10 Common Mistakes in Actuator Sizing for Valves and Fittings – and How to Avoid Them
The correct sizing of actuators for industrial valves is not just about connecting two parts; it involves a more complex process. A correctly designed actuator enables smooth and efficient operation of the system and helps to save energy and costs. However, mistakes are often made when selecting the right actuator.
1. Underestimated torques
One common mistake is the incorrect calculation of the required torque. If a smaller actuator with a smaller output torque is selected, the actuator cannot move the valve reliably. Whereas, when a large actuator is selected, unnecessary energy and procurement costs are incurred. Precise manufacturer data and a realistic safety factor are essential here.
2. Excessive safety factor “out of caution”
At first glance, choosing an overly generous safety factor seems reasonable, but it often leads to oversized drives. These are not only more expensive and energy-intensive, but can also overload the valve. The MAST value (Maximum Allowable Stem Torque) is crucial here – it defines the maximum permissible torque that the valve stem can withstand. If this is exceeded, there is a risk of damage to the spindle or seal. Instead of playing it safe across the board, the safety factor should always be based on the MAST value and the actual operating conditions.
3. Lack of consideration of the flowing medium
The medium to be controlled has a major influence on the drive. Viscous, abrasive, or particle-laden media significantly increase the resistance of the valve. Ignoring this fact risks functional problems. A thorough analysis of the medium properties should therefore always be part of the sizing process.
4. Ignoring temperature influences
Extremely high or low temperatures have a direct impact on actuators and valves. Seals become harder, lubricants lose their properties, and materials expand. It is often forgotten that heat, cold, moisture, or an aggressive environment also affect the actuator. To ensure reliable operation, it should always be suited to the actual operating conditions.
5. Selection of the actuating time
Drives that are too fast cause pressure hammers in pipelines, while those that are too slow prolong the response time of the entire process. In both cases, efficiency suffers. The optimum positioning speed must therefore be adapted to the process cycles, medium, and valve in order to prevent damages and delays.
6. Lack of explosion protection certification
In potentially explosive areas (ATEX zones), the use of non-certified drives is not only risky, but simply not permitted. Lack of approvals can result in high follow-up costs. Planners should therefore check at an early stage whether an ATEX or IECEx-certified drive is required.
7. Neglecting the type of power supply
An actuator is only as reliable as its power supply. Differences in line voltage, frequency, or phase number can lead to malfunctions during operation. Failure to observe the electrical parameters and interfaces can result in downtime or costly adjustments later on.
8. No consideration of installation position
Some drives can only function in certain positions. If the installation space is planned incorrectly, this can lead to restrictions in function or service life later on. Carefully reviewing the manufacturer's installation specifications can prevent costly modifications and breakdowns.
9. Negligence in maintenance
An actuator that is installed in a location that is difficult to access significantly increases maintenance work and thus operating costs. In addition, important inspections are often neglected. The serviceability of the installation location should be taken into account as early as the planning phase in order to ensure long-term efficiency.
10. Lack of planning for integration into the control technology
A good actuator is only effective if it works together with the control system. If the appropriate interfaces or protocols are missing, problems will follow. Planning early saves on retrofitting and makes automation easier. In addition, inadequate planning with respect to the necessary control accessories leads to higher overall costs for the system.
Conclusion: Precise sizing instead of costly mistakes
The actuator sizing for valves requires experience, technical knowledge, and forward planning. Avoiding the mistakes mentioned above will result in greater operational reliability, optimized energy efficiency, and lower costs in the long term.