Pumps Role in Plant Energy Efficiency

The Different Types of Pumps
There are many different types of pumps available for various applications. Positive displacement pumps are suitable for low flow rate, high pressure applications, while hydrodynamic pumps are more suitable for high volume flow rate and medium to low pressure applications. The most commonly used pumps are vane pumps, gear pumps, screw pumps, hydrodynamic pumps, centrifugal pumps or radial flow pumps, mixed pumps, and axial flow pumps.

Vane Pumps
Vane pumps are ideal for applications that require high flow rates and low pressure. They are often used in vacuum systems and hydraulic power units. Vane pumps are known for their quiet operation and good efficiency, and they are easy to maintain.

Gear Pumps
Gear pumps use two gears to move fluid from one side of the pump to the other. They are typically used in industrial and automotive applications, as they are capable of pumping large volumes of liquid at a relatively low pressure.

Screw Pumps
Screw pumps use a rotating screw to move fluid from one side of the pump to the other. They are usually used in applications that require high pressure, as they are capable of producing very high pressures.

Hydrodynamic Pumps
Hydrodynamic pumps are mainly used in applications that require large volumes of liquid to be pumped at medium to low pressures. They are usually used in large-scale industrial and agricultural applications.

Centrifugal Pumps or Radial Flow Pumps
Centrifugal pumps or radial flow pumps use an impeller to move fluid from one side of the pump to the other. They are usually used in applications that require large volumes of liquid to be pumped at medium to high pressures.

Mixed Pumps
Mixed pumps are a combination of both positive displacement and hydrodynamic pumps. They are usually used in applications that require both high pressure and high flow rate.

Axial Flow Pumps
Axial flow pumps are used to move liquid from one side of the pump to the other. They are typically used in applications that require large volumes of liquid to be pumped at low to medium pressures.

Pump Performance
Pump performance is typically measured in terms of flow rate, head, input power, efficiency, and speed. Flow rate is usually measured in units of volume per unit of time (ft³/sec, gal/min, m³/hr). Head is usually measured in units of ft or m. Input power is usually measured in units of work per unit time such as kW or hp. Efficiency is usually measured as a percentage. Speed is usually measured in rpm.

Pump Flow Control
Pump flow control can be achieved through throttling, bypass, or speed control. Throttling reduces the flow rate by blocking or reducing the size of the pipe, while bypass reduces the flow rate by diverting some of the fluid away from the pump. Speed control is the most efficient technique, as it reduces the system friction head.

Pumps are used in many different types of applications in a variety of industries. There are many different types of pumps, and they can be classified according to their theory of operation, type of fluid being pumped, and performance. Pump flow control can be achieved through throttling, bypass, or speed control. Understanding the different types of pumps and how to control the flow rate is essential for any successful pumping application.

Optimizing Pump Capacity for Maximum Efficiency

Pumps are the single largest electricity user in a refinery and account for close to half of all electricity use in motors. Optimal pump system design should focus on minimizing lifecycle costs, rather than initial capital costs, since energy costs can account for up to 95% of a pump system’s lifecycle costs. To maximize efficiency, there are two main ways to improve pump system performance: reducing friction in dynamic pump systems and adjusting the system to draw closer to its best efficiency point (BEP).

Reducing Friction in Dynamic Pump Systems

To reduce friction in dynamic pump systems, several measures can be taken. By correctly sizing the pipes, surface coating or polishing, and using adjustable speed drives, for example, the friction loss can be reduced, thus increasing the energy efficiency of the pump system. Additionally, correctly sizing the pump and choosing the most efficient pump for the applicable system will push the system closer to the best efficiency point on the pump curve.

Adjusting the System to Draw Closer to the Best Efficiency Point (BEP)

The best way to draw closer to the best efficiency point on the pump curve is by choosing the most suitable pump for the applicable system. This means selecting a pump that is specifically designed for the required operating conditions and is powerful enough to meet the demands of the task at hand. Additionally, using adjustable speed drives to regulate the speed of the pump can also increase the efficiency of the system. This is because adjustable speed drives allow the pump to operate at the most efficient speed for the given load.

Conclusion

Pump systems are a major energy user in refineries and other industries, and optimizing them for maximum efficiency is essential for reducing energy costs. To do this, reducing friction in dynamic pump systems and adjusting the system to draw closer to the best efficiency point (BEP) are the two main ways to increase pump system efficiency. By correctly sizing the pipes, surface coating or polishing, and using adjustable speed drives, the friction loss can be reduced and the system can be pushed closer to the best efficiency point on the pump curve.

Operations and Maintenance for Optimizing Pump System Efficiency

Proper maintenance of a pump system is essential for optimal efficiency. It includes the following:

• Replacement of worn out impellers, especially in caustic and semi-solid applications.
• Bearing inspection and repair.
• Bearing lubrication replacement, once annually or semiannually.
• Inspection and replacement of packing seals.
• Inspection and replacement of mechanical seals.
• Wear ring and impeller replacement.
• Pump/motor alignment check.

Monitoring for Maximum Efficiency

Monitoring is a key component of operations and maintenance for ensuring optimal pump system efficiency. It should include the following:

• Wear monitoring.
• Vibration analyses.
• Pressure and flow monitoring.
• Current or power monitoring.
• Differential head and temperature rise across the pump.
• Distribution system inspection for scaling or contaminant build-up.

Reducing the Need for Pump Capacity

To further optimize the efficiency of a pump system, the following steps can be taken to reduce the need for additional pump capacity:

• Use of holding tanks to equalize the flow over the production cycle.
• Elimination of bypass loops and other unnecessary flows.
• Reduction of process static pressure.
• Minimization of elevation rise from suction tank to discharge tank.
• Use of siphons to reduce static elevation change.
• Lowering of spray nozzle velocities.

Pump Efficiency: Increasing Efficiency to Save Energy

Pumps are a critical part of many industrial processes and their efficiency can have a dramatic impact on energy consumption. In order to maximize efficiency, there are a number of strategies that can be employed.

Choosing the Right Pump:
Selecting a pump that runs at the highest speed suitable for the application will generally result in a more efficient selection as well as the lowest initial cost. Exceptions include slurry handling pumps, high specific speed pumps, or pumps that require a very low minimum net positive suction head at the pump inlet.

Correct Sizing of Pump(s):
Pumps that are sized inappropriately can cause unnecessary losses. Peak loads can be reduced and pump sizes can be downsized. Oversized pumps can be slowed down with gear or belt drives or a slower speed motor.

Use of Multiple Pumps:
Using multiple pumps can be the most cost-effective and energy efficient solution for varying loads, particularly in a static head-dominated system. This can offer redundancy and increased reliability.

Trimming Impeller:
If a large differential pressure exists at the operating rate of flow, the impeller (diameter) can be trimmed to reduce the pump’s head. In the food processing, paper and petrochemical industries, trimming impellers or lowering gear ratios is estimated to save up to 75% of the electricity consumption for specific pump applications.

Controls:
The objective of any control strategy is to shut off unneeded pumps or reduce the load of individual pumps until needed. Remote controls enable pumping systems to be started and stopped more quickly and accurately when needed, and reduce labor.

Pump Energy Savings Through Adjustable Speed Drives, Throttling Valves and More

Pumps are often used in a wide variety of industrial applications, ranging from manufacturing to water supply and more. As such, they can be a source of significant energy costs if they are not properly maintained and used. Fortunately, there are several ways to achieve significant energy savings with pumps, including the use of adjustable speed drives (ASDs), throttling valves, correct pipe sizing, precision castings and surface coatings, sealing, and reducing clearance.

Adjustable Speed Drives (ASDs)

Adjustable speed drives (ASDs) are a great way to improve the efficiency of a pump system. By matching the speed of the pump to the load requirement, energy use can be reduced significantly. This is particularly true for pumps, where the flow rate is approximately proportional to the cube of the flow rate. By making small but proportional reductions in flow rate, considerable energy savings can be achieved.

In addition to reducing energy consumption, the installation of ASDs can also improve overall productivity, control and product quality while reducing wear on equipment and thus maintenance costs. Generally, a 10% reduction in flow rate can result in 20% energy savings, while a 20% reduction can result in 40% energy savings.

Throttling Valves

Throttling valves should always be avoided when possible as they can result in considerable energy losses. In most cases, the use of throttling valves is a sign that the pump is oversized. Variable speed drives or on-off regulated systems are much more energy efficient and can lead to significant savings.

Correct Sizing of Pipes

Correct sizing of pipes is essential for efficient pump operation. Pipes that are too small can cause significant energy losses, while pipes that are too large can lead to expensive investments in additional pump system components. The optimum pipe diameter should be selected based on a careful consideration of economics, flow velocity, internal diameter, and maximum flow velocity to minimize erosion.

Precision Castings, Surface Coatings, or Polishing

The use of castings, coatings, or polishing can reduce surface roughness and improve the efficiency of pumps, particularly smaller ones. In one case study in the steel industry, surface coating investments for 350 kW pumps cost nothing and were paid back in months in energy savings.

Sealing

Seal failure can account for up to 70% of pump failures in many applications. The use of gas barrier seals, balanced seals, and no-contacting labyrinth seals can help optimize pump efficiency and reduce seal failure.

Curtailing Leakage Through Clearance Reduction

Leakage can be reduced by reducing the internal clearance between the impeller and the pump casing. Clearances that are too large can lead to considerable efficiency losses, while clearances that are too small can increase wear rate. In most cases, the normal clearance in new pumps should range from 0.35 to 1.0 mm.