ABB AB91-1 HESG437479R1 | Legacy Power Plant Control Module

Technical Specifications

One source describes the AB91-1 as a processing/communication interface for Procontrol P13/P14, while another categorizes it as an arithmetic/adaptation unit.

Product Overview

The ABB AB91-1 HESG437479R1 is a legacy ABB control-system module associated with the Procontrol family used in power-generation and industrial control installations. The identifier HESG437479R1 represents the assembly reference, while HESG437899 is frequently associated with the underlying PCB. Keeping both numbers with the AB91-1 designation is useful when identifying an installed spare or confirming a replacement.

The ABB AB91-1 appears in secondary technical catalogs as a processing, communication, adaptation, or control/protection module within the Procontrol architecture. The available evidence is not consistent enough to safely assign a specific channel count, signal range, or communication protocol. For an installed Procontrol system, the module’s actual role depends on the rack, neighboring cards, hardware revision, and plant-specific configuration.

The ABB HESG437479R1 should therefore be purchased as an exact legacy assembly rather than substituted based on a generic description such as “analog input,” “DC output,” or “communication module.” Several current listings assign mutually incompatible functions to the same part number, which makes nameplate and system-document verification particularly important.

AB91-1 HESG437479R1 HESG437899

Main Features & Field Considerations

Legacy Procontrol architecture
The AB91-1 is associated with ABB’s older rack-based control architecture. Replacement is normally performed at the board/module level within an existing system rather than as a standalone modern PLC component.

Multiple identifying numbers
For procurement, retain the complete identification:

• — module designation
• HESG437479R1 — assembly number
• HESG437899 — associated PCB reference

This combination is more useful than searching for “” alone.

System-specific function
The available sources describe processing/communication or arithmetic/adaptation functions, while other vendors classify the same part as a protection or analog module. That conflict is a strong reason to verify the installed system documentation before specifying technical parameters.

Replacement risk
A physically identical board with a different revision may not be suitable if the Procontrol system depends on a particular hardware revision or configuration. Check the complete part number and revision before approving a substitute.

Replacement Checklist

Before purchasing , verify:

1. Exact designation:
2. Assembly number:
3. PCB number: HESG437899, if present
4. Procontrol system generation
5. Rack and slot position
6. Adjacent modules
7. Hardware revision
8. Existing wiring
9. Application/control configuration
10. Original board photographs
11. System documentation
12. Any plant-specific modification or engineering revision

Important Specification Warning

I would not use online claims that the is an 8-channel analog input card with universal voltage/current/RTD/thermocouple inputs and Modbus RTU. Those claims appear on reseller pages but are not supported by the more consistent Procontrol-oriented identification.

Likewise, another listing calls it a DC output card, demonstrating the extent of the conflicting catalog data.

For technical procurement, the safest description is:

ABB — Legacy Procontrol Control/Protection Module

with HESG437899 included when it appears on the original board.

Procurement Description

ABB — Legacy Procontrol Control/Protection Module, Associated PCB HESG437899

For a like-for-like replacement, specify + and, where applicable, , then verify the installed Procontrol rack, hardware revision, and application before substitution. The public documentation is too inconsistent to justify assigning unsupported electrical ratings to this part.