Daisy Chain or Series Connection of Open Center Hydraulic Valves: Understanding the Differences and Best Practices

[MikePhua]

Introduction
In hydraulic systems, particularly in construction and agricultural equipment, the configuration of valves plays a crucial role in the overall performance and efficiency of the machine. One of the common questions that arise when setting up a hydraulic system is whether to use a daisy chain (or series) connection for open-center hydraulic valves. Understanding the principles of these configurations is essential for proper setup, maintenance, and troubleshooting of hydraulic systems.
This article explores the concept of daisy chain or series connection in open-center hydraulic systems, how it differs from parallel connections, and the benefits and challenges associated with each setup.
1. What is an Open-Center Hydraulic System?
Before diving into the specifics of daisy chain or series connections, it’s important to first understand what an open-center hydraulic system is. In a basic open-center hydraulic system, the hydraulic pump continuously supplies flow to the system, but the flow is directed through the valve in such a way that when the valve is in the neutral position, the fluid flows directly back to the reservoir without performing any work.
The key features of an open-center hydraulic system include:

• Constant Flow: The pump delivers a constant flow of hydraulic fluid to the system, but this flow only performs work when it is directed through a valve.
  
• Neutral Position: In the neutral position, the valve doesn’t block the flow of fluid but simply redirects it, allowing it to return to the tank.
  
• Simple Design: Open-center systems are often simpler in design compared to closed-center systems, which require more complex valving and pressure regulation.
  

2. Daisy Chain (Series) Connection: How It Works
The daisy chain or series connection refers to the way multiple hydraulic valves are connected to each other in sequence. In this setup, the hydraulic fluid flows through one valve, then moves to the next, and so on. This configuration is commonly used in systems where multiple actuators need to be controlled, and each valve needs to direct fluid to different parts of the system.
Advantages of Daisy Chain Connections

• Cost-Effective: Daisy chaining valves is often more economical, as it requires fewer components compared to more complex parallel configurations.
  
• Simplicity: For simple applications where only one function needs to be operated at a time, daisy chaining is a straightforward approach that is easy to implement and maintain.
  
• Space Efficiency: Since the valves are connected in series, this method can help save space in the design of the hydraulic system.
  

Challenges of Daisy Chain Connections

• Flow Restriction: Because the hydraulic fluid flows from one valve to the next, there can be a buildup of resistance in the system, especially if there are several valves. This could lead to reduced efficiency or slower response times, particularly in systems with high flow demands.
  
• Control Limitation: In a daisy chain setup, if one valve malfunctions or is not properly adjusted, it can impact the flow to the other valves in the series, leading to operational issues across the system.
  
• Complexity in Troubleshooting: Diagnosing issues in a daisy chain system can be more challenging since the failure of one valve can affect the entire system.
  

3. Parallel Connections: An Alternative Approach
In contrast to daisy chain connections, a parallel connection involves each valve receiving a direct supply of hydraulic fluid from the pump. In this configuration, each valve operates independently, and the hydraulic fluid is split into different paths, allowing multiple valves to function simultaneously.
Advantages of Parallel Connections

• Independent Operation: Each valve operates independently, meaning that a failure in one valve does not necessarily affect the others. This is particularly useful in systems requiring precise control over multiple functions.
  
• Improved Flow Control: Since each valve receives its own supply of hydraulic fluid, there is less chance of flow restrictions, and each valve can operate at optimal efficiency.
  
• Simultaneous Functionality: Parallel connections allow for the operation of multiple functions at once, improving overall productivity in complex hydraulic systems.
  

Challenges of Parallel Connections

• Complexity and Cost: Parallel connections tend to be more complex and may require additional components like flow dividers, check valves, or more piping, which can increase the overall cost and maintenance requirements.
  
• Space Requirements: Because each valve needs a separate line for hydraulic fluid, the overall space requirement for a parallel configuration can be higher than that of a daisy chain setup.
  

4. Factors to Consider When Choosing Between Daisy Chain and Parallel Connections
Several factors influence the decision between using a daisy chain or parallel connection in open-center hydraulic systems:
System Complexity
If your system is simple and requires only sequential operation of valves, then a daisy chain setup might be ideal. However, if you need more control over multiple actuators or functions at the same time, a parallel connection would be more suitable.
Flow Requirements
For systems that require high flow rates or rapid actuation, a parallel connection will generally be more effective since it ensures that each valve operates with adequate flow. Daisy chain connections, due to the series setup, may create flow restrictions that can limit performance.
Cost and Maintenance
Daisy chain connections tend to be more affordable and easier to maintain, especially in less complex systems. Parallel systems, on the other hand, require more components and can be more expensive to set up and maintain. However, if system reliability and performance are paramount, the additional cost of a parallel connection may be justified.
Space Constraints
In situations where space is limited, daisy chain connections can offer a more compact solution, as they require fewer hoses and components. Parallel connections may need more space due to the extra hydraulic lines required for each valve.
5. Practical Applications of Daisy Chain and Parallel Connections
Both daisy chain and parallel hydraulic valve configurations are used in real-world applications, depending on the needs of the specific machine or equipment.
Daisy Chain Applications

• Agricultural Equipment: Simple farming machinery, such as tractors and small excavators, often use daisy chain configurations due to their simplicity and cost-effectiveness. For example, a single actuator may be enough to perform multiple tasks, such as raising a plow and adjusting the height of the tractor’s rear implement.
  
• Construction Equipment: In certain light-duty construction machines, like compact track loaders or mini-excavators, daisy chain configurations are used when sequential valve operation is sufficient.
  

Parallel Applications

• Heavy Machinery: Large earthmoving equipment, such as bulldozers, backhoes, and excavators, often use parallel connections because they require the ability to operate multiple hydraulic functions simultaneously. For example, an excavator might need to control the boom, arm, and bucket at the same time with minimal loss of hydraulic efficiency.
  
• Mobile Equipment: Equipment like cranes, which need to control various movements simultaneously with precise hydraulic flow, often uses parallel systems to maintain independent control over different hydraulic circuits.
  

6. Conclusion
The decision between a daisy chain (series) or parallel connection in open-center hydraulic systems depends on the complexity, flow demands, cost considerations, and space constraints of the specific application. While daisy chain connections are ideal for simpler systems where sequential control is required, parallel connections are better suited for systems that require simultaneous operation of multiple functions with independent control.
By understanding the advantages and limitations of both setups, equipment operators and maintenance personnel can make informed decisions that optimize the performance, efficiency, and reliability of their hydraulic systems.