Why Restriction Orifice is some distance from Blowdown valve?

Why Restriction Orifice is some distance from Blowdown valve ?


Why Restriction Orifice is some distance from Blowdown valve?

The restriction orifice is placed some distance away from the blowdown valve in steam boiler systems for a few important reasons:

1. Pressure drop: The restriction orifice creates a pressure drop, reducing the pressure of the steam/water mixture coming from the boiler drum before it reaches the blowdown valve. This lower pressure helps prevent excessive wear and erosion on the blowdown valve components.

  1. Flashing prevention: If the high-pressure boiler water were to pass directly through the blowdown valve, it could cause flashing (rapid vaporization) and vibrations, leading to valve damage and potential safety hazards. The restriction orifice helps control the pressure drop gradually, preventing this issue.

  2. Flow control: The restriction orifice helps regulate and control the flow rate of the blowdown stream. This controlled flow rate is important for proper boiler water chemistry management and minimizing thermal stress on downstream piping and equipment.

  3. Temperature reduction: The pressure drop across the restriction orifice also causes a corresponding temperature drop in the blowdown stream, making it safer to handle downstream of the blowdown valve.

  4. Accuracy: Separating the restriction orifice from the blowdown valve allows for more accurate measurement and control of flow rates and pressures. It ensures that the pressure drop across the orifice is consistent and predictable, leading to more reliable operation of the system.

By separating the restriction orifice and blowdown valve, the system design allows for better control, reduced wear and tear, and safer operation of the critical blowdown process in boiler systems. The distance between them is typically determined by factors like piping layout, space constraints, and accessibility for maintenance.