Energy efficient gear type rotary displacement pump used for handling viscous and semi-viscous liquids

Today more than 50,000 ROTODEL rotary gear pumps are in service saving considerable power for the nation.

considerable power for the nation.

Gear Pumps are the most versatile form of rotary positive displacement pumps used for widest range of applications. They can be broadly grouped into three categories based on their services i.e. 1) Lubrication and Cooling pumps for IC engines, compressors and machine tools 2) Highly precision high pressure pump for hydraulic & metering application and 3) General purpose, medium pressure pump used for loading, unloading and transfer of fuel oil, lube oil, molasses, magma, paints, varnish and various other viscous liquids.

The first category of pumps are invariably designed and manufactured by the OE manufacturer themselves meeting their specific requirement, the power required for s uch pump is a fraction of power produced or consumed by the equipment itself. The second category of pumps are by and large manufactured by multinational companies with their own R&D facility and here the overall efficiency of the pump is mainly governed by the hydraulic efficiency which is related with preciseness of the pump. The third category of pumps with a variety of applications are manufactured by small enterprises at least in India and are generally an outcome of adoption of old design pump without understanding the working principles.

The Challange
The general purpose gear pump could not make enough stride in India till 1980 due to inadequate R&D and improvement in manufacturing methods. The responsibility rests with sluggish attitude of the manufacturer of those days in this area. Added to this the adverse campaign by rotary pump manufacturers of other, types mainly the screw pump manufacturers made impossible, the very survival of gear pump. Consultants and users were made to believe that gear pumps are inefficient, obsolete design product, applications were minimum, uses were restricted. It was this time when we at DEL decided to enter into the business of design, development and manufacture of rotary gear pumps for general purpose applications with our own know-how.

The challenge was exceptional, the task was enormous with many hurdles at every stage. Unless an energy efficient gear pump is designed and developed the chances of entering the already shrinking gear pump market of this segment was bleak.

The Efforts
Our R&D team was given the task of examining the working of the pump. When one talks of efficiency, it is the power lost in the pump partly toward forbidden reason and the rest towards inadequacy of design. Rotary pumps, used for handling viscous liquid has to encounter this very typical nature of the liquid, which can be varied but could not be eliminated. There may be some possibility to reduce power loses towards this viscous encounter with improved design of the impeller. Our engineer took clue from high pressure, high efficiency is to the tune of 95% and it has to be, as one cannot afford to loose power in the transmission device itself. Power consumption in rotary pumps are of two types 1) no load power consumption for overcoming the viscous drag and friction and 2) hydraulic horse power required to develop pressure at desired flow with specific viscosity, nothing can be changed in this matter, thus the scope for improving efficiency lies only in reducing the no-load power consumption.

For high-pressure application, the noload power consumption howsoever high may still remain the fraction of total hydraulic horsepower, while in low-pressure application it is always substantial.

And the Outcome
The frictional losses in the rotary pumps are directly proportional to the viscosity and peripheral velocity. Reducing speed of the pump can simply reduce the peripheral velocity but in that case the pump size increases which costs more and the drive also becomes expensive. It will therefore be worthwhile to design a compact gear impeller capable of trapping the highest volume of liquids. A perfect balance has to be struck to get the best results. We designed and developed a modified profile compact impeller to carry substantial amount of liquid without increasing the peripheral velocity and we employed this impeller design to all our pumps. The volumetric efficiency was also maintained consistently high by blocking the leakage path in the pump through design.

The outcome was astonishing. We found that efficiency of our pumps are 20 to 25% more than conventional gear pump, 15 to 20% more than twin screw pump and even marginally high than triple screw pump for medium pressure application up to 21 bar.

We designed and developed more than 250 sizes and models employing this very concept. Use of gear pump, which was earlier restricted for small size up to 2″ with flow up to 200 LPM started expanding. We got an opportunity to supply pumps up to125 m3/hr with consultant’s recommendation for new projects. We even got preference by way of price leading towards saving in power. our journey did not stop here. From gear pumps up to 25 m3/hr capacity we developed twin gear pumps up to 125 m3/hr capacity and ventured to develop Triple twine gear pump up to 500 m3/hr capacity, here pumps up to 250 m3/hr capacity have already been tried and tested and development of the rest are in progress.

Today more than 50,000 ROTODEL rotary gear pumps are in service saving considerable power for the nation. This tempted us to even say that “we generate power though we are in gear pump business”, of course by way of saving substantial power. This makes us proud as also all those have switched over to ‘ROTODEL’ pumps.