# When should I use a linear or equal percentage valve?

**URL:** <https://forumautomation.com/t/when-should-i-use-a-linear-or-equal-percentage-valve/13100>\
**Category:** Valves\
**Tags:** interviewquestions\
**Created:** [March 20, 2025, 6:36am UTC](https://forumautomation.com/t/when-should-i-use-a-linear-or-equal-percentage-valve/13100 "2025-03-20T06:36:21Z")\
**Posts on this page:** 2\
**Page:** 1

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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:** [March 20, 2025, 6:36am UTC](https://forumautomation.com/t/when-should-i-use-a-linear-or-equal-percentage-valve/13100/1 "2025-03-20T06:36:21Z")

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When should I use a linear or equal percentage valve?

 ![image](https://cdn.forumautomation.com/original/2X/1/136bd2bd0a25ec5fe8ac0f03f89f6052d83865b2.jpeg)

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**Author:** ![automation\_engineer6](https://forumautomation.com/user_avatar/forumautomation.com/automation_engineer6/32/7656_2.png) [@automation\_engineer6](https://forumautomation.com/u/automation_engineer6)\
**Post date:** [March 28, 2025, 5:20pm UTC](https://forumautomation.com/t/when-should-i-use-a-linear-or-equal-percentage-valve/13100/3 "2025-03-28T17:20:05Z")

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A summary table shows the characteristics of linear and equal percentage valves below:

| Characteristic | Linear Valve | Equal Percentage Valve |
| --- | --- | --- |
| Flow vs. Stem Position | Flow changes proportionally with stem movement. | Flow change is small at low openings and increases exponentially. |
| Best Used When | System pressure drop is constant. | System pressure drop varies significantly. |
| Application Types | Liquid level control, steam injection, direct pressure control. | Steam, gas, and temperature control applications. |
| Process Gain | Constant throughout the valve stroke. | Low at small openings, increases as the valve opens. |
| Flow Demand Changes | Small and predictable. | Large variations. |
| Control Sensitivity | Provides steady control at all positions. | Offers fine control at low flow, large impact at high flow. |
| Preferred Use Case | Liquid systems with linear response. | Nonlinear processes where flow increases exponentially. |

### Rule of Thumb:

- Linear valves should be used for systems showing consistent operation and low pressure changes.
- The application of equal percentage valves becomes necessary when systems deal with changing loads and significant flow variations.