Rotary lobe technology is space-saver

Paul Boughton

Rotary lobe technology is space-saver

Erwin Weber explores the latest advances in pumps that are designed for high volumes in a limited space.

Erwin Weber

Page 82

Demand for crude oil and natural gas is increasing, even in the face of efforts to promote renewable energies. With that demand comes rising prices and interest in opening up new sources, including unconventional ones. Sources currently being investigated include methane from coal seams and highly viscous oil.

The commercial interest in such sources is tempered by the fact that they are very complicated to extract. To develop efficient production in this area requires conveying systems that are adapted to the media, to the environment and to each other.

Against that backdrop Netzsch has developed a range of specialised progressing cavity and rotary lobe pumps for the various fields of application in the upstream, midstream and downstream sectors.

A key feature of the Tornado T2 self-priming, valveless rotary lobe pump is its synchronised gear with belt drive, which - in contrast to standard timing gears - is extremely resilient and very easy to maintain. A belt with teeth on both sides transmits the power from the motor to both rotary lobes and synchronises them at the same time.

The strength of the Tornado T2 in the oil and gas sector is that it is compact and self-priming. It also offers high capacity, reversibility and solid matter compatibility. If a solid body that could not be conveyed were to block the pump chamber, this would not lead (as usually happens) to the gearbox being damaged or the shaft broken, but simply to the belt jumping - or rupturing, in the worst-case scenario. Users only have to undo two screws to replace it. This leads to a considerable reduction in downtime and costs in comparison to a complete gearbox overhaul. Likewise, the pump chamber can also be accessed for maintenance or cleaning after the removal of a few screws. This design enables a high level of reliability, which is an obvious benefit for pumps that may be deployed in regions where service engineers are difficult to get hold of.

Two variants of the solution

There are two models of the pump: one that has a specially shaped elastomer insert for the inside of the housing, which improves conveyance; and another that is all-metal, designed for more demanding media. The rotary lobes are manufactured from stainless, Hastelloy or duplex steel, depending on requirements. The advantage of steel over the elastomer bodies that are commonly used is that the steel lobes are less affected by the strong dynamic forces during rotation and therefore have a longer service life. They also expand less than rubber, which allows the components to handle higher temperatures and enables better performance. The full metal version runs without surface contact between lobes and housing or between the lobes - there are defined gaps. With the rubber-metal version, only soft surfaces are running on hard ones, so the pumps run quietly and hardly generate any vibration, noise or friction heat. The rotating components are therefore preserved and will last longer. Furthermore, expensive oil changes are a thing of the past, because the synchronisation works completely without oil.

The pump's direction of conveyance can easily be reversed, so that the same system can, for instance, be used both for filling and emptying. The possible conveyance rates over the various sizes range from 3m3/h to over 900m3/h. The system can also be installed in any orientation and it has a space-saving design due to the motor being attached directly above the pump chamber. This aspect was essential for application in the Ex Zone 1 of a preparation unit with a very narrow design into which the pump was directly integrated. There, the conveying system ensures the inflow of the pumped oil-sand mixture, with a kinematic viscosity of 30 to 35mm2/s and a temperature of 60°C, into a separator where the remaining sand and water are separated.

For more information at www.engineerlive.com/iog

Erwin Weber is head of the Tornado product line at Netzsch in Germany. www.netzsch.com.