What is a pilot valve and how does pilot valve work

What is a pilot valve and how does pilot valve work

A pilot valve is a small valve designed to control a limited-flow control feed to a separate, larger piloted valve. The primary function of the pilot valve is to provide a manageable, low-pressure control input that operates a high-pressure or high-flow system.

Key Points:

• Control Mechanism: The pilot valve uses a small feed to control the operation of a larger valve, which in turn manages the high-pressure or high-flow system.
• Advantages: By using a pilot valve, a system can be controlled with minimal effort or force. It eliminates the need for large actuators to operate high-pressure systems.
• Applications: Pilot valves are especially useful in critical applications such as emergency systems, Safety Instrumented Systems (SIS), and other safety-critical operations.
• Human Operation: Many pilot valves are manually operated, often designed as a push-to-activate system or dead man’s switch, ensuring the operator maintains control and the valve is released when necessary.
• Integration with Solenoids: Even in solenoid-operated systems, pilot valves are beneficial because they reduce the size and power requirements of the solenoid needed to control high-pressure systems.

Pilot valves are valves that can control high flows in a system. Mostly the pilot actuated valves are shifted by the pressurized fluids. When the set pressure is reached then the valve would open and release the pressure. When the pressurized fluid hits the valve piston then the flow directing element of the valve would change. The major advantage of a pilot operation is that it can create large shifting force without any impact or wear which could happen in a mechanically actuated valve. Pilot operated valves can be mounted in any remote location to which the pressure fluids can be piped. In this valve, there won’t be any spark or increase of heat and because of this, it can be used for flammable environments.

What is the use of a pilot valve and what does it do

A pilot valve can decrease the pressure in a system. Flow control can be achieved by using a pilot valve. A pilot valve can be used to remotely control the directional control valves, cylinders, pumps, or motors. A pilot valve can be considered as a pressure reducing valve. Some pilot valves can be used with a remote pilot source. So by this feature, a valve can be shifted from a remote pressure source by other valves in the logic circuit.

What are the features and advantages of a pilot valve

• Pilot valves have high seat tightness, this valve will be tight until it reaches the setpoint
• When it reaches the setpoint, the pressure in the chamber is removed very quickly by full opening
• Accurate closing can be achieved in a pilot valve
• Its construction is very rugged so it can’t be damaged quickly
• In case if there is ice in the valve due to certain applications, the icing would be broken during the quick lifting process so it won’t interrupt the valve operation
• This valve can be used as a combined pressure and vacuum safety valve

What is a pilot operated directional control valve and how is the DCV shifted

In order to control the system that has high flows, pilot operated DCV is used because the system would require a large force to shift the spool. So the pilot valves are installed on the top of the main valve. So the pilot valve would hydraulically shift the main valve. In this valve, the valve piston is indirectly actuated. In order to do this oil is provided to the pilot valve. So while energizing the pilot valve oil will be directed to one side of the main spool and because of this, the spool will be shifted. Thus the pressure port will be opened to the work port and the fluid will be directed a return to the tank. There are certain benefits of external piloting they are constant pressure supply and the source may be filtered separately to prevent the pilot valve silting. DCV valves which are pilot operated could be drained internally or externally according to the need.

What is a pilot check valve and how pilot operated check valve works

This valve has a valve body with inlet and outlet ports and it also has a poppet which is biased against a spring. In this valve, the flow will take place only in one direction. In order to provide flow to the blocked direction, pilot pressure is applied to the pilot pressure port of the valve. If the spring force of the poppet is lesser than the system pressure in the flow port then the poppet will be moved or pushed and the flow will take place. There won’t be any reverse flow because the fluid pressure will close the poppet. In order to allow the reverse flow, then pilot pressure must be provided to the pilot port.

How pilot-operated relief valve works and when do we use it

The pilot-operated relief valves are used for emergency relief functions like the overpressure. This valve operates in a different way than a pressure relief valve in a pilot-operated relief valve it uses a system pressure to seal the valve. The major parts of this valve is a pilot valve, main valve, pilot tube piston or disc, and a seat. This valve is also known as a pilot operated safety relief valve. This valve is really sensitive and it can reduce the pressure override. These valves are used for applications that need to relieve large flow with small pressure. The operation of the pilot valve takes place in two stages in the first one which is the pilot stage. In the pilot stage, a small spring-biased relief valve would control the main valve. The other stage is the balanced piston stage and in this, the hydraulic connections are made, so a balance piston is used for the diversion of full flow volume. The inlet pressure will help to hold the piston on its own seat with the help of a light spring. The pilot stage poppet will be lifted when the pressure in the valve is reached to the set value. The unbalance in hydraulic force will be created because of the decreased pressure in the upper chamber of the second stage piston. Poppet will be lifted if the hydraulic force is greater than the mechanical force of the spring. Balance piston will be lifted when the pressure difference upper and lower chamber is enough and full flow would take place. This process will take place until the system pressure is reduced

What are Pilot-Operated Valves?

Pilot-operated valves are pressure relief valves that use a smaller pilot valve to control the main valve’s inlet and outlet ports. These valves are an alternative to spring-loaded valves and are known for handling higher pressures and larger capacities, offering excellent performance in overpressure protection. They are particularly valued for their ability to function effectively in systems with high backpressure and improved system stability. These features make pilot-operated valves commonly used in industries like oil and gas, especially for upstream and offshore applications.

How Pilot-Operated Valves Work

Pilot-operated valves are designed to handle higher backpressure than traditional spring-loaded valves. They use a pilot valve to control the main valve:

• The main valve piston is balanced and protected, with no fragile components that are prone to failure.
• The main valve has the same pressure on both the inlet and the dome (upper part of the main valve).
• Due to the variation in sectional area, a force is applied to keep the piston in balance.
• When the system pressure increases and reaches the set point, the pilot valve opens, releasing pressure from the dome to the atmosphere.
• This causes the main valve piston to move, opening the main valve and relieving the system’s pressure.

In systems where several valves are connected to a common flare, backpressure can cause the main valve to open prematurely. The pilot-operated valve addresses this by using a dome area larger than the inlet seat, which helps maintain control even under high backpressure conditions.

Benefits of Pilot-Operated Valves

• Capacity to Modulate: Pilot-operated valves can handle significant pressure drops, providing better control and modulation compared to spring-loaded valves.
• Higher Pressure and Capacity: These valves have a higher pressure and size capability, making them suitable for larger systems and heavy-duty applications.
• Connection Flexibility: They can be directly connected to the vessel via static or remote sensing lines, offering flexibility in installation.
• System Stability: The pilot controls the main valve, ensuring that it remains open regardless of inlet pressure fluctuations, providing enhanced system stability.
• Compact Design: These valves are compact, making them easier to install and operate in space-constrained environments, such as offshore platforms.

How to do the maintenance and installation of a pilot valve

We must check the pilot valve before installation so that we could know if there is any damage. In order to avoid the damage to the lower flange surface, the valve must be placed on a soft clean gasket material until installation. The valve must be stored in a clean place before installation. The installation of the valve must be done vertically. During the valve installation, it should be smoothly lifted into position by using the lift eyes. The gasket must be checked and the nuts and studs must be lubricated. The valve must be properly set on the nozzle and the flanges. The maintenance of this valve is not a problem because it won’t give much trouble. A periodic inspection is required to check the seat. The valve must be removed from the tank in order to do the periodic inspection of diaphragm, gaskets, and seals.

FAQ on Pilot valve

What is the purpose of the pilot check valve?

A pilot check valve is designed to allow flow in one direction and block flow in the opposite direction unless a pressure signal (pilot pressure) is applied to unlock the valve. Its purpose is to:

• Lock pressure in hydraulic systems to maintain a cylinder or actuator in position, preventing backflow.
• Release pressure when pilot pressure is applied, enabling controlled movement when required.

Where is the pilot valve located?

A pilot valve is usually located near the system it controls, such as hydraulic actuators, cylinders, or larger control valves. It’s typically mounted in positions that allow it to easily interact with the actuator or the larger valve it controls, and the pilot pressure lines are routed from the control panel or pressure source.

What is the advantage of a pilot valve?

A pilot valve is used to control high-pressure or high-flow systems with minimal input effort. Its main advantages include:

• Reduced effort: Pilot valves use a small control pressure to operate larger valves or actuators, reducing the need for manual or electrical force.
• Efficiency: They are energy efficient, as they only require a small control input to manage large systems.

Precision control: Pilot valves provide better control over high-pressure systems by offering smoother and more gradual actuation.

Troubleshooting Chart for Pilot-Operated Valves

General Recommendations for Maintenance of Pilot Valves 

• Regular inspection and maintenance of pilot valves are crucial to ensuring smooth operation.
• Always follow the manufacturer’s guidelines for troubleshooting and replacing components.
• For complex issues or recurring problems, consult a professional for in-depth analysis.

What is the difference between a pilot valve and a solenoid valve?

This below table provides a clear comparison, showing how pilot valves are more suited for heavy-duty, high-pressure systems, while solenoid valves are preferred for applications requiring quick, precise electronic control.

What is the difference between pilot valve and unloader valve?

The pilot valve is used for controlling other valves or actuators using a small control input, while an unloader valve manages system pressure by releasing excess pressure when needed, typically found in air compressors and pressure control systems.

The below table comparison table that outlines the differences between a pilot valve and an unloader valve:

To get more info about the control valve check the following link:

• Poppet valve
• Pressure control valve types
• Directional control valve
• Unloading valve
• Bleed valve