Water hammer avoidance

Sudden vapor condensation in the pool may cause water hammer if the holes are too big and the pressure drop is too low Sonic hole velocity is desirable to avoid this problem. 

J. Kremers of Armstrong Machine Works provided the following useful article on avoiding water hammer. It is reprinted in total with permission. 

With a better understanding of the nature and severity of the water hammer problem, we can avoid its destructive forces. This greater understanding should also help with the introduction of more preventive measures into system designs and installations, which will help provide maximum safety for personnel, lower maintenance cost and reduce system downtime. 

Here is an additional tip on avoiding water hammer from the editor, Carl Branan. 

Kremers, J., Avoid Water Hammer, Hydrocarbon Processing, March, 1983, p. 67. 

The amount of moisture that air can hold is inversely proportional to the pressure of the air. As the pressure of the air increases, the amount of moisture that air can hold decreases. The amount of moisture air can hold is also proportional to the temperature of the air. As the temperature of the air decreases, the amount of moisture it can hold decreases. The pressure change of compressed air is larger than the temperature change of the compressed air. This causes the moisture in the air to condense out of the compressed air. The moisture in compressed air systems can cause corrosion, water hammers, and freeze damage. Therefore, it is important to avoid moisture in compressed air systems. Coolers are used to address the problems by moisture in compressed air systems. 

The above unit is economical, avoids water hammer, has excellent control, and is easy to start up. Contrary to popu-... 

Depending on the relief stream components (with or without noncondensable gases) and quenching efficiency, this arrangement often obviates the need for a subsequent scrubber and/or flare stack. The design of the quencher arm is critical to efficient condensation and avoidance of water hammer. Figure 23-55 is the more conventional passive type quench pool used in the chemical and nuclear industry. 

Figure 8.8 Avoiding water hammer in a condensate collection system.

Water hammer may cause extreme stresses at bends in pipelines. Consequently, liquid pockets should be avoided in steam lines through the use of steam traps and sloping of the line in the direction of flow. Quick-opening or quick-closing valves may cause damaging water hammer, and valves of this type may require protection by use of expansion or surge chambers. 

Another problem can cause vibration and sounds that make the operators refer to it as water hammer. Without going into the theory of long bubbles getting trapped in vertical downflowing pipes, the avoidance of problems will be discussed. For theory. Reference 2 is recommended. 

Example 7.11 makes clear that rapid valve closure can cause very high pressures at the valve. I That raises the obvious question of how slowly one must close a valve to avoid water hammer. The approximate answer is that if the time to close is longer than the time for a sound wave to make a round trip from the valve to the reservoir] then no significant water hammer will occur. Again, see Parmakian [1] for more jdetails. 

Undersized steam traps, dirty traps, and incorrectly installed traps should be avoided. Oversized traps can cause water hammer. 

Always open the valves in water lines slowly to avoid water hammer and likely damage to pipes and fittings. 

The shock wave may he several times the normal pressure and will travel to the end of the Une where it wUl he reflected back. The cycle will be repeated until all the energy is dissipated or relieved. The rapid closing of valves and piping layouts that are conductive to water hammer should be avoid. Surge tanks, pneumatic chambers, relief valves, or shock absorbers and arrestors are sometimes used to control water hammer concerns. Water Reactive Chemical... 

Inlet piping must be adequate to avoid water hammer and poor trap performance. They should not be undersized. To avoid sudden flashing of condensate, with its attendant problems, the line should be ... 

Confirmation of proper opening/closing speed to avoid water hammer. 

Water hammer can be a problem when performing a hydrostatic, high-pressure test. If water is introduced into a piping system too quickly a water hammer can result. This can damage the piping and should be avoided. Water hammer can be avoided by introducing water into a system at lower velocities. 

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