Bypass for large-diameter valves
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It is said that valves with larger diameters require a separate bypass or a balancing mechanism to be incorporated into their structure； For example, for gate valves of size 150#, those with a diameter of over 12 inches require a separate bypass, or this aspect should be taken into account during the valve manufacturing process ； This is said to be intended to prevent the valve from being damaged due to excessive impact forces when it is opened ； 1. Is there any standard basis for this? 2. Are gate valves, ball valves, globe valves, etc., all necessary? Thank you
On valves that lead in or out of a boundary zone on steam pipes with large diameters, a bypass is generally installed. Its functions are: (1) to prevent imbalances between hot and cold temperatures from affecting the valve
It is mainly to balance the pressure before and after the large valve, to facilitate opening.
A bypass is provided for large valves for use during pipe heating, to prevent excessive pressure differences from damaging the valve. Generally, a 80 or 50 mm bypass can be chosen, with two smaller valves connected in series.
Among globe valves, there is a type that utilizes a balanced design; this design reduces the difficulty of selecting the actuator and lowers costs, as unbalanced types require greater actuator thrust under the same processing conditions.
I agree with the opinion from the third floor; it is mainly to balance the pressure on both sides of the valve, thereby facilitating its opening and closing； If this bypass is not installed, operating large valves, such as those with a diameter of DN300 or more, becomes particularly difficult; a lever is often required to operate them. With the small bypass in place, the gas pressure on both sides is balanced, resulting in equal forces on either side of the valve disc, which makes operation easier