9.0 Guidelines for Root Valves

Isolating root valves are provided at take off connections to isolate the entire measurement system from the main pipe line/vessel when necessary. Following recommendations should be followed.

a. Root valves should not affect the pressure signal during normal operation.

b. Root valves should be capable of withstanding the maximum working pressure and temperature of the piping/vessel system to which the take off adapters or nipples are attached.

c. Isolating/root valves should be located immediately following the tapping point.

d. It is preferred to use gate valves for root valves in order to:
i) Avoid trapping gas bubbles in the valve structure, in case of liquid flow
ii) Avoid trapping liquid in the valve structure, in case of gas flow.

e. Root valve bore/should not be less than the inside diameter of impulse tubing/piping.

f. It is recommended that the root valves be ¾ inch unless special requirements necessitate a different size.

g. The root valves may or may not perform the function of the accessible isolation valve, dependent on its location.

h. Root valves should be of the same material as that of the pipe they are connected to.

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