TABLE OF CONTENTS Flow testing of distribution systems is typically accomplished by discharging water through hydrants. Through calculation or graphical construction, the flow characteristics of the system can then be derived. The information presented in this chapter builds on the basic hydraulic concepts presented in Chapters 1 and 5.
References required for this chapter are:
NFPA Fire Protection Handbook
SFPE Handbook of Fire Protection Engineering
Fire protection engineers must measure flow and pressure characteristics in closed piping primarily when testing stationary fire pumps with recirculating test assemblies. Manometers typically utilize mercury in a "U" tube to measure water pressure. They are used in conjunction with other types of flow measurement devices, such as venturi tubes, which give a reading in terms of differential flow pressures. The pressure is calculated by adding the displacement of the mercury below the equilibrium line on one side of the tube and the displacement above the equilibrium line on the other. The mercury head in inches can then be converted to water head in feet, at one atmosphere, by multiplying by 1.132.
The most widely used flow measurement devices on closed piping for fire protection purposes are venturi tubes and orifice meters.
Reading: NFPA Fire Protection Handbook, pp. 6-89 to 6-90, on flowmeters
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| Sample Question: Manometer readings taken from a standard (ASME) venturi tube located on a 4.0 in. inner diameter fire pump test pipe indicate a displacement from either side of the manometer datum... |
