Positioners – find manufacturers and suppliers

Positioners are devices that are used in automation and control circuits to precisely set the actuators of valves and dampers to a specified position and keep them stable even under changing operating conditions.

They are a central link between control systems such as the control system, PLC and the valve actuator. Without positioners, precise, reproducible and fast positioning of control valves in complex processes would hardly be possible.

Below is an overview of the function, types and use of positioners, as well as an overview of their advantages:

How positioners work:

A positioner works according to the principle of position comparison:

1. The control system sends a setpoint signal, e.g. 4-20 mA, 0-10 V, fieldbus, to the positioner.
2. The positioner measures the current position of the actuator via a position sensor, e.g. potentiometer, inductive or magnetic.
3. It compares the actual and target position and adjusts the actuator, pneumatically, electrically or hydraulically, until the desired position is reached.
4. In this way, the actuator - e.g. a control valve or a flap - is brought precisely, quickly and stably into the desired position.
5. In addition, modern positioners often offer functions such as self-diagnosis, characteristic curve adjustment and communication with control systems.

Types of positioners:

There are various types of positioners, which differ in terms of technology and area of application:

1. Pneumatic positioners:
   Work purely pneumatically. They control compressed air in the actuator and are particularly common in potentially explosive atmospheres or in simpler control circuits.
2. Electropneumatic positioners:
   Accept electrical input signals, e.g. 4-20 mA, and convert them into a pneumatic output signal for the actuator.
   They are the standard in many industrial plants today.
3. Digital / intelligent positioners:
   Microprocessor-controlled, with digital interfaces such as HART, Profibus, Foundation Fieldbus.
   They enable parameterization, self-calibration, diagnostic functions and online monitoring.
4. Electric positioners:
   Control electric actuators directly via motorized valves, for example.
   They are mainly used where compressed air is not available or where electric actuators are specified.

Use of positioners:

Positioners are used in all areas of the process and manufacturing industry where precise valve or flap positions are required:

1. Chemical and petrochemical plants:
Precise control of reaction and dosing flows.

2. Power plants and energy systems:
Control of steam, water and fuel valves.

3. Food and pharmaceutical industry:
Precise dosing in hygienic processes.

4. Building technology / HVAC:
Control of air dampers, mixers or zone valves.

5. Water and waste water technology:
Control of inlets and pressure regulation.

wherever actuators need to react quickly and precisely, positioners are indispensable.

Advantages of positioners:

The use of positioners offers numerous advantages:

• Greater accuracy: exact adherence to the target position even under fluctuating operating conditions.
• Fast positioning processes: Improved dynamics and shorter control times.
• Compensation of friction and dead travel: Automatic adjustment to position valves precisely despite wear or pressure fluctuations.
• Flexibility: Can be used for different signal types, actuator types and valves.
• Diagnostic and monitoring functions (for digital versions): Early detection of faults, condition monitoring, predictive maintenance.
• Energy efficiency: Less compressed air or energy consumption thanks to optimized control.
• Increased process reliability: Avoidance of over- or underdosing, more stable control loops.

Positioners are the brains of the actuator: they ensure that valves, butterfly valves and other control valves reach their setpoint position precisely and reliably. They are available in pneumatic, electro-pneumatic, electric and digital versions. They can be used in all industries, from chemicals and energy to building services engineering. Their advantages range from maximum control accuracy and process reliability to diagnostic options and energy savings.
This makes positioners indispensable components of modern automation and control technology.

Here is an overview of the most important criteria to look out for when buying positioners:

Positioners are indispensable components in automation and control technology. They ensure that valves, dampers and other actuators move precisely to the desired position and can be controlled reliably. An incorrectly selected positioner can lead to inaccurate control, increased energy consumption, failures or dangerous process deviations.
Purchasing therefore requires a systematic analysis of the process requirements, technical interfaces and environmental conditions before a purchasing decision is made.

• Precise definition of requirements: Before purchasing, it must be clear what the positioner is supposed to do:
• What type of actuator, valve, damper or gate valve, will be controlled?
• What type of signal is present at the input? E.g. 4-20 mA, 0-10 V, HART or Profibus?
• How large is the stroke or angle of rotation of the actuator?
• How high are the response speed and positioning accuracy required by the process?
• In what environment is it operated? Temperature, humidity, Ex zones, vibration?
• These basic data are essential for making the right choice.
• Design and operating principle? There are different types of positioners:
• Pneumatic positioners with a purely pneumatic control system.
• Electropneumatic positioners use an electrical input signal to generate a pneumatic output signal.
• Digital/intelligent positioners with a microprocessor provide diagnostic options and fieldbus communication.
• Electric positioners are suitable for electric actuators.
• The purchaser should check which type is best suited to the existing drive and control system and whether the desired functionality, e.g. self-calibration, characteristic curve adjustment or fail-safe, is available.
• A positioner must fit the actuator mechanically and electrically/pneumatically:
• Mounting interfaces such as NAMUR or VDI/VDE guidelines for easy mounting.
• Air connections and pressure ranges for pneumatic actuators.
• Signal and protocol compatibility with HART, Profibus, Foundation Fieldbus or 4-20 mA.
• Safety requirements: SIL certification, Ex approvals (ATEX, IECEx).
• Lack of compatibility leads to additional costs for adapters or even functional problems.
• The positioner must withstand the operating conditions:
• Protection class (IP class) against dust and water.
• Temperature resistance in hot or cold environments.
• Corrosion protection in aggressive atmospheres or with salty air.
• Explosion protection in hazardous areas.
• It is worth taking a look at the manufacturer's data sheets and certificates.
• Modern positioners often offer extensive setting options:
• Simple commissioning, e.g. through automatic self-calibration.
• Intuitive user interfaces or manual control units.
• Diagnostic functions for condition monitoring (predictive maintenance).
• Communication with control systems for remote monitoring.
• A user-friendly positioner saves time during installation, maintenance and troubleshooting.
• The life cycle perspective should also be taken into account when purchasing:
• Availability of spare parts and accessories for years to come.
• Service and support offers from the manufacturer.
• Training for maintenance personnel.
• This reduces long-term operating costs and increases reliability.
• It is not just the purchase price that counts, but the total costs over the service life:
• Energy consumption (e.g. compressed air requirements).
• Maintenance and servicing costs.
• Downtimes due to failures or complex operation.
• A high-quality positioner is often more expensive to purchase, but pays for itself over the years through fewer failures and greater precision.

Purchasing positioners is a strategic task. It is not enough to choose just any controller: A precise definition of requirements, the right design, compatibility with the actuator and control system, approvals, robustness as well as service and TCO considerations are crucial.
If you take these points into account, you not only get an actuator, but also a permanently reliable interface between the process control system and the actuator, which ensures stable processes, efficiency and safety.

Positioners can be purchased from various suppliers. Comprehensive information about manufacturers and suppliers of Positioners from all over the world can be found on Exportpages.