Part I - DESIGN OVERVIEW

The PRISM Topaz Rebreather

PRISM Topaz Underwater Breathing Apparatus

PRISM Topaz is a closed-circuit mixed gas underwater breathing apparatus (frequently called a "rebreather") designed specifically for the recreational diving marketplace. The PRISM Topaz model is the first of a new series of "third generation" PRISM rebreathers. As such, PRISM Topaz also serves as the development testbed for additional models based on third generation PRISM technology. Models optimized for deep diving andfor military applications will be developed from the PRISM Topaz foundation. This document presents the design goals and specifications of PRISM Topaz.

PRISM Topaz Application Considerations

Serving as a final development testbed for the third generation PRISM, the initial PRISM Topaz units will beoperated by Steam Machines at its training center on Cayman Brac and elsewhere only under direct supervisionof Steam Machines personnel. The units will be used by openwater certified divers in conjunction with Steam Machines "Closed Circuit Diver’ certification courses. This will be the first widespread use of such mixed gas closed circuit diving equipment by personnel who have not had extensive military or commercial training.

It is Steam Machines’ intent to maintain tight control of the operation of all PRISM Topaz units during this critical final "real world" test phase. The units are fitted with onboard digital data loggers and will be maintained by Steam Machines technicians. Regular performance and application suitability evaluations will be performed throughout the operational test phase. This evaluation phase will provide Steam Machines with invaluable data pertaining to actual use of closed-circuit diving systems (and, more specifically the use of PRISM Topaz) in the real world by civilian personnel. Final unit design review will incorporate changes that may result from analysis of this operational evaluation.

Steam Machines will set operational limits on the PRISM Topaz units used at the Steam Machines training centers. These limits will be targeted at operator, rather than hardware, capability considerations. Such operational limitations will include an operational depth limitation of 150fsw. Steam Machines test divers will perform manned testing of all PRISM Topaz units outside the restricted recreational diver test envelope. In addition, unmanned and manned testing beyond recreational limits is being undertaken in conjunction with various military projects.

PRISM Topaz Flexible Platform Considerations

PRISM Topaz is designed specifically for the recreational marketplace. An overwhelming design consideration for this market is unit size and ease of use. Extreme dive duration was sacrificed in exchange for overall small form factor and light weight. PRISM Topaz weighs about 38 pounds…about the same as an 80 cubic foot open circuit diving rig.

The PRISM Topaz design, however, is very flexible, allowing reconfiguration to more demanding applications with minimal component change. All breathing loop components are designed for minimal work-of-breathing at extreme depths. All major PRISM Topaz components are designed with an operational depth limitation goal of 500 fsw. Minor additional component changes could extend this depth. Since the PRISM Topaz series platform is designed to physically perform well at 500 fsw, minimum performance specifications of the PRISM Topaz version are determined primarily by gas cylinder and scrubber size.

The unique design of the PRISM Topaz series platform allows large increases in operational range by simple increase of gas cylinder size and scrubber length. A deep diving version of the PRISM Topaz will enter field testing by Steam Machines concurrently with final PRISM Topaz operational trials.

PRISM Topaz Operational Design Specification

Operating modes:

Closed circuit constant PPO2
Semi-closed circuit constant PPO2
Closed circuit, PPO2 monitored, manually controlled
Semi-closed circuit, constant mass flow, PPO2 monitored
Open Circuit bailout with regulator on breathable diluent

Major physical components:

Backpack mounted control/scrubber/cylinder assembly
Integrated buoyancy compensator with detachable back mounted wings, user-ditchable integrated weight and leg loops.
Twin, over-shoulder counterlungs. Approximately seven liter capacity, coated crushed neoprene. Water drain/dump valves fitted to both counterlungs. Variable volume overpressurization valve on left counterlung. Hydrostatic/manual diluent addition on lower right counterlung.
Control housing/manifold. Houses main system electronics and battery in sealed compartment fully isolated from breathing loop. Provides oxygen injection plenum, water trap pathways, sensor plenum and scrubber basket manifold. Positioned at top of backpack atop scrubber canister. Equipped with canister pressure transducer, O2 sensors, CO2 sensor.
Scrubber canister. Insulating outer canister housing with quick replaceable radial flow scrubber basket cartridge. Scrubber cartridge access through removable bottom plate. Accommodates Steam Machines proprietary sensor calibration system.
Scrubber basket. Interchangeable cartridge style, radial flow, accommodating 8-12 mesh size, 797 grade Sofnolime. Injection molded A3K nylon with integrated high flow screen. Screw top with foam compression pads.
Alternate scrubber: Steam Machines proprietary "solid state" scrubber. Fully water tolerant solid scrubber cartridge will directly exchange with loose fill basket.
Cylinders. 15 cubic foot steel oxygen and 15 cubic foot steel diluent. 3000 PSIg provided with crossflow DIN valves and "fill-in-place" fittings.
O2 sensors. Three Steam Machines proprietary galvanic designed for extended operation at elevated absolute pressures and elevated PPO2.
CO2 sensor. Proprietary Steam Machines bio-optical with low-cost disposable sensor element.
Primary instrumentation display. Wrist mounted human-factors engineered status display with shape and color keyed system status elements. Digital LCD display of current PPO2, oxygen cylinder pressure and diluent cylinder pressure. Connected by heavy duty cable to control unit.
Secondary instrumentation display. Jeweled movement analog PPO2 meter driven directly by the galvanic O2 sensors. Switch selectable to read sensors 1, 2, 3 or battery voltage. Used to verify primary display and control system and during manual operation with electronics offline. Connected by heavy duty cable to control unit. Normally stored in special pocket on buoyancy compensator.
Tertiary in-water training display. (optional) Duplicate of primary display status element section. Mounted at top of control unit. Allows easy viewing of system operational status by in-water training personnel.
Diluent addition valve. Mounted on the lower right counterlung. Adds diluent to maintain nominal ambient counterlung pressure. Diaphragm face button serves as manual diluent addition valve.
Oxygen injection valve. Low current, long life, pulse width modulated solenoid valve. Pulse duration proportional to PPO2 deviation from setpoint, providing proportional control with minimal complexity and maximum reliability.
Oxygen mode/manual bypass valve. Mounted at lower righthand corner of unit, protected by backplate and case. Provides three position switching of oxygen delivery mode: Automatic/OFF/Inject. Inject position is spring return to OFF mode providing intuitive quarter-turn lever for manual O2 injection.
Mass flow control valve. (optional) Mounted at lower righthand corner of unit, protected by backplate and case. Allows user/technician adjustable control of injected gas flow rates.
High volume mouthpiece/hose assembly. Large diameter, high compliance mushroom valves in removable large-area seats. Lever actuated, quarter-turn dive/surface valve with water purge in surface mode. 35mm minimum bore diameter hoses. Mouthpiece weighted for neutral buoyancy.

Physical Specifications:

Back unit overall dimensions: 14" X 17" X 9"
Overall system weight: Approx 38 pounds
Standard counterlungs approximately 7 liters capacity with user adjustable working volume. Counterlungs quickly changeable to accommodate larger capacity.
Scrubber Basket Size, radial flow, Topaz:
6" diameter X approx 6.5" overall
Minimum cross sectional area of approx 14.8".
Charge: 1.7 kg 8-12 grade Sofnolime
Scrubber duration, radial flow, Topaz:
2 hours minimum at 62LPM RMV, 32°F, 300fsw, 1.35LPM CO2
Maximum scrubber basket size, PRISM Topaz series platform:
6" diameter X approx 13" overall
Minimum cross sectional area approx 37.1"
Charge: 4.2 kg 8-12 grade Sofnolime
Maximum possible scrubber duration, PRISM Topaz series platform:
6.5 hours minimum (est.), 62LPM RMV, 32°F, 300fsw, 1.35LPM CO2
Solid State Scrubber ‡ duration, Topaz series platform:
1.3 to times Sofnolime duration, minimum. Preliminary testing indicates possible performance of up to 3X Sofnolime at extreme work rates and temperatures.
Cylinder capacity, Topaz: 15 cu ft oxygen + 15 cu ft diluent @ 3000 PSIg
Nominal depth limitation, PRISM Topaz series platform: 500fsw
Stated depth limitation, PRISM Topaz: 150fsw

‡ Steam Machines solid state scrubber technology is currently under development. All performance figures are preliminary.

[ Topaz Main - Part I - Part II - Part III - Part IV ]

435 North Pacific Coast Highway Suite 150 - Redondo Beach, California 90277 - Tel 310.937.7556 Fax 310.937.7555 - EMAIL-rbreathr@ix.netcom.com

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