Notes on Feed Water Systems for Steam Heating Boilers

Overview of Feed Water Systems for Steam Heating Boilers

  • Introduction to feed water systems in steam heating boilers
  • Discussion on various components used in these systems
  • Emphasis on safety mechanisms in boiler operations

Key Components of Feed Water Systems

  • Low Water Cutoffs

    • Function: Shut off the burner when the water level in the boiler is too low.
      • Acts as a safety mechanism
      • Prevents boiler damage due to low water conditions
    • Types:
      • Float Type: Operates based on the water level within the boiler.
        • Float drops when water level decreases, activating a switch to shut off the burner.
      • Can also control water input to the boiler by starting/stopping a pump or opening/closing a valve.

  • Combined Feeder and Cutoff Controls

    • Devices that can control water input to the boiler while also shutting off the burner when water is low.
    • Functionality includes both filling the boiler and cutting off the fuel supply when necessary.

  • Condensate Receivers

  • Return Loops, particularly the Hartford Loop

  • Condensate Pumps

  • Boiler Feed Water Pumps

  • Feed Water Control Valves

Safety Considerations in Boiler Operations

  • Importance of understanding Lowest Permissible Water Level (LPWL)
    • Definition: The minimum water level at which the boiler can operate safely.
    • Critical for low water fuel cutoffs to activate without allowing water to drop below this level.
  • Importance of compliance with safety codes:
    • CSA B51 Code: Requires at least two independent low water fuel cutoffs for unattended boilers.
      • Must be installed to avoid being rendered inoperative (e.g., no isolating valves).
    • CSD-1 Code: Specifies that at least one cutoff must be positioned above the LPWL and must not be lower than the visible part of the gauge glass.
      • Reasons for this requirement include ensuring that the level is high enough to prevent boiler damage.

Operational Procedures for Low Water Cutoffs

  • Low water cutoffs must lock out the burner and require a manual reset upon activation.
    • Emphasizes the need for troubleshooting before restarting after a lockout.
  • Training in labs often involves practical experience with low water cutoff reset procedures.

Combined Feeder and Cutoff Controls Explained

  • Functionality of combined systems that link feed water control and low water cutoff actions.
  • Detection of low water that triggers actions to restore water level and ensure safe operation.

Float Control and Switch Mechanisms

  • Description of float controls and how they manage water levels outside of the boiler for stability.
  • Mechanism involves:
    • Float movements responding to water level fluctuations
    • Integrated mechanical operations where float mechanisms also manage valve operations.
  • Float control switches can indicate high/low water levels, start/stop feed pumps, or act as low water cutoffs.
  • Usage of mercury switches as historical examples, though now less common due to toxicity concerns.

Summary of Electrical and Mechanical Operations in Float Controls

  • Explanation of how float controls work, including electrical wiring for actuating switches.
  • Importance of ensuring that operational switches maintain safe and effective control over boiler functions with various configurations (e.g., normally open/closed).