Lab3 Pumps

ENSC3003 Lab3: Pumps Page 1

ENSC3003 – Fluid Mechanics Lab 3

Pumps Student Name: __________________________________________________ Student No: __________________________________________________

Lab Date/Time: __________________________________________________ INTRODUCTION The objective of this laboratory is for you to gain skills in analysing real pumps and pumping systems. The rig being used differs from an industrial pumping system only in scale, so the skills learned are likely to be useful in your working future. The laboratory will also demonstrate a link between the theory learned in lectures and a real application. This lab is also designed to emphasise safe working practices likely to be found in industry. At the completion of this laboratory, you should be able to:

• Recognise pump and system components and their purpose • Determine a pump curve • Understand the effect of changes in the system on the operating point of the

pump • Appreciate the effect of assembly, installation and operating practices on the

life cycle of the pump • Be familiar with common pipe and pump symbols on P+ID’s • Have appreciation of ‘safe practice’ around industrial equipment

SAFETY BRIEFING The pump test rig located in G50M is an industry-sized facility using standard industrial equipment. The specific hazards involved in operating the test rig are discussed below. The following general safety guidelines must be observed.

1. Personal Protective Equipment (PPE). Long pants, Long-sleeved shirt, and enclosed footwear must be worn. Hooded jackets are not permitted. Where appropriate, long hair must be tied back. Safety Glasses are supplied, and must be worn when in the presence of the Pump Test Rig.

2. Be aware that the pump rotates at 1500 rpm. 3. Be careful of fragile instrumentation cables 4. Connect the motor electrical supply only when directed by supervisor.

Unplug the motor electrical supply when the laboratory is completed. 5. Be aware that the rotor in the Cut-Away Demonstration Unit can rotate.


HAZARD IDENTIFICATION The pump laboratory involves inspection of the pump and piping system, and operation of the motor and pump. The main hazards of running the pump are:

LABORATORY ORGANISATION Students attending each session are divided into two groups of (up to) 5, designated as Groups A and B (refer to the laboratory assignments spreadsheet to determine your group). Group A will start the lab session by undertaking Exercise 1, which entails pump component identification using the cut-away pumpset demonstration unit located in the main laboratory (G50K). They will then move on to Exercise 2, system component identification and pump curve measurement, using the pump test rig located in the southwest corner of G50M. Group B will undertake the exercises in reverse order, starting with Exercise 2 and moving onto Exercise 1. It is anticipated that each exercise should be completed in 30-45 minutes. Note that due to space restrictions, each group must remain at its designated workstation until it is time to change over (ie when both groups have completed the first exercise).

Unit Hazard Mitigation Electrical supply The power supply from the

wall to the motor is high voltage (440v).

Check wiring and plug condition. Do not stand on cable. Only plug in when ready to run the pump.

Motor Motor Fan Do not place anything near fan end of motor. A cowling guards the fan.

Pump coupling Spinning shaft/coupling The coupling and shaft are guarded by a cover

Suction side valves

Closing the suction valves will starve the pump of fluid resulting in a build up of temperature.

Ensure suction valves are open.

Discharge side valve

Closing the discharge valve completely will dead-head the pump resulting in a build up of pressure in the casing.

Do not completely close the valve. Do not run with the valve 5-20% open for long periods.

Rotor in the Cut-Away Demonstration Unit

Rotor can rotate causing fingers to jam.

Do not expose fingers or other body parts to small clearances in rotating equipment. Only 1 person to touch the Cut-Away Demonstration Unit at a time.


REPORT For your report, you are required to answer the questions in this procedure, using the spaces provided on this procedure document. This document is then to be handed in to the ENSC3003 Assignment Box by 4:00 pm on Friday, June 1st EXERCISE 1: PUMP COMPONENT IDENTIFICATION 1. Inspect the Cut-Away Demonstration Unit.1 2. Identify the components listed in the following Table 1A. Label the photograph below with the components and discuss their function.

1 This demonstration unit was prepared by a 3rd year Mechanical Student as an EP307 project.


Table 1A: Pump Component Identification Table Component Located Function Suction flange

Impeller

Impeller hub and shroud

Impeller locking nut

Seal chamber

Volute

Discharge flange

Casing seal

Pump bearings and type

Shaft spacer

Coupling

Shaft key

Grease Nipples

Motor bearings and type

Motor stator

Motor rotor

Pecker Head (US) Junction Box (Aust)

Pump and motor feet


QUESTIONS: EXERCISE 1 What are the potential failure modes of the following components and what techniques would you use to identify/detect each failure. a. Impeller b. Pump bearings c. Coupling d. Motor windings e. Pump and motor assembly


EXERCISE 2: SYSTEM COMPONENT IDENTIFICATION AND PUMP CURVE MEASUREMENT

1. Inspect the pump rig and identify its components. Starting at the tank, move around the rig and name each fitting. A P & ID (Piping and Instrumentation Diagram) with standard symbols is provided in Figure 2A. Several items on the drawing are incorrect, correct the drawing. (Mark on diagram) 2. Identify where the suction and discharge pressure gauges and flowmeter are located. Are they all located in the correct place on the P&ID?2 (Mark corrections on diagram if required) 3. In your group, discuss the purpose of each fitting – why is it necessary?

(Discussion only)

Identify on pump test rig Value + Units (if applicable)

Pump maximum impeller size

Pump actual impeller size

Pump make and model

Pump inlet diameter

Pump outlet diameter

Motor Voltage

Motor Frequency

Motor Power

2 In some situations the pressure gauge mounting points will not always be located right on the pump flanges. When this occurs the static head and friction head losses between the pump discharge and the location of the pressure gauge must be calculated and the measured value on the pressure gauge adjusted


Figure 2A: Piping and Instrumentation diagram (P&ID) for the Pump Test rig



EXERCISE 2 (Cont): PUMP CURVE DETERMINATION Part of the laboratory involves determination of the pump curve. A pump curve shows pump head against flow rate at a constant motor speed. The pump head is measured using pressure gauges on the suction and discharge of the pump. Flow rate is measured on the flowmeter and a kilowatt meter measures power. Turning on any pump rig involves several checking steps. Below are some basic checks: Checks before operation

1. Check for general hazards lying around the rig. 2. Check that there is water in the tank 3. Check that both the suction valves are fully open 4. Check that the discharge valve is HALF open 5. Locate the on and off buttons 6. Turn on the power to the VFD at the switch on the wall.

Procedure

1. Begin by turning the pump on and increasing the speed with the VFD until the motor is running at 50Hz/ 1500 rpm. Leave the pump operating at this speed throughout the test.

2. Wait until the system is static and record the flow rate for this setting in the

given table

3. Fill in the table by measuring the suction head and discharge pressure at this flow rate, and the power drawn by the motor.

4. The aim is to fill the table in at four different flow rates. The measurements

are used to determine the Total Head on the pump at each flow rate. This is then plotted as a curve on the actual pump curve and the design v actual curves compared.

5. Flow rate can be adjusted either by varying the speed of the motor (if there is

a variable speed drive) or more commonly by throttling the flow using valves. Identify the valve used to adjust flow – it is a large brass valve with a red handle on the discharge line.

6. Partially close/open the valve to obtain the different trial points. Wait for the

system to settle. Once again fill in the table with the suction and discharge pressures and the motor power. Repeat to complete the table. Perform the calculations (in bold print). You need to collect enough points to draw a Head-Flow curve for the pump across the flow range indicated on the pump curve on the following page.

7. At the end, turn off the pump, shut the main suction valve and turn off the

power.


Calculations A pressure gauge placed on the discharge of the pump will read the following terms.

)(. DLDDD hgzgpP ρρ +⋅+= From the General Energy equation in your notes, we derived an expression for the Total Head HP on the pump.

€

HP =˙ W H˙ m g

=PD − PS( )ρg

+UD

2 −US2( )

2g

$

% & &

'

( ) )

The values UD and US are the velocity in the pipe at the pump suction and discharge. This is a function of the flow rate Q and the line diameter D.

Trial 1 Trial 2 Trial 3 Trial 4

Flow Rate (Q) m3/hr

Flow rate (Q) m3/s

Suction Head – manometer level (m)

Suction Head (kPa) PS

Line velocity at suction gauge

(m/s) US

Us2/2g

Total Suction Head (m) HS

(Ps/ρg + U2S/2g)

Discharge Pressure (kPa) PD

Discharge Head (m)

Line velocity at disch. gauge (m/s)

UD

UD2/2g

Total Discharge Head (m) HD

Total Head HP (m)

Motor Power (kW)

Pump efficiency (%)

Table 1.6.3A: Pump operation data entry


(U = Q/A = 4Q/(πD2), U = line velocity m/s, Q = flow rate m3/s, A = inside pipe area m2, D = inside diameter m). If the line sizes are the same ID for suction and discharge, the velocity term can be ignored. The pump efficiency is a ratio between the energy transmitted to the fluid by the impeller and the energy transmitted from the motor to the impeller. ηP = Hydraulic Power (

€

˙ W H ) / Power input to the pump shaft from the motor ( MW ) where

€

˙ W H = ρgQHP and MW is the motor power in kW. (It is usually necessary to take into account motor efficiency as well). ACKNOWLEDGEMENTS The pump test rig was designed by Claire Dean (Honours, 2001), and built by Blakers Pump Engineers. Alicia Webb (Honours, 2003) developed the procedures and principles on which this laboratory is based, and Daniel Kefford and Melinda Hodkiewicz compiled the procedure that this document was based on.


QUESTIONS : EXERCISE 2 1. A copy of the manufacturers pump curve is attached. On this head-flow graph,

plot the values for your Total Head HP v Q graph. How does your curve compare with the design curve for this installation?

2. Why is the measured efficiency of the pump so low?


3. If the flow through the system is lower than expected, what are the possible causes?

EXTRA WORKING SPACE


Documents

Lab3 Pumps