Description
The Siemens 6ES5095-8FA01 is a fail-safe central unit (CPU) from the SIMATIC S5-95F series, purpose-built for high-availability and safety-critical automation applications that demand uncompromising reliability. Designed as a compact subunit for 1:1 hot-standby redundant systems, this PLC module enables two identical 6ES5095-8FA01 units to operate in synchronized lockstep, ensuring no single point of failure can compromise process safety .
The 6ES5095-8FA01 integrates 16 KB of work memory, 2048 flags, 128 timers, and 128 counters, along with onboard fail-safe I/O including 16 safety-related digital inputs and 8 safety-related digital outputs . Its dual-subunit architecture, certified by TÜV Bayern, continuously compares input signals, output states, and internal data via a fiber-optic link, automatically initiating error handling upon any discrepancy. This makes the 6ES5095-8FA01 the backbone of emergency shutdown systems, burner management, and other SIL-capable applications in the process industries.
Application Scenarios
Consider a chemical plant operating a continuous exothermic reactor where temperature runaway could lead to catastrophic consequences. The existing safety system, based on conventional relays, provided limited diagnostics and required cumbersome manual testing. By deploying a redundant pair of Siemens 6ES5095-8FA01 units with a fiber-optic synchronization cable, the plant established a 1:1 hot-standby safety PLC system . In this configuration, both 6ES5095-8FA01 subunits execute the identical user program in parallel, comparing every input signal—from temperature transmitters, pressure switches, and emergency stop buttons—at each cycle. When one subunit detects a deviation exceeding the configured discrepancy time (programmable as short as 1 ms for interrupt inputs), the system safely de-energizes the reactor heating elements and initiates emergency cooling, while the diagnostic buffer pinpoints the exact sensor or wiring fault . This upgrade reduced safety-related downtime by 80% and provided auditable proof of safety integrity for regulatory compliance.
In a power generation facility, the 6ES5095-8FA01 serves as the heart of a boiler flame monitoring and burner management system. The CPU’s onboard hardware counters, capable of up to 900 Hz, are used for speed monitoring of forced-draft fans, with overspeed triggering an immediate safety shutdown via the fail-safe digital outputs . The module’s self-test functions, executed during startup and cyclically during operation, verify the integrity of both subunits, the fiber-optic link, and all redundant I/O . Maintenance teams rely on the yellow battery failure LED and the system event database to schedule preventive battery replacement, ensuring the 6ES5095-8FA01 remains ready to protect the plant 24/7/365 .
Technical Specifications
| Parameter | Value/Description |
|---|---|
| Product Model | 6ES5095-8FA01 |
| Manufacturer | Siemens AG |
| Product Family | SIMATIC S5-95F |
| Product Category | Fail-Safe Central Unit (CPU) for Redundant System |
| Program Memory | 16 KB RAM (expandable with EPROM submodule) |
| Execution Time | 1.2 ms for 1024 binary statements |
| Self-Test Overhead | 20-30 ms per cycle |
| Flags | 2048 (512 retentive) |
| Timers | 128 (0.01-9990 s, non-retentive) |
| Counters | 128 (8 retentive) |
| Onboard Digital Inputs | 16, fail-safe, 24 V DC / 10 mA |
| Onboard Digital Outputs | 8 fail-safe (24 V DC / 750 mA) + 8 non-safety-related (24 V DC / 500 mA) |
| Onboard Counter Inputs | 2, fail-safe, 900 Hz |
| Interrupt Inputs | 4, fail-safe (3 ms / 10 ms response) |
| Programming Interface | PG / OP / SINEC L1 (AS511 protocol) |
| Power Supply | 24 V DC (20-30 V) |
| Current Consumption | 1 A per subunit at max. configuration |
| Operating Temperature | 0°C to +60°C (horizontal) |
| Storage Temperature | -40°C to +70°C |
| Dimensions (W×H×D) | 145 × 135 × 146 mm |
| Weight | Approx. 1.5 kg |
| Safety Certification | TÜV Bayern prototype-tested |
