Over the years people have been looking at steam turbine control valves to consider a number of traditional factors such as pressure ratings, pressure drops, flow media, temperature and cost. However, the situation has changed dramatically over the past 10 years, with much progress being made in the design of steam engine valves, and the cost-effectiveness of the manufacturing process has been significantly different from what it was before, leaving many of the traditional factors that have previously been taken into account when choosing a valve The importance of this has been greatly diminished. Dynamic Characteristics Although some traditional factors are still important, they only emphasize the "static" performance of the valve. In fact they are the result of measuring the valve on the "workbench," but the result is hard to say what kind of performance the valve will behave in real-world conditions. Traditionally, it has been suggested that careful adjustment of the static factor will give the valve (and hence the entire circuit) good performance. However, we now recognize that this is not always the case. Thousands of performance tests conducted by researchers and manufacturers demonstrate that up to 50% of valves in service, many of which are selected by considering traditional factors, have had little effect on optimal control loop performance. Subsequent studies have shown that the dynamic characteristics of the valve play a very important role in reducing process variability. In many key processes, different valves reduce process variability by a factor of 1 to dramatically increase productivity and reduce waste, resulting in more than $ 1 million in economic benefits. Obviously, this economic efficiency makes it entirely possible to deny the traditional approach, that is, only based on the initial purchase price of the valve to decide whether to buy. Second, the conventional wisdom has always been that improvements in process optimization always come from upgrades in control room control instrumentation. However, the test data shows that the dynamic characteristics of the valve can have a significant impact on circuit performance with the same control instrumentation. If the accuracy of the control valve can only be as low as 5%, it can not do much to spend a lot of money configuring an advanced control instrumentation system with a control accuracy of up to 0.5%. Valve Types When looking for a valve that matches your application, consider the four basic types of throttling control valves, cage ball, rotary float, eccentric and butterfly valves. Cage ball valves are available in a wide variety of trim forms to meet the needs of most applications, making them the first choice of any valve. There are many kinds of cage ball adjusting pieces, including balance adjusting piece, unbalance adjusting piece, elastic seat adjusting piece, constrained adjusting piece and full size adjusting piece. In many cases, the various trim configurations of a valve body are interchangeable. Cage ball valves also have several disadvantages. First, the size of the valve is limited (usually 16 inches); second sight valve with the same specifications (such as float valve or butterfly valve) compared to its capacity is relatively low; third is the higher price, especially large Cage ball valve. However, cage ball valves have excellent performance, often enough to compensate for these drawbacks, in reducing process variability. Rotating float valve flow than the same diameter cage valve larger. Although the control range of the rotary float valve is larger than the cage ball valve, it is still superior to most other types of valves. Rotary float valve allows the pressure drop and allowable temperature range smaller than the cage valve. Normally their pressure drop is limited to 7.0x105kg / m2, suitable for use at temperatures below 398 ° C. Float valves are not suitable for liquids that can be vacuoles and often give higher noise when used in gases with higher pressure drops.
High Speed Roll Up Door Parts, High Speed Roll Up Door Accessories, Fast Roll Up Door Parts, High Speed Rolling Door Parts, High Speed Fabric Door Parts
SHENZHEN HONGFA AUTOMATIC DOOR CO., LTD , https://www.hongfahsd.com