【 Weak current College 】 control valve technology for dynamic evaluation is the key---Power By 【 China power house network 】

Over the years when choosing control valve has been considered by the number of traditional factors, such as pressure ratings, pressure drop, mobile media, temperature, and cost. However, the situation in the past 10 years great changes have taken place, the valve design acquired quite a lot of progress in the production process of cost-efficiency features than ever before are very different, which makes many previously select valve must be taken into account the importance of traditional factors have significantly weakened. Dynamic characteristics of some traditional factors are very important, but they only have a strong bias towards valve "static" performance. They are actually in the "table" on the valve, the measurement of results, but this result is difficult to describe the actual valve in operating conditions will show what kind of performance. Traditional theory believes that careful adjustment static factors will make valve (which also makes the entire circuit) for good performance. However, now we realize that this is not always the case. Researchers and manufacturers of thousands of performance check shows that up to 50% of the valve (many of them are considered traditional factors selected) for optimization of control circuit performance failed to produce such a great effect. Subsequent research has shown that the dynamic characteristics of reducing process variability has played a very important role. In a number of key processes, different valves lowering process variability increases even if a difference of 1% will be in a position to significantly increase productivity and reduce waste to obtain more than $ 1 million in economic benefits. It is clear that such economic benefits so that we can deny the traditional approach, that is, according to valve's initial purchase price to decide whether to buy. Secondly, the traditional view always think, process optimization improvement always comes from the control room instrumentation upgrades. However,the test data indicate that, in using the same control instrument, valve dynamics can have significant performance on the circuit. If the control valve for precision can only achieve 5%, then spend a lot of money to configure a set of their control precision can reach 0.5% of advanced control instrument system and cannot be played. Valve type in search of a match with the use of the valve, the first thing you should look at four basic types of throttle control valves, i.e. cage type ball valve, rotating ball valves, butterfly valves and eccentric valve. Caged ball valve of the type of tab form is very extensive, so to meet the needs of most applications, making it the first choice of all kinds of valve. Cage type ball valve adjustment plate there are many, including balance adjustment plate, non-balance adjustment, the elastic seat of special-purpose tab, constrained adjustment and full size adjustment. In many cases, a body of various tab configuration are interchangeable. Cage type ball valve also has several drawbacks. First, this valve size limit (typically a 16 inch); the second is with the same specification for line valve (ball valve or butterfly valve), its capacity is relatively low; third, the price is high, especially for large-diameter ball valve of the cage. However, in terms of reducing process variability, cage-ball valve with excellent performance, often enough to compensate for these shortcomings. Rotate the ball the same caliber of flow ratio of cage type ball valve. Although the rotation ball control is greater than the cage type ball valve, but still better than most other types of valves. The rotating ball valve allows for the pressure loss and allows temperature range than the small cage-ball valve. Usually their pressure drop ceiling 7.0x105kg/m2, suitable for the temperature is below 398 ° c. Ball does not apply to ease up the vacuole liquid, but also for higher pressure drop in gas, can often make a considerable amount of noise. Eccentric valve friction than ball smaller, lower prices. Unique structural design enables to process variability of control more accurate. This is from Fisher company new product BV500. In addition, the advantages and disadvantages of eccentric valves and ball valves are similar. The performance of the valve, butterfly valve is low-grade valve. Butterfly valve the flow is large, the cheapest, but there are a variety of different diameter. However, butterfly valve, proportional characteristic curve is only one characteristic curve, this greatly limits the butterfly valves lowering process variability of performance. For this reason, the butterfly valve can only be used to load fixed occasions. Although the butterfly valve has a variety of different diameter, and can be used to create most of the cast alloy, but butterfly valves do not meet face to face dimensions ANSI on requirements, nor does it apply to ease up the bubble of fluid or greater noise, etc.