Size Deaerator (Two-Compartment)
- For a single-tank deaerator or a separate, single-tank deaerator as part of a two-tank (2T) system, refer to Size Deaerator.
- For a separate surge tank as part of a two-tank (2T) system, refer to Size Surge Tank.
Deaerator Design
Pump Flow Rate (Boiler Feed)
Each boiler feed pump on a deaerator is sized based on the total load of boilers fed by the specific pump. For boiler feed pumps running ON/OFF, the pumps are controlled by a boiler level controller.
Pump Flow Rate (Transfer)
Each transfer pump on surge compartment is sized based on total load of deaerator plus additional water to feed vent condensor that is included on atmospheric design.
Two-Compartment Deaerator Receiver Sizing
Two-Compartment Deaerator Receiver Size is determined from Pump Flow Rate (Transfer). The receiver size on two-compartment deaerators is typically based on the total system load (i.e., sum of all boilers fed by deaerator) with 20 minutes NET storage—10 minutes for deaerator compartment and 10 minutes for surge compartment.
Pump Discharge Pressure (Boiler Feed)
Assumes proper discharge pipe size of a velocity of 10 ft/sec or less. Pump discharge pressure MUST BE ABLE to overcome the boiler safety relief valve setting plus 3% of valve setting AND meet all state and local codes. Discharge pressure of pumps based on the larger amount. This amount is either the Safety Relief Valve setting on boiler + 3% OR Boiler Operating Pressure + Valve Pressure Drops + Safety Margin.
If boiler and deaerator are on the same floor, enter a value of "0" (zero) for feet of head. If boiler is located on a floor above the deaerator, enter vertical height (in feet) from the pump discharge on the deaerator up to the inlet piping on the boiler.
If the pressure differential between the boiler operating pressure and the setting of the safety relief valve on the boiler is greater than 20 psig, consider replacing the safety valve with one rated closer to the boiler operating pressure. Otherwise the motor horsepower of the boiler feed pumps will need to be oversized to provide a discharge pressure sufficient to overcome the rating of the safety relief valve on the boiler. The higher motor HP typically would require a more expensive pump and increases ongoing operating costs.
Pump Discharge Pressure (Transfer)
Pump Discharge Pressure (Transfer) is automatically calculated.
Stand Height
On all deaerators, the available NPSH is 0 feet of head unless deaerator tank is elevated above the boiler feed pumps. To calculate elevation of stand, determine required NPSH of boiler feed pump from curves (pump curves can be downloaded on Shipco® website for specific pump model) and add 2 feet as safety factor. Then look at transfer pump and select a transfer pump from curves that has an NPSH requirement less than the stand height all ready selected. If transfer pump has an NPSH requirement higher than stand chosen you must then check NPSH calculator and see if pump will still work since water temperature in the surge chamber is generally cool. After NPSH calculator is run for the transfer pump make sure your NPSH available is greater than transfer pump requirement or you must raise the stand even higher with 2 feet of safety factor.
- Each boiler feed pump on a deaerator is sized based on the total load of boilers fed by the specific pump.
- For boiler feed pumps running ON/OFF, the pumps are controlled by a boiler level controller.
- Each transfer pump on surge chamber is sized based on total load of deaerator plus additional water to feed vent condensor that is included on atmospheric design.
- If boiler and deaerator are on the same floor, enter a value of "0" for feet of head. If boiler is located on a floor above the deaerator, enter vertical height (in feet) from the pump discharge on the deaerator up to the inlet piping on the boiler.
- Assumes pressure drop through modulating valve of 10 psig or less.
- Assumes pressure drop through stack economizer of 20 psig or less.
- Assumes proper discharge pipe size of a velocity of 10 ft/sec or less.
- Pump discharge pressure must be able to overcome the relief valve setting of the boiler. Relief valve setting on the boiler should be adjusted or replaced so the setting of the relief valve is close to the actual operating pressure of the boiler.
- The receiver size on 2-compartment deaerators is typically based on the total system load (i.e., sum of all boilers fed by deaerator) with 20 minutes NET storage—10 minutes for deaerator compartment and 10 minutes for surge compartment.
- Pump discharge pressure MUST BE ABLE to overcome the boiler safety relief valve setting plus three percent of valve setting AND meet all state and local codes.
- If the pressure differential between the boiler operating pressure and the setting of the safety relief valve on the boiler is greater than 20 psig, consider replacing the safety valve with one rated closer to the boiler operating pressure. Otherwise the motor horsepower of the boiler feed pumps will need to be oversized to provide a discharge pressure sufficient to overcome the rating of the safety relief valve on the boiler. The higher motor HP typically would require a more expensive pump and increases ongoing operating costs.
- Pump flow rate is < 0.5 gallons/min (gpm). Contacting your Shipco® representative is advised.
- Pump flow rate is > 500 gallons/min (gpm). Contacting your Shipco® representative is advised.