The Ultimate Guide to Choosing hydraulic check valves

A hydraulic check valve, also known as non-return valve (NRV), is a mechanical device designed to allow fluid (typically a liquid) to flow in one direction and prevent reverse flow; it plays a crucial role in hydraulic systems to maintain the direction of fluid movement or to control pressure or flow rate.

Huade Hydraulic Product Page

Generally check valves are automatically operated; human intervention or any external control system is not required.

How Hydraulic Check Valves Work

Check valves have a body (often cylindrical) with inlet and outlet ports for fluid to enter and exit; inside there's a movable element (often a poppet, more rarely a ball) whose function is to block the flow in the reverse direction. When fluid flows in the desired direction, its pressure forces the poppet away from the seat, allowing the fluid to pass around the valve. Vice versa, if there's an attempt at reverse flow, pressure from the fluid pushes the poppet against its seat. This seals off the passage and prevents fluid from flowing backward. In most cases, a spring helps to close the poppet quickly and effectively when the flow direction changes, preventing backflow.

Check valves must necessarily be installed in the correct orientation; in fact, they are designed to allow flow in one specific direction, so improper installation will result in valves not functioning as expected. When fluid flows in the desired direction, the valve opens, and when there's an attempt at reverse flow, the valve closes to prevent backflow. This design is crucial for maintaining the efficiency and safety of hydraulic systems by preventing unintended fluid movement in the wrong direction.

Types of Hydraulic Check Valves

Check valves usually have a straight profile and one single body or two screwed semi-bodies. Inlet and outlet threads can be female or male type.

A special category is represented by parts where an orifice machined on the poppet allows controlled leakage of fluid in the direction in which the flow is normally prevented by the closure of the valve. This design trick makes check valves equipped with an orifice a flow control tool. There are also three-way valves (or 'shuttle' valves), which have the characteristic of conveying to the return line of the circuit the greater of the pressures of the two delivery lines.

Differences Between NRV and Check Valves

Understanding the nuances between NRV (non-return valves) and conventional check valves is crucial in hydraulic systems. While often used interchangeably, these terms essentially refer to the same component. The distinctions lie in regional preferences and industry jargon. In essence, whether you call it an NRV or a check valve, the functionality remains consistent, ensuring unidirectional fluid flow and preventing backflow. Clearing up any confusion between the terms is vital for precise communication within the hydraulic engineering realm.

Prevent Backflow: Explore Our High-Quality Hydraulic Check Valves

Maintain reliable flow control and prevent backflow with Faster's high-performance hydraulic check valves, designed for durability and efficiency.

Explore Solutions

Materials for Hydraulic Check Valves

In hydraulic systems, the choice of materials for hydraulic check valves is paramount, with carbon and stainless steel emerging as the most commonly utilized raw materials. These robust materials not only provide durability but also ensure the reliability and longevity of the check valves. The selection of carbon or stainless steel depends on the specific requirements of the hydraulic circuit. These materials play a pivotal role in maintaining the structural integrity of the check valves, contributing to their effectiveness in controlling fluid flow and preventing backflow. A careful consideration of these material options is essential in ensuring the optimal performance and longevity of hydraulic check valves in diverse applications.

Contact us to discuss your requirements of Electro hydraulic control valve. Our experienced sales team can help you identify the options that best suit your needs.

Hydraulic Check Valve Symbol

In the realm of hydraulic systems, the symbolic language of hydraulic check valves is conveyed through a stamped valve symbol on the external body. This symbol serves as a visual identifier, facilitating easy recognition of the check valve among other hydraulic components, and greatly helps to avoid installation mistakes as it shows the closing direction of the valve. This simplistic yet informative feature aids in the swift and accurate identification of check valves in complex hydraulic circuits. It is a valuable element for engineers and maintenance personnel, streamlining troubleshooting and ensuring efficient operation. The presence of a clear and standardized valve symbol enhances the overall functionality and usability of hydraulic systems, promoting ease of maintenance and optimal performance.

Common Hydraulic Check Valve Problems

As with all complex components in a hydraulic circuit, it's possible to experience issues with check valves too, the most common being the stuck of poppet in open or closed position, unexpected leaks, chattering or the valve not opening at the set pressure. Choosing products suiting the circuit specifications, installing them properly and performing some periodical maintenance can help prevent many of these issues from occurring in the first place.

Why Choose Faster Hydraulic Check Valve

With a long experience of design and production, Faster is the ideal supplier for top-quality check valves. Every day we deliver all types of valves (ball-type, poppet-type, shuttle-type, etc.) to our customers to allow control of directional flow, or pressure, or flow rate for a wide range of applications and for different markets.

Nozzle check valves

Nozzle check valves are designed with the disc connected to a central stem, moving along the horizontal axis. A spring is positioned between the disc and the diffuser sleeve. When flow enters the valve, the hydraulic force exerted onto the front face reacts against the spring, causing it to compress and allow the valve to open. When the flow stops, the spring forces the disc to return to the closed position.

Due to the spring-assisted closure and the short linear valve stroke, the nozzle check valve is one of the quickest acting check valves available and is commonly used in pumped systems where water hammer is a potential concern. The disc is constantly present in the flow stream which can result in slightly higher head loss compared to swing check valves.

For additional details please refer to our nozzle check valve product information.

Factors to consider when choosing check valves?

Choosing the ideal check valve for your application depends on several selection criteria. No single type of check valve suits every situation, and the following factors are essential to consider. However, they may not be equally important for all applications.  By evaluating these factors in relation to system requirements, you can select a check valve that ensures reliable performance, minimal maintenance and long-term operational efficiency.

Fluid compatibility

All check valves referred to in this article are designed for water and treated wastewater. However, for raw wastewater or sewage the presence of solids may impact valve performance, requiring careful consideration of design and material compatibility. 

Flow characteristics

Rapid closure of a check valve can protect upstream equipment such as pumps from damage. However, the rapid closure will not protect against the surges caused by pumps being started and shut down. If the valve opens (and closes) quickly, the flow will change rapidly and thus increase likeliness of surge occurrence. Consider the flow dynamics of your system to choose a valve that mitigates these risks effectively.

Head loss

Head loss is influenced by fluid velocity and valve design. Valves with unrestricted openings minimise head loss, whereas designs with narrower bores increase fluid velocity and, consequently, head loss. There are a number of values for head loss, among others zeta values, Kv and Kvs values.

Total cost of ownership

The total cost for your check valve is much more than the purchase price. Long-term costs such as maintenance, equipment protection and energy costs may be just as important as purchase price and installation costs. 

A simple valve construction generally requires less maintenance, and the higher the Kv value, the lower the energy consumption.

Non-slam characteristics