Steam and Condensate Water Hammer Overview

Inveno Engineering, LLC is a recognized global leader in steam system engineering, providing unmatched expertise and innovative solutions worldwide.
Today we would like to discuss water hammer in the steam and condensate system, which is a major safety issue and will cause reliability issues for plant operations.
Unfortunately, 82% of the steam systems in North America experience are experiencing some type of water hammer. Water hammer is unavoidable and a natural part of a steam and condensate system. This is an entirely false statement. Water hammer is a major safety issue. Water hammer is a global challenge, and we have worked with plants worldwide to assist in resolving water hammer issues.
Steam and condensate system water hammer. Water hammer is not only a system issue, but primarily a safety issue. It can injure or even cause fatalities, thus a major safety issue for plant operation. Eliminating water hammer needs to be a top priority for everybody in the plant. Understanding the water hammer will help plants implement necessary changes in the system design, startup, maintenance, operation, and installation to eliminate water hammer, ensuring plant personnel's safety, reduce maintenance costs, avoid system downtime, and of course increase production.
Where does water hammer occur? Water hammer can occur in the steam or condensate system. There are many causes for water hammer. No plant operation should be occurring water hammer. Water hammers is abnormal and should never be thought of as normal. Steam and condensate water hammer is totally abnormal.
Water hammer in steam system.
Installing steam lines improperly will cause water hammer. Example. Here you will see a steam line pipe expansion loop installed a downward location which causes a low point in the steam line. There was no steam line drip leg installed on the steam line to remove condensate. Therefore, excessive condensate will build up in the steam line expansion loop and generate water hammer.
Allowing high steam line velocities, failing to remove condensate properly from steam lines during operation, are typically causes for water hammer in steam systems.
Process water hammer
Processes at ambient conditions or startup mode, when high temperature steam is instantaneously introduced into the process can cause high velocity condensate rates, thus resulting in water hammer. Another common type of water hammer is known as flooded shock water hammer, where condensate will back up into the heat transfer application, causing water hammer. Flood shock water hammer can be due to several different things.
One item that can cause flooded shock water hammer in process applications, is using on/off steam control valves for heat transfer application instead of modulating control valves.
Next item would be piping steam trap condensate discharge pipe to an elevated condensate header above the heat transfer exchanger
Important note is on a modulating steam process application; the condensate must flow away from steam trap into a gravity condensate header with zero pressure.
Another cause is undersized steam traps. Improperly sizing steam traps or using steam traps with the wrong condensate discharge orifice will cause condensate back up into the heat transfer resulting in water hammer.
The condensate line is another major issue. Allowing abnormal high condensate line pressures, when the process steam system cannot tolerate high back pressures in the condensate system.
Condensate system water hammer
The condensate system can be two-phase, which is liquid (condensate) and vapor, which is flash or generated steam passing into the condensate line. When two-phase condition exists, where condensate coexists with generated steam or flash steam and if condensate line velocities can exceed 4,500 feet per minute then water hammer can occur. When that high condensate line velocity occurs and resulting in water hammer – the system will occur a banging sound like this in the video.
This type of water hammer is called differential shock water hammer.
Condensate removal from process applications.
The condensate needs to be removed as quickly as it's formed. Again, undersized or improperly sized condensate removal devices that allow condensate to back in the process will cause water hammer.
Or high condensate line pressures. A steam trap inlet pressure (P1) must be greater than steam trap outlet pressure (P2). A very simple statement, but a high percentage of times our engineering teams find that P2 is greater than P1, thus causing major problems.
Another major source of water hammer is that steam trap condensate discharge piped into the wrong location on the condensate header. As seen in the picture example, condensate pipes into the bottom of the condensate header, this piping arrangement will result in water hammer 100% percent of the time.