Characteristics of traditional valve stem processing technology
1.The traditional valve stem thread uses a spiral flying knife, and the thread accuracy is not accurate; while the traditional chipless rolling thread is easy to damage the rolling mold, which is easy to deform and twist.
2. The precision of the grinder used for the polished rod part is not high and it takes a long time.
3. The inverted part adopts two clamping, turning and pulling down sealing, with poor concentricity and inverted seal easy to leak.
4. The end part is indexed by a milling machine index plate, which is slow in processing, many processes and time-consuming.
Characteristics of valve stem manufacturing process:
1.The new valve stem thread adopts self-made extrusion, which has high thread strength and accurate precision.
2. The concentricity of the threaded part and the polished rod part overcomes the long-standing problems of easy distortion and easy damage to the thread rolling die in the domestic thread rolling process.
3. The precision of the polished rod part reaches the mirror effect, easy to open and close, and the sealing is good.
4. The inverted position is formed by CNC technology at one time, with high accuracy and good inverted sealing performance.
5.The T-slot at the end part adopts forging forming process, which has low cost.
Under strong corrosive, volatile and harmful process conditions, once the valve stem seal is damaged, strong corrosive, volatile and harmful process media leaks from the control valve stem, which will bring serious consequences to the surrounding environment and people .The use of bellows valve stem seal is a way to solve the above problems.Bellows are generally made of stainless steel.This special bonnet structure protects the stuffing box of the control valve from contact with fluid. Once the bellows is broken, the stuffing box structure above the bellows will prevent the serious consequences of the bellows from rupturing and failing.In engineering practice, the selection of the bellows seal should fully consider that the pressure rating of the bellows seal will decrease with the increase of temperature, there should be no solid particles in the fluid, and the cycle life of the bellows material.In places where stainless steel is not resistant to corrosion by certain process media, such as wet chlorine gas, the small amount of hydrochloric acid contained in the wet chlorine gas will quickly corrode the stainless steel bellows.