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Description
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BrandWartsila
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ModelESM21
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Product NameEngine Safety Module
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Place of OriginFinland
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Customs HS Code85371000
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Power Supply18 V DC to 32 V DC
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Dimensions240 mm height × 175 mm width × 55 mm depth
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Weight1.9 kg
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Operating Temperature-10°C ~ +55°C
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Storage Temperature-40°C ~ +85°C
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Warranty12 month
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Product Statusnew and original
Wärtsilä ESM-21 Working Principle
The ESM-21 (Engine Safety Module) is an independent hardwired safety protection unit integrated into the Wärtsilä UNIC engine automation system. It works separately from main engine control modules including CCM, IOM and COM. Adopting a fail-safe design concept, its protection logic is implemented via dedicated hardware circuits instead of main control software. This ensures emergency shutdown functions remain available even when the primary UNIC control system suffers a failure.
Signal Acquisition & Real-time Monitoring
The module continuously acquires analogue and digital signals from engine safety sensors, such as dual speed pickups, lubricating oil pressure transmitter, Pt-100 cooling water temperature sensors, local emergency stop pushbutton and external trip inputs (oil mist detector, bearing overtemperature, turbocharger protection, customer trip signals). It converts raw sensor data into process values and constantly compares these readings against predefined safety setpoints.
Meanwhile, continuous diagnostics run on every sensor channel to detect wire break, signal out-of-range and power supply anomalies. Once a sensor or wiring fault is detected, the corresponding trip channel will be locked and an alarm triggered to prevent false engine shutdown.
Trip Logic Judgment & Pre-warning
When a monitored parameter is close to the shutdown threshold, ESM-21 outputs a pre-warning alarm in advance. Operators may activate the override function to bypass non-critical trip channels. However, overspeed trip and hard emergency stop cannot be bypassed in any scenario.
Immediately after any critical parameter exceeds the preset safety limit, the internal latching protection logic will be engaged.
Hardwired Shutdown Output Execution
When a valid trip condition is confirmed, ESM-21 de-energizes two stop solenoid valves through dedicated hardwired output loops. The de-energized solenoids drive electro-pneumatic stop actuators to cut off fuel supply and shut down the engine.
All trip events are latched. The shutdown output stays active until manual reset. Reset operation is only allowed at zero engine speed and will be disabled if engine speed exceeds 2% of nominal speed to prevent unintended restart.
Status Indication & Alarm Transmission
Front-panel LEDs visualize the status of each trip channel, sensor faults, power supply and shutdown latch state. Multiple alarm outputs including major failure, common engine alarm, minor alarm and dedicated ESM alarm are transmitted to the UNIC monitoring system for remote display and event logging.
Redundancy Design
Overspeed protection relies on two independent speed measuring circuits. If the primary speed sensor malfunctions, the system automatically switches to the redundant speed channel to keep overspeed protection fully operational.
The ESM-21 serves as an independent standalone safety module belonging to the Wärtsilä UNIC engine automation system. Operating separately from the main engine control logic, it provides a hardwired connection to engine shutdown actuators. It delivers fail-safe protection, which remains effective even upon failure of the main control system.
Core Safety Functions
Overspeed shutdown-Dual redundant trip circuits receive signals from two separate speed sensors ST173 and ST174. When engine speed reaches 115% of rated speed, the module triggers engine trip and de-energizes two stop solenoid valves.
Low lubricating oil pressure shutdown-A dedicated safety transmitter PTZ201 (0–10 bar, 4–20 mA) initiates engine shutdown once the inlet lubricating oil pressure falls below the preset threshold (approx. 2.0 bar).
High HT cooling water temperature shutdown-Pt-100 temperature sensors TEZ402 (inline) and TEZ403 (B-bank for V-type engines) activate trip at around 110 °C. For V-engines, ESM-21 adopts the higher value between the two temperature measurements.
Emergency stop-Local pushbutton HS723 and external shutdown input OS7305 (External shutdown 4) will initiate immediate non-overrideable engine shutdown.
External and engine shutdown inputs-Configurable site-specific channels support either close-to-shutdown or open-to-shutdown modes with wire break detection. These channels connect to oil mist detector, bearing/liner overtemperature protection, turbocharger protection and custom customer trip signals.
Stop / shutdown override (OS7306)-This function enables bypass of non-critical trip signals under emergency conditions. Overspeed trip, external emergency stop and Engine Shutdown 1 cannot be bypassed at any time.
Shutdown pre-warning (IS7323)-Generates an advance alarm before automatic engine trip, providing operators with time to enable the override function.
Supervision and Diagnostics
Continuous fault monitoring covers sensors, solenoid valves and field wiring, including signal out-of-range, wire break and power loss detection. Once a sensor fault is identified, the corresponding trip channel will be locked and an alarm will be raised to avoid unwanted false shutdown.
Redundant speed measurement: The system automatically switches to the backup speed sensor when the primary sensor malfunctions.
Available alarm outputs: Major failure (NS886), Common engine alarm (NS885), Minor alarm (NS881), and ESM dedicated alarm (NS718).
Front panel LED indicators display status of each trip channel (lubricating oil pressure, A/B side HT water temperature, overspeed 1/2, stop solenoids, external shutdowns), sensor faults, power supply and shutdown reset status.
Q1: What is the Wärtsilä ESM-21 control module?
The Wärtsilä ESM-21 is a 10-channel isolated digital input (DI) control module designed for Wärtsilä marine engine automation and industrial monitoring systems. It collects switch and level signals from sensors, switches and safety devices, transmits data via Modbus-RTU over an RS-485 bus, and integrates with the Wärtsilä UNIC engine control platform for real-time speed, temperature and pressure protection.
Q2: What are the key technical specifications of the ESM-21?
The ESM-21 operates on a wide 9–30 VDC power supply with built-in reverse polarity, ESD, overvoltage and overcurrent protection, and offers 2500 VDC optical isolation on all DI channels (DI0–DI9). It supports baud rates from 9600 to 115200 bps, runs at −20 °C to +85 °C, mounts on a standard DIN rail, and features PWR / RUN / TXD / RXD status LEDs for fast field diagnostics.
Q3: Where is the Wärtsilä ESM-21 used?
The ESM-21 is primarily deployed in Wärtsilä main engine control rooms on commercial vessels, where it monitors engine safety parameters and triggers audible/visual alarms. It is also widely used as a spare replacement part in shore-based power plants, oil & gas stations, and retrofitted industrial automation lines running Siemens, Allen-Bradley or equivalent PLC/SCADA systems via Modbus RTU.
Q4: Is the Wärtsilä ESM-21 discontinued, and how can I source a replacement?
The original Wärtsilä ESM-21 has been phased into the aftermarket/spare parts channel, but fully tested, 100% functional units remain available through independent industrial automation suppliers. We stock ESM-21 modules in our overseas warehouses, ship worldwide within 24–48 hours, and provide a 12-month warranty plus pre-shipment functional testing reports for every order.
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