What is the maximum operating pressure for the ATS73 and ATS74 turbine air starters?

Both the ATS73-2 and ATS74 are rated to a maximum supply pressure of 150 psi. The standard recommended operating pressure is 100 psi, which delivers optimal cranking torque and starting performance while keeping all mechanical components within their design limits. The air receiver must be manufactured to an applicable pressure vessel code such as AS1210 or an equivalent recognised standard. Operating toward the 150 psi ceiling should be reserved for applications that genuinely require additional cranking torque rather than being the routine operating condition.

What is the difference between the ATS73-2 and ATS74 turbine air starters?

The ATS73-2 and ATS74 share the same turbine motor and silencer assemblies but differ in their pinion drive mechanism and overall dimensions. The ATS73 Series 2 uses an inertia drive: centrifugal force generated by the accelerating output shaft extends the pinion along a helical spline to engage the engine ring gear, then automatically retracts once the engine fires. The ATS74 uses a pre-engaged pneumatic piston drive, where compressed air pressure pushes the pinion positively into mesh with the ring gear before the turbine begins spinning. The ATS74 is longer overall at 16.752 inches (425.5 mm), reflecting its more substantial pre-engaged nose assembly.

Can the housing orientation be adjusted without full disassembly?

Yes. Both the ATS73-2 and ATS74 use a band clamp connection between the motor housing and the nose assembly that allows continuous 360-degree rotation of the two sections relative to each other without separating the sub-assemblies. Simply loosen the band clamp without removing it, rotate the housing to the desired port orientation, and re-torque to 4 ft lb (6 Nm). This makes it straightforward to redirect the air inlet and control ports to the most convenient angle for hose routing in space-constrained engine compartments or wherever installation geometry demands a non-standard port position.

What pinion and configuration options are available for the ATS73 and ATS74?

The ATS73 and ATS74 series support 9-tooth 3 MOD, 10-tooth 8/10 pitch, 11-tooth 6/8 pitch, and 12-tooth 8/10 pitch pinions in both right-hand and left-hand configurations. Additional build options include inertia drive variants, threaded exhaust outlets, Kelly spinner muffler, motor ports at 90 degrees, mining-grade cast iron housing, and specialist configurations for specific applications. ATEX-certified variants are also available. Please provide your engine make, model, and ring gear specification so we can confirm the correct full part number for your application.

Turbine Air Starters

Turbine Driven | 150 psi Rated | SAE 3 Flange

Engine Starting Systems · Turbine Air Starters · Pneumatic Starters

Austart ATS73 & ATS74 Turbine Air Starters – Reliable Compressed Air Cranking for Mid-Range Heavy-Duty Diesel and Gas Engines

The Austart ATS73-2 and ATS74 turbine air starters are compressed air-powered cranking systems purpose-built for dependable mid-range heavy-duty engine starting across mining, oil and gas, marine, and stationary power generation environments. Spark-free by design and rated to a maximum of 150 psi, both models convert compressed air into sustained cranking torque through a precision turbine rotor and three-planet epicyclic gear reduction, delivering that torque to the engine flywheel ring gear via an SAE 3 flanged pinion assembly. The ATS73 Series 2 uses an inertia drive for self-actuating pinion engagement, while the ATS74 uses a pre-engaged pneumatic piston drive for positive pinion mesh before cranking begins — covering engines including the Cummins N14, Caterpillar 3306, and Detroit 12V71 wherever electrical starting is impractical or presents an ignition risk.

Turbine Air Driven

150 psi Max Pressure

360° Indexable Housing

SAE 3 Flange Standard

Key Features

The Austart ATS73 and ATS74 turbine air starters are pneumatically driven cranking systems that channel compressed air through a precision turbine rotor, then step that high-speed rotational energy down through a three-planet epicyclic gear reduction to produce the torque required to reliably crank mid-range heavy-duty diesel and gas engines. The ATS73 Series 2 employs an inertia drive for automatic centrifugal pinion engagement, while the ATS74 uses a pneumatic piston pre-engaged drive that positively meshes the pinion with the engine ring gear before the turbine begins spinning. Both models are structured as three independently serviceable sub-assemblies — nose, motor, and silencer — and are designed for continuous-duty use in demanding industrial environments, with verified compatibility across platforms including the Cummins N14, Caterpillar 3306, and Detroit 12V71.

Turbine-Driven Compressed Air Operation — Fully Spark-Free: The ATS73-2 and ATS74 run entirely on compressed air, with no batteries, alternators, or electrical cabling in the starting circuit. This inherently spark-free design eliminates ignition risk in classified hazardous environments — oil and gas wellheads, gas compression stations, fuel handling facilities, and underground mining operations — where electrical starting equipment must meet stringent explosion-proof certification requirements. Cranking torque remains consistent across the full operating pressure range from the standard 100 psi up to the 150 psi maximum, ensuring reliable engine starts even when air receiver pressure is not at its peak level.
Dual Drive Architecture: Inertia (ATS73) and Pre-Engaged Piston (ATS74): The ATS73 Series 2 inertia drive harnesses the centrifugal force produced by the accelerating output shaft to extend the pinion along a helical spline into engagement with the engine ring gear, then automatically withdraws the pinion once the engine fires and its speed exceeds that of the starter. The ATS74 pre-engaged drive uses a pneumatically actuated internal piston to push the pinion positively into mesh with the ring gear before the turbine rotor begins spinning — guaranteeing full tooth engagement at the moment of peak cranking torque demand, irrespective of air pressure fluctuations during the start cycle. This choice of drive architecture lets engineers and procurement teams specify the mechanism best matched to each engine's ring gear geometry and application starting requirements.
SAE 3 Flange for Mid-Range Heavy-Duty Engine Compatibility: Both the ATS73-2 and ATS74 are built to SAE 3 flywheel housing standard, with a 3-hole bolt pattern on a 5.750-inch (146.1 mm) pitch circle diameter using Ø21/32-inch holes equally spaced. This positions them for engines in the mid-range heavy-duty bracket — including the Cummins N14, Caterpillar 3306, and Detroit 12V71 — where the SAE 3 housing is the established standard. The flange mounts directly and squarely to the engine flywheel housing, ensuring correct pinion-to-ring-gear alignment from first installation and maintaining that alignment throughout the service life of the starter.
360° Indexable Housing for Flexible Installation: The band clamp connecting the motor housing to the nose assembly allows the two sections to rotate continuously through 360 degrees relative to each other without separating the sub-assemblies. Loosening the clamp, rotating to the required inlet port orientation, and re-torquing to 4 ft lb (6 Nm) is all that is needed to redirect the air supply and control ports to the most convenient angle for hose and pipework routing. This adjustability is particularly valuable on engines where the flywheel housing area is restricted from certain directions, and allows the starter to be reconfigured in the field should installation requirements change.
Three-Planet Epicyclic Gear Reduction for Sustained Cranking Torque: Within the nose assembly, a three-planet epicyclic (planetary) gear set steps down the high rotational speed delivered by the turbine rotor to the lower cranking speed required at the engine ring gear, simultaneously multiplying torque to the level needed to turn over high-compression diesel and gas engines. The three planet gears run on precision bearings within the spider hub assembly and are packed with lithium-based grease during assembly and scheduled servicing. This planetary gear train is the critical torque-multiplying stage that bridges turbine power and practical cranking performance across the range of engine platforms this series is rated to start.
Integrated Silencer Assembly for Controlled Exhaust Noise: Each ATS73-2 and ATS74 starter includes a purpose-built muffler assembly that meaningfully reduces the discharge air noise generated when the starter exhausts at the end of each start cycle. The silencer uses stacked baffle plates, spacers, and retaining nuts that together provide progressive acoustic attenuation of the high-velocity exhaust airflow. Optional muffler and exhaust configurations — including threaded exhaust outlets and specialist muffler types — are available for installations with defined noise management requirements or where exhaust air must be directed rather than discharged directly to atmosphere.
Three-Piece Modular Design for Efficient Field Servicing: Both starters are engineered as three distinct, independently serviceable sub-assemblies — the nose assembly (housing the drive mechanism, planetary gear train, and pinion), the motor assembly (containing the turbine rotor, rotor shaft, and bearings), and the silencer assembly — secured by two band clamps. Any sub-assembly can be removed, inspected, rebuilt, and reinstalled independently using standard workshop tooling including a hydraulic press and circlip pliers, without disturbing the remaining sub-assemblies. A genuine Austart service kit covering all seals, O-rings, piston rings, and bearings is available to support scheduled maintenance, restoring the unit to full factory specification at each service interval.

Applications

Mining Equipment and On-Site Diesel Power Units: Surface and underground mining operations rely on mid-range diesel engines to drive pumps, compressors, generators, and auxiliary machinery — often in locations where electrical infrastructure is limited and ambient conditions include high dust, vibration, and temperature extremes. The ATS73 and ATS74 operate entirely on compressed air from the site supply network, delivering consistent starting performance without dependence on battery condition or electrical systems that are prone to failure in abrasive, high-humidity underground environments. Their spark-free operation also satisfies the safety requirements of gassy mine workings where ignition risk must be controlled.
Marine Diesel Propulsion and Auxiliary Engines: Commercial vessels, workboats, offshore support craft, and fishing vessels powered by mid-range diesel engines such as the Cummins N14 require a reliable starting system capable of operating in the salt-laden, high-humidity conditions of the marine environment. The robust construction of the ATS73 and ATS74, combined with their absence of electrical components in the starting circuit, makes them well suited to marine use where corrosion-related failure of electrical starter motors is a recurring maintenance concern and where dependable engine starting directly affects vessel safety and operational schedules.
Oil and Gas Engine-Driven Compressors and Pump Units: Gas engine-driven compressors and pump packages at wellheads, injection stations, and gathering facilities operate in Zone 1 and Zone 2 classified areas where electrical equipment must be explosion-proof. The inherently spark-free operation of the ATS73 and ATS74 makes them the standard specification for gas engine starting in hazardous areas, eliminating the complexity and cost of explosion-proof electrical starting systems. Their ability to handle the high start-duty cycles typical of oil field production equipment adds further operational value in continuous compression and fluid injection service.
Stationary Diesel and Gas Generator Sets: Standby power, prime power, and emergency generation sets driven by mid-range diesel or gas engines need a starting system that can turn over a cold, high-compression engine on demand, including during a complete facility blackout when the generator's own electrical bus is unavailable. The ATS73 and ATS74 deliver the cranking torque required at the engine ring gear through the stored energy in the compressed air receiver, providing a starting circuit that is fully independent of the generator electrical system and capable of initiating blackstart and emergency generation sequences without external electrical power.
Industrial Diesel Engines in Refineries and Process Plants: Process industry facilities — refineries, petrochemical plants, gas processing units, and LNG terminals — use mid-range diesel engines to drive emergency fire pumps, critical cooling fans, and standby process machinery in locations where managing ignition sources is a primary safety engineering requirement. The spark-free starting circuit of the ATS73 and ATS74, combined with available threaded exhaust outlet options for enclosed machinery room installations, allows these starters to be engineered into classified area applications without the additional regulatory burden associated with electrical ignition sources.
Heavy Construction, Drilling Rigs, and Remote Field Equipment: Large construction equipment, drill rigs, and remote field units powered by mid-range diesel engines such as the Caterpillar 3306 often operate at sites where reliable battery-based starting is difficult to maintain due to temperature extremes, infrequent operator presence, and high vibration conditions that accelerate battery deterioration. The ATS73 and ATS74 provide a starting solution that is unaffected by ambient temperature, requires no battery maintenance, and delivers the same cranking performance on the first start attempt after an extended shutdown as it does during normal continuous service.

Technical Specifications

Specifications listed below apply to the Austart ATS73-2 (Series 2) and ATS74 turbine air starters. Model-specific values are indicated where the two variants differ.

Parameter	Specification
Starter Type	Turbine Air Starter (Pneumatic)
ATS73-2 Drive Mechanism	Inertia Drive — Series 2 (centrifugal pinion engagement on acceleration)
ATS74 Drive Mechanism	Pre-Engaged Pneumatic Piston Drive (positive pinion engagement before cranking)
Standard Operating Pressure	100 psi
Maximum Operating Pressure	150 psi
Control Port Size (Inlet & Outlet)	1/8" NPT (both models)
Minimum Supply Hose I.D. (up to 15 ft / 5 m)	1" (25 mm)
Minimum Supply Hose I.D. (over 15 ft / 5 m)	1-1/2" (40 mm)
Control Line Size	Minimum 1/4" (6 mm) O.D.
ATS73-2 Overall Height	11.734" (298.0 mm)
ATS74 Overall Length	16.752" (425.5 mm)
ATS74 Overall Height	11.908" (302.5 mm)
ATS73-2 Flange to Pinion	1.875" (46.8 mm)
ATS74 Flange to Pinion	1.865" (47.4 mm)
Flange Standard	SAE 3
Flange PCD	5.750" (146.1 mm)
Mounting Hole Pattern	3 holes · Ø 21/32" (16.7 mm) · equally spaced on 5.750" PCD
ATS73-2 Muffler End Diameter	Ø 5.000" (127.0 mm)
Housing Indexing	360° continuous indexing (both models)
Pinion Rest Position	Flange-to-Ring-Gear (FRG) spacing less 1/8" (3 mm)
Pinion Options (Right-Hand)	9TH 3MOD · 10TH 8/10 · 11TH 6/8 · 12TH 8/10
Pinion Options (Left-Hand)	9TH 3MOD · 10TH 8/10 · 11TH 6/8 · 12TH 8/10
Compatible Engines (Examples)	Cummins N14 (SAE 3 · 11TH) · Caterpillar 3306 (SAE 3 · 12TH) · Detroit 12V71 (SAE 3 · 11TH / 14TH)
ATS73-2 Relay Valve	AR1000 (1" NPT, mounts directly to starter inlet port)
ATS74 Relay Valve	RS1000M (mounts directly to starter inlet port)
Y Strainer	YS1000 · 100 mesh · 1" NPT
Band Clamp Torque	4 ft lb (6 Nm)
Turbine Rotor Special Nut Torque	25–30 ft lb (30–40 Nm)
Re-start Delay	Minimum 15 seconds between start attempts
Special Options Available	Inertia drive · Threaded exhaust outlets · Kelly spinner muffler · Motor ports 90° · Mining-grade cast iron housing · U-configuration · ATEX certified
Warranty	12 months from date of purchase (first user) · 6 months on service work

Technical FAQ

Common Questions Answered

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Both the ATS73-2 and ATS74 are rated to a maximum supply pressure of 150 psi. The standard recommended operating pressure is 100 psi, which delivers optimal cranking performance while keeping all mechanical loads within design limits. Operating toward the 150 psi ceiling should be reserved for applications that genuinely require additional cranking torque and must not become the routine operating condition. The air receiver must be manufactured to an applicable pressure vessel code such as AS1210 or an equivalent recognised standard.

The ATS73-2 and ATS74 share the same turbine motor and silencer assemblies but differ in their pinion drive mechanism. The ATS73 Series 2 uses an inertia drive: as the turbine accelerates, centrifugal force drives the pinion into the engine ring gear, and it automatically retracts when the engine fires. The ATS74 uses a pre-engaged pneumatic piston drive that pushes the pinion positively into mesh before the turbine starts spinning, ensuring full engagement at peak cranking torque. The ATS74 is also longer overall at 16.752 inches (425.5 mm), reflecting its more substantial pre-engaged nose assembly.

The ATS73 and ATS74 are configured for mid-range heavy-duty diesel and gas engines with SAE 3 flywheel housings, including the Cummins N14 (11-tooth, SAE 3), Caterpillar 3306 (12-tooth, SAE 3), and Detroit 12V71 (11-tooth or 14-tooth, SAE 3). The series supports multiple pinion configurations — 9-tooth through 12-tooth in right-hand and left-hand variants — covering a broad range of ring gear specifications. Please provide your engine make, model, and ring gear details so we can confirm the correct full part number for your application.

The ATS73-2 uses the AR1000 relay valve (1-inch NPT) and the ATS74 uses the RS1000M — both mount directly onto the starter air inlet port using two screws and the supplied sealing O-ring. Both models require the YS1000 Y strainer (100 mesh, 1-inch NPT) installed upstream of the relay valve to protect the starter internals from contamination in the air receiver. A 1/4-inch (6 mm) control line connects the SC25 starter control button to the relay valve and starter to complete the pneumatic control circuit. Installation of the Y strainer is a mandatory condition of the product warranty.

A minimum of 15 seconds must elapse between consecutive start attempts. This pause ensures all rotating components — including the starter turbine rotor and the engine itself — have fully stopped before re-engagement. Attempting to restart while any component is still spinning can cause severe damage to the pinion, ring gear, and internal drive components, and will void the product warranty. Always confirm visually that all components have come to a complete stop before initiating the next start attempt.

Yes. Both the ATS73-2 and ATS74 use a band clamp connection between the motor housing and nose assembly that permits continuous 360-degree rotation of the two sections relative to each other without separating the sub-assemblies. Loosen the band clamp without removing it, rotate the housing to the required port orientation, then re-torque to 4 ft lb (6 Nm). This allows the air inlet and control ports to be redirected to the most convenient angle for hose routing — particularly useful in space-constrained engine bays or where installation geometry demands a non-standard port position.