Pump shock

A pump that has no moving parts and will not be blocked – a pipe dream? That’s exactly what it is. Roger Brownlie reports on a highly innovative pump design based on an open bore tube.

Over 45% of all fuel burnt by US manufacturers is consumed to raise steam, says the Office of Industrial Technologies at the US Department of Energy.

‘We all thought we’d come out of the steam age. Well that’s proof that we haven’t,’ says John Heathcote CEO of Pursuit Dynamics which has developed the PDX pump system for the process industries.

The pump has no moving parts, no impellers, and the fluid moves through an open bore eliminating maintenance and even the possibility of blockage. Steam exits the tube from the top then enters the fluid flow via a nozzle at a complimentary angle and immediately condenses.

Mike Todman, the chief technical officer, explains its operation: ‘Steam comes out and accelerates through the nozzle and enters the actual flow of liquid. This creates a sudden reduced pressure that will draw in anything you wish into this highly energetic region, so you finish up with mixing, heating and entrainment, as well as a pump. When steam condenses it is 1600th of its previous volume. On reaching the flow, it condenses almost instantaneously which gives you a huge pressure drop, but the pressure drop happens in all directions with no net thrust. The trick is in how you make it directional.’

Unfortunately for Design Engineering magazine the exact angle and geometry of the steam nozzle inlet is the company’s trade secret. What can be ascertained is the continual collapse and condensation of steam forms a standing shockwave.

The secret is how the steam collapses to create a one way flow system.’As steam reaches the end of the nozzle,’ explains Mike, ‘it is travelling over twice the speed of sound. On entering the flow it sends shock waves into the fluid to form a shock zone. As you increase the steam flow that zone grows to form a doughnut shape. Inside the zone you have a mix of steam and water at an almost molecular level moving at an incredibly high velocity.’

Inside the shockwave it is only about 65% vacuum so anything in the flow is stretched by the velocity change and is then faced with a massive pressure drop. Any sort of soft substance just explodes.

‘We can send through fabric straps with metal hooks, latex gloves and rags. Things like eggs, tomatoes, and sausages just get pulverised. Eggbox material just comes out a fine mush at the other side.’

From a phenomena discovered in 1997, but not fully explored by its original owners, Pursuit Dynamics acquired the IP and refined the technology to a level today where it can be licensed to manufacturers.

‘The manufacture behind this is very simple, the physics and engineering behind it are staggeringly complex, says John Heathcote. ‘We’ve had some of the leaders in various fields tying their brains in knots over this for a couple of years.’

Typically a 47mm bore PDX mounted in a 30 metre pipe system has demonstrated a flow capacity of 45,000 litres per hour.

‘The supersonic shockwave really is one of the core bits of this system,’ says John Heathcote. ‘It effectively acts as a one way valve. We know how to get around the issue of cavitation. Obviously you have imploding steam, and you might think ‘wow’ what a terrible thought, but actually it’s not a problem. It’s going to be as robust as the material you make it out of.

‘What our system does better than anything else is handle solids and slurries. Where you need the application of mixing, heating, maceration, entrainment, we can do that too. A good sand pump can handle 4-6% sand by volume. We can handle up to 30% by volume.’

Most process plants have their own steam source on site and those that don’t usually have a heat source that can be utilised fairly readily. But what about the processes where water contamination is not allowed?

‘For any application where you cannot have steam contamination – PDX is not suitable,’ explains Heathcote. ‘Also there are several applications where you don’t want the shear problems associated with this system. And if you want smooth laminar flow – we’re not going to achieve that’

With such a simple design geometry and such a massive potential market there is much to protect in terms of IP and patents. Because it’s quite a definable phenomena, Pursuit Dynamics works closely with patent attorneys to protect the design. It currently has 19 patents surrounding the technology.

‘We use patent agents all round the world, says Heathcote. We have a huge IP protection budget and we carry out insurance. So we give it our best shot, and like anything else in life, you put yourself in as strong a position as possible, and if someone steps out of line, just be prepared to give them a bloody nose!’