The metal expansion joint exploded? Don't rush to shake the pot, check these 4 links first
There was a loud noise at the scene, the pipeline burst, and the medium gushed-all the brothers who have worked in factory operation and maintenance know this feeling of suffocation. Many people's first reaction is to scold the manufacturer: "The quality of this broken expansion joint is too poor!" But to be honest, I have seen hundreds of accidents of metal expansion joints exploding. Tracing back to the source, 90% of pot manufacturers have been wronged. The real problem often lies in the four links of type selection, installation, operation and regular maintenance. Today, let's talk about it one by one.
1. Exploding is not metaphysics, but a mine buried in design selection
If you choose the model wrong, all the later efforts will be in vain. For example: high-temperature steam pipeline, with a design temperature of 600℃, bought a general-purpose corrugated expansion joint in the field map to save trouble. As a result, the elastic modulus of the corrugated pipe dropped sharply in the over-temperature environment, and it was directly torn after half a year. This is not an isolated case. Another example is the acidic medium in the desulfurization system. Someone took an ordinary metal hose to top it. As a result, the corrosion-resistant layer was corroded by sulfate ions and festered. A few months later, it exploded with a bang. Four parameters should be stuck in the selection: medium temperature, pressure, corrosiveness and displacement direction. These parameters don't match, and it is only a matter of time before it explodes. When you encounter corrosive media, don't hesitate to go directlyPTFE-lined hoseOrPTFE compensator； High temperature and large displacement scene, honest and practicalCompound hinge transverse expansion jointOrCurved tube pressure balance typeDon't expect a general-purpose package to win the world.
2. The effort saved during installation will turn into a loud noise when it explodes
They pretendHigh temperature axial expansion jointWhen, it was too troublesome to do pre-stretching. After the pipeline heats up, the bellows is forcefully compressed to 120% of the design limit, and the weld seam collapses directly. Who do you say is to blame? There is even more exaggeration-someone installed the guide tube backwards, and the medium directly washed the inner wall of the bellows, which wore out in a few months. It is clearly written in the installation manual: how to screw the nut of the expansion joint of the large tie rod, whether the screw is removed or not, and where the arrow is facing. But on-site workers often come by their feelings, and anyway, "it's almost OK". And the result? After the bombing, the boss scolded the purchasing, and the purchasing scolded the manufacturer. The manufacturer ran over to have a look-no one could save the installation error. Remember:Large tie rod expansion jointThe screw must be removed after the installation is completed, otherwise the displacement cannot be compensated; The direction of the arrow must coincide with the direction of the media flow. These details, not suggestions, are iron rules.
3. Fatigue and corrosion neglected during operation are the real hidden killers
And guess what? What metal expansion joints fear most is not one overpressure, but dozens of small vibrations every day. of the power station industryCorrugated expansion jointCement industryMetal corrugated expansion jointLong-term operation under alternating stress, the material fatigue crack propagates from the inner wall bit by bit, and one day suddenly brittle fracture. In this failure mode, the pressure gauge never alarms. Anddirectly buried expansion joint— — Buried in the soil, it looks intact on the outside, and the inner stainless steel has been corroded out of the honeycomb holes by chloride ions. When it leaks or explodes, it often has caused a shutdown accident. Can daily inspections find it? Basically not. Ultrasonic thickness measurement and penetration detection can't be done once a year in many factories. Therefore, don't think that "it's okay if you don't leak". Fatigue and corrosion, the two invisible killers, never say hello in advance.
4. To prevent explosion, we must start with design calculation and regular replacement
What is the real reliable approach? When selecting, let the manufacturer do stiffness calculation and fatigue life evaluation. Don't just look at the nominal pressure on the sample. For example, when there is corrosive medium, choose decisivelyPTFE-lined hoseOrPTFE compensator； High temperature and large displacement scenarios, withCompound hinge transverse expansion jointOrCurved tube pressure balance type, avoiding stress concentration on a single corrugation. After it is put into operation, it will be inspected every two years. If it exceeds the design fatigue life (generally 1,000 full displacements), it will be replaced directly-this money is more than ten times less than the emergency repair cost after the explosion. Many bosses calculate small accounts but not big accounts: an expansion joint costs thousands of dollars, and it is distressed to change it again; After the bombing, it stopped production and lost hundreds of thousands a day, so I regretted it at that time. Is that the truth? Also, don't ignoreSleeve type pipe expansion joint、External pressure single axial expansion jointThe applicable scenarios of these special structures can greatly improve the system reliability if selected correctly.
It is never an accident that a metal expansion joint explodes. From design selection to installation execution, from operation monitoring to regular replacement, every link has clear rules. Don't wait until the scene is a mess to remember to find the reason-the day lilies are cold at that time.