Water Hammer and Swagelok Energy Advisors Prevention Tips

The right time to fix it is now, and then work on preventing recurrence

	Shown above is a steam trap installation. To download a copy of SEA's  Steam Systems Best Practices PDF, click here.

If you think water hammer is just a nuisance, check out what happened when it caused a rupture in a steam pipe under the streets of New York in 2007. Of course water hammer doesn't always result in this degree of catastrophe, but even in its less severe forms, water hammer will wear out components and cause leaks. It can overstress pressure gauges, crack steam trap bodies, rupture pipe fittings, break welds, and cause valves to fail.

Unfortunately, most steam systems experience some type of water hammer, leading some people to mistakenly believe that water hammer is unavoidable. It isn't. If the system is properly designed and operated, water hammer in any form will not occur. The better you understand the nature and severity of water hammer in a steam and condensate system, the better you can avoid it.  

Listen

Often, a steam system will tell you when there's a water hammer problem.

“SEA is often called in to identify the cause of water hammer” says Tristian McCallion, ‎sales supervisor at Edmonton Valve & Fitting. "You'll hear the pipes rattling or hear them shaking, or there will be a failure analysis of a steam system component that identifies water hammer as the root cause of the failure."

In fact, tracking down the source of the problem is one of the main reasons we are called out for audits.

But sometimes water hammer is silent. For example, a small steam bubble may collapse inside the system, creating a thermal shock that is not heard by the human ear. Even so, damage to steam and condensate components is still occurring.

Prevention

As with many problems in life, prevention is the best cure. Some proactive measures that prevent or eliminate water hammer include:

1. Proper training for plant personnel.

2. Correct steam and condensate piping design.

3. Have documented standard operation procedures (SOPs) for steam system startups and shut downs.

4. Have installation standards for steam components.

5. Specify and place steam line drip steam traps on the steam system to ensure proper condensate drainage out of the steam system.

6. Correct condensate piping connections of branch lines to the main condensate line and enter only on the top.

7. Ensure that steam traps are properly sized and appropriate for the application.

8. Use warm up valves on steam line isolation valves larger than 2 inch.

9. Checking or repairing the pipe insulation to reduce the build up of condensate in the steam lines.

10. Correct condensate line sizing. Under-sizing the condensate lines is one of the largest contributors to water hammer.

11. A system that has a modulating control valve should have a drip leg trap upstream of the valve to remove condensate during a closed condition for the valve.

12. Always use gravity to drain condensate  away from the process applications that use a  modulating control valve.

13. Condensate can be drained into a pressurized condensate return line only if proper differential is maintained.

14. Properly label the steam and condensate lines.

15. Isolate and remove abandoned steam and condensate lines from the system.

16. Have a proactive maintenance program.

Even if your system is designed properly at the start, people often add and remove components as needs change over the years, McCallion says. It's smart to have someone check the piping configuration to make sure the system has proper drainage and functional steam traps on a regular basis.

Swagelok Energy Advisors has a more detailed description of water hammer and its prevention. It includes detailed descriptions of the four kinds of shock that water hammer can produce. The PDF is free for download online.