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Critical factors when selecting fieldbus valve manifolds

Pneumatic fieldbus valve manifolds have a number of advantages over traditional hardwired solutions and the latest designs offer substantial improvements in the area of application, performance, and maintenance. In this article we look at five of the critical factors that must be considered before selecting pneumatic fieldbus valve manifolds.

In today’s highly automated machines, fieldbus valve manifolds are replacing conventional hardwired solutions. They more easily perform vital functions by integrating communication interfaces to pneumatic valve manifolds with input/output (I/O) capabilities. This allows programmable logic controllers (PLCs) to more efficiently turn valves on and off and to channel I/O data from sensors, lights, relays, individual valves, or other I/O devices via various industrial networks. The resulting integrated control packages can also be optimised to allow diagnostic benefits not previously available.

However, there are five critical factors that must be considered before selecting pneumatic fieldbus valve manifolds.

1. Commissioning: save time by removing DIP switches

Following installation, fieldbus manifolds must be tested and commissioned. When many connections are involved, time and costs quickly add up and users need to look for opportunities to reduce these costs. For example, some manufacturers now offer SPEEDCON M12 connectors, which need only a half-turn to gain a secure connection, reducing commissioning costs. Buyers should also look for well-spaced I/O layouts as these minimise the time needed to connect all necessary cables.

While connections are tedious, configuration can be worse with the prime reason being the dreaded DIP switch. Manipulating these tiny switches is an exercise in frustration. The user must constantly consult cryptic instructions in unfriendly user manuals to identify each switch’s function and settings. Visual feedback is limited to subtle positioning of the switch itself.

A recent innovation is the introduction of pneumatic fieldbus valve manifolds that actually embed a small graphic display on each module. This offers plain-language messaging that clearly identifies network addresses, baud rates, and other parametric data. Pushbuttons enable navigation through intuitive menus and users receive instant visual feedback of set values with error proof selections. This simple system represents a revolution in pneumatic fieldbus manifold interfaces, enabling control engineers to simplify and greatly speed up complex operations.

2. Distribution: flexibility enables savings

Historically, conventional pneumatic fieldbus valve manifolds with integrated I/O modules have been designed within a relatively rigid architecture.

Dedicated fieldbus I/O modules would handle either valves or I/O — one or the other, but not both. So the OEM engineer would specify different modules for each task. He or she would also install multiple dedicated communication nodes on the machine’s industrial network – each having high hardware and associated commissioning expenses.

However, newer designs offer more flexible, significantly more cost-effective architectures. These provide fieldbus nodes that can handle valves and I/O as well as the mutual distribution of I/O and valve manifold functionality around a given machine. Therefore, this allows a large number of I/O distribution options that optimise the physical layout of the machine while using only a few basic multifunctional modules.

Optimising distribution lets the user lower network hardware investment, save time, and decrease the number of nodes on the network – thus optimising network traffic and enhancing topology opportunities for network and power distribution.

These new systems take advantage of sub-bus technology that allows the same modules that traditionally were part of a centralised manifold to be detached and used in a distributed architecture. Perhaps more importantly, on industrial Ethernet applications, this architecture enables a reduction in the number of Ethernet switches and communication nodes. This directly decreases overall cost and system complexity.

For instance, a conventional design might require the use of four pneumatic fieldbus valve manifolds arranged with four EtherNet/IP network nodes. Instead, users should look for a system that allows optimal distribution. The user specifies only one main EtherNet/IP pneumatic fieldbus valve manifold, along with three sub-bus manifolds. Each sub-bus module is a lower cost than an EtherNet/IP module, and requires no costly commissioning.
In this example, the costs could be as much as 22% below those for a system requiring four conventional EtherNet/IP fieldbus manifolds.

Thus, new distribution designs offer the potential for substantial reductions in the combined costs of hardware, commissioning, and inventory. They can also accommodate and optimise various machine topology and application requirements.

3. Modularity: allows easy assembly

Traditional fieldbus valve manifolds suffer from a fairly low degree of modularity. This presents challenges for OEMs and end users alike.

For instance, testing or usage may indicate that a particular I/O module is malfunctioning, or a late change order during assembly may require making an alteration. Conventional non-modular designs force the user to dismantle the entire assembly to get access, dismount the offending module, replace it, and then reassemble the whole fieldbus manifold or system.

By contrast, some new fieldbus manifold systems offer modular designs that simply connect together via easily removable clips and screws. This allows easy assembly and effortless last-minute changes for OEMs.

In another example, a user may wish to move the valve modules closer to the valves or cylinders they will be operating. With the new modular designs, the user simply unclips the module from the main pneumatic fieldbus valve manifold and positions it on the machine within reach of the user point and connects it back to the main I/O module via a sub-bus cable. All without disrupting the I/O mapping.

For the end user, modularity permits quick, trouble-free field changes. I/O modules can be removed and replaced without forcing the user to dismantle the entire pneumatic fieldbus valve manifold system. Further flexibility is provided by allowing the same module to be used in either centralised or distributed applications, reducing inventory requirements.

4. Diagnostics: easy to use graphic displays replace LED’s

If something should go wrong with the network or with a pneumatic fieldbus valve manifold on the plant floor, diagnostic indicators play a key role in locating the problem and identifying its cause to get the machine up and running quickly. Unfortunately, conventional pneumatic fieldbus manifold designs have given diagnostics little consideration. Today, most fieldbus manifolds allow diagnostic data to be signalled to a human/machine interface (HMI), often located in a control room some distance from the machine or on a different part of the machine, away from the problem area. Moreover, this option requires programming at setup, and is considered too expensive by many users.

Another option allows the pneumatic fieldbus valve manifold to interface with a proprietary handheld HMI device. Simply plug this unit into a manifold module, interact via pushbuttons, and read diagnostic data off a small screen. But this optional handheld represents an extra expense over the manifold cost. It takes training to utilise properly. And when needed most, the handheld always seems to be hidden away.

Finally, most fieldbus manifold designs offer diagnostic LEDs on the manifold system itself, right at the point of use. Unfortunately, this may be the worst choice of all. Many users carry painful memories of consulting cryptic instruction manuals while peering past tangled coils of cables and connectors at small LEDs.

Fortunately, new designs offer more functional alternatives. Most innovative is the module integrated graphic display with plain-language messaging mentioned earlier. It provides users and OEMs with a wealth of point-of-use status and diagnostic information, plus set-up and version tracking data at both the I/O-module and communication-node levels.

This arrangement places visual status and alarm indication away from tangled cables, in a clearly visible display area at one end of each module. It involves no programming or extra cost, and takes no training to use. Error messages are generated and cleared automatically, and blink to draw the viewer’s eye immediately to the problem module. The display’s associated pushbuttons allow the user to navigate quickly through intuitive menus for easy and effective troubleshooting. Some systems even log errors for future or remote analysis.

5. Recovery: automatic and transparent

A final topic closely related to diagnostics is recovery. In a conventional pneumatic fieldbus valve manifold, this is usually difficult and time-consuming. Once the user has finally isolated a fault to a particular module, he or she must then disassemble the entire system, remove the old part, and then start consulting manuals and determining DIP switch settings to enable the replacement part to operate properly. In effect, the new part must be commissioned from scratch, reloading all configuration settings. Once these have been finally set and rechecked, the new module can then be replaced and the fieldbus manifold system reassembled. Again, this is not a process for an untrained user and it virtually guarantees substantial machine downtime.

The latest advancements in fieldbus valve manifold designs provide a much better solution by including an auto-recovery module option. During a critical failure, this module stores and protects all commissioning and configuration parameters. When a new communication or I/O module has been clipped into place, this device recognises it as a replacement unit and reloads all settings, configuration parameters, and other pertinent information into it. The technology works automatically and transparently, without user interaction.

Innovation provides new solutions

Choosing the best pneumatic fieldbus valve manifold for a given automated machine application presents several challenges. Of special concern are the problems that many conventional pneumatic fieldbus valve manifolds exhibit in the areas of commissioning, distribution, modularity, diagnostics, and recovery. Control engineers, specifiers and buyers should consider newly available designs that apply proven technology in innovatively simple ways to resolve these problems. Users report that these solutions are delivering greater cost efficiency and wider application opportunities, while considerably improving commissioning, use, and maintenance.

Many of these improvements are combined in models such as G3 fieldbus valve manifold from ASCO Numatics.

The modular ASCO Numatics G3 valve island with graphic display is easy to assemble, install, commission and maintain.

For example the ASCO Numatics G3 valve island is an electronics platform for fieldbus applications and helps address commissioning and diagnostic concerns by banishing the dreaded DIP switch and the equally ineffective status LED. Instead, these systems integrate a plain-language graphic display on every module, with accessible pushbuttons and intuitive menus for easy configuration, status checking, and point-of-use diagnostics.

ASCO Numatics UK
West Pimbo, Lancashire
Kan gecontacteerd worden op:
Tel: + 44 (0) 1695 713600
Fax: + 44 (0) 1695 713633
E-mail: [Email protected]
Web: www.asconumatics.eu

ASCO Numatics UK

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