PTVM-100 Hot-Water Boiler Control System

The process-control system described here serves three gas- and oil-fired PTVM-100 hot-water boilers, units 1–3, each with a thermal output of 100 Gcal/h. The boilers cover peak heat demand and can also serve as a primary heat source. Water circulates through each boiler in a two-pass arrangement.

Control functions

• Collect, process, display, log and archive process data;
• Provide warning and emergency alarms and record operator actions;
• Regulate boiler operation automatically and control valves remotely;
• Apply process protections and interlocks;
• Support operating optimisation through post-operation review of archived data;
• Exchange information with the plant-wide “Operative TEP” system.

Redundant control architecture

The system uses primary and standby Siemens SIMATIC S7-300 controllers with CPU317-2DP processors and ET 200M remote I/O stations, one cabinet per boiler. The standby processor continuously monitors the primary processor and takes over control if it detects a failure, including loss of power, hardware or software faults, or loss of communications with an ET 200M station. Signal modules can be replaced while the remote station remains powered.

The controllers connect over Ethernet to two operator stations and over PROFIBUS to the engineering workstation. The engineering workstation also passes process information over Ethernet to the plant-wide “Operative TEP” system. Operator and engineering stations are located at the boiler operator’s desk in panel room 2; the controllers are in panel room 2, and the remote I/O cabinets are in panel room 1.

Operator and engineering stations

Operator stations provide the operator–system interface and retain local process archives. They connect to the lower-level controllers over Ethernet through an eight-port SCALANCE X-100 switch. The engineering station supports database and process-diagram editing, system time synchronisation, data archiving, data exchange with the plant-wide system and backup operator functions. Data is archived at the operator stations and the engineering station.