The 3500/33 is a full-height module under the 3500 Machinery Protection System that provides sixteen independent relay outputs. This module is designed for complex applications requiring a large number of relay outputs, offering extremely high flexibility and scalability. It is the ideal choice for protecting large rotating equipment, multi-unit plants, and complex process control logic. Any number of 3500/33 modules can be installed in any slot to the right of the Transient Data Interface (TDI) Module, providing users with unparalleled output channel density.
The 3500/33 consists of a fixed front card (149986-01) and four different types of Output rear cards (see the Ordering page for details). The 149986-01 can form a complete system when paired with any one of the rear cards.
As the final execution unit of the 3500 system, the core function of the 3500/33 is to translate the system's complex internal monitoring alarm statuses (such as Danger, Alert, Channel Not-OK) and process variable alarm points into physical contact signals required for controlling external equipment through user-programmable "Alarm Drive Logic." Its excellent logic programming capability enables it to implement everything from simple single-alarm triggers to highly complex multi-parameter "voting logic," ensuring safety interlocks, shutdown protection, and sequential control for critical equipment.
Features
High-Density Independent Channels: Provides sixteen completely independent relay channels. Each channel can be individually programmed to perform different logical functions and control different external devices, significantly saving rack space.
Powerful Programmable Alarm Drive Logic (Voting Logic): The operation of each relay can be controlled by complex logic equations.
Rich Logic Input Sources: Can use alarm statuses (Danger, Alert), Channel Not-OK status, or any Process Parameter Limit (PPL/MV) point from any monitor channel within the rack as trigger conditions.
Flexible Logic Combination: Use the 3500 Configuration Software to freely combine the aforementioned input sources through AND and OR logic gates, building complex voting logic (e.g., 2oo3, 2oo4, etc.) to achieve the highest level of protection reliability and prevent maloperation.
High-Performance Relays & Optional Types: Offers two types of relay contacts, Standard and Low Current, to adapt to different load requirements.
Relay Type: Single-Pole, Double-Throw (SPDT), providing both Normally Open (NO) and Normally Closed (NC) contacts.
Environmental Sealing: Epoxy-sealed, resistant to vibration, moisture, and dust, suitable for harsh industrial environments.
Arc Suppression: Standard built-in 250 Vrms arc suppressor effectively protects contacts and extends service life.
Grouped Operation Mode Selection: The sixteen relays are divided into four groups (four relays per group). Each group can be uniformly set via a single switch for Normally De-energized or Normally Energized operation, simplifying fail-safe configuration.
Comprehensive Status Indication: The module front panel is equipped with an independent CH ALARM LED indicator for each channel, which illuminates when the relay is in an alarm state, providing precise local status diagnostics. It also includes OK LED (module operating normally) and TX/RX LED (rack communication status) indicators.
Low Current Relay Option (Gold Contacts): This is a unique advantage of the 3500/33. For applications requiring the switching of tiny signals (e.g., PLC/DCS digital inputs), Low Current relays (gold contacts) are available as an option.
Minimum Switching Capability: Can reliably switch微小电流 (tiny currents) as low as 1 mA @ 1 Vdc, perfectly solving the problem of unstable contact resistance under low-level loads common with standard silver-contact relays.
Automatic Degradation Feature: Even if the gold plating is damaged due to accidental overload, the contacts can still function as standard silver contacts, providing additional reliability.
Flexible Installation & Seamless Integration: Occupies one full-height front slot and one full-height rear slot (I/O module) in the 3500 rack. Fully compatible with all 3500 monitor modules, seamlessly integrating into the entire system.
Extensive International Certifications: The module has passed multiple international explosion-proof certifications such as cNRTLus, ATEX, and IECEx (applicable to Class I, Division 2 / Zone 2 areas), as well as safety and maritime certifications like CE, DNV GL, and ABS, meeting installation requirements for various harsh environments worldwide.
Working Principle & Technical Details
The working principle of the 3500/33 module is a precise process from "software logic configuration" to "hardware physical action."
Signal Acquisition & Logic Configuration:
The module reads the channel status, alarm status, and process variable values of all monitor modules (e.g., vibration, temperature, pressure monitors) in real-time via the high-speed backplane bus of the 3500 rack.
Using the 3500 Rack Configuration Software, users define a unique "Alarm Drive Logic" for each of the sixteen relay channels. This logic is a user-customized Boolean logic equation that can use AND and OR operators to mix multiple statuses from multiple monitors. Example: Relay 5 Activate = (Unit A Vibration Danger) AND (NOT (Unit A Lube Oil Pressure Normal)) OR (Unit A Overspeed Danger).
The processor built into the module solves these sixteen logic equations in real-time and determines the status of each relay based on the results.
Relay Driving & Output Mode:
Normally De-energized Mode: Coil is not energized when there is no alarm. NC contact is closed, NO contact is open. Upon alarm, the coil is energized, NC opens, NO closes.
Normally Energized Mode: Coil is energized when there is no alarm. NO contact is closed, NC contact is open. Upon alarm, the coil is de-energized, NO opens, NC closes. This is the fail-safe mode.
When the logic operation result for a channel is "true," the processor commands the driver circuit for that channel to change the power state of the relay coil.
Grouped Mode Control: Using the four DIP switches on the module, the sixteen relays are divided into four groups for mode setting.
Contact Connection & Load Control:
The relay output contacts are connected to field terminal blocks via the rear I/O module.
Users connect the external devices that need to be controlled (e.g., shutdown solenoid valves, alarm lights, DCS/PLC input cards, starters, etc.) to the corresponding contact loop.
The relay activates based on logic triggers, thereby connecting or disconnecting the external circuit to execute the final control command.
Important Technical Details & Warnings:
Standard Relay (Silver Contacts) Ratings:
DC (Direct Current): Maximum switched voltage 125 Vdc, maximum switched current 5A (maximum power 70W @ 24Vdc).
AC (Alternating Current): Maximum switched voltage 250 Vac, maximum switched current 5A, maximum power 1200 VA.
Low Current Relay (Gold Contacts) Ratings:
DC (Direct Current): Minimum reliable switching 1 mA @ 1 Vdc; Maximum withstand 100 mA @ 48 Vdc.
Warning: Gold-contact relays are strictly prohibited from being used for loads exceeding 100 mA or 5 mA @ 120 Vac, otherwise the gold plating will be permanently damaged.
Safety System Limitations: When the module is used in a Functional Safety (SIL) system or installed in a Hazardous Area (ordered with explosion-proof certification option), the maximum operating voltage is strictly limited to 30 Vdc / 30 Vac to comply with safety standards. The use of higher voltages is strictly prohibited.
Specifications
| Item | Specification Description |
|---|
| Number of Channels | 16 independent channels |
| Relay Type | Single-Pole, Double-Throw (SPDT), epoxy-sealed |
| Contact Type | Standard: Silver contacts; Optional: Low Current Gold contacts |
| Contact Life | 100,000 cycles |
| Arc Suppression | Built-in, 250 Vrms |
| Operation Mode | 4 groups x 4 channels, selectable per group: Normally Energized or Normally De-energized |
| Standard Ratings (Silver) | DC: 5A, 125Vdc, 70W (24Vdc)
AC: 5A, 250Vac, 1200 VA |
| Low Current Ratings (Gold) | DC: 1mA @1Vdc (Min) ~ 100mA @48Vdc (Max) |
| Power Consumption | 5.8 Watts (typical) |
| Operating Temperature | -30°C to +65°C |
| Module Dimensions (HxWxD) | Main Module: 241 mm x 24.4 mm x 242 mm |
| Rack Space | 1 front slot (Main Module) + 1 rear slot (I/O Module) |
| Explosion-Proof Certification | cNRTLus (CL I, Div 2), ATEX/IECEx (II 3G Ex nA nC ic IIC T4 Gc) |
Application Scenarios
The 3500/33 16-Channel Relay Module is an ideal choice for the following high-density, complex control scenarios:
Comprehensive Protection for Large Compressor Sets & Turbines: Provides comprehensive shutdown, pre-alarm, and auxiliary equipment control outputs for large units with multiple monitoring points (vibration, temperature, pressure, position).
Centralized Control for Multi-Unit Plants: In oil & gas, chemical, and power plants, enables centralized management of protection outputs for multiple units within a single rack, saving costs and improving reliability.
Complex Sequential Control & Interlocking: Used to drive complex process interlock logic, such as unit start/stop sequence control, pump switching logic, and valve interlocking.
Signal Transmission to Control Systems: Reliably sends a large number of alarm and status signals to DCS, PLC, or SIS systems. Its low-current version perfectly matches the digital input cards of control systems.
Redundant Fault-Tolerant Systems: Implements high-level voting logic (e.g., 2oo3, 2oo4), providing extremely high availability and safety for the most critical applications.
Offshore Platforms & Ships: Offers significant advantages in the maritime sector, where space is precious and reliability requirements are extremely high, thanks to its high density and maritime certifications.
