Fluid FlowTWO-PHASE FLUID FLOWSteamHammerSteam hammer is similar to water hammer except it is for a steam system. Steam hammer is agaseous shock wave resulting from the sudden starting or stopping of flow. Steam hammer isnot as severe as water hammer for three reasons:1. The compressibility of the steam dampens the shock wave2. The speed of sound in steam is approximately one third the speed of sound inwater.3. The density of steam is approximately 1600 times less than that of water.The items of concern that deal with steam piping are thermal shock and water slugs (i.e.,condensation in the steam system) as a result of improper warm up.OperationalConsiderationsWater and steam hammer are not uncommon occurrences in industrial plants. Flow changes inpiping systems should be done slowly as part of good operator practice. To prevent water andsteam hammer, operators should ensure liquid systems are properly vented and ensure gaseousor steam systems are properly drained during start-up. When possible, initiate pump startsagainst a closed discharge valve, and open the discharge valve slowly to initiate system flow.If possible, start-up smaller capacity pumps before larger capacity pumps. Use warm-up valvesaround main stream stop valves whenever possible. If possible, close pump discharge valvesbefore stopping pumps. Periodically verify proper function of moisture traps and air traps duringoperation.Rev. 0 Page 45 HT-03
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