Hose pumps for quarry duties

The transfer of solids laden water encountered in quarrying demands a type of pump that is extremely robust, low maintenance and capable of standing up to the aggressive nature of the pumped liquid. Whilst rotating pumps containing open impellers can perform outstanding service, there is always going to be the problem of impeller wear and damage to the pump housing, making maintenance a constant requirement along with frequent parts replacement. An alternative pump type that should be considered is the, hose pump. Suitable for applications ranging from precision dosing through to transferring sludges and slurries the hose pump delivers leak-free operation, is ideally suited to challenging open environments and most significantly, is easy to maintain.

The main features of the peristaltic pumps include:
• Sealless design
• Valve-free
• Dry self-priming
• Gentle pumping action
• Dry running
• High suction lift
• Abrasion resistant
• Low maintenance
• No slip
• Reversible

The hose pump is a positive displacement pump where the fluid is contained within a hose or tube inside the casing. The fluid is moved into and out of the tube/hose by the action of rotating rollers or shoes which alternatively compress and relax the tube/hose. This 'peristaltic' process ensures that the fluid is transported accurately and without any variation in the volume. What's more, the dosing pump is economic with the liquid pumped because at the end of the processing cycle or operation, the pumping motion can be reversed and any fluid remaining in the hose/tube can be returned to its source for future use and the tube/hose is drained.

Shoes or Rollers
The decision to use a shoe or roller hose pump is largely dependent on the application and the operating pressures required for the application. Rollers are more suited to lower pressure applications, typically up to 4 bar, and usually limited to a maximum of 8 bar. Therefore, smaller drives are required which results in less power being consumed. Roller technology is easier to maintain, with simple hose replacement and less waste fluids due to the elimination of hose lubricant. Shoe compression pumps are more suited for applications demanding operating pressures up to 16 bar and higher flowrates. This pump is a robust, workhorse built for the most arduous of operating conditions and fluids.

The hose pump is now regarded as a mature product and a proven technology, so making improvements can present a challenge to pump designers. However, AxFlow has recently introduced a new design of hose pump offering users a combination of pressure versus flow options. The four models in AxFlow's realax pump range provide capacity rates from 0.16 ml/rev through to 20 l/rev and pressures from 2 to15 bar.

The realax APY Series is the smallest of the pumps being a roller compression hose pump developed for low volume, low pressure dosing applications. The ISI (Fig.1) and IP Series are both roller compression pumps with capacity rates from 0.023 l/rev to 10 l/rev at pressure between 2 and 8 bar. Both pumps can be used where sludges and slurries are to be transferred. The RP Series (Fig.2) is a shoe compression pump providing pressures up to 15 bar and capacity rates of between 0.3 l/rev and 20 l/rev. Each model comes in four versions: bare shaft, gear reducer (fixed speed), integrated inverter and mechanical variable speed.

Accessories for the realax pump range include: leakage detector, batch controller, vacuum equipment and discharge pulsation dampeners. For quarry applications natural rubber hoses offer optimum abrasion resistance for long service life.

The realax pump range also addresses the issue of making maintenance easier and incorporates a new design of inspection window on the pump housing. Generally, the inspection window of a hose pump enables the operator to check the oil lubricant level in the pump housing. AxFlow's large inspection window eliminates the need to remove the front cover of the pump case, making it easy for the operator to access the rotor and the hub and easy to change the number of shims in order to accommodate pressure changes demanded by the application.

Pump development programme
For quite some time, our customers have demanded a hose pump that operates efficiently at low pressures while continuing to give high levels of accuracy," comments Hakan Bjernér, Manager of Business Development, AxFlow Holding AB. "Easier maintenance was another key issue. This new range of peristaltic pumps enables AxFlow to address the low pressure end of hose pump applications."

Whether the application involves dosing small, precise quantities of fluid at low pressures or high accuracy pumping of large volumes of viscous or abrasive products, peristaltic and hose pumps provide an excellent solution.