Pumps find applications in the domestic, commercial, industrial and agricultural sectors and in the provision of municipal water and wastewater services. Thus, owing to their utility in a wide range of applications across sectors, these are available in various sizes and functions to suit diverse needs. Pumps range from very large to very small, from handling gas to handling liquid, and from those suited to high volumes to others better for low volumes. Based on the operating principle and the design feature, there are two main types of pumps available in the market – dynamic pumps and positive displacement pumps.
Dynamic pumps account for a major chunk (95 per cent) of the total pump market in India. Typically, these pumps operate on the principle of increasing the pressure energy of the liquid by its dynamic action. This dynamic action of the liquid is carried out by an impeller, which is a revolving wheel with curved vanes.
Dynamic pumps can be further classified into two key subcategories. These are rotary pumps (comprising centrifugal pumps, axial flow pumps and mixed flow pumps) and special pumps (such as jet pumps, electromagnetic pumps for liquids and metals, and fluid actuated/gas lift or hydraulic pumps).
Among all the types of dynamic pumps, centrifugal pumps are the most commonly used. These find use in a plethora of applications in industries such as food processing, dairy, pharmaceutical and cosmetic. The application need and fluid viscosity define the model of a centrifugal pump that should be used. The rotational energy in these is derived from an engine or electric motor. In the water industry, centrifugal pumps are used in handling clear cold fresh water that is devoid of any sharp particles and chemically active elements. These pumps can be used for domestic water supply, as lawn sprinklers, in gardens, small farms, irrigation, agricultural applications, draining of wells and tanks, filling water in swimming pools, etc. Besides, these are also widely used in petroleum and petrochemical pumping. Some of the key characteristics of centrifugal pumps are higher discharge vis-à-vis regenerative pumps, exceptional hydraulic performance and high operating efficiency.
Overall, dynamic pumps are preferred over positive displacement pumps owing to their lower maintenance requirement. Besides, their capability of operating at high speeds and high fluid flow rates also make them beneficial. However, these pumps are usually characterised by lower efficiencies than positive displacement pumps.
Positive displacement pumps
Positive displacement pumps, accounting for around 5 per cent of the total pump market in India, operate on the principle of filling and displacing liquid from a cavity. These pumps ensure a steady flow and volume of liquid and are devoid of any discharge pressure or head. Hence, they are a type of constant flow machine. These pumps are most effective when used in low flow-high pressure combination and other niche applications.
Positive displacement pumps can be classified into the following main subcategories – reciprocating pumps (piston/plunger pumps); diaphragm pumps (single diaphragm, double diaphragm); and rotary pumps (single rotary and multiple rotary pumps).
Positive displacement pumps or rotary pumps are considered very efficient owing to their ability to remove air from suction lines, thereby eliminating the need to remove air from the lines manually. Besides, these pumps are effective in dealing with liquids with high viscosity. Meanwhile, the drawbacks include slow rotation due to the requirement of very close clearance between the rotating pump and the outer edge; and the possibility of liquids /being erosive when the pump is operated at a high speed. Further, it is also not advisable to operate a positive displacement pump against a closed valve on the discharge side of the pump since it has no shut-off head unlike centrifugal pumps. In case it is operated against a closed valve, production of flow continues and the pressure in the discharge line increases until it ultimately bursts or is severely damaged.
The three main types of rotary positive displacement pumps are gear pumps – which are simple rotary pumps where the liquid is pushed between two gears; screw pumps – in which two screws turn against each other to pump the liquid; and rotary vane pumps which have a cylindrical rotor sheathed in a similarly shaped housing.
In reciprocating pumps, the liquid is discharged due to a simple to-and-fro motion or reciprocating motion of the piston or plunger working in the cylinder of the pump. These are typically used in cases when a relatively small quantity of liquid has to be handled and the delivery pressure is high. Reciprocating pumps find applications in the oil and gas sector, power plants, sugar industries, petrochemical plants and refineries, water treatment plants, etc.
Key parameters determining pump selection
Identifying the right type of pump for an application is critical to reduce the operational costs of a system and improve the life of the pump and the system as a whole. One of the key factors determining the choice of a pump is its size. Ironically, in some cases the use of multiple pumps instead of a single pump aids in containing energy consumption. This holds true in cases where demand is cyclical. Accordingly, in low demand phases, one small pump is sufficient while in higher demand phases, multiple pumps working in tandem with each other are useful. Besides, it is also important to determine the feasibility of operating a large pump vis-à-vis a small one at the onset of an operation.
Focus on technological advances in pumps
Companies engaged in the manufacture of pumps in the country are constantly striving to develop and implement the latest technology in pumps and valves. Smart, sustainable and energy-efficient pumps have been gaining traction globally, with India being no exception.
Pump dimensions and technologies have seen significant advancements. Recent innovations in this field include solar-based pumping systems, lowest life-cycle cost pumps, high-capacity concrete volute pumps and vertical turbine pumps.
Moreover, technological advancements have also been made for reducing pumping requirements. For instance, increasing the net positive suction head available to a pump, allowing a higher cooling water temperature rise across heat exchangers to reduce cooling water pumping requirements, and heating a viscous process fluid prior to pumping to reduce viscosity have all been useful developments.
Further, India has also been receiving external support for ensuring efficiency in pumps. For instance, in October 2016, the Asian Development Bank committed a $200 million loan to Energy Efficiency Services Limited (EESL) to finance the installation of energy-efficient lights and water pumps in the country. As part of the $400 million project, EESL is planning to install 225,000 new pumps in the country.
The way forward
Although at present the Indian market is small relative to the global pump industry, the level of exports from the country seems to be on the rise. It is thus imperative for Indian pump manufacturers to maintain a high quality standard so as to be able to compete globally. Besides, even for domestic use, considering the extreme nature of chemicals and liquids that pumps are exposed to, maintaining quality is vital to avoid any mishaps.
Notably, domestic players are continuously working on the productivity, quality and service of their pumps. Going forward, a greater focus on the use of new materials for manufacturing pumps with better efficiency and reliability, as is the case in international markets, will prove to be beneficial for driving the market for Indian pumps.