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Monobloc piping has manifold advantages
Fluidic manifolds have established themselves as the preferred solution among many machine users, yet some design engineers are still unclear about switching over from conventional pipe and tubing. Phil Burnside of Parker Hannifin's KV Division offers this overview.
A manifold is a mono-bloc unit onto which a number of valves are mounted; internal passages connect the valves in a manner bespoke to the individual application. In contrast a 'manifold module' supports a single valve and can be interconnected with a number of other modules to provide a multi-valve platform. These are often referred to as valve islands in the UK. It is useful to maintain this distinction.
In operation a valve island does a very similar job to a manifold, but the critical difference is that a manifold can be installed or reinstalled by almost anyone, whereas a valve island requires the skills of a specialist. Differences in cost of ownership and serviceability can be significant.
There are two basic ways of making a manifold: cross drilling and laminar machining. If the manifold design is simple, it can be produced by cross drilling a slab of material (typically aluminium, steel or engineering plastic). For more complex manifolds a laminating process is required: the air passages are milled onto one side of the plate and valve mounting drilled from the other side. A cover is added to the milled surface, which has to be welded, glued or sealed to create an air tight network of passages. Most laminar manifolds will also require some cross drilling, while complicated manifolds can be created in two, three or more layers.
Flow rate and pressure
With both production methods the internal passages can be shaped, contoured and sized to accommodate virtually any flow rate and pressure. Similarly, careful routing that avoids multiple or sharp turns will mean pressure drop is practically non-existent. The overall size and shape of a manifold is often defined by the space into which it must fit. Manifolds offer the machine designer many advantages and even more to the machine builder, but their real strength is in use. For the designer, a manifold makes the control engineering element of a job a single discrete task. Most manifold-based systems will take up far less space (30-60%). They will require only one FRL (filter-regulator-lubricator) and far fewer ancillary parts. As a result build and assembly costs will be far lower than for discrete pipe and tubing solution - half the price is not atypical.
For the machine builder, the cost savings can be significant. A single part has to be mounted, as opposed to fitting any number of pipe, connections, fittings and ancillaries, any of which could be wrongly placed, could leak, could fail. A skilled and patient fitter would be required for what could be quite a long period of time. The reduction in build cost will be significant and welcome to all.
But perhaps the greatest advantages are for the users, as the cost of ownership plummets compared to discretely piped systems. A manifold is hugely robust; in fact they are unlikely to ever go wrong. They can be fitted, removed, serviced, and replaced in moments. They cannot be tampered with or 'adjusted'.
Manifold solutions are regularly adopted in a wide spectrum of applications, from the mundane to the exotic. They can be used to reduce build or operating costs, to simplify design and/or maintenance, replace delicate valves with a robust solution suitable for deployment to remote areas, or many other reasons.
On a recent job completed by Parker KV, for example, when a railway coach builder wanted to upgrade the pneumatic door actuation system, the new control system had to fit into a very tight space. A manifold design helped with this and also produced a robust drop-in module that could be replaced rapidly to speed the regular service procedure.
In anaesthesia there is a need to switch from nitrous oxide to Air. The valve has to provide positive indication that the changeover has been successful and while electronically driven, a simple manual over ride was also required. A manifold design met all the design criteria, while enhancing reliability and serviceability.
Neonatal ventilators need to fulfil many roles. Complicated and sensitive machines, they have to be quiet, reliable, and robust as well as be small and light enough to be moved around easily. Their design is constantly evolving, but manifold fluidics is always at the heart of the machine.
It is worth considering a manifold solution from as few as three or four valves, certainly of there is to be a serial production run, if the deployment is to be in a harsh or demanding environment, where servicing is a major consideration. In short manifolds should be at least considered for nearly every fluidic job.
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