The two key questions to select a hydraulic valve - LinkedIn

Know More. Grow More.

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By Matt Clift (Director of Global Product Management & Marketing)

In terms of variety of product options to choose from, hydraulic valves have some of the widest array of options to choose from. There are quite literally hundreds of different configurations possible!

However, it doesn’t need to be complex. In this article of our Know More, Grow More series, we will simplify the process and will present the two primary questions you need to ask when selecting a hydraulic valve.

As a reminder, for more information about selecting the right valve, or in fact any product in your drip irrigation system, make sure you check out Module 2 of Rivulis Knowledge Hub.

Selecting the right valve type may seem complex, but it becomes straightforward by answering two key questions:

• What is the valve’s primary function?
• How will the valve be operated or controlled?

Question 1: What is the Primary Function of the Valve?

The first question focuses on the primary function, or "what the valve does." There are nine different primary functions for hydraulic valve as follows:

• Basic: A valve body without any accessories, often used by growers and dealers who wish to build their own valves. 

• On/Off: This valve is either on or off, with no pressure regulation or flow control since there is no pilot. Ideal for simple in-field operation and small farms without automation.
• Pressure Reducing (PR): Reduces downstream pressure for consistent water pressure, and subsequent uniformity in each block regardless of upstream pressure fluctuations. The majority of valves are PR valves in most irrigation systems.

• Pressure Sustaining (PS): Maintains upstream pressure, important for components such as filters that require a minimum pressure for back-flush.
• Pressure Reducing & Pressure Sustaining (PR/PS): Combines both functions, eliminating the need for two separate valves.
• Electric Control: Controls valve opening through electric automation, allowing remote operation.
• Quick Relief: Acts as a safety valve by relieving system pressure above a preset value. Unlike PR valves, quick relief valves are for quickly expelling excess pressure when spikes occur.
• Flow Control: Restricts flow to a determined rate. These are different to PR valves as the valves restrict to a specific flow through differential pressure. An example of use is to restrict the flow of back-flush discharge from a media filter during flushing.
• Level Control: Opens and closes valves based on set tank points, useful for maintaining storage water levels.

Question 2: How Will the Valve be Controlled?

We now know what the valve will do. The second question addresses how the valve will be operated. There are three main options:

• Manual: Involves a ball valve for manual operation. Often remotely controlled valves will have a manual override added to the valve in addition.

• Hydraulic: Utilizes water pressure transferred through a hydraulic tube to control the valve’s diaphragm via a hydraulic relay. 

• Electric: Uses a solenoid where current through a wire creates a magnetic field that moves the piston.

By answering two questions above, you streamline the process of selecting the right hydraulic valve for your system.

Next Steps

Once you have determined the primary function and control method of your valve, the next steps involve specifying the valve's parameters and accessories:

For more Superimposed Relief Valve ZDB10​​information, please contact us. We will provide professional answers.

• Material: Choose between plastic or metal based on your application. Plastic valves are lighter, more economical, and corrosion-resistant. Metal valves are necessary for higher pressure and larger size applications.
• Size: Choose the size based on the required flow and head loss. This is chosen according to the needs of your system’s hydraulic design.
• Connection Type: Select the connection type according to your region (standard for your country) and application need (flange, thread, etc).
• Pilots: Are chosen to the pressure regulating requirement of the hydraulic design and the system components.
• Throttling: Controls how much a valve can open. It does not regulate pressure, i.e. it does not respond to pressure variations. It only puts a limit on how much the valve can open.
• Solenoids: Are available in a wide range of variations, and your selection will depend upon your control system and valve application.

Dive deeper about hydraulic valve selection in the Valves Section on the Rivulis Knowledge Hub, or download Book 2 for the complete guide for drip irrigation component product selection.

Read more about Rivulis’s hydraulic valve product offering in the valve section on rivulis.com.

Please note. This article is provided as a high level overview only. It is important that you verify what is best for your specific application, including for design, installation, operation, and maintenance. For both personal and irrigation system protection and before use, it is important to read the relevant suppliers’ instructions (for non-Rivulis products such as pumps, chemicals, fertilizers, etc), to consult with applicable professionals, and to read the relevant section of the Rivulis Drip Guide/Knowledge Hub, particularly with respect to safety and handling information, and more detailed instructions for use.

To ensure the protection of hydraulic system components, hydraulic relief valves play a critical role in restricting system pressure and limiting the system's maximum output force. These valves operate by balancing the hydraulic force with a variable spring force, releasing heat when they open in response to a predetermined pressure. Properly adjusted relief valves ensure the system functions optimally and regulates the amount of heat generated.

However, it is essential to set up relief valves correctly and monitor them consistently to prevent malfunctions that could cause harm to the hydraulic system. The following steps outline the process of setting a pressure relief valve:

Step 1: Refer to machine drawings to identify the circuit that requires adjustment and locate the circuit relief valve, typically connected to the pump in parallel and placed close to the pump.

Step 2: Disconnect the hydraulic hose from the relief valve's system side, using appropriate JIC caps or plugs to seal the hose and valve. The relief valve's return or tank side should not be capped, as this can prevent hydraulic fluid loss and system contamination.

Step 3: Attach a pressure gauge between the pump and the relief valve using an available port or an adapter if needed.

Step 4: Loosen the pressure relief valve adjustment to reduce pressure as much as possible. Start the machinery and activate the hydraulic circuit, ensuring the pressure gauge reads nearly zero.

Step 5: Gradually turn the relief valve adjustment clockwise until the gauge reading matches the specified pressure in the machine specifications, determining the valve's "cracking" pressure. Securely tighten the adjuster lock nut to maintain the desired setting.

Step 6: Verify the relief valve setting once the gauge reading corresponds to the required pressure, preventing unintentional adjustments by firmly tightening the adjuster lock nut.

Recognizing signs of pressure relief valve failure is crucial for timely maintenance and safety. Three indicators of potential valve failure include:

1. Failure to reach proper pressure: If the relief valve releases pressure before the system reaches its maximum pressure, or if it continuously leaks or chatters, there may be an issue with the valve's calibration or functionality.

2. Overpressure without valve activation: If the system is over-pressured, and the pressure relief valves have not activated, it indicates a potential valve malfunction due to contaminants or misalignment.

3. Leaking valves: Valve leaks can lead to reduced efficiency and productivity in the system, requiring thorough evaluation and maintenance to identify the cause and ensure proper functioning.

In case of a pressure relief valve failure, it is crucial to investigate the underlying cause rather than simply replacing the valve. Troubleshooting should be performed to determine the root issue for effective resolution and to maintain a safe operating facility. Properly installing, monitoring, and maintaining pressure relief valves in hydraulic systems are vital aspects of ensuring system safety and performance.