Motorised Valve limit setting
The motorised valve is used in industry as a final control element, shutdown valve according to the application. The control valve uses a pneumatic supply to operate the valve, MOV uses the motor coupled with the valve to open/close. Hence it uses a motor the start and stops point has to be configured properly to avoid hazardous incidents.
In pneumatic valves normally operated at 4-6 bar according to the valve size and capacity. The air pressure is controlled by a regulator before passing into the control valve. So even in case of failure of regulator, if high pressure passes into the system the diaphragm inside the control valve may get damaged, the regulator may explode and the airline may be removed without withstanding the pressure above the limit.
But in the case of MOV, the hazards are greater compare to the control valves. If you set the limit for one side and the other side limit got disturbed, and you try to operate the valve then the MOV will not get cut off keeps on operating. It may lead to damage to the process line. It’s very important to configure the limit setting properly before operating.
But the MOV is provided with torque protection if the valve keeps on operating beyond the limit the torque switch senses the tension and trip the motor immediately. If the valve stem is not properly lubricated or the valve located in a corroding process condition. The valve will not operate properly at such condition the torque may be bypassed to solve the problem at that instant. It’s not a safer act it may lead to a severe damage.
Limit setting methods
You can find MOV with different manufacturers the limit setting procedure differs for everyone. Some move used the mechanical gear to cut the open and close limit. And you have to manually rotate the gear to set the open and close limit. Nowadays the MOV uses an infrared remote to set the limit. The encoder is used to detect the movement of the shaft and stop the motor if the limit is reached. And it’s a very simple process and increased safety in motorised valve.
Let’s see the basic step to follow while setting the limit in the MOV.
* Before starting the limit make sure the valve operating smoothly while opening and closing. You can use the manual hand wheel to operate the valve. If any problem exist clear that before starting limit setting.
*Next open the valve fully with the help of a handwheel, if the valve is large it will take more time and manpower to manually open the valve. Enable the manual mode and operate the valve up to 95% then stop the operation, now open the remaining portion of the valve with a handwheel.
* After the valve is fully opened set the open limit, If the limit is properly set you can able to find it in the digital display in smart MOV as 100% open. And in another type, the open contact will get closed. You can able to check it in the terminal of the MOV. And close the valve manually or automatically until the limit gets released and again open the valve. To check whether the valve get to stop at the desired point you have set the limit.
*Same procedure you have to do for close limit setting. Close the valve fully and set the close limit and after setting check the valve whether the valve is getting stopped at the close limit.
*And we have to set the torque limit according to our need. Some time during open time valve may trip frequently due to over-torque in such case you may increase the torque limit and keep the close torque as Normal.
*In analog type MOV after setting the limit check whether the valve operating linearly for 0-100%. If there is a mismatch you can able to adjust the analog signal and feedback.After adjusting check the operation again.
If you are new to limit setting, it is a simple procedure. Any MOV you can able to set the limit with confidence just by knowing the methods which different manufacturer build but the procedure remains the same.
