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What is the difference of bellow valve

Bellow construction
The bellow cartridge is welded to both the Valve Bonnet and the Valve stem. The bellow cartridge has a number of convolutions and these convolutions become compressed or expanded depending upon the movement of Valve stem. (Scientifically speaking the bellow gets compressed when the Valve is in the open position and expanded when the Valve is in the closed condition). It is important to properly install the Valve bodies. The bellow can be sealed to the Valves in two different ways. Firstly, the bellow can be welded to the Valve stem at the top and the Valve body on the bottom. In this case the process fluid is contained inside the bellow or in second method the bellow is welded to the Valve stem at the bottom and the body on the top. In this case the process fluid is contained in the annular region between the Valve Bonnet and bellow (from the outside).
The bellow is a critical component and forms the heart of the bellow seal Valves. To avoid any twisting of the bellow the Valve must have a stem with linear movement only. This can be achieved using a so-called sleeve-nut at the Yoke portion of the Valve Bonnet. A hand wheel is fitted onto the sleeve-nut which effectively transfers a rotary motion of the hand wheel into a linear motion in the Valve stem.

Bellow types
There are two main types of bellow: the Forged Bellow and the Welded Bellow. Formed-type bellows are made from rolling a flat sheet (thin wall foil) into a tube which is then longitudinally fusion welded. This tube is subsequently mechanically or hydrostatically formed into a bellow with rounded and widely spaced folds. The welded leaf type bellow is made by welding washer-like plates of thin metal together at both the inner and outer circumference of the washers - like plates. A welded leaf bellow has more folds per unit length as compared to forged bellows. Thus, for the same stroke length, forged bellows are two to three times longer than their welded leaf counterparts.
Reportedly, mechanically forged bellows fail at random spots, while the welded leaf usually fails at or near a weld. To ensure full penetration of bellow ends and end coller welding it is advisable to fabricate using micro plasma welding.

Bellow design
The multi-ply bellow design is preferred for handling higher pressure fluids (generally two or three plies of the metal wall). A two ply bellow can increase its pressure rating by 80% to 100% as compared to a single ply bellow of the same thickness. Alternatively, if a single ply bellow of a thickness equivalent to a pressure rating of a two ply bellow is used, the stroke length is reduced. Thus, a multi-ply bellow design offers a distinct advantage over a single ply bellow. It is clear that the bellow is subject to metal fatigue and this fatigue can induce weld failure. The bellow fatigue life is affected by the material of construction, fabrication technique, stroke length and stroke frequency, in addition to the usual parameters such as fluid temperature and pressure. Bellow materials
The most popular stainless steel bellow material is AISI 316Ti which contain Titanium to withstand high temperatures. Alternatively, Inconel 600 or Inconel 625 improve fatigue strength and corrosion resistance as compared with stainless steel bellows. Similarly, Hastalloy C-276 offers greater corrosion resistance and fatigue strength than Inconel 625. Fatigue resistance can be improved by using a multiply bellows system and reducing the stroke length; this can significantly increase the bellow service life.
Time : 2018/6/9




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Zhejiang AIV Fluid Technology Co., Ltd.

Zhejiang AIV Fluid Technology Co., Ltd. is a professional bellows valve manufacturer, which is headquartered in Wuxing work area, Dongyuan Town, Qingtian County, Lishui City, covering an area of 20000 ㎡ and building area of 15000 ㎡. It integrates valve casting, whole machine R&D, production and sales. The company was founded in 2016 with a registered capital of more than 11 million RMB. With a complete industrial chain, the company strives to be the first in industry with best competitive cost performance. It is a key investment attraction high-tech enterprise in Lishui City. The company has more than 200 employees, including more than 20 people with middle and senior professional titles, and 80% of all kinds of valve professionals.
In recent years, the company has invested heavily in the purchase of casting assembly line, processing center, intelligent special CNC machine tools, welding robots and other sophisticated special machinery processing equipment, and introduced full-automatic testing equipment, large caliber high-pressure testing platform, desktop spectrometer and various laboratory testers to ensure the high-quality realization of the whole process from research and development to production line.
Following the enterprise spirit of "creating value for customers", the company is positioned as a professional OEM processing manufacturer, specializing in OEM processing for domestic and foreign brands. With a complete industrial chain and one-stop upstream and downstream supporting capacity, the company aims to build the bellows valve products with the highest cost performance ratio in the industry, highlight the core competitiveness of the enterprise, win-win with partners, and achieve considerable development.
Time : 2018/2/21