High Noise at Globe Vent Valve

[ada6618]

Dear All,
In our process, presently a dia 8 inch butterfly type valve is installed as process gas vent valve. Existing valve leakage class is iv further passing problem has to be faced. Accordingly, replacement with new globe valve of leakage class V is under consideration. Following problem is being faced in valve selection.
Required globe valve size is 12 inch which require piping modification, however inline with inlet line size discharge vent header size 24 inches.
new valve Actuator type is piston (shutoff pressure 35kg/cm2g). Therefore, valve height with actuator is 2.4 m from ground.
calculated Noise level after installation of 2 low DB plates size 18 / 24 inch at valve downstream is high against required less than 90 dBA for vent service valves i.e
At Normal flow (292000Nm3/hr) : vlave outlet 87dBA after 02 Low DB plates 107 dBA
At Max flow (321200Nm3/hr) : valve outlet 88dBA after 02 Low DB plate 109 dBA

Please give your valuable inputs for finalize valve selection with this noise level.

Regards

Adnan

 

[georgeverghese]

You can get special low noise trim control valves for this service - they are usually some type of perforated cage trim; definitely not globe trim. Check with the CV vendor if class V is possible with this low noise trim.

 

[ada6618]

Dear Georgeverghese

Trim is specialized whisperIII.

 

[georgeverghese]

Adding noise insulation to the piping will cut noise down further at grade, as will thicker walled pipe. But there is a risk of corrosion under noise insulation, which you could address by applying a TSA coat on the pipe - thermally sprayed aluminum ( if CUI could occur on this pipe).
Good that you have lo noise trim.
What is a DB plate, and why does noise level rise to 107-109dBA after adding the 2 DB plates?