. The nut is loose every three days, and it can't be tight.
Listen to the sound. The sound of the normally operating expansion joint is very smooth, and when installed backwards, there will be a "click-click" metal impact sound, like someone throwing a stone inside.
How to fix it when you find it installed backwards? Don't take it hard, shut it down
The first step is to stop the machine immediately and relieve pressure. Don't feel bad about that little output. High-pressure and high-temperature medium runs hard in the expansion joint installed backwards, and the pipe may burst at any time, so safety comes first.
If you are usingStraight pipe pressure balanced expansion jointOrCompound hinge transverse expansion jointThe structure is more complicated. When disassembling and assembling, you have to check whether the tie rod and hinge are deformed due to the force of reverse assembly. If the hinge is deformed, don't think about adjusting it back, just replace it with a new one.
Remember to replace all the old bolts before putting them back in. The weld of the guide tube has been washed by the medium before, and there may be burrs or pits. Take a grinder to grind it again and smooth it before welding. If the bellows has been slightly deformed or has minor cracks-don't feel bad, just replace it with a new one. In our stationUniversal corrugated expansion jointFully stocked and delivered same day by saying hello, it's a hundred times better than taking the plunge and tinkering.
Remediation after the fact is better than prevention before the fact: A habit kept me from rolling over again
At the end of the day, training before installation is a hundred times more important than remediation after the fact. Pipes in chemical plants have high temperatures and high pressures, especiallyCorrugated expansion joint for power station industryThis high-demand model, if it is installed in the wrong direction, it will cost tens of thousands of dollars plus potential safety hazards.
After arrival, check the product nameplate and drawings first to confirm the model, pressure level and arrow direction. Then let the two masters check each other, one person to the drawings, one person to the real object, shout "the arrow is facing east", and the other to see if it is really facing east. After installation, take a hydraulic pressure test, raise it to 1.5 times the working pressure, listen to whether there is any abnormal noise, and see if the bellows has any abnormal bulge.
By the way, we're standingDouble-sealed single-axis circular baffle doorThe installation is often confused-the positive and reverse mistakes lead to lax seal. I'll write a separate article to talk about this pit later.
The three-second rule, but it really works
Alas, after that rollover, I got into the habit of crouching down and staring at the arrow for three seconds before installing the expansion joint. The old master calls this the "three-second rule"-you look at the first second to confirm the position, the second second to go through the medium flow chart in your mind, and the third second to sweep the direction of the deflector. It's a little dirty, but it works. Since then, the pipeline I handled hasn't been installed backwards.
Did you meet at the sceneChemical metal expansion jointIs it a weird thing to act backwards? Come to the comment section to chat about your rollover experience, or go directly to our technical department to help you troubleshoot hidden dangers for free. After all, the pipe can be changed if it is installed backwards, and there is no regret for taking the medicine if there is a safety accident.