There are two types of plastic bellows, one is complete […]
There are two types of plastic bellows, one is completely airtight and watertight, such as for propellant transportation of carrier rockets, gas, and water heaters; the other is continuous winding with tape, and ordinary bellows are used for Protect cables, such as magnetic card phones, machine tools, and the corrugated tube of the table lamp is sandwiched with steel wire during the production process.
Classification by forming process
⑴ Hydroforming bellows
Hydroforming is the most common method of forming bellows. Using the liquid pressure in the tube blank, the tube blank expands in the confinement ring until yielding occurs in the ring direction, and then the tube blank is compressed to the required length. This method is mostly used for small diameter bellows.
⑵ Roll forming bellows
The roll forming process is mainly used for processing large corrugated pipes. It is formed by rolling formed by a forming wheel provided in the tube blank. It can be rolled by a single wave, and some devices can also be formed into several corrugations at a time.
⑶ Mechanical bulging bellows
The tires expanded inside the tube blank are expanded and compressed into corrugations one by one, and after initial forming, they are customized with internal and external rollers. ⑷ Welded corrugated tube For the corrugated tube with high wave height or special wave shape, the stamping welding process is mostly used. When the wave height exceeds the limit, the material elongation is no longer allowed to adopt the overall forming process, or due to the complex waveform and the overall forming is extremely difficult, welding is also used. This type of bellows is not suitable for the flexible section of the expansion joint because it cannot withstand the internal pressure.
⑸ Deposition forming bellows
In this process, the electrodeposition method is used to deposit the bellows material on the mandrel, and then the mandrel is ablated. This bellows material is a very soft pure nickel metal material and is non-porous, so it can withstand high vacuum and can be welded. This type of bellows is not suitable for the flexible section of the expansion joint because the cost is too high and it is limited to nickel.
Sort by layer
(1) Single-layer bellows Single-layer bellows are mostly used for bellows with displacement compensation under static load, which is simple to manufacture and low in cost. On the premise of ensuring the required pressure capacity, compensation, stiffness and fatigue life of the design, single-layer bellows should be preferred.
⑵ Multi-layer bellows For multi-layer bellows with alternating load or more important pipelines, more than two layers are used. Compared with the single layer, under the same bearing capacity, the stiffness is smaller and the fatigue resistance is also better.