Chilled Water System Hammering - Air Trapped

[RobsVette]

Hi Guys,

I am working at a hospital in NYC and we had a contractor install some 10" chilled water pipe for us.

The pipe ran through some closets and high ceilings so I personally never actually looked at the run.

Today we started up a 125hp chilled water pump and the system was hammering alot. Every minute or so we would here a loud boom and the pipes would shake.

After some investigation I discovered a spot up in a ceiling where the pipe rises and comes back down and no air vent was left on the top. I assume this is the problem that would cause the boom but wanted to see what you guys would think.

The piping that got installed was to tie a new chiller and pump into an existing system. The existing system runs fine.

I know air trapped in a pipe can do some wild stuff, but I have never seen an air trap of this size before. The pipe work consists of a horizontal run of 10" pipe, a back to back elbow increasing elevation and then a straight run of about 15', then a drop down about 5'

We ran the pump for only a few minutes before shutting it off today, but apparently in that time we broke a small fitting on the existing sysem and caused a major flood. Apparently, everyone in the whole building heard the booming from the chilled water system.

Always interested to hear what you guys think. Its simply unfamiliar to me and I'm looking for insight.

Thanks in advance for any help.
Rob

 

[SAK9]

Air trap is the reason your pipework is vibrating.If the vibration frequency is close to the natural frequency of the pipe work installtion,it can get wild.
When you have pipework that runs up and down creating inverted "U" loops,you need to install automatic air vents at the high points.

 

[willard3]

Vent the loop, you've got air.

 

[DRWeig]

Good time to install an air vent up there since you accidentally drained some of the system...

Best to you,

Goober Dave

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[fineartsnyc]

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