The document is a technical maintenance manual for the Apeks DST First Stage Regulator.
Function Description
The Apeks DST First Stage Regulator is a critical component of a scuba diving system, responsible for reducing the high pressure from a scuba cylinder to a more manageable intermediate pressure for the second stage regulator. It is designed for use with enriched air nitrox (EAN) up to 40% O2 (EAN40) when properly cleaned and assembled. The first stage is subjected to high inlet pressures, leading to adiabatic compression or heating of the gas. Its primary function is to provide a stable intermediate pressure to ensure safe and consistent air delivery to the diver.
Important Technical Specifications
Torque Specifications (Table 3):
- Yoke Connector (32) / DIN Handwheel Connector (34): 14.7 ft-lbs (20 Nm)
- Turret Retaining Bolt (15): 70 in-lbs (8 Nm)
- MP Hose (AP0203): 40 in-lbs (4.5 Nm)
- Blanking Plugs (9, 18, 19): 40 in-lbs (4.5 Nm)
Test Bench Specifications (Table 4):
- Leak Test: Inlet 3000 psig (206 bar), no leaks allowed.
- MP (Medium Pressure): Inlet 3000 psig (206 bar), 130-145 psi (9-10 bar).
- MP Creep: Inlet 3000 psig (206 bar), 5 psi (0.25 bar) max for 15 seconds after cycling (purging) regulator.
Exploded View Components (XTX 50 FIRST STAGE - DST Style) (Page 19):
The exploded view details numerous parts, including:
- Spring (1)
- Spring Carrier (2)
- Diaphragm (3)
- Valve Lifter (4)
- Body (5)
- Distance Piece (6)
- O-rings (7, 10, 13, 16, 17, 20, 29)
- Turret (8a, 8b)
- Blanking Plugs (9, 18, 19)
- HP Valve (11)
- Spring (12)
- Thrust Washer (14)
- Turret Retaining Bolt (15)
- Diaphragm Clamp (21)
- Spring Adjuster (22)
- Hydrostatic Transmitter (23)
- Hydrostatic Diaphragm (25)
- Environmental End Cap (26)
- Yoke Clamp (27)
- Protective Cap (28)
- Yoke Clamp Screw, Comolded (30)
- Filter Guard (31)
- Yoke Clamp Connector (32)
- Protective Cap DIN (33)
- Handwheel Connector (34)
- Handwheel 300 Bar (35)
- Conical Filter (36)
Usage Features
The DST First Stage Regulator is designed for reliable performance in various diving conditions. Its compatibility with EAN40 makes it suitable for nitrox diving, provided proper cleaning and maintenance protocols are followed. The design allows for both Yoke and DIN configurations, offering versatility for different cylinder valve types. The environmental end cap (26) and hydrostatic diaphragm (25) suggest a design intended for cold water or contaminated water diving, providing environmental sealing to prevent freezing or ingress of contaminants. The presence of a spring adjuster (22) indicates tunability for optimal intermediate pressure settings.
Maintenance Features
The manual provides comprehensive instructions for the technical maintenance of the DST First Stage Regulator, emphasizing the importance of factory-authorized training and the use of genuine Aqua Lung parts.
Scheduled Service:
- Less than 50 dives/year: Overhaul every other year, with an inspection in "off" years.
- More than 50 dives/year or heavy/frequent use (rental, instruction, commercial): Complete overhaul at least twice a year, or more often depending on conditions.
- All inspections and overhauls must be documented to maintain the Limited Lifetime Warranty.
Official Inspection Consists Of:
- Pressurized immersion test for air leakage.
- Checking for stable intermediate pressure within range.
- Checking for opening effort within range.
- Checking for smooth operation of control knob and venturi switch.
- Visual inspection of the filter for debris or discoloration.
- Visual inspection of the exhaust valve for condition and proper seating.
- Visual inspection of the mouthpiece for tears or holes.
- Checking hose security in crimps by pulling back protectors.
- Failure of items 1-4 necessitates a full overhaul. For items 5-8, a full overhaul is at the technician's discretion.
General Guidelines:
- Follow each step exactly in order.
- Perform service in a clean, well-lit, and equipped work area.
- Segregate reusable components from non-reusable parts and parts from other units.
- Protect delicate parts (inlet fittings, crowns) from damage.
- Use only genuine Aqua Lung® parts from the overhaul parts kit.
- DO NOT reuse mandatory replacement parts.
- Use a calibrated torque wrench for reassembly, adhering to specified torque values.
- For EAN40 compatibility, clean, lubricate, and assemble in a clean environment using powderless latex gloves.
Disassembly Procedures:
- Detailed steps for removing hoses, HP blanking plugs, environmental end cap, hydrostatic diaphragm, spring, spring carrier, spring adjuster, turret retaining bolt, o-rings, blue thrust washer, HP valve, and MP blanking plugs.
- Specific instructions for Yoke and DIN disassembly, including removal of the yoke screw, protective cap, yoke clamp connector, distance piece, conical filter, dust cap, handwheel, and handwheel connector.
- Emphasizes using plastic or brass o-ring removal tools to prevent damage to sealing surfaces.
- Cautions against prying or digging around the diaphragm edges.
Reassembly Procedures:
- Instructions for installing the valve lifter, diaphragm, spring carrier, spring, spring adjuster, diaphragm clamp, turret, blue washer, o-rings, turret bolt, filter guard, yoke clamp connector, distance piece, and conical filter.
- Specific torque values are provided for critical connections.
- Emphasizes proper seating of o-rings and vertical installation of yoke/handwheel connectors to prevent HP leaks.
Adjusting the First Stage:
- Detailed steps for installing port plugs, MP hose, and MP test gauge.
- Instructions for attaching to a calibrated test bench or cylinder.
- Procedure for slowly opening and closing the cylinder valve and bleed valve to check MP.
- Method for adjusting MP using a 6mm hex key to increase or decrease pressure to 130-145 psi (9-10 bar).
- Instructions for checking MP stability (max 5 psi rise in 15 seconds) to detect leaks.
- Warnings regarding high pressure, overpressure relief, and incorrect hose connections.
Final Testing:
- External Leak Test: Submerging the pressurized regulator in a test tank of clean fresh water and observing for bubbles over a one-minute period. Bubbles indicate a leak and require disassembly and inspection.
- Cautions against confusing trapped air bubbles with true leaks.
Cleaning and Lubricating (Procedure A):
- For EAN40 compatibility: Regulators must be properly cleaned to remove condensed hydrocarbons. Only hyper-filtered compressed gas (< 0.1 mg/m3 hydrocarbons) should be used.
- Cleaning Brass and Stainless Steel Parts: Pre-clean with warm, soapy water and a nylon brush. Thoroughly clean in an ultrasonic cleaner with soapy water or white distilled vinegar (for stubborn deposits). Rinse with fresh water, then distilled water, and blow dry with low-pressure filtered air.
- Cleaning Anodized Aluminum, Plastic & Rubber Parts: Soak and clean in warm water with mild dish soap using a soft nylon toothbrush. Rinse in fresh water and blow dry with low-pressure filtered air. Cautions against using acid solutions on these parts.
- Cleaning Hoses: Ultrasonically clean fittings with soapy water (vinegar for tough corrosion). Run soapy water through the hose if needed, rinse thoroughly, and blow out before installing.
- Lubrication and Dressing: Wear powderless latex gloves. Lubricate all o-rings with Christo-Lube® MCG-111, applying a very light film and removing excess. Cautions against applying excessive grease. Silicone rubber parts require no lubrication.
Tools and Service Kits (Table 2):
- MP Test Gauge (111610): For medium pressure testing.
- Brass O-ring Tool Kit (944022) / Plastic O-ring Tool (103102): For o-ring removal and installation.
- Seat Installation Tool (109437): For seat (18) removal/replacement.
- Pin Spanner (AT30): For diaphragm clamp (21) and environmental end cap (26) removal/installation.
- Vise Mount Tool (100395): For mounting the first stage into a bench vise.
- Wrenches (9/16", 5/8", 11/16") / Hex Keys (5mm, 6mm): For disassembly and assembly.
- Torque Wrench (30-120 in-lbs / 10-150 ft-lbs) with Crow Foot (9/16") and Hex Key Adapter (5mm, 6mm): For applying specified torque.
- 3/4" Box Wrench: For specific torque applications.
- Magnifier with Illumination: For sealing surface inspection.
- Ultrasonic Cleaner: For brass and stainless steel parts cleaning.
- Christo-Lube MCG-111: For lubrication.
- Powderless Latex Gloves or Finger Cots: To keep finger oils off parts.
- Test Bench: For testing.
- First Stage Service Kit (AP0241/AA): Contains service parts.
Recommended Cleaners and Lubricants (Table 5):
- Christo-Lube MCG 111: Lubricant for all o-rings, sourced from Aqua Lung or Lubrication Technologies.
- Oakite #31: Acid bath for reusable stainless steel and brass parts, sourced from Oakite Products, Inc.
- White distilled vinegar: Acid bath for reusable stainless steel and brass parts ("Household" grade).
- Liquid dishwashing detergent (diluted with warm water): Degreaser for brass and stainless steel parts; general cleaning solution for plastic and rubber ("Household" grade).
- Cautions against using silicone rubber with grease/spray and muriatic acid for cleaning.
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