Control Valve Positioner Action & Travel Scale

K

Thread Starter

Kazim

Dear All,

I would like to share my experience and troubles i am facing in my current project. (NGL Recovery Unit).

1- we are using control valve with FF type positioners (Masoneilan FVP-110). we have 2 kind of actuators Air to Open (ATO) & Air to Close (ATC). All valves with ATO actuators are working normally with FVP-110 but all valves with ATC actuators, there positioner is acting reverse:-
for example:

Case-1 (ATO)

1.1 For ATO (NC) at fully closed condition we are getting 0% and fully open condition we are getting 100%;

1.2 Scale movement is from fully closed to fully open (0, 25, 50, 75, 100) downward to upward.

1.3 Means when we connect air supply and start giving signals from 0% -> 100% valve stays close at 0% and starts moving according with the input signals from down to up (Close to Open)

Case-2 (ATC)

2.1 For ATC (NO) at fully open we are getting 100% and fully closed condition we are getting 0%;

2.2 Scale movement is also from fully closed to fully open (0, 25, 50, 75, 100) downward to upward.

2.3 Means when we connect air supply and start giving signals from 0% -> 100% valve immediately go to the fully closed at 0% and starts moving according with the input signals from down to up (Close to Open)

In that scenario the section 1.3 & 2.3 are acting in same way,
So, now my understanding is that in FF type positioners no matters whatever is actuator function ATO (NC) or ATC (NO), whenever we gives 0% signal valve stays or moves to fully closed condition.

The case-1 is considered as direct acting and case-2 is considered as reverse acting.

As per actual project requirement; we want ATC (NO) valves in the way as below:

when we connect air supply and inject 0% signals valve should stay open and starts moving from fully open position to fully close position according with the increase in signals; means from up-> down.

If any one can helps me regarding this ,I will be very thankful,

Regards,
Kazim
 
> What are the settings in parameter ACT_FAIL_ACTION for the ATO and ATC positioners?

ACT_FAIL_ACTION for ATO is fail to Close. (as per project Instrument Data Sheet)

For ATO Actuators air supply inlet is from the Bottom of actuator.
Manufacturer: DRESSER
MODEL: 88

ACT_FAIL_ACTION for ATC is fail to Open. (as per project Instrument Data Sheet)

For ATO Actuators air supply inlet is from the Top of actuator.
Manufacturer: DRESSER
MODEL: 87
 
J
1) >ACT_FAIL_ACTION for ATO is fail to Close. (as per project Instrument Data Sheet)

2) Here's what the Masoneilan FF manual [GEA19791 formerly Masoneilan Doc ID EW4000 February 2012] says:

1. Select the acting direction of valve by setting the value, 1 or 2 in the parameter.
ACT_FAIL_ACTION corresponding to the acting direction of the valve. This setting
determines the relationship between the pneumatic input signal and 0-100% of the valve position, where the 0% position means complete closure.
❑ 1 = air to open
❑ 2 = air to close

3) What is the actual configured variable for ACT_FAIL_ACTION setting in the positioner? It should be a numeral one or two.
 
I also read the reference manual for FVP-110.

Currently ACT_FAIL_ACTION parameter is set as:
❑ 2 = air to close.

But are not allowed to make changes in the ACT_FAIL_ACTION, because our Instrument Data Sheet and project design specification requires these Control Valves to work as "Air to Close" and Fail Safe condition should be "Fail to open".

In the same manual for FVP-110,
If you look at page# 161 (Table-48), Page# 163 (Table-49), Page# 193 (Table-61/21), Page# 196 (Table-61/95) & Page# 216 (Table-70)
They have defined some more option related to the Positioner Direction as Direct or Reverse.

I have tried all the possible options, some of them are blocked (read only), some are not taking effect permanently (when we change the parameter and comes out from the function block it goes bake to default parameters), and others are not effective.

Kazim.....
 
I
Please take note that there are 3 actions/parameters which determines the final valve travel direction after an input has been applied to the positioner. these are:
* Positioner action...direct/reverse
* Actuator action
* Transducer scaling

In my experience i have found out that people most often misinterprete the first two parameters/terms.

When the data sheet specifies that the valve should be direct acting, they are refering to the action of the positioner and not the actuator. A direct acting postioner means the output pressure increases with an increase in electrical signal ( 4-20mA) and vice versa. Now the final valve travel direction will depend on the actuator action....air to close or air to open.

If a direct acting positioner is used on an air to close actuator then it means as you increase 4-20mA signal, the valve will be moving towards 100% close position.

To change action of positioner you have to go to AO block; then I/O Options, there you have to tick parameter no. 5 " Increase to Close" and this will reverse the action of positioner to reverse acting. By default from factory the postioner is set to direct acting. Do not temper with transducer scaling settings, you might mess the whole thing coz like i said these three parameters should match each other.
In most cases, the positioner action should be left on direct acting and only specify the actuator action.

any further querries you can contact me on email adress: [email protected]
 
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