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Phil Burnside of Parker Hannifin’s KV division provides an overview of fluidic manifolds and advises design engineers on switching over from conventional pipe and tubing.

The first thing to decide, he said, is what actually constitutes a manifold, as there seems to be some confusion.

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.

In operation, a valve island does a similar job to a manifold, but the main difference is that a manifold can be installed or reinstalled by almost anyone, whereas a valve island requires the skills of a specialist.

The differences in serviceability and cost of ownership can be significant.

Manifolds are regularly used in pneumatic applications and in low-pressure mixed-media projects, such as medical gas supply.

They are also used in hydraulics and, while the principles are the same for high- and low-pressure design, they are, in real terms, separate disciplines.

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.

In fact, most laminar manifolds will also require some cross drilling, while very complicated manifolds can be created in two, three or more layers.

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.

A manifold makes the control engineer element of the designer’s job a single discrete task.

Most manifold-based systems will take up far less space (30-60 per cent) – an increasingly important consideration in most projects.

They will require only one filter-regulator-lubricator (FRL) and far fewer ancillary parts.

As a result, build and assembly costs will be lower than for a discrete pipe and tubing solution – it is difficult to put a figure on this as it will vary from job to job, but 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 pipes, connections, fittings and ancillaries, any of which could be wrongly placed or could leak or fail.

A skilled fitter would be required for what could be quite a long period of time.

The reduction in build cost will be significant.

However, perhaps the greatest advantages are for the users, as the cost of ownership plummets compared with discretely piped systems.

A manifold is said to be robust; in fact, according to Burnside, it is unlikely to ever go wrong.

It can be fitted, removed, serviced and replaced in moments.

A manifold cannot be tampered with or ‘adjusted’.

Manifold solutions are regularly adopted in a variety of applications, from the mundane to the exotic.

They can be used to reduce build or operating costs and, consequently, to simplify design and/or maintenance.

They can replace delicate valves with a robust solution suitable for deployment to remote areas.

On a recent job completed by Parker KV, for example, an instrument was developed for accurately analysing the content of cigarette smoke – something that is subject to rigorous guidelines.

Relatively complex circuitry was required to direct measures of smoke to different particle counters and other test heads.

However, as many of the instruments were destined for export to areas where service would be difficult, a simple and compact yet physically robust design was required.

This was achieved using a manifold instead of discrete valves; in this case, the manifold also acts a structural part of the instrument, which enhances simplicity and reliability.

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 drop-in module that could be replaced rapidly to speed up the regular service procedure.

A supercritical railway application involved the emergency brake system.

As well as applying the brakes, the system had to operate many ancillary functions, such as a horn, whistles and the internal and external doors.

The system is activated automatically if the train passes a red light.

By using a manifold, the system is highly reliable and indestructible, said Burnside.

In anaesthesia, he added, there is a need to switch from nitrous oxide to air.

The valve has to provide a positive indication that the changeover has been successful and, while electronically driven, a simple manual override is also required.

In a recent application of this type, 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 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.

Manifolds are the de-facto solution in many other fields, such as road tankers, axle lift systems, milking machines and other agricultural equipment, for gas analysers and machinery used in offshore and marine environments.

It is worth considering a manifold solution from as few as three or four valves, certainly if there is to be a serial production run or if the deployment is to be in a harsh or demanding environment, where servicing is a major consideration.

In short, manifolds should be considered for nearly every fluidic job.

Parker Hannifin — Parker Sales UK

With annual sales exceeding $10bn, Parker Hannifin is the world's leading manufacturer of motion and control technologies and systems, providing precision-engineered solutions for a wide variety of commercial, mobile, industrial and aerospace markets.

To meet its customers' needs in motion and control, Parker provides the broadest range of products available from any single supplier. This is supported by expertise in nine major technologies:

  • Hydraulics
  • Pneumatics
  • Electromechanical
  • Filtration
  • Process control
  • Fluid and gas handling
  • Sealing and shielding
  • Climate control
  • Aerospace

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