ISA 77.44 : 1995

1 Scope
2 Purpose
3 Definitions
4 Minimum design requirements for a superheat steam
    temperature control system
    4.1 Process measurement requirements
    4.2 Control and logic requirements
    4.3 Final control element requirements
    4.4 System reliability and availability
    4.5 Minimum alarm requirements
    4.6 Operator interface
5 Minimum design requirements for a reheat steam
    temperature control system
    5.1 Process measurement requirements
    5.2 Control and logic requirements
    5.3 Final control element requirements
    5.4 System reliability and availability
    5.5 Minimum alarm requirements
    5.6 Operator interface
Annexes
A - References
B - Steam temperature control
    B.1 Purpose
    B.2 Requirements
    B.3 Principles and methods of steam temperature
          control
    B.4 Saturation protection/water induction
    B.5 Two-stage attemperation
    B.6 Use of cascade spray valve control
    B.7 NOx control
    B.8 Redundancy
    B.9 Reset windup prevention
C - Figures
    C.1a- Typical superheater single-stage attemperator
          arrangement
    C.1b- Typical superheater two-stage attemperator
          arrangement
    C2 - Typical single-element superheat steam temperature
          control
    C3 - Typical two-element superheat steam temperature
          control
    C4 - Typical three-element superheat steam temperature
          control
    C5 - Typical two-stage attemperation superheat steam
          temperature control
    C6 - Typical two-element fuel nozzle tilt control
    C7 - Typical two-element flue gas pass damper control
    C8 - Typical two-element flue gas recirculation
          control
    C9 - Typical compartmented windbox temperature
          control
    C10 - Typical single-element reheat steam temperature
          control
Table B.1 Summary of typical control systems

Deals with the major steam temperature control subsystems in boilers having a steaming capacity of 200 000 lb/hr (25 kg/s) or more. These include, but are not restricted to, superheat temperature control and reheat temperature control. Specifically excludes turbine bypass control, combustion control, motor control logic, sootblower control, and those controls connected with fluidized bed- and stoker-fired furnace combustion units.