Difference between revisions of "Chapter Six: Pumping Systems"

From Ministry of Water DCOM Manual
Line 32: Line 32:
 
| Positive displacement || Reciprocating || Suction (shallow well)
 
| Positive displacement || Reciprocating || Suction (shallow well)
 
|-
 
|-
|  || Example || Lift (deep well)
+
|  || || Lift (deep well)
  
 
|-
 
|-
 
|  || Rotary || Helical Rotor
 
|  || Rotary || Helical Rotor
 
|}
 
|}
 +
(Source: Modified from Uganda water design manual 2013)
 +
 +
== 1.4 Pumping System Setup ==
 +
When setting up the pumping system, carefully calculate the driver Horse Power (HP) required based on the data on the flow, pressure and efficiency of the pump. Check the pump RPM and drive RPM and select the proper size pulleys to achieve the desired flow. Review the maximum horsepower per belt to assure that the pump receives adequate power to deliver the desired flow. The correct belt length and centre distance must be established to achieve the proper HP. If in doubt, consult your pump and/or drive supplier for their recommendations.
 +
 +
== 1.5 Source of Pumping Power ==
 +
The different types of power sources commonly used for water supply pumps include:
 +
 +
* Electrical grid power
 +
* Diesel/gasoline generators and engines
 +
* Natural gas/biogas generators
 +
* Solar Energy
 +
* Wind Energy
 +
 +
The choice of pumping energy depends on several factors namely:
 +
 +
* Availability of and proximity to grid power,
 +
* Capital costs of the alternatives,
 +
* Operational costs of the alternatives.
 +
 +
In Tanzania when deciding on the pumping energy, grid power is considered as the basic source in the sense that when available it becomes the 1st choice. It is only when the grid source is too far from the pumping point that the other sources are considered. The three alternatives to grid power namely diesel/petrol/natural gas/biogas generators or engines have both positives and negatives. In the following subchapters each alternative shall be discussed.
 +
 +
== 1.6 Pumping system design pump selection ==
 +
Pump selection involves selecting the type of pump that fits the application and sizing the pump to be able to deliver the required pressure and flow to the point of delivery.  The factors which should be considered in the selection and sizing of a pump include:
 +
# Depth to the water level and its seasonal variations;
 +
# Pressure ranges needed for adequate water supply;
 +
# Heights through which water has to be lifted, both below and above the pump;
 +
# Pump location;
 +
# Pump durability and efficiency.
 +
 +
The type of pump selected for a particular installation should be determined on the basis of the following fundamental considerations:
 +
# Yield of the well or water source;
 +
# Daily needs and instantaneous demand of the users;
 +
# The “usable water” in the pressure or storage tank;
 +
# Size and alignment of the well casing;
 +
# Total operating head pressure of the pump at normal delivery rates, including lift and all friction losses;
 +
# Difference in elevation between ground level and water level in the well during pumping;
 +
# Availability of power;
 +
# Ease of maintenance and availability of replacement parts;
 +
# First cost and economy of operation;
 +
# Reliability of pumping equipment; and
 +
# Pump start-up problem and time.
 +
 +
Tables 6.2(a) and (b) shows the operation ranges of different type of pumps according to the head required and the flow rate needed. For water supply pumps the two have to be considered for a good pump. Examples of pump duty calculations is provided in Appendix E.

Revision as of 20:48, 30 April 2020

1 Chapter Six: Pumping Systems

1.1 1.1 Introduction

This section describes the water supply pumping systems. Brief presentation of types of pumps are provided. Also, it describes how to design and select pumps for a water supply system. Lastly, it gives key considerations in their installation. It is important to understand the different types of pumps, design procedures, source of pumping power, motor starting, machine protections and economics of electric power systems. However, more details on pump types and their functioning are given in Appendix E.

1.2 1.2 Rationale

The main goal of any pumping plant and pumping system is to lift water from a lower to a higher level.

1.3 1.3 Common Types of Pumps used in water supply

There are two main pump types used in the water supply projects which are different in design and application. Table 6.1 shows the most commonly used pump types. Further details of each type of pumps can be seen in Appendix E of this DCOM manual.

1.3.1 Table 6.1: Most Commonly Used Pump Types

Main Types Sub-types Specific types
Rotordynamic Centrifugal Single-stage
Multi-stage shaft driven
Multi-stage submersible
Peripheral Axial flow
Mixed flow
Turbine
Submersible
Positive displacement Reciprocating Suction (shallow well)
Lift (deep well)
Rotary Helical Rotor

(Source: Modified from Uganda water design manual 2013)

1.4 1.4 Pumping System Setup

When setting up the pumping system, carefully calculate the driver Horse Power (HP) required based on the data on the flow, pressure and efficiency of the pump. Check the pump RPM and drive RPM and select the proper size pulleys to achieve the desired flow. Review the maximum horsepower per belt to assure that the pump receives adequate power to deliver the desired flow. The correct belt length and centre distance must be established to achieve the proper HP. If in doubt, consult your pump and/or drive supplier for their recommendations.

1.5 1.5 Source of Pumping Power

The different types of power sources commonly used for water supply pumps include:

  • Electrical grid power
  • Diesel/gasoline generators and engines
  • Natural gas/biogas generators
  • Solar Energy
  • Wind Energy

The choice of pumping energy depends on several factors namely:

  • Availability of and proximity to grid power,
  • Capital costs of the alternatives,
  • Operational costs of the alternatives.

In Tanzania when deciding on the pumping energy, grid power is considered as the basic source in the sense that when available it becomes the 1st choice. It is only when the grid source is too far from the pumping point that the other sources are considered. The three alternatives to grid power namely diesel/petrol/natural gas/biogas generators or engines have both positives and negatives. In the following subchapters each alternative shall be discussed.

1.6 1.6 Pumping system design pump selection

Pump selection involves selecting the type of pump that fits the application and sizing the pump to be able to deliver the required pressure and flow to the point of delivery. The factors which should be considered in the selection and sizing of a pump include:

  1. Depth to the water level and its seasonal variations;
  2. Pressure ranges needed for adequate water supply;
  3. Heights through which water has to be lifted, both below and above the pump;
  4. Pump location;
  5. Pump durability and efficiency.

The type of pump selected for a particular installation should be determined on the basis of the following fundamental considerations:

  1. Yield of the well or water source;
  2. Daily needs and instantaneous demand of the users;
  3. The “usable water” in the pressure or storage tank;
  4. Size and alignment of the well casing;
  5. Total operating head pressure of the pump at normal delivery rates, including lift and all friction losses;
  6. Difference in elevation between ground level and water level in the well during pumping;
  7. Availability of power;
  8. Ease of maintenance and availability of replacement parts;
  9. First cost and economy of operation;
  10. Reliability of pumping equipment; and
  11. Pump start-up problem and time.

Tables 6.2(a) and (b) shows the operation ranges of different type of pumps according to the head required and the flow rate needed. For water supply pumps the two have to be considered for a good pump. Examples of pump duty calculations is provided in Appendix E.