Electricity + Control April 2017

ROUND UP

EARTHING + LIGHTNING PROTECTION FLOW MEASUREMEN

Effective flow measurement leads to leakage detection Information from ABB

Losses attributable to water leakage are a major concern in any water network.

tribution system that can be isolated by valves and for which the quantities of water entering and leaving can be metered. The subsequent analysis of flow and pressure, especially at night when a high proportion of users are inactive, enables leakage spe- cialists to calculate the level of leaks in the district. This can be used to determine not only whether work should be undertaken to reduce leakage, but also to compare levels of leakage in different districts and thereby target maintenance in those areas where it will have the greatest impact. Easy access Installing and accessing DMA meters can be difficult, especially in busy urban areas where the ground is already crowded with an array of underground assets, or where a pipeline runs under amajor road. Converse- ly, meters in remote areas may be nowhere near a potential power supply. Thankfully, today’s battery technology means that meters such as ABB ’s AquaMaster 3 can be sited pretty much anywhere, without hav- ing to worry about the availability of power supplies or the need for frequent access. It offers zero pipe diameters upstream or downstream with no loss of accuracy mak- ing it the perfect flowmeter for installations with limited space.

Accessing the data is the next challenge, but the latest technology can help here too. The transmitters have flow and pressure measurement capabilities, integral data loggers with possibilities of one minute logging and GSM text messaging, so that leakage managers can collect all the flow and pressure data from the comfort of the office. Conclusion Water utilities have been making do with an accuracy of ±2 % on mechanical flow meters. By using the electromagnetic meter with an accuracy of ±0,5% (or even better at 0,25%), the meter pays for itself within less than a month simply by measuring and charging the water more accurately. Further increased revenue come from the maximum and minimum flow rates, or op- erating range, of an electromagnetic meter compared with that of a mechanical meter. Its unique low flow rate capability enables previously unrecordableminimal night flow rates to be properly metered, which could double the saving potential. ABB has a wealth of experience and expertise in water management issues. Enquiries:Tel. +27 (0) 10 202 5000 or email instrumentation@za.abb.com With laminar flow, the distribution ratios of both gas quantities remain constant.This is important for the calculation of the flow volume.There are two temperature measur- ing points (RTD elements) in the measuring tube arranged in sequence (one behind the other). The gas flowing through is subjected to a constant amount of heat.The gas molecules absorb that heat and carry it away.This cre- ates a temperature difference between the sensors that increases with the amount of gas that flows through. The temperature difference creates a resistance difference in the RaTD elements. It is now only necessary to convert the tem- perature difference into the standard mass flow.

Even a small leak could potentially result in the loss of thousands of litres of water if left undetected. Given that each litre of this wasted water has been treated and energy has been expended pumping it around the network, such losses also represent lost revenue for water operators. DMAs – a key weapon against leaks District metering is an ideal starting point in the war against leaks. A District Metered Area (DMA) is a defined area of the dis-

Mass flow measurement of gases

KOBOLD, represented locally by Instrotech , has on offer type MAS mass flowmeter that works according to the calorimetric method of meas- urement, and was specially conceived for gas flow measurement. Since gases can be compressed, the volume changes with pressure and temperature. In practice this means that calibration should be done for a particular working pressure and temperature. This conversion is not needed with the MAS electronic mass flowmeter, because only the mass flow of the gas is determined by measuring the heat transfer. The gas is led through a sophisticated, laminar-flow-bypass that gives it a laminar stream. Due to the pressure difference

that arises, a small quantity of gas branches off into the measuring pipe.

Enquiries:Tel. +27 (0) 10 595 1831 or email sales@instrotech.co.za

Electricity+Control April ‘17

28