Refrigeration tower bottom vapor control valve
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The steam control valve at the bottom of a distillation tower requires precise control; is an eccentric butterfly valve better, or a single-seat valve? The valve is DN200
I’ve never encountered this before, but the leakage from the butterfly valve seems to be quite significant; it’s likely difficult to control as well
Butterfly valves are generally used for regulating water flow; they are not suitable for use with steam. The reason is that the sealing performance of butterfly valves is poor, and steam leakage can occur even after the system is shut down. When selecting a steam control valve, it is necessary to consider not only the diameter but also the pressure rating and the backpressure (the pressure difference before and after the valve), as well as the steam flow rate. These parameters should be provided to the valve manufacturer, who will need to prepare a calculation report in order to select a more appropriate control valve.
Since precise control is required, a single-seater is the obvious choice. Butterfly valves are generally linear in operation, and their performance is inferior to that of equal percentage valves. Furthermore, HG20507 stipulates that globe valves should be given priority; for process pipelines with a diameter of 200, a single-seat valve may suffice, and maintenance is also straightforward. If the diameter exceeds 200, butterfly valves are a good choice unless there are special requirements
Using a single-seat control valve is convenient as it allows for easy adjustment
1. In terms of control performance, a single-seat control valve is superior to a butterfly valve, as butterfly valves do not provide good linear control； 2. The price of a single-seat control valve with a DN200 diameter is higher than that of a butterfly valve (of the same grade) ； 3. Since it is a distillation tower and optimal control performance is desired, it is recommended to use a single-seat valve. 4. For applications where the flow rate of liquids does not require high precision in regulation, butterfly valves have an advantage due to their larger diameter.
Precise adjustment is of course achieved with a single-seat valve, that is, a dedicated proportional control valve. But the price is relatively high. If precision is the top priority, a V-type adjustable ball valve can be chosen; it is relatively cheaper than regular control valves