The influence of air presence on flow measurement related to water supply system

ABSTRACT

In water supply networks, valve maneuvers and pump stop, for example, can cause air to enter the pipelines and, in some situations, this air can be eliminated through home connections, with the potential to increase registered volumes by the water meters. This has been a cause for concern by the part of inspection agencies, concessionaires and consumers, mainly in large Brazilian cities. Despite the great importance of the subject, it is observed that there is still a small amount of studies and technical-scientific works on this subject. The present research had as objective to present parameters and procedures that help the understanding of the operation of water meters under the presence of air and the consequent influence on the recorded volumes. A simple and effective method was developed to perform bench tests that made it possible to quantify the volume of air flow that is effectively recorded by a water meter typically used in residential connections. The results show that the volume of air registered in the water meters can reach values up to 90%, when the flow rates are high, around 1,600 L/h. At low flow rates, this percentages drops, becoming null when the flow rates are less than 430 L/h. In case of flow inversion occurring in the water meter, the recorded values are smaller than those measured when the flow occurs in the nominal sense, not fully compensating the possible volumes of air accounted for during the water supply.

Keywords:
water supply; air in pipes; micro-measurements