Pumps: complete guide for choosing them

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Choosing the most suitable centrifugal pump for an industrial plant is not easy. To help you in your choice, we offer you our complete guide for choosing pumps.

The main elements to be considered in order to guide you in choosing the one that fits you are first of all:

  • required flow rate (i.e. the complete volume to be conveyed in the unit of time);
  • characteristics of the hydraulic circuit (head, pressure drops, accessories, etc.);
  • characteristics of the fluid to be pumped (composition, concentration, temperature, etc.).

In a guide for choosing the one that fits your need, we must also consider the complete economic aspects relating to the investment for the plant.

Gathering all this information will make the choice easier. You will be capable of choosing the type of pumps that best suit each application, with the perfect impeller and with the right motor power.

Among the various types available, centrifugal ones are undoubtedly the most versatile, and they can boast a complete and wide range of applicability.

Guide to the different types of pumps

As in a complete guide, we want to talk about the different types of centrifugal pumps on the market and show you that they share the main constituent elements:

  • impeller (moving part that transfers energy);
  • complete body, which channels the flow in and out;
  • shaft (usually connected to the motor) on which the impeller is fixed;
  • engine (usually electric or internal combustion).

However, it is possible to distinguish among the different types of pumps according to the number of impellers. In our complete guide we can summarize in:

  • single-stage, i.e. with a single impeller;
  • multistage, with two or more impellers.

Then, depending on the position of the shaft, it is possible to distinguish between different types:

  • horizontal;
  • vertical.

The latter are particularly suitable in case of space problems.

A further, fundamental classification to consider when choosing among different types of pumps leads us to distinguish:

  • submersible;
  • surface.

The main criterion for choosing between these two different models is given by the suction height. If the complete depth of the liquid is greater than 7 meters, surface pumps will not be suitable for moving it, and you will have to use a submersible one.

Complete guide for choosing multistage pumps for liquids

To increase the suction capacity, we want to guide you in choosing multistage pumps for liquids, i.e. with two or more impellers instead of just one.

The single-stage one is designed for large volumes of liquids, but it performs best when operating at its nominal capacity or just below. In different conditions it becomes less effective and is more exposed to wear, because of forcing the rotation speed to compensate for the lower pressure.

Let’s see below what are the complete characteristics of multistage pumps for liquids, which make them preferable to single-stage ones.

Features

The features that differentiate multistage liquid pumps from single-stage ones can be identified in four areas:

  • performance
  • duration
  • complexity of operation
  • cost.

In terms of performance, multistage liquid pumps can be arranged in series or in parallel and they offer just a two-in-one service. When operating in the volume position (parallel), they equal the performance of single-stage ones. In the pressure position (series), they operate up to 70% of their rated capacity more efficiently (with a lower motor speed) than a single-stage pump.

The most peculiar characteristic of multistage liquid pumps is certainly the duration. Thanks to their greater efficiency, they are more resistant to wear than single-stage, especially if often used for low capacity and high pressure applications.

Regarding the complexity of operation, a single-stage pump is simpler than a multistage one, because the operator of the latter has to decide whether to place the pump in parallel or in series. However, the training required to learn how to carry out this step effectively is minimal.

Finally, about costs, the initial additional investment for liquids is amply offset by lower operating costs and above all by longer life than single-stage ones.

Applications

Multistage pumps are used in applications that require a higher head. In fact, they guarantee greater process reliability, high efficiency and lower operating costs than the single-stage pumping system.

In our complete guide we find the main applications of multistage liquid pumps in the following industrial sectors:

  • mining, extractive and processing industries;
  • ceramic industries:
  • stone processing (marble and granite sawing);
  • treatment of the organic fraction of urban solid waste;
  • water purification plants;
  • steel industries
  • chemical, petrochemical and pharmaceutical industries.

Guide for choosing submersible pumps

In our complete guide for choosing pumps, we want to talk about submersible ones. They are centrifugal pumps that can be positioned directly into the fluid. They become essential when the liquid is deeper than 7 meters.

They have sealed motors and casings and offer the advantage of never having to be primed. In fact, unlike surface pumps, they do not need to suck fluid through a pumping line. The liquid enters through an opening in the lower part of the device, then the centrifugal force of a motorized impeller pushes it into the collector duct, from where it is conveyed into the discharge pipe and then out of the pump.

If used on a single site, high quality submersible pumps such as those in the PEMOPUMPS range can be left permanently at the application site. They are extremely resistant and they are not subject to damage caused by humidity.

Repairs or replacements can be more complex, because they can be constantly immersed in liquids or sludge, even tens of meters underground and sealed within piping systems. However, subjecting them to regular routine checks which are defined together with the manufacturer, allows us to guarantee them a life expectancy of up to 30 years.

Features

They have features designed to operate completely immersed in liquids and / or sludge, and a hermetically sealed motor coupled to the body.

Usually, the watertight casing around the engine is filled with oil, to protect it from damage by preventing the entry of any liquid that could cause a short circuit.

When the element is submerged, the fluid exerts positive pressure at its inlet. From this pressure depends the greater efficiency of submersible pumps, which require less energy to move the fluid.

In fact, they work by “pushing” the fluid, rather than pumping it. The prevalence of the liquid is used for the operation, without using additional energy to suck it into the pump.

The overheating of its motor is averted by the cooling action caused by the liquid or mud in which it is immersed.

Here are some of their main characteristics, which can make them really advantageous.

  • They do not require priming: operating below the surface, they are self-priming;
  • They are not subject to cavitation, being completely submerged;
  • They are efficient and require less energy, due to the positive pressure they exert at the pump inlet;
  • They are very silent in most applications.

Given their location, in addition to important features, they also face some challenges.

  • Accessibility: especially in deep well applications, this type of pump is often not easily accessible for inspection or routine maintenance;
  • Risk of corrosion: they are often used to handle corrosive and abrasive liquids, and therefore the seals are particularly subject to wear, which can cause leaks and damage to the engine;
  • Cost: to counteract corrosion, they must be made of particularly resistant materials (e.g. cast iron, epoxy coating), which can make them more expensive than other types of pumps of the same capacity.

It is possible to overcome these challenges by relying on competent and highly experienced manufacturing companies, such as Perissinotto S.p.a.

Applications

They are generally very reliable, and suitable to operate even in extreme conditions.

Here are the main applications in which they can be used:

  • wastewater – they are widely used in the sand and wastewater industry, often in pumping and lifting stations;
  • sewage treatment: they often reduce the waste material into particles, to facilitate handling and downstream treatment;
  • mining sector: they are used, for example, for the removal of tailing ponds;
  • dredging: port authorities often use them, designed to handle high solids liquids, to dredge a port;
  • water wells, to bring the water to the surface;
  • oil and gas industry: they bring the resource to the surface by taking it from deep wells.

Guide for choosing surface pumps

The surface pumps are located outside the fluid they have to move and extract it thanks to a suction pipe. They are designed to pump liquids or slurry up to 7 meters deep. Over this depth the risk of cavitation increases and submersible pumps are the solution.

They can be of different sizes and types: from those intended for use also in the domestic context (for washing machines, dishwashers, toilets) to industrial ones.

Thanks to an electric motor, they create a suction by rotating one or more impellers at high speed, depending on whether they are single-stage or multistage pumps.

Unlike submersible pumps, depending on the position of the shaft, they can be horizontal or vertical. The latter are particularly suitable on limited surfaces.

Therefore the elements that influence the choice:

  • the depth of the liquids or sludge to be pumped;
  • their characteristics.

Features

Let us see their main features.

  • Operation: they must be primed, that is, enabled to suck the fluid. This can take place through a suction line, or by self-priming;
  • the need to suck the fluid requires a greater use of energy for the operation of the surface pumps;
  • ease of access: since they are not completely immersed, the surface pumps are more accessible and maintenance interventions are facilitated (and usually less expensive);
  • however, complete maintenance may have to be more frequent, as they are more exposed to external agents;
  • their cost is lower than that of others;
  • their noise level is higher than that of submersible pumps, whose noise is muffled by the surrounding fluid.

To have the certainty of making the choice that best suits your needs, it is good to turn to producers who can guarantee quality and competence. Perissinotto S.p.A. is definitely one of them.

Active since 1947, our company has built and delivered over 40,000 industrial pumps all over the world and it is able to adapt all the models of the PEMOPUMPS range to the needs of any customer.

Applications

They are suitable for different applications:

  • power plants and desulphurisation plants;
  • mining, quarrying and washing of inert materials;
  • transfer of coal, sewage and sludge;
  • chemical, ceramic and paper industry:
  • management of OFMSW (organic fraction of municipal solid waste).

Guide to lifting pumps

Lifting pumps are submersible pumps inserted in a lifting system (or station).

This type of plant is necessary when fluids (especially waste water) have to be discharged because they cannot flow naturally. For example if the collection basin is in an elevated position with respect to the draft point).

The main building blocks of a lifting station are

  • a retention tank;
  • one or more pumps;
  • a trigger and regulation system.

Operation is simple: when the fluids reach a certain level inside the retention tank, they come into action and push the water to the desired discharge point.

The priming and control system is adjusted according to the flow of water arriving in the tank and its volume. In this way the lifting pumps never work in vain.

Features

Their features must take into account several factors:

  • characteristics and granulometry (or granular passage) of the fluid;
  • pump flow;
  • lifting height of the waters.

The particle size indicates in millimeters the maximum size of particles and impurities that can pass through them without clogging them.

The wastewater can be:

  • black water, very dirty, containing solid materials, paper, etc, the pumps must tolerate a particle size greater than 50 mm (and possibly include a shredder at the inlet);
  • gray, slightly dirty, solid particles of small size and not very concentrated water: in this case the particle size is between 20 and 50 mm;
  • white or treated water, for which lifting pumps with granulometry from 5 to 20 mm are ideal.

The flow is expressed in liters per minute (l/mn) or in cubic meters per hour (m3/h). It is the main feature of any pump, and is closely related to the total manometric height (ATM), which is expressed in meters. Their ATM must allow the flow so as to arrive intact at the outlet.

On the other hand, the lifting height of the water, determines the size and shape of the retention tank. If the height is limited, it will be possible to use a column tank, while if the lift is large, it will be necessary to install a tank.

Applications

Lifting pumps are mainly used for the collection and lifting of clear, rain and waste water.

They are also suitable for use in the oil and gas industry, to bring fuels from deep wells to the surface.