Exploding Plastic Tanks to Simulate Water Hammers

Using the KineticSystems DAQ518 Portable High-Speed Data Logger

CHESTERLAND OH—November 14, 2011

CAS DataLoggers recently provided the datalogging solution for a large manufacturer of plastic water tanks. The customer manufactured heavy plastic tanks, as thick as an industrial Pelican case, designed to install in toilets. Normally a water system such as a toilet contained about 40-80 lbs of pressure, so the manufacturer usually tested their toilets to two or three times that for safety reasons. However, a common plumbing problem could develop in the form of a ‘water hammer,’ a sudden spike in water pressure occurring when a valve suddenly closed at an end of a pipeline system, such as when a home’s occupants turned off a water flow from a dishwasher, a laundry machine, or a toilet. With the valve closed, the water suddenly had to stop or change direction. Since the mass of water was still moving forward with high velocity, in the worst-case scenario, a water hammer could spike the pressure in the toilet’s tank to as much as 250lbs–enough to burst the heavy plastic tank! To design even stronger containment structures and help prevent any potentially harmful occurrences, the company needed to measure the amount of force that could be generated during a tank explosion. These tanks were normally pressurized to 40-70 PSI, but under certain fault conditions the pressure could exceed 200 PSI, causing the tank to violently rupture. The company’s demanding quality assurance tests on the tanks required a powerful yet portable datalogging solution offering a large number of analog inputs, wireless Ethernet connection to a PC or laptop, and user-friendly configuration and display software.

The customer installed a KineticSystems DAQ518 Portable High Speed Data Logger in their testing area and connected it to load cells installed in several toilet tanks under test to record the force generated by sudden tank ruptures. The DAQ518 was a complete 18-channel multiplexed signal conditioning system featuring 16 differential input analog channels with fixed gain and filters, 2 frequency inputs, and an external trigger input. This compact system provided 2 channels of direct strain gauge input with programmable excitation voltage, internal signal amplification and filtering, and the ability to record at up to 50 kHz with an aggregate sampling rate of up to 32k samples/second. Using the data supplied by the load cell manufacturer, personnel quickly configured the DAQ518 to excite the load cells, amplify the resulting signal, and scale the data to force. Charts and numeric displays built into the software simplified the configuration of the test set-up by providing immediate feedback as changes were made.

For the safety tests, the manufacturer built a test fixture with one free wall to contain the tank. This free wall needed to be instrumented in such a way as to measure the peak force generated during the event. Two compression “load button” load cells from Interface Technology were selected because their small size and low height allowed them to be easily affixed between the free wall and the fixed structure of the test fixture. The load cells selected had a range of 0-500 lbs with a 150% overload rating. Internally, the load cells used a 4-wire bridge circuit that required a voltage or current excitation and provided a nominal output of 2 mV/V of excitation at the rated load. The tanks were then subjected to intense water hammer events and the force of the resultant ruptures was recorded.

Another important feature of the DAQ518 datalogger was its ability to break large data sets into multiple, smaller files for easier manipulation and analysis. Over the course of these tests, the heavy-duty tanks could take anywhere from several hours to several days to fail under stress. Consequently, data was sampled at 1 kHz to capture the peak force generated during the failure; this could potentially generate more than 300 million points, making it impractical to try to analyze this much data in a single file. By breaking the data into multiple smaller files, it was much faster and easier for engineers to zoom into the area of interest.

The DAQ518 datalogger comprised a rugged, portable stand-alone data logging system with up to 64 channels, removable Flash memory and Ethernet communications for industrial and in-vehicle applications. Auto-configuration on power-up was supported for stand-alone applications. The ultra-compact and fully enclosed chassis weighed only 2.5lbs (1.13kg), making it an ideal portable solution. The logger featured 2 analog input channels with bridge signal conditioning, programmable gain and filter, along with 16 analog input channels with fixed gain and filter. The datalogger also featured an external trigger input and 2 additional frequency measurement channels, 16-bit analog-to-digital converter resolution, and a maximum aggregate sampling rate of 50 kHz. Local CompactFlash data storage was also standard. 10BaseT Ethernet connectivity to a PC or laptop enabled wireless communication with the data logger for setup, data display and processing.

VersaDAQ software was included free with the data logger and managed and controlled the datalogger’s operations including setup, data acquisition, and data recording. VersaDAQ ran on a PC or laptop and connected to the datalogger’s chassis via the 10Base T Ethernet connection. The software’s user-friendly interface allowed quick setup for data collection and storage, and also configured channels, sample rate, record mode and calibration.

The plastic tank manufacturer benefitted in several key ways following installation of the DAQ518 Portable High Speed Datalogger in their quality assurance testing, foremost of which was the ability to accurately record the force of the controlled explosions, directly resulting in a safer and more reliable product. The datalogger offered testers both portability and wireless Ethernet connection, making logging convenient and hassle-free. Additionally, the included software was easy to learn and easily controlled the logger’s many setup, configuration and recording functions.

Check out the DAQ518 Portable High Speed Datalogger product page here.

For further information on the KineticSystems DAQ518 18-Channel Portable High Speed Datalogger, other KineticSystems portable data acquisition and datalogging systems, or to find the ideal solution for your application-specific needs, contact a CAS Data Logger Applications Specialist at (800) 956-4437 or visit the website at www.DataLoggerInc.com.

Contact Information:
CAS DataLoggers, Inc.
12628 Chillicothe Road
Chesterland, Ohio 44026
(440) 729-2570
(800) 956-4437
sales@dataloggerinc.com
http://www.dataloggerinc.com

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