A Web-Based Approach to Evaluate and Enhance Pump Performance Using Embedded Optimisation

Abstract

Selection and configuration are widely met tasks in design; this is an example of a web-based selection/configuration tool with embedded optimisation. Pumps inevitably deteriorate over their product lifecycle, in which interaction generally occurs in terms of flow, pressure and electricity consumption. Practical implementations of pump scheduling suggest that a 10% of the annual expenditure on energy costs may be saved. The object is to minimise the energy cost incurred, while selecting the best schedule of legal available pumps. The results illustrate that the recording of pump characteristics over the internet provides an efficient method of pump performance and evaluation.

Introduction

This paper describes the development of a secure web-based database that gives support to hydraulic engineers enabling them to select cost efficient pump combinations over the Internet Throughout the water industry, many methodologies of cost management have been adopted to enable the reduction of significant energy costs. Methods such as the refurbishment of deteriorated pumps, the use of high efficient motors, employing the most efficient pumps and ensuring that water is pumped using the smallest hydraulic head will enable substantial savings. The techniques of optimal scheduling are relevant to many areas of manufacturing and production engineering, such as scheduling of material flow, production planning, tool and plant scheduling, job shop scheduling and single machine scheduling. Optimal scheduling will effectively reduce the average job response. time, thus improving system efficiency and cost reduction. Using the combined methods of pump modelling, factorial analysis, linear programming and the Internet technologies, will provide an efficient process to enable the monitoring of pump performance and evaluation.

General Description and Methodology

Figure 1 illustrates a typical high-lift water pumping station (WPS) that consists of five fix speed water pumps connected in a parallel configuration. Each pump extracts clean water from a close by water supply tank and provides the customer with clean water via a water storage tank. The pumps are operated over a twenty-four hour period and individually monitored using micro-controller processors (MCP). The MCP’s enable the parameters of pump flow, pressure and energy consumption, on the delivery side of the pumps, to be recorded (Darbyshire & Waterworth. 2004). Figure 2 illustrates the total power consumption produced by the pumps over a twenty-four hour period.

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Figure 1: Water Supply System Schematic

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Figure 2: Total Pump Power Consumption

Figure 3 illustrates how the logged data is transmitted to the ‘pump control room’ through an outstation, commonly known as a remote telemetry unit (RTU) (Reynolds. 2004). The hydraulic engineer may then analyze the data and enable the construction of pump characteristic models and cost effective schedules to improve system efficiency.

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Figure 3: Data Transfer between WPS and Pump Operator

Since the WPS consist of five high-lift pumps, there are 32 (25) possible pump combinations during each two hourly switch over. The cost of generating electricity is more economical throughout the night than during the expensive daytime period. Due to this nightly rebate, optimum pumping is more cost effective through the hours of 1800hrs to 2400hrs (Darbyshire & Waterworth 2003). The electricity tariff for nightly use is 1.2p per hour, where the more expensive day period i.e. 0000hrs to 1800hrs is 2.86p per hour. The cost function for the applied problem is illustrated as follows:

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Other constraints for the optimisation model are that the maximum discharge capacity of the WPS must not exceed 2500m³ and the minimum must not fall below 1250m3 as illustrated below:-

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(2)

While constrained to the maximun and minimum limits:

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(3)

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(4)

Web Technologies

Over the last decade, the use of the Internet has been used broadly to circulate information globally. Due to the rise of Web 2.0 technologies such as e-commerce, online learning and online resources etc, there is the increased need for server side applications. Using the existing technologies of Hypertext Mark-Up Language (HTML), Java Server Pages (JSP) and Server Query Language (SQL), with a secure web based server, power, flow and pressure produced by the individual pumps may be monitored over the Internet (Lee & Scheeman. 2000). JSP enables the use of static HTML content with server side scripting to produce a dynamic output and is implemented as a classic three-tier client/server as illustrated in Figure 4.

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Figure 4: Client / Server: Three-Tier Architecture

The Java Database Connectivity (JDBC) Application-Programming Interface (API) allows the hydraulic engineer situated in the control room to interact with the SQL database server. Using Microsoft Excel and Direct Data Access (DDA), pump characteristics may be displayed in the form of a spreadsheet. The information may then be used to construct pump models using Matlab®, to calculate their best efficiency point (BEP) of operation as illustrated in Figure 5. A pump is then selected so that it runs at its best efficiency BEP relating to the expected system curve at the pumps BEP (Bunn. 2009). This is achieved using the pump affinity laws to help derive maximum flow, power and pump efficiency.

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