Valve Terminals vs Manifolds: Key Differences Engineers Must Know

A valve terminal is an evolution of the valve manifold. Valve manifolds are still used in modern industrial applications, but the purpose has shifted from being a control center to becoming a reliable fluid distribution device for high-volume flow and mechanical isolation. In comparison, valve terminals are control devices that have evolved from analog to digital. By integrating onboard electronics with mechanical manifolds, valve terminals optimize system footprint, provide energy efficiency, and reduce lifecycle cost.

This article will explore the key differences between the two essential components of any pneumatic network. It will provide key insights valuable for professional engineers. By the end, you will have a clear idea of where and when to use valve terminals and manifolds, respectively, in your application.

What Are Valve Terminals in Pneumatic Systems?

Definition

Valve terminals are a centralized controlling hub that allows or blocks the flow of fluid. It does that by providing the desired rate to its ports using digital signals from a computation device. They are the backbone of modern industrial pneumatic systems. 

Parts of Valve Terminal

• Fieldbus Interface: Converts network information to valve commands.

• Electrical Connection Block: Entry point for power and communication cables.

• On-board Controller: For standalone control, some valve terminals feature PLCs.

• Multi-pin Connection: Alternate connection to the fieldbus.

• Manifold Block: Mechanical foundation housing all the ports and channels.

• Solenoid Valves: electromagnetic devices that direct the flow of air.

• Pilot Air Supply: Assists the solenoid in case of very high or low pressure downstream.

• Manual Overrides: Mechanical button/switch to trigger loss of power.

• Sensors: Instrumentations to monitor pressure, flow rates, and vacuum levels.

• Exhaust Ports: Venting points are usually fitted with silencers to reduce the noise. 

• LED Status Indicators: Diagnostic lights showing power, communication, and actuation.

• Blanking Plates: Covers for unused valve positions.

Types of Valve Terminals

Valve terminals come in different shapes, features, and control configurations. We can divide them into three main categories:

• By Communication: Multipole, Fieldbus, IO-Link, and Integrated Control

• By Physical Configuration: Modular and Compact

• By Functionality: 5/2, 3/2, and 5/3 way or mixed

What Is a Manifold in Pneumatic Systems?

Definition

It is a valve interface and a mechanical device that routes air or fluid through its metal housing. There are internal passages machined into the manifold. It can handle 6,000 psig of pressure and is cherished for their space saving design in comparison to a tubing network.

Parts of the Valve Manifold

• Manifold Block: It is the metal block that contains the fluid distribution network.

• Common Inlet Port: Entry point for compressed air or fluid supply.

• Work Ports: Points for connection of actuators and cylinders.

• Exhaust Ports: Outlets that vent the spent air or fluid back to the reservoir or atmosphere.

• Individual Valve Mounting Faces: Standalone valve mounting location.

• Internal Galleries: Tunnels inside the manifold block to route fluid.

• Tie Rods or Assembly Bolts: A stressed rod that keeps the manifold slices together.

• End Plates: Metal caps that seal the end of internal galleries.

• Seals and O-rings: Elastomeric rings that keep the high pressure air from leaking.

• Mounting Holes: Points for securing manifolds to a frame.

Types of Valve Manifold

The types of valve manifolds are based on the number of valves they can support. Let's examine each type:

• 2-Valve: Used for basic blocking and bleeding fluid for the system.

• 3-Valve: Two valves are used for blocking, and one for equalization. These are ideal for differential pressure application to protect against one-sided overpressurization during startup.

• 5-Valve: For comprehensive setups that include venting valves for calibration or maintenance activities.

How Do Valve Terminals and Manifolds Work?

To understand how a valve terminal and manifold work, we need to understand how they collectively play a role in pneumatic systems. We can divide the whole working mechanism of these components into two main parts: the electronic control portion and the pneumatic execution portion.

Electronic Control Layer

The control center of the valve terminal receives signals from a PLC using a communication protocol, which can be Profinet or EtherNet/IP. What happens is that a single cable carries these multiplexed signals from a computational device and brings them to the valve terminal. An Ethernet port on the valve terminal receives the signal and activates the internal bus to open or close a solenoid valve. The energization of the solenoid valve allows pilot air to pass through to move large internal spools, starting the high pressure air flow.

Pneumatic Execution Layer

Once the electromagnetic device lifts the spool via pilot air, the physical components ensure that the air reaches the designated point. The pneumatic manifold sub-base distributes the high pressure air safely. It routes the compressed air from the common inlet through internal galleries to the designated outlet ports.

It can have 2/2, 3/2, 5/2, or any other spool configurations. The manifold ensures that the air is delivered at the required volume and pressure to the actuator. Finally, the air leaves the manifold and enters the actuator, which can be a pneumatic valve, robotic arm, or cylinder. For the next cycle, the manifold also has an exhaust cycle with integrated silencers to make the system ready for the next cycle.

Core Functional Differences Between Valve Terminals and Manifolds

To understand the core functional difference, we can put their specifications/features head to head for comparison in a tabular form:

Key Advantages of Valve Terminals and Pneumatic Manifolds

Valve Terminals

• Simple Setup: Instead of running individual compressed air supply tubing or power wires for every single valve, these terminals group them. It reduces wiring and physical space requirements.

• Smaller Footprint: Instead of installing them side to side on a DIN rail. Modern valve terminals are designed for serial stacking. It allows high I/O density in a compact space.

• Speed and Energy Efficiency: Putting the valve terminal directly near the physical actuator reduces the purging requirement time, boosting machine cycle speed by 30% and cutting wasted energy by 50%.

• Smart Diagnostics: Modern valve terminals come with a diagnostics tool indicating which valve has a broken wire or pressure drop. These reduce troubleshooting and maintenance time.

• Environmental Versatility: With features such as rugged IP67 rating and hyper-sanitized VDI 2083 for clean-room semiconductor manufacturing, valve terminals are highly adaptable.

Pneumatic Manifolds

• Leak Prevention and Compliance: Using piping to provide a pathway to fluid leads to more connections and a higher chance of leakage. Manifolds reduce the number of connections. This is crucial for meeting strict environmental emission standards, like API 624.

• Self Cleaning: The lines leading to instruments can clog. These manifolds have integral purge blocks with filters that clean the lines to ensure proper flow.

• Calibration: The biggest advantage of the valve manifold is to use the 2, 3, or 5-valve setups for isolating an instrument, bleeding the trapped pressure, and calibrating the gauge without shutting down the main process line.

• Extreme Conditions: These use graphite seals, which allow them to operate at continuous temperatures of up to 1000 C.

When to Specify Valve Terminals Instead of Manifolds

To fully understand when to invest in a valve terminal instead of a manifold, we need to dive deep into the system requirements that necessitate its use. Here are the usage scenarios:

When the Application Demands Speed and Intelligence

If your system requires rapid movements and quick position changes like a robotic arm gripping, rotating, and releasing, then the valve terminal is the way to go. The installation of valve terminals near the actuators ensures shorter tube length, essentially reducing the cycle time and improving response time. A sophisticated machine like a robot may have tons of sensors and limit switches. Valve terminals collect the data and send it back to the main computer using a single cable. It eliminates the need to route hundreds of wires.

When the System Needs to Adapt and Survive

For future proofing, modular valve terminals are ideal. In case you are going to add more valves every year or month. You can simply snap new valve slices onto the existing block. Valve terminals also come with internal diagnostics that alert the operators to pressure drops, indicating leakages. Moreover, they are robust enough to survive in wet and dusty conditions without failure.

Conclusion

We can conclude that valve terminals are dynamic devices and suitable for an automated pneumatic system. Manifolds are static devices that are robust due to their static nature, but lack the integration of electronics. Both of them are used for routing high pressure compressed air to downstream devices. Valve terminals are for controls, whereas manifolds are for high-volume fluid distribution and precise mechanical isolation. As a professional engineer, evaluate the scalability, lifecycle costs, and communication protocols. Analyze your system requirements and opt for either of the options.

Get High-Quality Valve Terminals and Manifolds from Titan Automation

If you pick valve terminals for your setup, then consider Titan Automation as your supplier. Based in Ningbo, China, Titan Automation has over 26 years of OEM experience in industrial automation. They offer modular valve terminals with IO-Link and fieldbus options. Explore their comprehensive product line-up and customized solutions to enhance your pneumatic systems.

Visit Titan Automation at https://www.titan-automation.com/valve-terminal.html.

FAQs

Q1: What is the main difference in application between valve terminals and manifolds?

Valve terminals are dynamic devices that are ideal for compressed air supply automation. In comparison, manifolds are static, robust compressed air distribution devices that offer isolation and calibration options for instruments in process measurement.

Q2: Can valve terminals handle different valve types in one unit?

Yes, they support mixed 3/2-way, 5/2-way, and 5/3-way valves for versatile functions like single- or double-acting cylinder control. For advanced fail safe features, 5/3 way provides locking in a mid-position.

Q3: How do manifolds reduce installation costs?

Manifolds are static mechanical devices that provide the distribution of fluid with safety. It integrates valves into a single block. The result is a reduction in piping and connections. Both labor and material expenses are reduced by up to 50%.