Pressure Recorders/Loggers 1

[utilengr]

We are looking to replace old chart recorders with newer equipment also capable of capturing pressure spikes/water hammer. There are a couple that we've been looking at:
1) ITT Unit:

http://www.globalw.com/products/pl200_h.html

2) Telog Unit:

http://telog.com/Portals/31/documents/HPR_LPR31i.pdf

There are 2 key differences
1) Price
2) Sampling rate - The ITT unit can capture 10 samples/sec, while the much more expensive Telog Unit can capture 20 samples/sec.

I've been trying to determine if the additional sampling rate is needed to be able to get useful information from the unit associated with pressure spikes. Both advertise the same ability to capture pressure spikes. Could a peak be missed if only sampling at a 10th of second rate? Any thoughts on this would be appreciated - as well as any feedback on these particular units (or others) if there is direct experience with either/both.

 

[bimr]

If the water hammer occurs in milliseconds, a sampling rate of 20 samples per second is too slow to capture the spike.

http://www.omega.com/techref/waterhammer.html

 

[utilengr]

In looking at some empirical data generated by others on-line I was seeing this possibility as well. Some of the high resolution graphs of the spikes showed a complete cycle occurring within .1 sec. So with the .1 sec sample rate it could be pure chance that a data point was close to the peak. Sampling at 500ths of sec. - same thing, as you point out.

I'm think that maybe we go with the cheaper unit for general data collection and maybe install it with a double needle, pressure holding gauge when trying to pick up hammer issues in our systems. I've not looked at the peak holding gauges yet but assuming they are fairly responsive it might give more information about an event than a higher price data collector. -?

 

[mjpetrag]

installing a check valve in front of a pressure gage might be a cheap fix if you're trying to find the peak system pressure

-Mike

 

[bimr]

try this unit:

http://www.hwm-water.com/dataLoggingPressure.htm