# Would it be possible to use a control valve without a positioner?

**URL:** <https://forumautomation.com/t/would-it-be-possible-to-use-a-control-valve-without-a-positioner/12093>\
**Category:** Valves\
**Tags:** interviewquestions\
**Created:** [May 24, 2024, 8:02am UTC](https://forumautomation.com/t/would-it-be-possible-to-use-a-control-valve-without-a-positioner/12093 "2024-05-24T08:02:29Z")\
**Posts on this page:** 2\
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**Author:** ![Sundar\_Iyalunaidu](https://forumautomation.com/user_avatar/forumautomation.com/sundar_iyalunaidu/32/7404_2.png) [@Sundar\_Iyalunaidu](https://forumautomation.com/u/Sundar_Iyalunaidu)\
**Post date:** [May 24, 2024, 8:02am UTC](https://forumautomation.com/t/would-it-be-possible-to-use-a-control-valve-without-a-positioner/12093/1 "2024-05-24T08:02:30Z")

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Would it be possible to use a control valve without a positioner ?

 ![image](https://cdn.forumautomation.com/original/2X/6/635d753f89c58f6edf3165f9793422795417d75e.jpeg)

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**Author:** ![Instrument\_Engineer](https://forumautomation.com/user_avatar/forumautomation.com/instrument_engineer/32/6734_2.png) [@Instrument\_Engineer](https://forumautomation.com/u/Instrument_Engineer)\
**Post date:** [May 29, 2024, 9:42am UTC](https://forumautomation.com/t/would-it-be-possible-to-use-a-control-valve-without-a-positioner/12093/2 "2024-05-29T09:42:22Z")

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Yes, it is possible to use a control valve without a positioner, but whether it’s advisable depends on the specific application and requirements. Here are some key points to consider:

### Basics of Control Valves and Positioners

- **Control Valve** : A device used to regulate the flow of a fluid by varying the size of the flow passage.
- **Positioner** : A device that ensures the valve reaches the desired position by comparing the control signal (usually from a controller) to the actual position of the valve and adjusting it accordingly.

### Using a Control Valve without a Positioner

1. **Direct Control** : In the simplest systems, the control valve can be operated directly by the control signal (pneumatic, electrical, or hydraulic). The controller sends a signal to the actuator of the valve, which moves the valve to a position that corresponds to the signal.
2. **Advantages** :

- **Simplicity** : Fewer components mean a simpler system with potentially lower costs and reduced maintenance requirements.
- **Lower Initial Cost** : Positioners add to the initial cost of the control system.

1. **Disadvantages** :

- **Accuracy and Precision** : Without a positioner, the accuracy of the valve position may be reduced, especially if the control valve is subject to varying loads or friction.
- **Hysteresis and Deadband** : Direct control may suffer from issues like hysteresis (lag between input signal and movement) and deadband (range in which no movement occurs), leading to less precise control.
- **Non-linearity** : Many control valves have a non-linear relationship between the input signal and the valve position. Positioners can linearize this relationship, improving control performance.
- **Response Time** : Positioners can improve the response time of the valve, which is critical in fast-acting control loops.

### Applications Where Positioners Are Not Essential

- **Simple On/Off Control** : In applications where the valve is either fully open or fully closed, a positioner is often unnecessary.
- **Slow Processes** : In processes where the fluid dynamics are slow and do not require highly precise control, direct control without a positioner might be sufficient.
- **Constant Conditions** : If the process conditions (pressure, temperature, etc.) are relatively constant and do not impose significant variations on the valve, a positioner may not be needed.

### Applications Where Positioners Are Beneficial or Necessary

- **High Precision Requirements** : Processes requiring precise control of fluid flow, pressure, or temperature will benefit from the enhanced accuracy provided by a positioner.
- **Variable Conditions** : When process conditions change frequently or significantly, a positioner helps maintain accurate valve positioning.
- **Complex Control Strategies** : Advanced control strategies, such as PID control, typically require the enhanced performance that a positioner provides.

While it is technically feasible to use a control valve without a positioner, the decision should be based on the specific requirements of the control system. For simple, low-precision applications, omitting the positioner can be a cost-effective choice. However, for applications demanding high precision and responsiveness, a positioner significantly enhances control performance and reliability.