Small displacement liquid pump

Centrifugal pumps include a wide variety that are customized for different functions. While these pumps have slight differences depending on their purposes, they share a few similarities. This category of pump includes all pumps with one or more impellers. They can be used for all types of liquids but function best for those with lower viscosity. We carry several types of high-quality centrifugal pumps from reliable companies such as Sundyne, Sunflo, Barnes, and Crown.

Here are a few types of centrifugal pumps:. They are typically for dewatering services where the pump must be located above the suction vessel. This type is best for pumping water and relatively thin liquids. Submersible pumps have a motor that can function when submerged. These pumps have different impellers that can accommodate solids. They are usually used for sewage treatment, from small-scale residential services to sewage treatment plants. Axial flow pumps, also called propeller pumps, achieve high flow rates with low head.

This type is best for handling flood water and for irrigation. Canned motor pumps are a sealless type of centrifugal pump with the impeller directly attached to the motor rotor. An external gear pump consists of two interlocking gears supported by separate shafts one or both of these shafts may be driven. Rotation of the gears traps the fluid between the teeth moving it from the inlet, to the discharge, around the casing.

No fluid is transferred back through the centre, between the gears, because they are interlocked. Close tolerances between the gears and the casing allow the pump to develop suction at the inlet and prevent fluid from leaking back from the discharge side. An internal gear pump operates on the same principle but the two interlocking gears are of different sizes with one rotating inside the other. The cavities between the two gears are filled with fluid at the inlet and transported around to the discharge port, where it is expelled by the action of the smaller gear.

Gear pumps need to be lubricated by the pumped fluid and are ideal for pumping oils and other high viscosity liquids. For this reason, a gear pump should not be run dry. The close tolerances between the gears and casing mean that these types of pump are susceptible to wear when used with abrasive fluids or feeds containing entrained solids.

In the case of the lobe pump, the rotating elements are lobes instead of gears. The great advantage of this design is that the lobes do not come into contact with each other during the pumping action, reducing wear, contamination and fluid shear.

Vane pumps use a set of moveable vanes either spring-loaded, under hydraulic pressure, or flexible mounted in an off-centre rotor. The vanes maintain a close seal against the casing wall and trapped fluid is transported to the discharge port. A further class of rotary pumps uses one or several, meshed screws to transfer fluid along the screw axis. The basic principle of these pumps is that of the Archimedes screw, a design used for irrigation for thousands of years.

There are two main families of pumps: Centrifugal pumps are capable of higher flows and can work with lower viscosity liquids. However, there are a number of applications for which positive displacement pumps are preferred. For example, they can handle higher viscosity fluids and can operate at high pressures and relatively low flows more efficiently. They are also more accurate when metering is an important consideration.

In general, positive displacement pumps are more complex and difficult to maintain than centrifugal pumps. They are also not capable of generating the high flow rates characteristic of centrifugal pumps. Positive displacement pumps are less able to handle low viscosity fluids than centrifugal pumps.

To generate suction and reduce slippage and leaks, a rotary pump relies on the seal between its rotating elements and the pump housing. This is considerably reduced with low viscosity fluids. Similarly, it is more difficult to prevent slippage from the valves in a reciprocating pump with a low viscosity feed because of the high pressures generated during the pumping action. A pulsing discharge is also a characteristic of positive displacement, and especially reciprocating, pump designs.

Pulsation can cause noise and vibration in pipe systems and cavitation problems which can ultimately lead to damage or failure. Pulsing can be reduced by the use of multiple pump cylinders and pulsation dampeners but this requires careful system design. Centrifugal pumps, on the other hand, produce a smooth constant flow. The back-and-forth motion of a reciprocating pump can also be a source of vibration and noise.

In a valveless pumping system, no valves or physical occlusions are present to regulate the flow direction. The fluid pumping efficiency of a valveless system, however, is not necessarily lower than that having valves. In fact, many fluid-dynamical systems in nature and engineering more or less rely upon valveless pumping to transport the working fluids therein.

Meanwhile, the embryonic vertebrate heart begins pumping blood long before the development of discernible chambers and valves. In microfluidics , valveless impedance pumps have been fabricated, and are expected to be particularly suitable for handling sensitive biofluids.

Ink jet printers operating on the Piezoelectric transducer principle also use valveless pumping. The pump chamber is emptied through the printing jet due to reduced flow impedance in that direction and refilled by capillary action.. Examining pump repair records and mean time between failures MTBF is of great importance to responsible and conscientious pump users.

For the sake of convenience, these failure statistics often are translated into MTBF in this case, installed life before failure. A total of 15 operating plants having nearly 15, pumps were included in the survey. The smallest of these plants had about pumps; several plants had over All facilities were located in the United States.

In addition, considered as "new", others as "renewed" and still others as "established". Many of these plants—but not all—had an alliance arrangement with John Crane. In some cases, the alliance contract included having a John Crane Inc.

Not all plants are refineries, however, and different results occur elsewhere. In chemical plants, pumps have historically been "throw-away" items as chemical attack limits life. Things have improved in recent years, but the somewhat restricted space available in "old" DIN and ASME-standardized stuffing boxes places limits on the type of seal that fits.

Unless the pump user upgrades the seal chamber, the pump only accommodates more compact and simple versions. Without this upgrading, lifetimes in chemical installations are generally around 50 to 60 percent of the refinery values. Unscheduled maintenance is often one of the most significant costs of ownership, and failures of mechanical seals and bearings are among the major causes.

Keep in mind the potential value of selecting pumps that cost more initially, but last much longer between repairs. The MTBF of a better pump may be one to four years longer than that of its non-upgraded counterpart.

This does not include lost opportunity costs. One pump fire occurs per failures. Having fewer pump failures means having fewer destructive pump fires. This includes costs for material, parts, labor and overhead. Pumps are used throughout society for a variety of purposes.

Early applications includes the use of the windmill or watermill to pump water. Today, the pump is used for irrigation, water supply , gasoline supply, air conditioning systems, refrigeration usually called a compressor , chemical movement, sewage movement, flood control, marine services, etc.

Because of the wide variety of applications, pumps have a plethora of shapes and sizes: Typically, a liquid pump can't simply draw air. The feed line of the pump and the internal body surrounding the pumping mechanism must first be filled with the liquid that requires pumping: An operator must introduce liquid into the system to initiate the pumping.

This is called priming the pump. Loss of prime is usually due to ingestion of air into the pump. The clearances and displacement ratios in pumps for liquids, whether thin or more viscous, usually cannot displace air due to its compressibility.

This is the case with most velocity rotodynamic pumps — for example, centrifugal pumps. For such pumps the position of the pump should always be lower than the suction point, if not the pump should be manually filled with liquid or a secondary pump should be used until all air is removed from the suction line and the pump casing. Positive—displacement pumps, however, tend to have sufficiently tight sealing between the moving parts and the casing or housing of the pump that they can be described as self-priming.

Such pumps can also serve as priming pumps , so called when they are used to fulfill that need for other pumps in lieu of action taken by a human operator. One sort of pump once common worldwide was a hand-powered water pump, or 'pitcher pump'. It was commonly installed over community water wells in the days before piped water supplies. In parts of the British Isles, it was often called the parish pump.

Though such community pumps are no longer common, people still used the expression parish pump to describe a place or forum where matters of local interest are discussed. Because water from pitcher pumps is drawn directly from the soil, it is more prone to contamination. If such water is not filtered and purified, consumption of it might lead to gastrointestinal or other water-borne diseases. A notorious case is the Broad Street cholera outbreak.

At the time it was not known how cholera was transmitted, but physician John Snow suspected contaminated water and had the handle of the public pump he suspected removed; the outbreak then subsided.

Modern hand-operated community pumps are considered the most sustainable low-cost option for safe water supply in resource-poor settings, often in rural areas in developing countries. A hand pump opens access to deeper groundwater that is often not polluted and also improves the safety of a well by protecting the water source from contaminated buckets. Pumps such as the Afridev pump are designed to be cheap to build and install, and easy to maintain with simple parts.

However, scarcity of spare parts for these type of pumps in some regions of Africa has diminished their utility for these areas. Multiphase pumping applications, also referred to as tri-phase, have grown due to increased oil drilling activity. In addition, the economics of multiphase production is attractive to upstream operations as it leads to simpler, smaller in-field installations, reduced equipment costs and improved production rates.

In essence, the multiphase pump can accommodate all fluid stream properties with one piece of equipment, which has a smaller footprint.

Often, two smaller multiphase pumps are installed in series rather than having just one massive pump. For midstream and upstream operations, multiphase pumps can be located onshore or offshore and can be connected to single or multiple wellheads. Basically, multiphase pumps are used to transport the untreated flow stream produced from oil wells to downstream processes or gathering facilities.

This means that the pump may handle a flow stream well stream from percent gas to percent liquid and every imaginable combination in between. The flow stream can also contain abrasives such as sand and dirt. Multiphase pumps are designed to operate under changing or fluctuating process conditions. Multiphase pumping also helps eliminate emissions of greenhouse gases as operators strive to minimize the flaring of gas and the venting of tanks where possible.

A rotodynamic pump with one single shaft that requires two mechanical seals, this pump uses an open-type axial impeller. It's often called a Poseidon pump , and can be described as a cross between an axial compressor and a centrifugal pump. The twin-screw pump is constructed of two inter-meshing screws that move the pumped fluid.

Twin screw pumps are often used when pumping conditions contain high gas volume fractions and fluctuating inlet conditions. Four mechanical seals are required to seal the two shafts. When the pumping application is not suited to a centrifugal pump, a progressive cavity pump is used instead. This pump is mainly used on surface applications where the pumped fluid may contain a considerable amount of solids such as sand and dirt. The volumetric efficiency and mechanical efficiency of a progressive cavity pump increases as the viscosity of the liquid does.

These pumps are basically multistage centrifugal pumps and are widely used in oil well applications as a method for artificial lift. These pumps are usually specified when the pumped fluid is mainly liquid.

Buffer tank A buffer tank is often installed upstream of the pump suction nozzle in case of a slug flow. The buffer tank breaks the energy of the liquid slug, smooths any fluctuations in the incoming flow and acts as a sand trap. The challenge is selecting the appropriate mechanical seal arrangement and support system to ensure maximized seal life and its overall effectiveness.

Pumps are commonly rated by horsepower , volumetric flow rate , outlet pressure in metres or feet of head, inlet suction in suction feet or metres of head. The head can be simplified as the number of feet or metres the pump can raise or lower a column of water at atmospheric pressure.

From an initial design point of view, engineers often use a quantity termed the specific speed to identify the most suitable pump type for a particular combination of flow rate and head.

The power imparted into a fluid increases the energy of the fluid per unit volume. Thus the power relationship is between the conversion of the mechanical energy of the pump mechanism and the fluid elements within the pump.

In general, this is governed by a series of simultaneous differential equations, known as the Navier—Stokes equations. However a more simple equation relating only the different energies in the fluid, known as Bernoulli's equation can be used. Hence the power, P, required by the pump:.