Figure 4. — Part of main wet laboratory . Plastic sheeting isolates tanks 

 at rear for behavioral observations. 



where it flows out a 6-inch cast iron line into the bay, or 

 into 3-inch PVC recirculating pipes which deliver the 

 water to the sump tank for recirculation (Fig. 5). 

 Three-inch caps on Y fittings are located every few feet to 

 allow entry to the recirculating lines. 



All piping and valves in the system are schedule 

 80-PVC. Piping is in straight runs with threaded caps 

 serving as cleanouts at each end. All seawater lines are 

 dual to allow for maintenance, except for piping down- 

 stream from the UV sterilizer, where cleaning is minimal. 



TEMPERATURE CONTROL 



The seawater can be cooled to a set temperature (± 2° 

 C). Although this temperature can be adjusted for the 

 entire system, investigators must vary temperature in 

 their tanks by individual cooling and heating devices. 



A 750,000 BTU (British thermal unit) air-cooled 

 compressor (Trane Model CGAA-6004-MA) cools ethylene 

 glycol, which is circulated by one of two centrifugal pumps 

 (Allis Chalmers Model F2L1, cast iron) through an all 

 glass heat exchanger (Corning Model 600-GRB). An 

 air-operated temperature probe in the seawater effluent 



1^ 





\ 



"-ij*^j!L["a 



line from the heat exchanger controls the compressor 

 through Ave steps of capacity. At the maximum step of 

 capacity, 450 1/min can be cooled 10°C. The Corning heat 

 exchanger is similar to that described by Lasker and 

 Vlymen (1969). 



SALINITY CONTROL 



The salinity can be adjusted to any level above 

 ambient (±0.5%o). A 41,600-liter fiber glass brine tank is 

 filled pneumatically with 31,745 kg of rock salt (Fig. 3). 

 This salt is the unreflned product of a salt company 

 located in the San Francisco Bay area. A typical analysis 

 is given below: 



Component 



Percent 



Figure 5. — Recirculating line in trench. Y fittings serve as entry 



points. 



Freshwater enters the tank, controlled by a float 

 valve, and becomes saturated brine solution. This is meter- 

 ed into the seawater line by g^ravity flow through a stain- 

 less steel air-operated proportional valve, controlled by 

 a conductivity meter pneumatic control system (Fig. 6). 

 This system, patterned after Hettler et al. (1971), features 

 conductivity meters with platinum probes mounted in the 

 seawater line, a pneumatic controller, and chart recorder 

 (Fig. 7). The temperature-compensated conductivity signal 

 is converted to salinity, then recorded on a 7-day chart 

 and fed into the pneumatic controller. The salinity is 

 dialed on the controller, the instrument measures the 

 difference between measured salinity and the set point, 

 and sends a variable air pressure (4-15 pounds) to adjust 

 the proportional valve. Variation in the salinity has been 

 controlled to ±0.5%o. By adding another proportional 

 valve connected to a freshwater source, one could lower 

 the salinity if needed. 



ALARM SYSTEM 



An alarm has been incorporated into this system to 

 avoid loss of fish and research time from component 

 failures (Fig. 7). Specifically, the system alarms if: 1) 

 water temperature exceeds high or low set points; 2) 

 saUnity exceeds high or low set points; 3) the water level 

 is too high in sump tank; 4) the water level becomes too 

 low in the reservoir; or 5) the electric power fails. An 

 alarm signal activates a bell and timer. If the alarm 

 persists past a preset time interval (30-300 s), a telephone 

 dialer is activated, sending a signal to a local alarm 

 company that has 24-h service (they have a list of people 

 to call for corrective maintenance). 



PERFORMANCE AND MAINTENANCE 



The Tiburon Laboratory seawater system has been 

 operating since April 1973. As of October 1974, after some 

 modifications, the system is meeting the objectives of high 

 water quality year-round. 



