When choosing a two-way flow control valve, what factors should consider? Fast, easy, and simple-to-source might be appealing. These factors, however, will increase the performance, reliability, and product longevity of your control valves.
Chemical Plant
First, the medium. Construction materials can determine by their erosive- or corrosive properties. A fluid’s temperature can also affect the choice of materials and valve assembly construction methods.
Moreover, the inlet pressures and presume pressure drops for each flow condition should be taken into account. Control valve types can determine by this, and are shown below.
Apart from the control valve type, the size of the inlet pipe (diameter) and the require flow rate should also be consider. According to this, one can determine a relative valve range size that one should focus on and also the rangeability requirements for turndown (maximum flow vs. minimum controllable flow).
Before selecting a control valve, it is important to consider these factors. Other considerations will likely include previous successes and failures, space / location of the valve, as well as actuation and accessory requirements. In order to get start, once you have answer all your questions, you can review the characteristics and best uses of each type of control valve.
Control valve trim styles
When it comes to rotary 1*4-turn control valves, there aren’t many trim style options that influence initial valve selection. In the case of the globe style control valve, however, there are a few different trim styles that must be discuss for proper application selection:
Single seat unbalanced
Elastomeric cylinder seals for medium flowing differential pressures up to about 450°F, with clean fluids.
Double seat, balanced
It may be more cost-effective to use balanced valves because they offer higher close-off pressures with smaller actuators. However, the double-seat design is only rate up to ANSI Class III leakage, and that is only at room temperature.
Generally, the valve stem is made of a different material than the valve body; as a result, the inherent temperature growth rate between these two metals will cause greater leakage as the fluid temperature increases from ambient (as with steam). Therefore, a double seat valve is not use for steam, but can perform better for dirty or turbid water compare to other balanced designs.
Single seat, cage-retained-seat (caged), unbalanced
Small to medium flowing differential pressures can be met with this medium cost option.For larger size globe valves, it may become impractical because of the cost of actuation. Trims with better reliability and serviceability.
Single seat, cage-retained-seat (caged), balanced
A medium-cost solution for medium-flow differential pressures up to about 450°F, with clean fluids, for elastomeric cylinder seals. Better reliability and serviceability of the trim. Several MFGs offer higher temperature seals but they usually leak at ANSI Class II.
Single seat, cage-balanced, multi-stage trim
The highest cost is for severe-service, high-pressure drops. The trims are classified into two major categories: (1) anti-cavitation trim in 1, 2 or 3-stage reductions for liquids, or (2) aerodynamic trim which tunes the noise frequency to the human inaudible range for gases and steam. They are both expensive and, due to the inherent control valves reductions, generally require larger valves. There are other design alternatives to consider, such as multiple control valves sequenced to keep the pressure above the vapor pressure, and silencers and noise-absorbing insulation blankets to reduce aerodynamic noise.
Finally, when choosing control valves, the type of control valves you choose plays an important role in overall performance, reliability, and system longevity.
In the end, it is always recommend to have your full process conditions verifi against your control valves choice by computerized valve size and selection software. As well as a historical history report.
Aira Euro Automation is An Actuated Control Valve Manufacturer in India. Aira has a wide range of control valve such as Angle type Valve, diaphragm control valve, high pressure control valve and also other control valves.
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