① Ergonomic hand wheel design
② Bellows transition connection
Improve welding quality
③ Conical disc or other customized disc
④ Double seal design(bellows+packing)
⑤ Sealing surface overlay welding alloy layer
Roughness ≤0.5um
Conical seal:The sealing surface has self-cleaning function and is not easy to adhere to impurities, which can achieve linear sealing.
Balanced disc seal:Small disc relieves pressure and drives large disc to open easily.
Flat soft seal:The surface of the soft seal can prevent the sparks when opening and closing,it's suitable for gas media and corrosion resistance conditions.
| Name | Material |
| Body | Gs-C25,JS1049,CF8,CF8M,CF3M |
| Seat | 13Cr,SS304,SS316,Stellite |
| Disc | 13Cr,F304,F316,Stellite |
| Bellows | SS304,SS316L |
| Stem | 20Cr13,F304,F316 |
| Bonnet | GS-C25，JS1049，CF8,CF8M,CF3M |
| Nominal Pressure | PN(MPA) | |
| Test Pressure | Shell Test | 1.5 x Pr |
| Sealing Test | 1.1 x Pr | |
| Air Test | 0.6 | |
| Bellows Assembly Test | 1.5 x Pr | |
| Suitable Temp | -196℃~600℃ | |
| Note: Pr is the pressure rating of the material at room temperature, the unit is MPa | ||
According to the performance of the medium, temperature, pressure, flow rate, and other characteristics combined with the process, operation, safety and other factors, we can select the corresponding valve specifications.
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.
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.
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.
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 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.
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).
