Naval Surface Warfare Center
9500 MacArthur Blvd
West Bethesda, MD 20817
25 October, 2000Mr. Larry Shroyer
P.O. Box 85
Union City, MI 49094
Dear Larry, Thank you very much for providing a loaner Ener-Tec device for our Summer, 2000 field test. This letter describes last summer’s field test of Ener-Tec Inc’s biofouling control device and gives the biomass results from the Ener-Tec test line.
1. Ener-Tec Device and Test Line
The Ener-Tec device produces a DC magnetic field in the range of 100-200 Gauss. It consists of a unit containing the magnet that is less than 1 foot long that mounts over the titanium tube to be protected. There is also a small control unit that is mounted nearby.
2. Test Setup
The field test was performed at the NSWCCD Marine Corrosion Test Facility in Dania, FL. The test lines were fed by coastal seawater drawn from the mouth of the Port Everglades shipping channel. The system was fed by a two-stage pumping system. The first stage was a Pacer model SE2ELNC2.OC pump (total dynamic head of 30 psi and maximum flow of 110 gpm) which drew from the Intracoastal Waterway Inlet, approximately 50 yards upstream from its exit to the Atlantic Ocean. This pump fed into a 1500-gallon plastic tank. The second stage pump for all but the chlorinated test line was a Hayward Model SP2621X25 pump (maximum total dynamic head of 30 psi and maximum flow rate of 95 gpm) which also drew from the tank and fed a 2” PVC manifold to which the test lines were connected. The second stage pump for the chlorinated test line was a Hayward Model SP2610X15 pump (maximum total dynamic head of 40 psi and maximum flow rate of 100 gpm) which drew from the tank and fed a 2” PVC manifold to which the chlorinated test line was connected.
Each test line consisted of an approximately 8’ long piece of 5/8” diameter titanium tube connected to the supply manifold by a hose. In addition to the Ener-Tec test line, there was an untreated control test line, a test line that was treated with 200 ppb of chlorine for 2 hours a day followed by an 8 ft/sec flush for 15 minutes, and a test line treated with an ultraviolet unit. The chlorinated and UV test lines were included to provide a comparison of the effectiveness of the Ener-Tec device with alternative methods for biofouling control. The UV unit was an Aquafine model RBE-SL1 rated at 10 gpm for freshwater. Due to the turbidity of the Ft. Lauderdale seawater, it was expected that the effectiveness of the UV unit would be fairly limited. The interior of the titanium tubes was washed with bleach prior to the beginning of the test to remove adventitious material. During the test, seawater flowed through the tubes continuously. The flow rate was set to 1.8 ft/s in all test lines and was readjusted once a day on each line. The flow rate of 1.8 ft/s was chosen to match that used in previous chlorine minimization tests conducted by NSWC. The Ener-Tec device ran continuously until August 23, 2000, at which time the test was shut off.
3. Biomass Measurements
On August 23, the sea water flow was terminated and the titanium tubes sectioned into approximately 1’ long sections. The tubes were stored wet, in a refrigerator, until biomass measurements were performed approximately 2 weeks later. Biomass measurements were performed as follows. Each tube section was rinsed gently with water. Loosely bound material that was washed out of the tubes was collected, dried and weighed. The rinsed tubes were dried at 105 oC overnight and weighed. Each tube was then swabbed gently with a test tube brush under flowing water to remove all remaining biological material from its interior. The tube was then weighed again. The weight difference before and after swabbing gives the mass of biological material that was strongly bound to the tube. The sum of the loosely bound and strongly bound material was normalized to the tube inside surface area. The biomasses for each 1’ tube section were averaged and are reported in the Table below.
4. Biomass Results
|Test Line||Average Biomass (mg/cm2)|
|Ener-Tec Device (LKC)||0.710.07|
The biomass results are given in the Table for the untreated control titanium tube, the chlorinated titanium tube, the UV tube and the Ener-Tec titanium tube. The error bars are standard deviations of the mean of the biomass values of the tube sections from a given test line.
5. Conclusion and Recommendation
The titanium tube on which the Ener-Tec resonator was mounted appears to be somewhat cleaner than the control titanium tube. However, the biomass difference between the two tubes is likely less than the error bars on the measurement, as would be determined by running replicates. Therefore, I recommend that the Ener-Tec device be tested again in the same or similar test format in the NSWC Summer, 2001 field test in Ft. Lauderdale, FL. This additional test will provide us more data to assess the significance of the result given above. Please let me know if you would be interested in again providing a loaner Ener-Tec device for this field test. I would expect the test to begin approximately late April or early May of 2001.
Robert A. Brizzolara