When it comes to managing pressure within an industrial system, not all valves are made equal. There are several types of pressure reducing valves (PRVs), each designed to handle specific tasks depending on the needs of the application. Whether you’re dealing with steam, gas, or liquids, understanding the different types of PRVs is key to ensuring safe, efficient, and reliable operations.
One common challenge faced by many facilities is choosing between direct acting and pilot operated valves. Though both serve the purpose of regulating pressure, they function differently and are suited for different scenarios. Knowing their distinctions will help you choose the right valve for your system, reduce downtime, and maintain safe working conditions.
What are pressure reducing valves?
A pressure reducing valve, or PRV, is a device that automatically reduces a higher inlet pressure to a lower outlet pressure. It’s commonly used in piping systems to ensure that pressure remains within a safe and usable range. By doing so, it protects downstream components and equipment from potential damage due to overpressure.
While the goal of all PRVs is similar, the internal mechanisms differ significantly between direct acting and pilot operated versions. Each type has its own advantages and drawbacks, which should be carefully considered depending on your system’s flow rate, pressure needs, and environmental conditions.
How direct acting valves work
Direct acting valves are relatively simple in design. They use a spring-loaded diaphragm or piston to control the flow and reduce pressure. When downstream pressure drops below the set point, the valve opens, allowing flow to resume. Once the set pressure is reached, the spring compresses and the valve closes partially or fully.
This type of valve is typically used in applications with low flow rates and minimal variation in demand. Due to their straightforward construction, they are easy to install and maintain, and they respond quickly to pressure changes.
Pros of direct acting valves:
- Quick response to pressure fluctuations
- Compact and cost-effective
- Ideal for small systems or light-duty applications
Limitations:
- Less accurate at maintaining set pressure under varying flow conditions
- Not suitable for high flow rate or complex systems
Understanding pilot operated valves
Pilot operated valves are more complex and are often used in larger or more dynamic systems. They function by using a smaller pilot valve to control the main valve. This setup allows for more precise control over pressure, especially in situations with large flow rates or variable demand.
The pilot valve responds to downstream pressure and regulates the opening of the main valve accordingly. Because of their enhanced sensitivity and better control, pilot operated valves are widely used in applications that require stable pressure and high flow capabilities.
Pros of pilot operated valves:
- High accuracy and pressure stability
- Suitable for larger industrial systems
- Can handle higher flow rates and pressure differentials
Limitations:
- More expensive than direct acting valves
- Require a minimum differential pressure to function properly
- Slightly more complex to maintain and install
Key differences between direct acting and pilot operated valves
To make an informed decision, it’s helpful to compare the two types side by side:
| Feature | Direct Acting | Pilot Operated |
| Complexity | Simple | Complex |
| Cost | Lower | Higher |
| Response Time | Fast | Moderate |
| Pressure Accuracy | Lower | Higher |
| Flow Capacity | Low | High |
| Maintenance | Easy | Requires more attention |
If your system demands high precision, large volume flow, and stability under varying conditions, a pilot operated valve would generally be the better option. On the other hand, if you’re working with a relatively stable, low-flow system, a direct acting valve may be all you need.
Real-world applications
- Direct acting valves: Used in HVAC systems, small process applications, and lab setups where flow and demand remain relatively steady.
- Pilot operated valves: Preferred in oil and gas facilities, power plants, water treatment facilities, and other large-scale operations requiring consistent performance under fluctuating conditions.
Don’t forget safety valves
In addition to choosing between direct acting and pilot operated PRVs, it’s equally important to consider the role of safety valves in your system. A pressure safety valve is designed to open at a predetermined pressure to prevent over-pressurisation, ensuring the safety of equipment and personnel.
A safety relief valve combines the functions of both pressure safety valves and relief valves, offering reliable protection for systems where rapid pressure changes can occur. These valves are essential backups to your PRVs and should always be part of your pressure management strategy.
Moreover, common issues with pressure reducing valves can arise due to poor installation, wear and tear, or using the wrong type of valve for your system. That’s why getting the selection right from the start is so crucial.
Conclusion
Direct acting and pilot operated valves each have their own place in industrial systems, and the right choice depends on your specific operational needs. By understanding how they work and what they’re best suited for, you can ensure your system remains both safe and efficient.
If you’re unsure which valve is best for your setup or if you need quality, reliable components for your industrial operations, Techmatic Controls offers a wide range of pressure control solutions tailored to meet your needs. From pressure reducing valves to safety and relief systems, our team is ready to support your business with trusted products and expertise.
