Boiler Observation Sight Hole

The observation sight hole is an important monitoring component of boiler equipment, used for real-time observation of combustion conditions inside the furnace, the state of the heating surfaces, and the ash accumulation. It also serves as a channel for maintenance access.

Classification of Observation Sight Hole

• Furnace observation sight hole:

  • Location: Often installed on the front wall, side wall, or roof of the furnace, near the burner area.

  • Function: To observe the fuel combustion status (e.g., flame color, shape, fullness), and check for coking, flameout, or deflagration.
  • Features: Must withstand direct radiation from high-temperature flames. The observation window glass requires the highest high-temperature performance (quartz glass is commonly used, with a temperature resistance of over 1000°C) and must be equipped with a cooling device (such as an air-cooling jacket) to prevent the glass from shattering due to overheating.

• Flue observation sight hole:

  • Location: Located on the flue wall where heating surfaces such as superheaters, reheaters, and economizers are situated.

  • Function: To observe whether the heating surfaces have ash accumulation, slagging, wear, or leakage (e.g., red-hot pipes, deformation, or smoke leakage) and to monitor the flue gas flow.
  • Features: The temperature is lower than in the furnace (typically 300-800°C), but the flue gas has a high dust content, so the glass surface needs to be cleaned regularly to ensure clear observation.

• Grate observation sight hole (for layer-fired boilers, such as chain grate boilers):

  • Location: On the side or bottom of the grate.

  • Function: To observe the combustion of the coal bed (e.g., ignition point location, burnout degree) and check if the grate is operating normally (e.g., no jamming or deviation).
  • Features: Must allow for both observation of the coal bed and the mechanical movement of the grate. The observation port size is small but must be easy to open frequently.

• Explosion-proof observation sight hole:

  • Special design: In high-pressure or potentially explosive boilers (e.g., gas boilers), the observation glass is explosion-proof (e.g., laminated glass) , or the observation sight hole cover is designed as a “bursting disc” that ruptures to release pressure when the internal pressure suddenly increases, protecting the boiler body.