Feeling the pressure

Louise Smyth

Innovation in pressure regulation from Oxford spin-out business

Opening, closing, dosing, mixing and distribution are all procedures essential to the process engineering sector.

Integral to all these processes is proper pressure regulation. And the powerhouse behind all these applications is the trusty valve.

The right valve can improve efficiency, safety and profitability. The wrong valve does quite the opposite.

There are a great many different pressure control valves on the market for the process engineering sector but they are not without their faults.

Central to many of the issues is the diaphragm, which is essential to the function of a traditional valve.

In a typical regulator, the diaphragm will constantly modulate with the changing pressure, and therefore needs to be flexible to provide accurate control.

However, it is this very flexibility, normally provided by a limited range of elastomers, which leads to the fatigue, erosion or embrittlement that most frequently signals the end of the life of the typical regulator model.

A new solution

It is the limitations of the diaphragm-controlled regulator that led to the creation of the Oxford Flow model of pressure regulation.

The device was invented when Tom Povey, a professor at Oxford University and now the technical director of Oxford Flow, was conducting R&D into various applications such as gas turbines, jet engines and scramjets in partnership with a leading manufacturer.

To carry out his research he required PRVs that were able to withstand the very high pressures seen in the aviation industry. Unfortunately, finding such a device proved difficult. Not even the best pressure regulators on the market were capable of handling the very high pressures and flows that the tests he was carrying out required.

Not prepared to let his research be limited by the issue, Professor Povey did what any engineer worth their salt would do and set about solving the problem himself. The result was the highly innovative Oxford Flow regulator, which makes the complex and failure-prone diaphragm arrangements found in other regulator designs redundant.

In Povey’s model, the diaphragm is replaced by a direct sensing piston actuator, which not only greatly simplifies the design of the regulator but also removes the main reason cause of failure.

In contrast, Oxford Flow’s portfolio of regulator designs uses a patented balanced sensing piston. One side of the piston is exposed to downstream pipeline pressure while the other side is balanced against a pressure cavity controlled by a pilot regulator. The sleeved piston actuator operates over an optimised feed-hole configuration to provide precise, stable control across the entire operating range. During operation, the piston moves inward, reducing the size of the cavity when the downstream pipeline pressure exceeds that within the pressure cavity set by the pilot regulator.

The movement of the piston actuator progressively covers the feed holes; reducing the flow rate to maintain a stable downstream pressure. When demand increases, the downstream pressure falls below that set by the pilot and the reverse operation occurs; the cavity expands, as the pilot feeds it, uncovering the feed holes, which increases flow and maintains a stable downstream pressure.

Extensive testing against current market-leading regulators at Oxford University’s Osney Thermo-fluids Laboratory proved that the device could match and more often out-perform the other models being used in industry. 

Spin-out business

The now patented flow regulator is being produced and marketed by Oxford Flow, a technology business originating from the University of Oxford and supported financially by Oxford Sciences Innovation (OSI), a new £320m fund created to support ambitious Oxford technology companies and backed by names such as Google and the Wellcome Trust.

The business has now created several models for different industries: the IHF series for gas, the IP series for water, the IM series for gas or liquid and the IHP series wafer type high-pressure regulator for all gases.

Oxford Flow’s technology offers a number of different benefits when compared to conventionally designed valves. For example, the Oxford PRVs weigh considerably less than other models on the market. A 4in IHF Series weighs 10kg, whereas 2in valves from leading competitors can weigh as much as 60kg.

This means fewer technicians are required for installation and reduces the need for heavy lifting equipment. It also confers considerable health and safety benefits – the lower the weight, the smaller the risk of injury when installing or performing maintenance.

And indeed, maintenance needs to happen much less often. Because of the piston-led design and the fact that the model only has one moving part, these devices are much less prone to failure and can generally stay in service for longer than conventional diaphragm-operated PRVs on the market.

Extensive testing has also revealed that new regulators offer various performance benefits, including reduced hunting, minimised flow turbulence and reduced minimum pressure head-drop.  With noise pollution a considerable health and safety issue in so many process engineering settings, the fact that it is also far less noisy than comparable devices is a major benefit.

Another benefit comes from the structure of the valve itself. Traditional regulators also tend to have complex flow paths, with a lot of ‘dead space’ where errant matter from fluids can stray and many moving parts, both of which increase the potential for failure. With just one moving part and an axial flow mechanism, the new valves offer obvious advantages in this regard.

In addition, the simple design lends itself to use of specialist hardened materials if particular resistance is required for specialist applications, such as the use of corrosive materials in chemicals manufacturing.

The device is currently undergoing testing with a number of major utilities companies, including Anglian and Morrison and the business is also working on bespoke solutions for a number of clients. 

Discussing how the device might be used in the process engineering sector, Steve Busby at Oxford Flow says: “Imprecise control of gas and liquids can have a negative impact on various industrial processes, leading to system malfunction and downtime that businesses can ill-afford.

“Valves are undoubtedly a ‘pressure point’ for failure in process engineering, so selecting the right one is essential. Oxford Flow has developed an entirely innovative design from first principles and using all of the mathematical, computational and design technologies available in the 21st century. We believe our devices are an improvement over traditional regulators in virtually all areas, offering considerably improved performance over a much longer life span, while still staying competitive – three qualities that all businesses in the process industry are looking for.”

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