Pump selection: all the parameters

As pump manufacturers, we daily face with a lot of inquiries that are often not complete because of the lack of data that are essential to let us quote the correct pump solution. In order to help our customer to get their way out of the jungle of the parameters, we have defined a table of the main variables that should be considered during the pump selection. This article would like to be a light vademecum to simplify the communication requesting for a quotation.

Variables of the pump selection

The following table includes the indispensable variables that our technicians have to know during the selection. We strongly recommend our customers to communicate the following data so that we can proceed with the selection.

pump selection

Thanks to these references, our technical department will be able to select the best solution for every inquiry.

Moreover, once the selection is done, our technical department will provide the customers with some helpful derived parameters that are necessary for the plants.

Parameters confirmed by the pump technicians

Indeed, after the selection, our technicians, first of all, confirm the actual head and flow that pump can reach and the diameter of the impeller. Then they give the customers the data shown in the table below. This information let our customer be able to technically evaluate our proposal according to the construction features of the plant.

after the pump selection

 

Is it more clear now? Should you need any further information, please contact us at info@gemmecotti.com. We will be glad to dissipate all your doubts.

Don’t forget to save this post in your bookmarks, in order to easily recover it! And to select the right material for the pump, take a look also at our chemical compatibility guide.

References:

https://en.wikipedia.org/wiki/Net_positive_suction_head
https://web.archive.org/web/20170603124924/https://www.ksb.com/blob/333370/f0c49eb441d360b61f48f08ec47d78ab/pdf3-data.pdf

 

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AODD pumps: 4 reasons to choose diaphragm pumps

 

AODD pumpsThe AODD pumps, Air Operated Double Diaphragm pumps, appeared in the pump market for the first time about sixty years ago. Thanks to the constant technological improvement, they have managed to set themselves as the best choice for pumping high-viscosity fluids.

There are four reasons why you should prefer a double diaphragm pump as our HAOD pumps for your plant. Here they are:

  1. VERSATILITY AND VARIETY OF APPLICATION

    The AODD pumps find application in a wide range of installations, thanks to their versatility and to their features. For example: the ability to self-prime, the possibility to run dry, the potential to be submersible, and the possibility to pump high-viscosity fluids. Moreover they are available in different materials in order to overcome any problems of fluid compatibility.

  2. DESIGN AND SIMPLICITY

    The design and the ease of use of the AODD pumps are among the reasons they are so appreciated in the chemical pumps market. Indeed they are often described as “plug-in-and-play” or “set-and-forget” pumps, because once installed and connected to a compressed airline they can work for themselves in full autonomy. They can be provided in a multiplicity of dimensions, easily meeting every customers’ needs.

  3. SAFETY AND ECOLOGY

    Thanks to its closed design, the usage of compressed air as the only power source, and its stall-prevention pneumatic system, AODD pumps are one of the safest pumping system for hazardous liquids, together with the mag-drive pumps. Moreover the ecological design of AODD pumps allows them to realize up to 60% saving in air consumption. Thanks to this saving, their impact on environment decreases significantly. Less air consumption means indeed the possibility to use smaller air compressor, with consequent energy and money saving.

  4. MONEY SAVING

    The money saving, especially in the long-period, is amongst the reasons why you should consider to select a diaphragm pump. The improvements made in diaphragms construction have indeed dramatically increased the life of the diaphragm pumps. They can work properly for years with a very low maintenance, especially thanks to their static seals. These seals maintenance indeed tends to be infrequent and inexpensive.

Have we convinced you? Visit the webpage of our HAOD in order to learn more about air operated pumps. For further information contact us at info@gemmecotti.com. Our technical and sale departments will be glad to lead you to the best choice.

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Pressure vs head, what is the difference?

The pump selection of a pump is driven by the following main parameters:
– Head (H)
– Flow rate (Q)
– Fluid characteristics (ρ, γ, T ….)
Sometimes head can be confused with pressure during pump choice. As a matter of fact there is a strict relation between them which is defined by the fluid specific gravity, so the relation is fluid dependent. So what is the difference between pressure and head?

Definition of head and pressure

Head is the height given by the pump to the fluid and it is measured in meters of liquid column [m.l.c.] or simply indicated in meters [m]. The given head is fluid independent: different fluids
with different specific gravities are all lifted at the same height.
Pressure, instead, is fluid dependent and it is affected by the liquid density. In fact the force of a fixed height liquid column over a unitary area will change with different specific gravities. So in this case the same head generates different pressures.

Measurements: Pressure or Head?

Head is not directly measured. Manometers on the pump suction and delivery line give the measure of the pressure. Measurements given by manometers indicate differential pressures imposed by the pump between suction and discharge. These measures are read in [bar] [atm] [psi] [ft H2O] etc.. Specific gravity γ has to be considered to evaluate the correspondent head.

Conversions & Practical Example

As stated before, the same pump at the same working point will give always the same head with different pressures in accordance with the density γ of the working fluid.
For example, a mag drive centrifugal pump HTM 10 working at a given point Q= 7.5 m3/h H = 10 mlc operating with water and concentrated H2SO4 gives the same head (H=10m) to water ( γ= 1kg/dm3) and to sulfuric acid (γ = 1.8kg/dm3), while measurements of differential pressures between suction and delivery will be:

equazione pressione 12

The mathematical relationship is reported in the following equation:

equazione pressione 1
Also power consumption is influenced by the previous relationship of pressure, as:

equazione pressione 2curve pressure

Notes for technicians

– Previous relations are valid for low viscosity fluids (water equivalent), along with increasing viscosity, pump performances have to be reduced using pump derating rules.
– At a fixed rotational speed a centrifugal pump generates head related to the flow rate following its characteristic curve.
– The computation of the needed head that should be delivered by the pump, is not so straight as the evaluation of the desired height difference. Needed Head is composed by the following terms:

  • Geodetic head: difference between suction and delivery height expressed in meters of liquid column

equazione pressione 3

  • Difference between absolute pressure of the delivery and suction reservoir

equazione pressione 4

  • Distributed and concentrated friction losses also expressed in m.l.c.
    equazione pressione 5
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How to read a pump curve

If you are new in the pump field, reading a pump performance curve (usually just called “pump curve”) can be difficult and sometimes confusing. That’s why we want to help you by offering a simple guide for a first approach to a pump curve.

What is a pump performance curve and why do you need to know how to read it?

A pump curve is a graphical representation of the performance of a pump based on the tests of the pump manufacturer. Every pump has its own curve and it varies very widely from pump to pump. The variation depends on many factors such as the kind of pump (centrifugal pump, turbine pump, vane pump etc.), size and shape of the impeller. Pump curves can be used to provide many information of pump performance and absorbed power which are important for a user to determine the working point and motor power and size.

What information can I find on a pump curve?

1- In the simplest and widely used pump curve (commercial multi-pump curve) you can see two vital pump performance factors: flow and head.

The flow or capacity (Q) is measured in m3/second according to the international standards but usually you can find it expressed in m3/h, l/min or gpm (in the US). It is the volume of liquid moved in an amount of time. On the curve below (Picture 1) you can see the flow marked in red on the horizontal axis.

The head (H) is the height at which a pump can raise a liquid up. It is measured in meters (m or mlc meter of liquid column) or feet and you can see it marked in blue on the vertical axis on the picture below.

Pump performance curve with flow and head

PICTURE 1 MULTI-PUMP CURVE 

How can you read this pump curve?

To select the right pump model you should, first of all, identify the capacity and the head needed for  your system.

If you need for example a flow of 15 m3/h at 20 m you can find the right pump curve and consequently the right pump in the intersection of the two red arrows in the chart. In the example below the pump suitable is magnetic drive centrifugal pump model HTM 31.

 

 

The curve enables you to see how the pump will perform at any given point within its performance range. For example, the same pump model HTM 31 at 15 m3/h will produce a head of 20 m, or at 24 m of head the pump will generate a flow of 8 m3/h.

Once you have chosen the right pump type whether centrifugal, turbine, vane or any other, you can study in details the specific curve of the selected pump model with other technical information.

2– In picture 2 you can see an example of a centrifugal pump curve (HTM 31 PP/PVDF) with additional details than curve in picture 1 such as for example the impeller diameter (curve A circled in red), the NPSHr (curve B) and the absorbed power (curve C). In some case you can also find the pump efficiency.  This kind of curve is usually used by pump manufacturers to select the correct pump model among their set of performance curves.

Performance curve centrifugal pump

PICTURE 2

How can you read this pump curve?

In the title box at the top you can find the pump model, the number of poles of the motor, the frequency, the RPM and the pump material (selected according to the liquid to pump).

In curve A you can see the flow and head as described in the paragraph above but there is also a reference of the impeller diameter. For this pump model the available impeller diameters vary from a  minimum of   110mm to a maximum of 134 mm. The impeller would be trimmed by the manufacturer to whatever diameter needed to meet your conditions of service. If the impeller selection is 122 mm at a flow of 10 m3/h the head is about 19 mlc. The manufacturer would determine the proper impeller diameter for your conditions and trim it to the correct diameter.

Curve A - centrifugal pump

In curve B you can see the NPSHr of the pump measured in meters or feet in accordance with the capacity required. This is the minimum head at the suction of the pump that allows the pump to work properly. If sufficient NPSH available is not supplied by the plant (NPSHa) the pump will cavitate and this will affect both the performance and the pump lifetime. In case of 10m3/h capacity you have to find the intersection with the curve of the selected impeller diameter and read the value on the left.

Curve B - centrifugal pump

In curve C you can find  the absorbed power required for pumping a liquid with a SG of 1. Once determined the impeller diameter and the flow you can find the intersection where you can read the absorbed power, which is necessary to determine the relevant motor power.

Curve C - centrifugal pump

The correct selection of a pump using a pump curve is essential to permit a proper working of your system. A working point too far out on the curve, or too far back, can cause damage to the pump, excessive energy consumption, poor performance and pump failure.

For further information don’t hesitate to contact us www.gemmecotti.com

 

 

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Video: how to assemble and disassemble magnetic drive turbine pump HTT

Here is the new GemmeCotti video tutorial: how to assemble and disassemble magnetic drive turbine pump series HTT PP/PVDF. Enjoy!

MAIN FEATURES OF PUMPS HTT PP/PVDF:

Magnetic drive regenerative turbine pumps series HTT are made of thermoplastic non-metallic materials (polypropylene-PP and PVDF) and are suitable to pump high corrosive and dangerous liquids. Thanks to the innovative sealless mag drive system, pumps model HTT reduce risks of leakage and emissions and the maintenance costs are very low. The transmission of the motion occurs through magnetic joints without any mechanical seal. This design guarantees the maximum safety and efficiency.

Max capascity: 9 m3/h

Max head: 50 mlc

Max temperature: 70°C for PP pumps and 90°C for PVDF pumps

Contact our office for more information: info@gemmecotti.com

 

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Mag drive pump HTM 31 PP/PVDF now suitable for 4kw

Sealless Magnetic Drive pumps model HTM 31 PP/PVDF are now suitable also for 4 KW motor size 112. This pump model can be coupled to three different motor sizes:

SIZE 90 – 2,2KW
SIZE 100 – 3KW
new SIZE 112 – 4 KW
You can contact our sales department for more details.

 

What are the characteristics of mag drive pump model HTM PP/PVDF?

HTM PP/PVDF pumps are mag drive centrifugal pumps made of thermoplastic materials (PP and PVDF) and are suitable to pump high corrosive liquids.

Max capacity: 45 m3/h, Max Head: 33 mlc, Max
Temperature: 90°C Max viscosity: 200 cSt, Pressure rating NP 4 at 20°C.

Click here to find out more.

 

How does a magnetic drive pump work?

Sealless mag drive pumps have a particular sealless design that is suitable to pump corrosive and dangerous liquids thanks to the high chemical resistance and absence of leakage and emissions. The structure is really simple and requires a very reduced maintenance with consequent save in terms of repairing and spare parts costs during the pump life.
The external magnet, placed on the drive shaft, transmits the motion to the internal magnet connected to the impeller which rotates and moves the fluid through the pump.

Here is a sketch of the functioning of magnetic drive system.Mga drive pumps

 

 

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A1-13Y – DRY-RUNNING PROTECTION DEVICE

How can you prevent dry running of pumps? 

To safeguard magnetic drive pumps against damage caused by insufficient liquid, GemmeCotti offers the Emirel A1-13-Y dry-running protection device. Specifically designed for these pumps, this device prevents dry running, closed discharge, and blocked suction scenarios. Its adjustable threshold and timer allow for customization of minimum power and operational time settings. If power falls below the set value, the pump is automatically stopped, ensuring protection. This device is especially valuable during tanker unloading operations and in any application where liquid shortage poses a risk.

Main features

  • Single Phase CURRENT RELAY
  • Multirange 15-35A
  • 2 set points MAX / min
  • Also for motors with INVERTER
  • Direct insertion TA through
  • LCD Display

What happens when a pump runs dry?

When a pump works without fluid there is a sudden increase of the internal temperature with destructive results of some pump parts. For example, when a plastic pump (in PP or PVDF) runs dry, the main damage occurring are:

1- the shaft in ceramic may break due to a thermal shock.

2- the rotating bushing may block on the shaft.

3- melting of some plastic parts (impeller, rear casing, internal magnet etc.) due to the sudden temperature rise.

 How is it possible to prevent dry running?A1-13Y – DRY-RUNNING PROTECTION DEVICE

To avoid the inconvenience of the dry running you can simply install a dry running protection device which stops the pump immediately in case of danger of dry-running. As a matter of fact, the device checks constantly the active power of the motor, which is the minimum value of the instantaneous power absorbed by the pump, through the reception of information about the voltage, the cosφ and current variations. Through a set point and a timer, which are adjustable, it’s possible to set the minimum power and the triggering time of the device. If the power goes under the established value, the pump stops and the device must be switched on again manually. In case of continuous intervention on the apparatus,  check the presence of liquid and/or the correct functioning of the plant to find the cause of working of the device.

Click here to find out more.

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Do you know that GemmeCotti pumps can be used in car washing machines?

pumps in car washing plantsGemmeCotti pumps are used in many industries for different applications among which also car washing plants. Chemical pumps in car washes are installed with the main purpose of dosing and spraying water containing detergents and chemicals of various kinds through high-pressure jets. So it is necessary to use an efficient and reliable high-pressure pump to guarantee clean and shiny vehicles.

Our experience in car washes

We have a lot of experience in this particular field and recently we have worked on a new project which required a pumping equipment with very high pressure for a wheel rim cleaning system in a car wash machine. The customer required a pump suitable to transfer a detergent from a 40-liter-tank to the oscillating jets of the machine. The fundamental requirement for the pump was the discharge pressure which had to be at least 6 bar. We studied carefully the application and in the end we proposed our metallic rotary vane pump series HTP that can reach a maximum pressure of 13 bar.

High pressure vane pumps for car washing machines

The pump model HTP that we selected for the application is a positive displacement pump with vanes made of stainless steel AISI316. In this pump the vanes in graphite are mounted in a rotor and they move inside a cavity sliding into and out of the rotor. In this way the fluid is pumped outside the pump with a pressure up to 13 bar and a maximum flow of 2000 l/h. Click here

GemmeCotti rotary vane pumps model HTP

Mag drive vane pump HTP

to watch how a vane pump works.

Vane pumps model HTP in AISI 316 are suitable for detergents, hydrocarbons, solvents, heat transfer oils, refrigerants and cryogenics or other thin no-lubricating liquids. Thanks to the mag drive design these pumps are useful for low flow and high pressure applications such as car washes, pilot plants, sampling, flushing of mechanical seals and cooling units.

 

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How does a mag drive rotary vane pump work?

In a magnetic drive rotary vane pump two pumps design are combined together: the sealless magnetic coupling and the positive displacement system with vanes.

With the magnetic coupling the torque is transmitted through contactless magnetic forces from the external magnet which is coupled to the motor shaft to the internal magnet which is connected to an impeller or rotor. This design ensures a hermetic and reliable separation between the pump and the motor making it the best solution when pumping chemicals and acids because it prevents leakage and emissions.

A rotary vane pumping system consists of vanes mounted in a rotor that rotate inside a cavity. When the rotor moves thanks to the above mentioned mag drive system, the vanes slide into and out of the rotor creating vane chambers that do the pumping work.

For further information you can watch the video below or visit our website 

mag drive rotary vane pump GemmeCotti

 

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Video: how to assemble and disassemble metallic mag drive pump series HTM SS316

Here is the new GemmeCotti video tutorial: how to assemble and disassemble mag drive pump HTM SS316.

MAIN FEATURES OF MAG DRIVE PUMPS HTM SS316

Mag drive centrifugal pumps model HTM SS316  are seal less pumps suitable to pump hydrocarbons, solvents and dangerous liquids and are made of AISI316. These metallic pumps have a special design in which the transmission of the motion occurs through magnetic joints (external magnet and internal magnet) without any mechanical seal. The external magnet is placed on the drive shaft and transmits the motion to the internal magnet connected to the impeller which rotates and moves the liquid through the pump.
This simple structure guarantees a very reduced maintenance with consequent save in terms of repairing and spare parts costs during the pump life. Click here for more information about HTM SS316 pumps.
Enjoy our video tutorial!

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