Jo26
Mechanical
- Aug 29, 2012
- 1
Good Day Everyone,
Breif Background: Recently, we requested a new valve to replace a valve that we have which was beyond repair. This valve was automated with a pneumatic actuator connected to it since the 1980s. When we recieved the new valve, which has the same size (10 in.) and pressure rating (150#) we found that it has different stem dimensions as well as a different manufacturer (I guess that's what happens when you don't go for a single source ..)
so the issue now is that we have an existing actuator that needs to be connected to a new valve. Since no one was around, I was handed the job. From my mechanical background, I knew that Torque is the factor affecting the sizing and I researched about the subject to find out what I need although no clear way was found. moreover, I stumbled upon this great website which I think you guys can help a lot.
Technical Info Collected:
New Valve Torque Requirements:
Break-To-Open Torque: 704 N.m
MAST: 3038 N.m
Existing Actuator Torque Capabilities:
@ Min Operating Pressure of 50 PSI: 150 m.kg = 1471.5 N.m
@ Max Operating Pressure of 125 PSI: 375 m.kg = 3678.75 N.m
Based on what I researched, this actuator can operate the valve safely given that the pressure doesn't exceed 100 psi (Based on linear interpolation of the actuator data, since Torque = Area * Radius * Pressure, so if we consider Area & Radius to be constant, the relation would be linear [correct me if I am wrong, my mechanical background might be wearing].
From my interpolation, I found out that at 100 psi, the actuator gives 2940 N.m which is around 100 N.m less than MAST)
Also, from my research, I have read that to size an actuator, the BTO Torque is usually multiplied by a factor of 1.25 - 1.3 to determine the minimum torque requirement of the actuator. Now this actuator is about double the BTO Torque at its minimum operating pressure, will that be a problem ?
Supporting Info:
The old valve manufacturer was contacted to specify the torque requirements of the old one and this info is what I received:
BTO Torque (@ Max DP): 1073 ft.lb = 1455 N.m
MAST: 2011 ft.lb = 2726.5 N.m
When I received this info, I was a bit hesitant about my conclusion. I mean if this actuator was able to rotate the old valve easily given that it had higher BTO Torque, it will rotate the other one for sure to the extent it might break it ! (That I am not sure about)
Can you please help me in this issue ? That is, is my conclusion that the actuator will safely rotate the valve given the fact that the supply pressure doesn't exceed 100 psi ?
since the actuator torque @ min operating pressure is double the new valve BTO Torque, will that create a problem ?
Thanks a lot for your help
Best wishes,
Joseph
Breif Background: Recently, we requested a new valve to replace a valve that we have which was beyond repair. This valve was automated with a pneumatic actuator connected to it since the 1980s. When we recieved the new valve, which has the same size (10 in.) and pressure rating (150#) we found that it has different stem dimensions as well as a different manufacturer (I guess that's what happens when you don't go for a single source ..)
so the issue now is that we have an existing actuator that needs to be connected to a new valve. Since no one was around, I was handed the job. From my mechanical background, I knew that Torque is the factor affecting the sizing and I researched about the subject to find out what I need although no clear way was found. moreover, I stumbled upon this great website which I think you guys can help a lot.
Technical Info Collected:
New Valve Torque Requirements:
Break-To-Open Torque: 704 N.m
MAST: 3038 N.m
Existing Actuator Torque Capabilities:
@ Min Operating Pressure of 50 PSI: 150 m.kg = 1471.5 N.m
@ Max Operating Pressure of 125 PSI: 375 m.kg = 3678.75 N.m
Based on what I researched, this actuator can operate the valve safely given that the pressure doesn't exceed 100 psi (Based on linear interpolation of the actuator data, since Torque = Area * Radius * Pressure, so if we consider Area & Radius to be constant, the relation would be linear [correct me if I am wrong, my mechanical background might be wearing].
From my interpolation, I found out that at 100 psi, the actuator gives 2940 N.m which is around 100 N.m less than MAST)
Also, from my research, I have read that to size an actuator, the BTO Torque is usually multiplied by a factor of 1.25 - 1.3 to determine the minimum torque requirement of the actuator. Now this actuator is about double the BTO Torque at its minimum operating pressure, will that be a problem ?
Supporting Info:
The old valve manufacturer was contacted to specify the torque requirements of the old one and this info is what I received:
BTO Torque (@ Max DP): 1073 ft.lb = 1455 N.m
MAST: 2011 ft.lb = 2726.5 N.m
When I received this info, I was a bit hesitant about my conclusion. I mean if this actuator was able to rotate the old valve easily given that it had higher BTO Torque, it will rotate the other one for sure to the extent it might break it ! (That I am not sure about)
Can you please help me in this issue ? That is, is my conclusion that the actuator will safely rotate the valve given the fact that the supply pressure doesn't exceed 100 psi ?
since the actuator torque @ min operating pressure is double the new valve BTO Torque, will that create a problem ?
Thanks a lot for your help
Best wishes,
Joseph