FLOW THROUGH and UNDERWAY DAQ SYSTEMS
aboard USCGC HEALY
Report on work accomplished during Leg2, Science Ice Trials
by Anthony F. Amos and Andrea C. Wickham-Rowe
the University of Texas at Austin Marine Science Institute
750 Channel View Drive
Port Aransas, TX 78373
afamos@utmsi.utexas.edu, wickham@utmsi.utexas.edu
INTRODUCTION
Our task during Leg2 of the Science Ice Trials aboard Healy was to test 1) The Uncontaminated Science Seawater System (USSS), that supplies 2) the Sea-Bird model 21 Thermosalinograph (TSG) instrument and 3) the Turner Designs model 10 AU Fluorometer. In addition, we were tasked with testing the flow to the on-deck incubator (not yet installed) which we did in collaboration with Terry Whitledge (see separate report). The test protocols (Test Description Sheets) were not supplied to the UTMSI team until after we debarked from St. Johns at the start of Leg 2, hence we were not aware of some of the test requirements, especially for the Fluorometer, until sailing time. Consequently there were certain supplies and equipment not available to us to complete the tests as in the test specifications. However, we have used the test protocols as guidelines to do the work, but have also drawn on our experience with flow through systems to modify the procedures and comment in this report on deficiencies and make appropriate suggestions. Formal test numbers are as follows
1) 8C521D541 Proper operation of the USSS system
2) 8C666D542 Operational readiness of the TSG in a cold weather environment
3) 8C666D541 Operational readiness of the Fluorometer, Model 10-AU-005 in a cold weather environment.
4) 8C666D544 Demonstrate Healy’s capabilities of the Uncontaminated Science Seawater Incubator.
We also came prepared to work on a software system that Amos has devised to acquire data from the various environmental sensors, including the TSG and Fluorometer. Interest in having such a software system for Healy had been expressed by participants at various Research Vessel Technical Enhancement (RVTEC) meetings by Coast Guard attendees. A preliminary version of the software was sent to the USCG following the International Marine Technical (INMARTECH) meeting held at Scripps Institution of Oceanography in October 1998 but no follow-up ensued. The Amos system was modified during Leg2 and is currently up and running in a prototype version (see Appendix).
1) The Uncontaminated Science Sea Water System supply
(8C521D541).
There are several critical aspects of any USSS that must be met:
· By definition, that the water supply be uncontaminated by ship-generated chemicals and oils (not part of this test).
· That there be adequate flow rate.
· That the temperature of the supply at any point where available for use match that of the ambient sea-surface water. This is particularly important in a vessel like Healy that operates in a cold water environment.
· That the USSS intake must not be blocked by ice while the vessel is in the ice pack.
· That the supply not be infused with air bubbles during operation of thrusters and the Dynamic Positioning System (DPS). If this is unavoidable, that a de-bubbling unit be installed in those lines where cavitation would give false readings.
Test Procedure
We first located all of the USSS outlets. Some location had two outlets on the same lines (table 1). We tested all of these. There are a total of 21 individual outlet points (Fig 1) in the USSS, of which we tested 20 (one was capped off and unavailable). The interior outlets had spigots and hose attachments that facilitated the performance of the tests. Many of these had thermistors permanently inserted with a data logger and printout available (see report by John Freitag). None had flow meters in-line, nor was there a flow meter available for the test as required by 8C521D541. To measure flow rates, we made up a hose that was long enough to reach available sinks (many of the interior outlets are located above spaces that should be kept dry). A 2-gallon bucket was found and calibrated using a measuring container borrowed from the galley. A digital immersion thermometer measuring to the nearest 0.1C, as required by the test protocol, was borrowed from Jim Arias. The range of this instrument (-50 to +350C) was too wide to provide accuracy of the degree desired.
The measuring method employed was to attach the hose and lead the end to a sink, open the spigot fully, and allow the water to run with the immersion thermometer inserted into the hose end until an equilibrium was reached. Then the bucket was filled to the calibration mark and the elapsed time noted using a digital watch. Data were entered in a log sheet (included in the attachments to this report). The thermistor data logger was set to 30-second intervals during these tests and the underway logging system recorded the TSG temperature throughout. There is no way measure the flow at the sea chest as required in 8C521D541. Two thermistors are inserted in the USSS line close to the intake. These record on a separate data logger that was set to record at once per minute. The data loggers seemed to be overly complicated and it took John Freitag and Jim Arias a long time to get them to record the temperatures properly. There was an RS232 data port but they were not able to configure, so we recorded all data on the “Grocery Tape” printer. Later these data were transferred to a spread sheet by hand entry.
None of the outlets on the weather decks were equipped with spigots or hose bibs. These had been secured with flange caps that were removed by the MSTs before we performed the tests. Essentially the same procedure was used as with interior locations, but the water from each outlet had to be discharged on to the deck Here we had to rely solely on the digital thermometer for discharge temperature measurements. Unfortunately, moisture got inside the thermometer electronics and, although the instrument was still functioning, reading the faint display was difficult and prone to error (only the top half of each digit was displayed).
Results (with reference to 8C521D541Demonstration Procedure page2 where appropriate
1 UNCONTAMINATED SCIENCE SEAWATER SUPPLY FLOW TEST
1.1 The PUMP RUNNING indicator light at local start/stop control point is working .
1.2 Cannot verify that there is 50 GPM flow at the sea water pump. It is doubtful that 50GPM is available, nor is it desirable for most USSS applications.
.
1.3 Sea water temperature at pump measured successfully. Figure 2 graphs the data at one-minute intervals throughout the duration of the test (1030 to 1420 local time, 06 June 2000, blue trace). It was fortuitous that during this interval we traversed from open water with sea surface temperatures of >4C to the ice and the required 8/10 cover at <-1C.
1.4 Table 2 lists the flow rates (last column) measured at the locations specified. Rates vary from 0.9 to 6.5GPM. The low rates are in the climate control chambers and are due to the small diameter delivery spigots available there. Highest flow rates are on the 02 level science van supply outlets that do not have spigots installed yet. The mean flow for all supply outlets is 4.3 GPM. In Table 2, the temperature at each outlet is listed as measured by the thermistor at those locations where they are installed, by the digital thermometer, and by the supply thermistors at the time the flow rates were measured.. The data are also graphed in Figure 2. Note that degree of warming in the pipes as indicated by this test varies from -0.1 to +1.4C, depending on location. The mean is +0.6C. The mean difference between the two temperature measuring devices is 0.0C, although the standard deviation is quite high. However, we believe that the mean of the two thermistors at the pump intake is within 0.1C of the actual temperature at the intake depth of 8m. An important outlet is C4 in the biochemical laboratory. This supplies the Fluorometer with its flow through supply. The temperature difference here is +0.4C and the flow rate 4.5GPM, perfectly adequate for the Fluorometer operation. Perhaps the most important of all in respect to knowing the degree of warming in the pipes is the Thermosalinograph supply. This is plumbed in such a fashion that its temperature and flow rate cannot be measured directly. Flow to the TSG must be turned off before one can externally monitor the flow rate and temperature ( see the next section).
2 SHUTDOWN PROCEDURES
2.1 Pump was secured at entrance to Nuuk harbor.
2.2 Entire system not drained as it will be used on Leg 3
Problems and Recommendations will be listed at the end of this report.
1) The Thermosalinograph or TSG (8C666D542)
The protocol called for a testing time of 2 hours but we felt that it would be much more instructive to run the TSG throughout the cruise. Measurement was required at a sea water temperature of 27.5F (-2.5C). There is no normal temperature in the world ocean that is -2.5C. The temperature range throughout the cruise was from -1.1 to +4.8C ( 30.3F to 40.6F), most of which was encountered during the testing phase above.
Test Procedure for Thermosalinograph with reference to 8C666D542 (page 2)where necessary
1 PREREQUISITES
1.1 We have no knowledge of previous testing of the TSG before Leg2
2 TEST CONDITIONS
2.1 The vessel was in a cold water environment throughout the test.
2.2 As noted above, the sea water temperature requirements are not attainable, except at the upper limit.
3 TEST INITIALIZATION
3.1 System Configuration
1. There was no figure 1 in the test description sheet but we confirm that the TSG is properly configured.
3.2 Initializing communications
The TSG was turned on as per 1 through 5 in the Test Description Sheet and operated normally. We consider that the prime test for the veracity of the TSG operation is to compare the TSG output both in temperature and salinity with that obtained at the same time by a CTD cast with accurate sensors measuring at the depth of the USSS intake (8m). Additional data may be collected by drawing water from the USSS line and running the salinity on the Guildline Salinometer. We noted that the TSG frequently showed considerable noise on the trace as displayed on the data acquisition computer. This was obviously due to bubbles in the line. When noise occurred, It could sometimes be quieted by adjusting the flow rate to the TSG using the valve on the port side forward bulkhead in the biochemical laboratory. Bubbles can be heard coursing through the pipe. The adjustment is not always successful. We noted that the problem was frequently exacerbated by the operation of the thrusters and the DPS. We noted no particular increase in the noise when Healy was in the ice during Leg2. The appearance of noise, other than when thrusters were on was random. A de-bubbling device has been delivered to the ship but we could not plumb this in to the line due to lack of appropriate hose and plumbing fittings. It is expected that the noise problem will be minimized when the de-bubbler is installed.
Table 3 shows the differences encountered between CTD and TSG. In these tests, the temperature difference can be considered to be warming in the pipe as both CTD and TSG sensors are essentially the same. The mean warming is 0.43 C and a correction of -0.43 applied to the TSG would correct the output to within +- 0.1C. It is interesting to note, and almost counter-intuitive to observe, that the colder the sea temperature at the intake, the greater the degree of warming. This can also be seen by examination of Figure2. The degree of warming, around 0.4C, is in agreement with that obtained during the flow through tests.
The salinity comparisons are not so encouraging. Two outliers of -0.224 and +0.296ppt are unacceptable (Table 3). Normally, we don’t expect salinity differences of consequence between the CTD and the Thermosalinograph. It should be noted that there are problems with one or both CTD conductivity sensors, but these test were conducted using samples from the Carousel, run on the Salinometer and hence independent of CTD data. We have complete confidence in these results We have asked Rich Findley if he would collect some more samples to run on the Guildline Salinometer during leg 3.
Test Procedure for model 10-AU-005 Fluorometer ( 8C666D541).
We did not perform the detailed test procedures outlined in this test description sheet. These were mostly involved with setting up and calibrating the Fluorometer using samples and blanks. Healy has no material or equipment necessary for performing such tests. Although a discrete sample cuvette and holder is available, the Fluorometer is set up to be used in flow through mode with a flow through cell. It is our experience that scientists coming aboard to use the Fluorometer in this mode would wish to do their own calibrations and would do this by filtering samples collected at intervals and doing chlorophyll extractions. The extractions would be run on a separate Fluorometer set up for discrete sampling (it is not practicable to alternate between flow through and discrete sampling with the same Fluorometer during a cruise. The procedure would mean taking the flow through instrument off line and losing data in the process.
We did set up the Fluorometer with hoses to the sink in the biochemical laboratory and followed the usual procedures of setting up the 10 AU using the menu as described in the test procedure. The Fluorometer was operated continuously throughout the cruise and the values appeared to be reasonable and varied as expected in the cruise area. There was not much of a change in the surface Chl-a in this region at this season and no phytoplankton blooms were observed..
PROBLEMS AND RECOMMENDATIONS (not listed in any particular order)
· The sinks in the science laboratories must be provided with proper drains. Presently they overflow onto the lab floors.
· The Fluorometer needs to be re-plumbed to avoid having hoses snaked along the floors and draining into the sink.
· The de-bubbler should be installed in-line with the Fluorometer and TSG to reduce the noise on the record caused by air bubbles in the USSS.
· The Thermosalinograph is capable of outputting three decimal digits yet the data string on the Shipboard Data Network (SDN ) contains only two. Perhaps the TSG output should be sent directly to the (SDN) rather than through a dedicated computer (although the monitor display is useful to have in the lab).
· Some data losses seem to occur when perhaps stray RF fields from equipment start ups cause RS232 lines to drop out. This occurred with the air temperature sensor data line. A dropout of GPS data also occurred earlier in the cruise but this might have been due to other problems.
· We recommend that an electronic barometer and relative humidity sensor be added to the suite of meteorological equipment.
· Other equipment that would be useful additions to the underway system are solar radiation for the meteorological system and a transmissometer for the flow through.
· We would like to have the NMEA string BWC (waypoints) added to the data available on the SDN.
· Spigots and hose-bibs must be attached to the weather deck outlets of the USSS. Until this can be done, the protective flages removed for our tests should be re-installed
In general, the Healy is a fine ship and she is an excellent scientific platform for work in the Arctic. Although we did not experience rough weather on this leg, her sea-keeping capabilities are first rate. The problems described are generally minor and mostly “growing pains. We enjoyed our brief stay aboard and are glad that we were able to contribute to Healy’s growth as a research vessel. The officers and crew were friendly and most capable. We hope to be back on board soon.
APPENDIX
I (Tony Amos) was pleased to be able to contribute a modified version of my underway software to the ship. I had hoped to write a detailed description of the system and further modifications that could be made to the programs. This appendix contains daily log sheets and plots acquired through the underway program (with the exception of the first two and the final day). Note how the data density improved dramatically after the program was compiled and shifted to another computer. Most of the gaps before then were due to conflicts of running the program on my laptop while trying to develop the Healy version and do other tasks at the same time. I will communicate with the ship after returning to Texas and will be available electronically, so to speak, if you have problems.