1. Industry pain points: The sealing performance of non-metallic compensators is supported by welds-but most welds are unqualified
Has your non-metallic expansion joint (that is, fabric fiber expansion joint) ever leaked after three months of operation? If so, don't rush to scold the material merchant. It's probably something wrong with the weld.
No matter how strong the flexible compensation ability of non-metallic compensator is, once the weld is cracked or false welded, the leakage risk of the whole pipeline system will skyrocket. How demanding are the requirements for welds under high-temperature corrosion conditions such as power station desulfurization pipelines, cement plant air ducts and flue gas baffle doors? Manual welding workers' emotions fluctuate, change their postures, and come through a draft, and the uniformity of the weld seam immediately goes out of shape. Can you expect a welder to keep his hands quiet for eight hours straight? The reality is-the pass rate of weld airtightness test of manual welding is 75% ~80% on average in the industry. The remaining 20% is a hidden danger.
Second, the core difficulty of automatic welding: how to weld nonmetallic materials and metal flanges together?
A non-metallic compensator is not an all-metallic construction. The main body is a fabric fiber and rubber layer, and the connecting ends are usually carbon steel or stainless steel flanges. Two completely different materials, directly attacked by conventional arc welding? The non-metal layer burns through in seconds, and the black smoke is light.
Precise control of thermal inputAndInterlaminar adhesion strength。 When the heat input is large, the nonmetallic layer is carbonized and blackened; If the heat input is small, the weld seam will be falsely welded and will be pulled off. At present, there are two mainstream schemes: hot press fusion welding, or argon arc welding with ceramic liners. The former uses hot plates and pressure to fuse the non-metallic layer with the flange surface layer, the latter uses argon to protect the arc, and the ceramic liner covers the molten pool to prevent burning through. But no matter which scheme, parameter matching is the soul-the same welding machine, if you change to a non-metallic cloth, the parameters will have to be re-adjusted.
3. Automatic welding scheme in actual combat
We have done a batch of automatic welding tests with rectangular non-metallic expansion joints. The amount of plate lapping is controlled at 15~20mm, the preheating temperature is 60℃, the welding speed is 200~300mm/min, and the current setting is about 15% lower than that of manual welding. And the result? The pass rate of weld airtightness test soared directly from 78% of manual welding to 96%.
Hand-equipped laser tracker can adapt to the unevenness of non-metallic cloth-think about it, those non-metallic expansion joints in the cement industry have potholes on the cloth surface. Manual welding can only be adjusted by the master according to his feeling, while machine welding relies on laser to scan the weld trajectory in real time to automatically compensate the deviation. This trick is particularly useful in non-metallic expansion joints in the cement industry, and the weld forming consistency rolling labor.
4. Quality control must stare at three parameters
Engaging in automation is not about putting the equipment on. Whether your welded seam is qualified or not, three indicators have the final say:
- Weld width fluctuation shall not exceed ±1.5mm— — Too wide, the heat-affected zone is large, too narrow, and the strength is not enough.
- Carbonization blackening cannot occur in the heat affected zone— — Once blackened, it means that the non-metallic layer has been damaged and the sealing performance is scrapped.
- The peel strength after cooling should be greater than 80% of the base metal— — Pull it with a tension machine, and the data speaks for themselves.
How to monitor? The infrared temperature measuring gun stares at the weld area in real time, and immediately alarms to reduce the welding speed when it exceeds 120℃. In addition, plasma treatment on the surface of the non-metallic layer before welding can improve the bonding strength by more than 30%-don't underestimate this step, the cost will increase by a few cents, and the effect will be immediate.
V. Efficiency changes brought about by automatic welding
Take a rectangular non-metallic expansion joint with a diameter of DN600 as an example: manual welding requires two skilled workers to work for half a day (4 hours), and it is necessary to ensure that the two people's skills are similar. Instead of automatic welding with a double-station turntable, it takes 45 minutes to get it done-a worker looks at two machines, and the labor cost is directly cut by 70%.
More critical is quality traceability. The parameters of welding current, voltage, speed and temperature of each weld are recorded. For the severe working conditions of desulfurization flue gas baffle door, which need to be opened and closed frequently, the reliability of weld directly determines the overhaul cycle of equipment. In the past, manual welding had to be removed for inspection in half a year; The automatic welding seam will not leak for two years-do you think it will be worry-free?
VI. Summary and Suggestions
If your non-metallic compensator often has weld leakage after 3~6 months of operation, don't rush to change materials. Let's see if the welder is smart enough first. Automatic welding is not a panacea, but it is indeed the optimal solution to reduce costs and increase efficiency for batch and high-demand pipeline compensation systems-especially in power stations, cement and desulfurization industries.
Don't just look at the price when choosing a welder. Let the manufacturer try to weld your own non-metallic expansion joint sample, and parameter matching is king. Weld it out and take it for air tightness test, and then pay for it when it is qualified. Don't ask why – anyone who has suffered losses knows how important this step is.