Complete Guide to Chalwyn & AMOT Diesel Engine Safety Systems: Preventing Runaway in Hazardous Zones

Operating diesel-driven machinery—including air compressors, generator sets, hydraulic power packs, vacuum tankers, and mobile trucks—within petrochemical plants, oil refineries, and offshore drilling platforms carries significant fire and explosion hazards. In environments where combustible gas, hydrocarbon vapor, or atmospheric dust may escape, a conventional diesel engine can inadvertently transform into an uncontrolled ignition source.

The single most critical failure mode in these environments is Diesel Engine Runaway.

What Causes Diesel Engine Runaway?

Unlike gasoline engines that rely on throttle plates and spark ignition, diesel engines operate strictly via compression ignition, continuously drawing in unthrottled ambient air.

When airborne hydrocarbons or flammable vapors leak into the atmosphere:

1. The engine begins ingesting the external vapor cloud directly through the air intake manifold.

2. The gas acts as an uncontrolled, unmetered fuel supply.

3. Cutting off the primary diesel fuel feed or switching the ignition key to "OFF" will not stop the engine.

4. The engine accelerates uncontrollably past its maximum governed RPM, leading to valve float, catastrophic mechanical explosion, turbocharger disintegration, or backfire flash fires that ignite the surrounding atmosphere.

The only proven, certified engineering solution to shut down a runaway diesel engine is complete and immediate air intake isolation.

1. Chalwyn D-Series Automatic Overspeed Shut Down Valves (Bendix Poppet Type)

The Chalwyn D-Series (D45, D51, D57, D64, D70, and D80) is an industry-standard range of spring-loaded poppet valves engineered to shut down an engine automatically by choking the intake air.

How It Operates:

• Self-Actuating: Operates purely on airflow mechanics without requiring external electrical power, wiring, or pneumatic air supplies.

• Aerodynamic Closure: Intake airflow passing through the valve builds up closing force against an adjustable internal spring. When airflow velocity exceeds the preset limit during an overspeed event, aerodynamic force overcomes spring resistance, snapping the valve firmly closed.

• Automatic Latch: Once shut, the poppet remains locked closed until the engine comes to a complete standstill.

Technical Selection Matrix:

2. AMOT Model XT Positive Air Shutoff Butterfly Valve

The AMOT Model XT is an advanced butterfly-style positive air shutoff valve engineered for modern heavy-duty engines. It delivers rapid, positive closure across high boost pressures and harsh operating conditions.

Key Specifications:

• Flange Bore Diameters: 3.5" (89 mm), 4.0" (102 mm), 5.0" (127 mm), 5.5" (140 mm), 6.0" (152 mm), 7.0" (178 mm), and 8.0" (203 mm).

• Actuation Methods: 12 VDC or 24 VDC electric solenoids (Standard or Heavy Duty) and pneumatic cylinder actuation (1/8-27 NPT port).

• Extreme Temperature Tolerance: Rated from -40°C to 125°C.

• Ingress & Pressure Ratings: IP67 and IP69K sealed; handles up to 5 bar (72 psi) charge-air boost pressure.

• Integrated Options: Optional manual override handle, relay enclosure box, and valve-position microswitches (Weather Pack connectors).

3. REVGUARD 2 Electronic Speed Switch (Model 1520-001)

Manufactured by Roda Deaco / AMOT, the Revguard 2 provides electronic overspeed monitoring. It continuously reads engine RPM pulses and energizes a 4A trip relay to instantly snap the AMOT XT valve closed when pre-programmed speed limits are exceeded.

Features & Advantages:

• Universal Supply Voltage: 12V to 32V DC operation with built-in reverse polarity protection.

• Wide Signal Acceptance: Compatible with 100 Hz to 10,000 Hz input signals from magnetic flywheel pickups or alternator W-terminals.

• Safe In-Field Testing: Built-in test pushbutton simulates overspeed trips at 10%, 20%, 30%, or 50% reduced RPM, allowing complete functional tests without dangerous engine over-revving.

• Rugged Enclosure: IP54-rated, fully encapsulated electronics resistant to moisture, fuel spray, vibration, and thermal shock (-40°C to 85°C).

4. Chalwyn ASX Series Flameproof Alternators

Standard vehicle alternators are a primary source of brush arcing and electrical sparks, making them unsafe in hazardous atmospheres. Chalwyn ASX Series Flameproof Alternators provide a certified, heavy-duty replacement for mobile and stationary diesel equipment.

Models & Compliance:

• 12V Models: ASX-240 (side entry gland) and ASX-241 (rear entry gland).

• 24V Models: ASX-340 (side entry gland), ASX-341 (rear entry gland), and ASX-350 (self-exciting 24V).

• Hazardous Area Ratings: Certified to ATEX, IECEx, and UKEX (Ex db T4 Gb, Ex tb IIIC T135°C Db, IP66 enclosure).

• Built-in Speed Signal: Direct frequency pulse output for pairing with the Revguard 2 speed switch.

• Pulley Options: Available with SPA, SPB, and 6-Groove Poly-V pulleys.

Turnkey Retrofits, Installation & Maintenance in Saudi Arabia

Selecting and installing diesel overspeed equipment requires strict adherence to engine manufacturer CFM specs and local facility regulations.

Emdad Technical Services Company (ETS) provides complete engineering and installation support across the Kingdom:

• Engineering Sizing: Matching displacement, boost pressures, and intake geometry on Cummins, Caterpillar, Perkins, and Deutz engines.

• Turnkey Fleets: Supply, mounting, and wiring on mobile power packs, vacuum tankers, SPMT prime movers, and wellhead support assets.

• Certification & Testing: Functional trip verification, annual maintenance schedules, and compliance documentation for Saudi Aramco, SABIC, and Royal Commission facility gate access.

Contact Our Engineering Specialists

• Head Office & Facilities: Dammam | Riyadh | Jeddah

• Direct Telephone / WhatsApp: +966 50 080 7522 | +966 53 213 3242

• Email: info@etsarabia.com | sales@etsarabia.com

• Website: www.etsarabia.com