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Title: A Methodology For Community Involvement In Leaps
Author: E J Downs S
Author: Environment Agency
Document Type: Monograph
Annotation: Environment Agency Project ID:EAPRJOUT_305, Representation ID: 66, Object ID: 1651
SHEETS Information for Domestic and Agricultural Licence Holders Information for Spray Irrigation Licence Holders Information for Industrial and Commercial Licence Holders (including Electricity Generation) Information for Public Water Supply Licence Holders Version 3.1 February 2002 (iv) R and D Technical Report W84 Contents Abstraction Metering Good Practice Manual LIST OF TABLES Table 2.1 - Breakdown of licences 2-1 Table 3.1 - Performance types from WIS 7-03-01 3-14 Table 4.1 - Applicable meter types 4-1 Table 4.2 - Summary of measurement methods in part filled pipes 4-25 Table 4.3 - Recommended totaliser precision 4-27 Table 4.4 - Summary of characteristics of closed pipe flowmeters 4-28 Table 5.1 - Severity of flow disturbance 5-2 Table 5.2 - Distances of flowmeter from sources of disturbance 5-3 Table 5.3 - Summary of IP ratings from IEC 529 5-11 Table 6.1 - Key to meter types in Table 6.2 6-2 Table 6.2 - Intervals for flow checking (in years of use) 6-3 Table 6.3 - Distances from meter when using an insertion probe 6-9 Table 6.4 - Distances from meter for using a clamp-on 6-11 Table 6.5 - Flow checking with a clamp-on ultrasonic flowmeter 6-12 Table 6.6 - Remedial actions 6-19 LIST OF FIGURES Figure 1- Pipe dimensions ix Figure 2- Example of a flowmeter performance graph showing various key points xii Figure 3- Fully developed velocity profile xiii Figure 4- Velocity profile downstream of a bend xiii Figure 3.1 - Example of accuracy expressed as per cent reading and per cent full scale 3-1 Figure 3.2 - Relationship between accuracy and repeatability 3-2 Figure 4.1 - Typical Venturi installation 4-4 Figure 4.2 - Differential pressure transducer 4-5 Figure 4.3 - Variable area flowmeter 4-6 Figure 4.4 - Rotary piston meters 4-7 Figure 4.5 - Typical Woltmann meter 4-8 Figure 4.6 - Typical combination meter 4-10 Figure 4.7 - Irrigation meters 4-11 Figure 4.8 - Fluidic oscillator 4-13 R and D Technical Report W84 (v) Version 3.1 February 2002 Abstraction Metering Good Practice Manual Contents Figure 4.9 - Electromagnetic flowmeter 4-13 Figure 4.10 - Operating principle of an electromagnetic flowmeter 4-14 Figure 4.11 - Earthing an electromagnetic flowmeter 4-16 Figure 4.12 - Ultrasonic Doppler flowmeter 4-17 Figure 4.13 - Transit time ultrasonic flowmeter 4-18 Figure 4.14 - Electromagnetic insertion probe 4-20 Figure 4.15 - Alignment of insertion probes 4-21 Figure 4.16 - Averaging pitot tube 4-23 Figure 4.17 - "Watering can" meter for part filled pipes 4-24 Figure 4.18 - Typical totaliser display 4-26 Figure 5.1 - Poorly fitted gaskets can cause flow disturbance 5-1 Figure 5.2 - Always install electromagnetic meters downstream of pumps 5-2 Figure 5.3 - Bad and good installation practice 5-4 Figure 5.4 - Designs of flow straightener 5-5 Figure 5.5 - Vertical installation 5-5 Figure 5.6 - Installation of electromagnetic and ultrasonic instruments 5-6 Figure 5.7 - Installing the meter to maintain a full pipe 5-6 Figure 5.8 - Suitable and unsuitable meter locations 5-7 Figure 5.9 - Avoid installation in direct sunlight 5-9 Figure 5.10 - Avoid sites where chemical leaks or spillage may occur 5-9 Figure 5.11 - Avoid positions where vibration may be present 5-10 Figure 5.12 - Meter should be supported 5-10 Figure 6.1 - Examples of how to include a transfer standard 6-7 Figure 6.2 - Reservoir drop test 6-8 Figure 6.3 - Testing with an insertion meter 6-10 Figure 6.4 - Thermodynamic method 6-13 Figure 6.5 - Tracer dilution method 6-14 Version 3.1 February 2002 (vi) R and D Technical Report W84 Health and Safety Abstraction Metering Good Practice Manual HEALTH AND SAFETY IMPORTANT NOTE This manual contains procedures which may have to be applied in hazardous situations. The requirements of the safety policies of the Environment Agency and the abstractor must be observed at all times. The following have been identified as potential hazards: a working with electricity a working near water a confined spaces a lone working a pipelines under pressure a lifting heavy objects, e.g. drain covers a chemicals (e.g. tracers or cleaning/disinfection agents). Further guidance may be found in the following Agency documents: a Environment Agency Management Safety Standards No 3.2.1 Confined Spaces a Environment Agency Management Safety Standards No 3.2.3 Control of Substances Hazardous to Health (COSHH) a Environment Agency Management Safety Standards No 3.2.8 Lone Working a Environment Agency Management Safety Standards No 3.6.5 Working in or near Water Where the rules of the abstractor differ from those of the Environment Agency, the more stringent code shall be followed. R and D Technical Report W84 (vii) Version 3.0 August 1997 Abstraction Metering Good Practice Manual Health and Safety This page is left blank intentionally Version 3.0 August 1997 (viii) R and D Technical Report W84 Glossary Abstraction Metering Good Practice Manual GLOSSARY More complete explanations of some of these terms can be found in the main text. The relevant section number is given in brackets where this is the case. Accuracy - Qualitative assessment of the reading given by an instrument compared to the true value over a defined range of flows (Section 3.1.1). Bi-directional - Measures flow passing through the meter in either direction. Bore - Internal diameter (i.d.) of pipe, see Figure 1. Calibration - Determination of the relationship between flow rate and reading which may include mechanical or electrical adjustments to produce a desired characteristic. Cavitation - Release of gas dissolved in the fluid or vaporisation of the fluid due to the local static pressure dropping below the vapour pressure of the fluid. Liner (if present) Pipe wall Wall thickness Liner thickness Internal diameter (i.d.) Outside diameter (o.d.) Figure 1 - Pipe dimensions R and D Technical Report W84 (ix) Version 3.0 August 1997 Abstraction Metering Good Practice Manual Glossary Combination meter - Meter which comprises a main meter, usually a Woltmann type, with a smaller meter mounted in a by-pass, with an integral valve to divert flow through whichever meter is appropriate for the flow rate (Section 4.5.2). Conductivity - The ability of a fluid to pass an electric current, commonly expressed in micro-Siemens per centimetre (AMicro/cm). D (diameter) - Nominal bore (internal diameter) of a pipe, see Figure 1. Multiples of pipe diameters are a useful dimension for specifying pipe lengths, e.g. for the distance between a flowmeter and a fitting. Differential pressure cell - Device for measuring the difference in pressure between two points (Section 4.2.2). Electromagnetic flowmeter - Flowmeter which utilises the Faraday effect, i.e. an electromagnetic field is generated across the pipe and the movement of a conductive fluid, e.g. water, through the field causes a voltage to be produced which is measured and used to calculate flow rate (Section 4.7). Error - Difference between a single measured value and the true value, often expressed as a percentage of the true value. Flowmeter - Device which measures either the rate at which fluid is flowing past a certain point or which gives the total amount of fluid which has passed a certain point in a known time. NOTE: In this report, the term flowmeter, or meter, is taken to include the flow sensor and any associated secondary device, electronics or automatic data recording device. Flow checking (Verification) - Testing whether a meter is reading to the desired accuracy by comparing its readings with those obtained simultaneously by another method or meter of known accuracy. Flow rate - Quantity of fluid passing a particular point per unit time. Flow straightener - Device placed in the flow to help recover a fully developed velocity profile (see below) after a source of disturbance (Section 5.1.3). Full scale - The maximum flow rate that the flowmeter will read to a specified accuracy. Head loss - A measure of the energy required for the fluid to pass through obstructions and fittings in a pipe, expressed as a drop in pressure. Helix meter - See Woltmann meter. Impeller meter - See Woltmann meter. Insertion flowmeter - Flowmeter which is inserted through the wall of a pipe via a gland (Section 4.9). Version 3.0 August 1997 (x) R and D Technical Report W84 Glossary Abstraction Metering Good Practice Manual In-situ - Without removing the instrument from the pipeline. Integrator - See Totaliser Jet meter - Flowmeter where the fluid is forced through one or more small orifices onto the blades of a rotor (Section 4.5.3). Local or point velocity - The fluid velocity at a discrete point in the flow. Mean axial velocity - The volumetric flow rate divided by the cross sectional area at the point of measurement. Multimeter - Instrument for measuring electrical currents and voltages. National Standard - The National Standard flow rig is at the National Engineering Laboratory (NEL) in East Kilbride. It can trace its measurement of the mass of water passed directly to the National Standard kilogram. By definition, it is the most accurate test rig in the UK against which other rigs should be compared. Non-intrusive - Meter has no parts intruding into the flow and hence causes minimal disturbance and head loss. Oscilloscope - Instrument for measuring electrical voltages and displaying the wave form on a screen. Positive displacement flowmeter - Meter which divides the fluid up into discrete, known quantities (Section 4.4). Primary device - A device which generates a signal enabling the flow rate to be determined. Q - Flow rate, often used with a suffix to indicate particular flow rates, see Figure 2: Qmin - the minimum flow rate that an instrument can measure to the maximum specified error. Qmax - the maximum flow rate at which the flowmeter will operate for short periods of time without deteriorating. Qt - the transitional flow rate, i.e. the rate at which the maximum permissible error changes in value Qn - the nominal flow rate of a flowmeter. Repeatability - The ability of an instrument to record the same value for the same flow under the same conditions in a short period of time (Section 3.1.3). R and D Technical Report W84 (xi) Version 3.0 August 1997 Abstraction Metering Good Practice Manual Glossary Reproducibility - The ability of an instrument to record the same value for the same flow over the long term. Secondary device - A device which receives a signal from the primary device and displays, records, converts and/or transmits it as a measure of flow. Strainer - Device placed in the flow to remove weed, gravel and other debris (Section 5.3.5). Swirl - A component of flow which is rotating around the longitudinal axis of a pipe. Totaliser (Integrator) - Device which records the total quantity of liquid to have passed through the meter. This may be integral to the meter or a separate unit (Section 4.12). Transfer Standard - A flowmeter calibrated to a known uncertainty against which another flowmeter can be compared (Section 6.2.1). Error as per cent measured value 10 5 2 0 Qmin Qt Qn Qmax Flow rate -2 -5 -10 Figure 2 - Example of a flowmeter performance graph showing various key points Turbine flowmeter - Flowmeter which has a rotor mounted in the flow (Section 4.5). Turndown - Ratio of the maximum and minimum flows measurable by a device to a stated uncertainty. Ultrasonic flowmeter - Flowmeter which operates using pulses of ultrasound (Section 4.8). Version 3.0 August 1997 (xii) R and D Technical Report W84 Glossary Abstraction Metering Good Practice Manual Uncertainty - Band around the measured value within which the true value lies with a stated probability, usually 95% (Section 3.1.1). Uni-directional - Measures flow in one direction only. Velocity profile (Sometimes referred to as aflow profilea) - The distribution of point velocities over the cross section of the flow. Frictional forces between the flowing fluid and the pipe wall will slow down the fluid close to the wall so that it has a lower velocity there than the centre of the pipe. The operation of the types of flowmeters likely to be used for abstraction purposes assume that the velocity profile on inlet to the meter will be what is known as afully developeda, see Figure 3. Deviations from this shape caused by bends, Figure 4, valves and other fittings are likely to cause inaccuracies in the flowmeter reading amounting to several per cent. Figure 3 - Fully developed velocity profile Figure 4 - Velocity profile downstream of a bend R and D Technical Report W84 (xiii) Version 3.0 August 1997 Abstraction Metering Good Practice Manual Glossary Verification - See Flow checking Volumetric flow - The volume of fluid passing a certain point per unit time. Woltmann meter - Type of turbine meter with a helical rotor (Section 4.5.1). Version 3.0 August 1997 (xiv) R and D Technical Report W84 Introduction Abstraction Metering Good Practice Manual 1.
Publisher: Environment Agency
Subject Keywords: Community participation; Integrated catchment management; Environment Agency
Extent: 148
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