Fire hydrant testing and water hammer - training resources and video

[77JQX]

Hi everyone. I work for a municipal water company. After yet another main break associated with water hammer from fire hydrant testing, I have been asked to provide some training to the fire department on the theory and effects of water hammer. I'm hoping some of you can point me toward some short but dramatic videos of water hammer, or other appropriate materials, that will get the attention of those lovable lugs who've been cranking the hydrants shut. I will be doing my own googling, so don't feel like I'm asking you to do that for me. But if you've seen something good, I'd appreciate a link. Any and all suggestions are welcome. Thanks.

 

[bimr]

You might talk to someone in your office that is responsible for SCADA. I know that some SCADA systems record water pressure and it is possible to document line breaks caused by water hammer with the SCADA system. It might spark some interest knowing that improper procedures are recorded,

 

[rconner]

While not necessarily so (maybe particularly in the case of long/extensive lines), I have always heard that water hammer can be a quite abrupt and transitory event that is not always seen on conventional pressure gauges or even some past chart recorders etc. It is indeed much more likely when very high velocities (probably non-obvious to many) are created via fire hydrant operations, air in lines and/or quick closures of same or valves etc.
While I do not have any direct experience with same, I have also heard that there are now small devices however that can be remotely mounted on fire hydrants claimed capable of recording up to 20 or more pressure readings per second (I guess thus claimed more likely to catch the wave, so to speak - you could proably google e.g. "Telog" to find out more about those.)

 

[rconner]

[bimr provided some links to some pretty darn good videos very recently at

http://eng-tips.com/viewthread.cfm?qid=360712

]

 

[LittleInch]

What you might think about is a mixture of dynamic analysis and practical show. The dynamic analysis would show the pressure spike for a rapid turn off and a much lower or no spike if you do it a bit slower. There are a number of pipe transient analysis programs able to do this.

On a more "practical" video / demonstration why don't you fit a small spool piece between the hydrant and the main or connect a spool to an open port on your hydrant fitted with a large flow pressure relief valve set higher than normal pressure but below the pressure which breaks your main. Then when you turn the hydrant off too quickly you should get a sudden burst of water from the relief valve which then shuts off. Then when you close it even a bit more slowly - no burst of water. Should make quite a good video / demonstration if you do it right.

Have a good search on you tube - I found this which is a bit twee, but shows the point.

http://www.youtube.com/watch?v=f9LY0-WP9Go

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[77JQX]

Thank you everyone. Your responses have been helpful. I'll be using portions of the videos linked by bimr and Littleinch. I was really hoping for some videos of field-scale pipes banging and jumping - I know I've seen one such video, but I haven't been able to locate it. We'll go ahead with lab scale demonstrations and some theory in our training to the fire department.

Our SCADA records, while sometimes helpful at identifying the times of breaks, don't do much in identifying the magnitude of transients since the scan time exceeds the duration of the transients. Rconner, I have three of the Telog hydrant mounted pressure recorders (models HPR-31 and HPR-31i) in my office right now. They're good units, and the newer units sample pressure at 20 Hz. With advance notice of where and when flushing would occur, we could cooperate with the fire department and capture some waveforms during the hydrant flushing.

We have a generally good relationship with the fire department, and we have been able to identify when their activities have caused several main breaks (in one instance where we wound up owning a pickup truck that feel into the resultant sinkhole). I say generally good, because sometimes they take the attitude that they're doing us a favor by helping us identify weak points in the distribution system, and are reluctant to pay for repairs. This is part of an ongoing effort to keep the rank and file up to speed on the care and handling of a water system during hydrant operations.

Thanks again.