Motor Operated Valve Questions

Hello All,

I just finished programming some solenoid valves. I have to now program some Motor Operated Valves. The Controllogix PLC has 2 120VAC digital outputs going to the valve, 1 to OPEN and 1 to CLOSE the valve.

When programming these motor valves do I need to take anything special into consideration or can I just program them like solenoid valves (by the way for the solenoid valves I had only one output to control them).

Please let me know what factors I need to keep in mind to make sure that the valve has been opened and closed properly.

Look forward to your suggestions.

Thanks.

Just make sure you don't turn the 2 outputs on at the same time and be sure the end travel switches are wired correctly and you should have a feedback signal from them to the PLC input so you know the valve is fully open/closed.

elmatador said:

Hello All,

I just finished programming some solenoid valves. I have to now program some Motor Operated Valves. The Controllogix PLC has 2 120VAC digital outputs going to the valve, 1 to OPEN and 1 to CLOSE the valve.

When programming these motor valves do I need to take anything special into consideration or can I just program them like solenoid valves (by the way for the solenoid valves I had only one output to control them).

Please let me know what factors I need to keep in mind to make sure that the valve has been opened and closed properly.

Look forward to your suggestions.

Thanks.

Click to expand...

I am sorry but crystal ball is broke and ESP just blew fuses.
Having difficulty visualizing what you are doing.

From having worked with MOVs little to big (50 HP motors driving them) need details on
limit switches, torque switches, overloads, interlocks just for starters.

Dan Bentler

From the P&ID's. There are two limit switches for OPEN and CLOSE status. And two digital control outputs from the PLC. This valve is to be controlled such that when a OPEN cmd is sent, it is to be fully OPEN and when a CLOSE cmd is sent it is to be fully closed. There are not other I/O coming from the MOV coming into the PLC such as STOP or SD. Unfortunately, I have still not received the MOV manufacturer information from the client so I won't be able to get into the guts of it.

Please let me know from your experience how you program these types of valves

also, there are no overloads on this MOV. It is only a 120VAC MOV. I dont have the HP rating for the motor.

Some MOV's are more forgiving than others. For example, some will tolerate having the SHUT input stay true after the valve IS shut, some won't.

My rung would look like:

XIC Valve Shut Command
XIO Valve Shut Status (Limit Switch Input)
XIO Valve Open Command
OTE Valve Shut Output

Next rung, use the Shut Status Input to reset the Shut Command bit.

Then, use the Valve Shut Output bit to run a timer. If the valve does not get to the Shut Limit Switch within an acceptable period of time, set an alarm bit.

Does that help at all?

Bill

Most of these units will normally have a SPDT switch for each position. The NC contact will be wired in series with your outputs (usually internally, but not always) such that when you give the valve an open command (for example), when the open position is made, the NC contact opens up and the motor is deenergized regardless of your command. Same for the close position. In addition, the NO contact will be wired back to your PLC as indication. That way, even with a PLC input failure (or programming error) you aren't driving the motor against a hard stop.

Some units ONLY have the NC contacts and you should use them as hardwired overtravels, not as Open/Close status relying on the PLC to stop them. You can still get status back by wiring off the backside of the NC contact back to your PLC as an input. Such that you have Output wired to common side of contact (A). The NC side (B) is wired both to the 120VAC coil on the MOV and back to the PLC Input for status.

As for programming, Bill pretty much covered it in the previous post.

My issues with MOVs have been making sure you have the proper device that can handle the Amp load of the MOV. I have had people think anything can run from a PLC directly.

Another thing I always put into my code is a fault condition if I command the valve to open or close and the proper open / closed return input does not activate in a certain amount of time. This is usually set to create some form of alarm, and to stop driving the valve.

I also have a customer which requires any MOV run directly by a PLC to have some form of overcurrent device (fuse, breaker) to be used on both open / close outputs. It is much easier to replace a fuse or reset a breaker than replace an output module that just burnt up an output.

Just my $0.02

If you are using the MOV for proportional control you will need to use a timer to drive the valve Open/Closed in pulses proportional to the error e.g. drive Open for 1/2 second, wait 10 then drive Open again.
Roy

One thing in addition to the above will require the valve operator diagram to determine. Many motor operated valves are or can be wired so that when the "Open" contact is closed momentarily and then opened the valve will continue to travel in the open direction until either the open limit switch is tripped or a "Stop" contact is opened. Similarly if the "Closed" contact is closed the valve will travel in the close direction until the "Stop" is opened or the closed limit switch trips.

Others require the valve travel contact to remain closed continuously for the motor to operate.

I recommend that a contactor or relay electrically and/or mechanically interlocked be used to prevent trying to move the valve in two directions at once. You can put the logic in the program to prevent this, but the outputs can fail or be forced to operate simultaneously.

Thank you gentlemen for your insight on MOV's and the factors to watch out for when controlling them. I understand them a lot better now. I have programmed the MOVs such that you when the open/close command is sent the valve open/close output will be latched until there is a OpenStatus/closeStatus and it will unlatch.

Also, I included the alarming incase the valve does not open or close within a specified amount of time. Generally how fast acting are these valves. Would a duration of 1-min be sufficient to alarm? Or should I extend the time some more?

Again, I appreciate everyone's feedback on this topic. Don't know what I would do without you guys help.

Well the MOV valve specs should specify "time to open" and "Time to close" I have some valves that take 60 seconds to open, so I fail after 65 seconds. Some MOV valves operate differently under pressure load from the substance the valve is blocking. I have some valves that open in 2 minutes and I put a slightly larger time than that for the alarm. What I have found the need to watch for is to make sure I have a good average time to open and close and use that for the alarm setup. I have some MOV valves that close faster than they open and sometimes they open faster than they close.

Hope this helps.

tmyersdv said:

Well the MOV valve specs should specify "time to open" and "Time to close" I have some valves that take 60 seconds to open, so I fail after 65 seconds. Some MOV valves operate differently under pressure load from the substance the valve is blocking. I have some valves that open in 2 minutes and I put a slightly larger time than that for the alarm. What I have found the need to watch for is to make sure I have a good average time to open and close and use that for the alarm setup. I have some MOV valves that close faster than they open and sometimes they open faster than they close.

Hope this helps.

Click to expand...

Thank you for the information. I will contact the vendor and determine the specs on the valve and program the alarm timing accordingly. Again, thank you all.

I agree with Tom about using a relay to ensure that you never send an open and close command at the same time. We use a SPDT relay with the Close command wired to the NC contacts and the Open command wired to the NO contacts. When you want to open the valve you simply energize the relay. Another advantage of this is that you only need 1 output from your PLC.

rta53 said:

I agree with Tom about using a relay to ensure that you never send an open and close command at the same time. We use a SPDT relay with the Close command wired to the NC contacts and the Open command wired to the NO contacts. When you want to open the valve you simply energize the relay. Another advantage of this is that you only need 1 output from your PLC.

Click to expand...

Thats very interesting. I will keep this in mind when drafting the electrical wiring for the MOV's on the next project. This is my first project in the oil&gas industry so I have tons of learning ahead of me.

I really value all you guys' input on this topic.