Basics of Pump Assessment

The work performed by a pump is a function of the total head and of the weight of the liquid pumped in a given time period. Pump shaft power (Ps) is the actual horsepower delivered to the pump shaft. It can be calculated as follows:

Pump Shaft Power (Ps) = Hydraulic power (hp) / Pump efficiency (ηpump)

Pump Efficiency (ηpump) = Hydraulic power / Pump shaft power (Ps)

Pump output, water horsepower or hydraulic horsepower (hp) is the liquid horsepower delivered by the pump, and can be calculated as follows:

Hydraulic Power hp = Q (m3/s) x (hd - hs in m) x ρ (kg/m3) x g (m/s2) / 1000

            Where:

            Q = flow rate

            hd = discharge head

            hs = suction head

            ρ = density of the fluid

            g = acceleration due to gravity

Difficulties in Pump Assessment

• Absence of pump specification data to assess pump performance - Pump specification data are required to assess the pump performance. Most companies do not keep original equipment manufacturer (OEM) documents that provide these data. In these cases, the percentage pump loading for a pump flow or head cannot be estimated satisfactorily.
• Difficulties in flow measurement and flows are often estimated - It is difficult to measure the actual flow. The methods are used to estimate the flow. In most cases the flow rate is calculated based on type of fluid, head and pipe size etc, but the calculated figure may not be accurate. Another method is to divide the tank volume by the time it takes for the pump to fill the tank. This method can, however, only be applied if one pump is in operation and if the discharge valve of the tank is closed. The most sophisticated, accurate and least time consuming way to measure the pump flow is by measurement with an ultrasonic flow meter.
• Improper calibration of pressure gauges & measuring instruments - Proper calibration of all pressure gauges at suction and discharge lines and other power measuring instruments is important to obtain accurate measurements. But calibration has not always been carried out.  Sometimes correction factors are used when gauges and instruments are not properly calibrated. Both will lead to incorrect performance assessment of pumps.

If you have any queries regarding pump assessment, feel free to get in touch with Darling Pumps. Our ability to integrate different systems to provide customized technical solutions has made us the leader for custom pumping solutions in India. 
For further details, visit www.darlingpumps.in or call +91 99819 92838.

Why does Pump Motor Burn?

Pumping systems account for nearly 20% of the world’s electrical energy demand. Furthermore, they account for 25-50% of the energy usage in certain industrial plant operations. The use of pumping systems is widespread. They provide domestic, commercial and agricultural services. In addition, pumping systems provide municipal water and wastewater services, and industrial services for food processing, chemical, petrochemical, pharmaceutical, mechanical and other industries.

Problems Faced with Pump Motor

When a pumping motor has been installed properly, it can run for several years with minimal maintenance. One of the most commonly faced problems is failure of pump motor. There is a common misconception that motor fails due to voltage. But, it needs to be understood that motor does not fail because of voltage, in fact it burns because of current.

•          Over Load – Voltage fluctuations, mechanical and electrical malfunctioning, phase failure (single phasing). 
•          Under Load - Dry run, reverse rotation, mechanical failure, phase failure (single phasing)

To safeguard pump motor, we can monitor and control the current variation for its higher and lower allowable value.

Why it is critical to use control panel along with the pump?

A reliable & proper control panel is very critical for proper running of any pump set. A pumping motor does not understand -

• When it is under load.
• When it is running in reverse direction.
• When it is getting over heated.
• When it is running dry
• When it is getting overloaded

By adding a control panel to the system -

·         You can ensure consistent & stable electric supply that is not within our control under normal setup.

·         Pump by itself is not an intelligent device & panel, in turn, acts as an intelligent device of the pump.

Darling Control Panel is designed with advanced technology based system. It is safe and complete failure proof solution for long life, trouble free and continuous pump operation. Darling Control Panel positively monitors and controls current variations and safe guard’s pump set during those critical moments.

Different Types of Control Panel –

• Direct Online (D.O.L)
• Star delta (Y-Type)
•  Auto transformer (A.T.S)

For further details on submersible pumps and pump control panels, visit www.darlingpumps.in or call +91 99819 92838.

Energy Efficiency Opportunities for Pumps

There are several factors that affect pump performance and its energy efficiency. The main areas for energy conservation include:

1. Selecting the right pump

In selecting the pump, suppliers try to match the system curve supplied by the user with a pump curve that satisfies these needs as closely as possible. The operating point is where the system curve and pump performance curve intersect (as explained in the introduction).

The Best Efficiency Point (BEP) is the pumping capacity at maximum impeller diameter, in other words, at which the efficiency of the pump is highest. All points to the right or left of the BEP have a lower efficiency. The BEP is affected when the selected pump is oversized. The reason is that the flow of oversized pumps must be controlled with different methods, such as a throttle valve or a by-pass line. These provide additional resistance by increasing the friction. As a result the system curve shifts to the left and intersects the pump curve at another point. The BEP is now also lower. In other words, the pump efficiency is reduced because the output flow is reduced but power consumption is not. 

 

This figure shows a typical vendor-supplied pump performance curves for a centrifugal pump where clear water is the pumping liquid. 

 

2. Controlling the flow rate by speed variation

A centrifugal pump’s rotating impeller generates head. The impeller’s peripheral velocity is directly related to shaft rotational speed. Therefore varying the rotational speed has a direct effect on the performance of the pump.

The pump performance parameters (flow rate, head, and power) will change with varying rotating speeds. To safely control a pump at different speeds it is therefore important to understand the relationships between the two. The equations that explain these relationships are known as the “Affinity Laws”:

• Flow rate (Q) is proportional to the rotating speed (N)
• Head (H) is proportional to the square of the rotating speed
• Power (P) is proportional to the cube of the rotating speed

As can be seen from the above laws, doubling the rotating speed of the centrifugal pump will increase the power consumption by 8 times. Conversely a small reduction in speed will result in a very large reduction in power consumption. This forms the basis for energy conservation in centrifugal pumps with varying flow requirements.

Controlling the pump speed is the most efficient way to control the flow because when the pump’s speed is reduced, the power consumption is also reduced. The most commonly used method to reduce pump speed is Variable Speed Drive (VSD).

3. Pumps in parallel to meet varying demand

Operating two or more pumps in parallel and turning some off when the demand is lower, can result in significant energy savings. Pumps providing different flow rates can be used. Parallel pumps are an option when the static head is more than fifty percent of the total head.

4. Eliminating flow control valve

Another method to control the flow by closing or opening the discharge valve (this is also known as “throttling” the valves).

While this method reduces the flow, disadvantages are -

• It does not reduce the power consumed, as the total head (static head) increases. The figure shows how the system curve moves upwards and to the left when a discharge valve is half closed.
• It increases vibration and corrosion and thereby increases maintenance costs of pumps and potentially reduces their lifetimes

VSDs are a better solution from an energy efficiency perspective.

5. Eliminating by-pass control

The flow can also be reduced by installing a by-pass control system, in which the discharge of the pump is divided into two flows going into two separate pipelines. One of the pipelines delivers the fluid to the delivery point, while the second pipeline returns the fluid to the source. In other words, part of the fluid is pumped around for no reason, and thus is energy wastage. This option should therefore be avoided.

6. Start/stop control of pump

A simple and reasonable energy efficient way to reduce the flow rate is by starting and stopping the pump, provided that this does not happen to frequently. An example where this option can be applied is when a pump is used to fill a storage tank from which the fluid flows to the process at a steady rate. In this system, controllers are installed at the minimum and maximum level inside the tank to start and stop the pump. Some companies use this method also to avoid lower the maximum demand (i.e. by pumping at non-peak hours).

7. Impeller trimming

• Changing the impeller diameter gives a proportional change in the impeller’s peripheral velocity
• Changing the impeller diameter is an energy efficient way to control the pump flow rate. However, for this option, the following should be considered:
• This option cannot be used where varying flow patterns exist.
• The impeller should not be trimmed more than 25% of the original impeller size, otherwise it leads to vibration due to cavitation. It decreases the pump efficiency.
• The balance of the pump has to been maintained, i.e. the impeller trimming should be the same on all sides.
• Changing the impeller itself is a better option than trimming the impeller, but is also more expensive and sometimes the smaller impeller is too small.

To know more details about pump performance and its energy efficiency, contact us today at +91 99819 92838 or visit our website at http://www.darlingpumps.in/.

Know The Basic of Slurry Pumping

Slurry can be really tough on pumps! Being thick, abrasive & with high specific gravity, slurry is one of the most challenging fluids to move. 

 

What is slurry?

Slurry is a mixture of solids and liquid, generally water. The particles can be both abrasive & non abrasive, although abrasive particles are very much common. The purpose to move slurry can be transporting as much solids particles as possible, hydraulically, along with the given liquid.

Factors to be Considered in Slurry Pumping

• Particle size- d85= 3mm- means 85% of particles have a diameter of 3 mm or less.

• Specific gravity of solids particles (SGs)

• Specific gravity of liquid (normally water which is 1)

• Concentration of solids by volume (Cv)

• Concentration of solids by weight (Cm) (where Cv, Cm is given in % it means it is for slurry)

• Specific gravity of slurry (SGsl)

• Mass fraction (% of particles below 75 μm)

• Shape of particles (Round or Flat)

Characteristics of Slurry

1. Non – Settling Slurry - In this particle size is less than 60-100 μm. A non settling slurry can be defined as a Homogenous Mixture. It is comparatively easy to pump non-settling slurry.

2. Settling Slurry- In this particle size is greater than 100μm. Settling slurry can be defined as Pseudo-Homogenous Mixture OR Heterogeneous Mixture. This is where the demand on slurry pumps increase.

Few Slurry Pump Applications

• Steel Plant- Pumps for mill scale transportation.

• Thermal Power Plants- Pumps for fly Ash slurry handling.

• Hydel Plants & projects- Pump for removing silt and sediment from tailing dams, trenches, channels, Dam gallery, coolant sumps, etc…

• Mineral Processing Units.

• Mines & Quarries

• Various industrial uses like E.T.P, Cement plants, Fertilizer & Pharmaceutical Plants.

• Sand dredging, washing and cleaning.

• Lagoon cleaning & dredging near dockyard and ports.

Why Darling Pumps?

Darling Pumps with its comprehensive series of pumps can provide unique solutions for pumping of both - Settling as well as Non Settling Slurries.

We handle water of all types & quality.

• From clear water pumping to slurry handling we have solution for all.

• As we understand water better, we can help you handle it in a more effective manner.

• We provide customized solutions to all your pumping needs.

Check out our range of slurry pumps at http://www.darlingpumps.in/slurry_pumps.html To know more, call 

+91 99819 92838.

Oil Filled Pumps – A Quick Analysis of its Pros and Cons

The debate between air filled and oil motors is an ongoing one! So, basically what is an oil filled motor and what is an air filled motor? An oil filled pump is defined as having the motor cavity filled with oil, usually to cover the upper bearing and windings. An air filled pump is one that does not use any oil to fill the motor cavity. Wondering whether you should consider oil or air filled pumps for your application? Well, talk to the experts in pump industry today to get reliable solutions for your pumping problems.

Oil filled motors lower the winding temperature through extra heat transfer away from the stator, to the housings, and then out into the liquid. Heat kills electrical components so anything that is done to lower the temperature inside the pump will give a long lasting product.

Other advantages of oil filled pumps include –

• Better lubrication of bearing
• Lesser frequency of maintenance
• Ensure long life of pumps
• Transfer heat easily
• Easy to maintain

The downsides to oil filling are the environmental consequences and a lower overall efficiency due to churning losses when compared to an air filled type motor. The environmental issue can be easily resolved by using a type of oil that is environmentally friendly. The lower efficiency carries about 2% increase in overall energy costs. Both of these penalties are pretty easy to offset when the pros of oil filling are explored.

Why Choose Darling Pumps?

• Darling pumps do not require any oil replacement since it never gets heated up beyond its limits.
• The pumps are generally designed for 360 volts to 440 volts Electric supply, which to certain extent negates the damage caused due to voltage fluctuation.
• Extra heavy duty Bearings does not require frequent maintenance.
• Our Oil filled design ensures proper lubrication to bearings even in case of continuous duty.
• As Darling Pumps are wound with PVC Insulated winding wire, in case of emergency the motor can easily rewound at site itself. You don't have to send it to factory for repairs.

For further details, get in touch at +91 99819 92838 for further details.