Selection and Application of DG Boiler Feed Pump

The DG type is a horizontal single‑suction segmented multi‑stage centrifugal pump, specially designed for boiler water supply. It transports de‑oxidized clean water free of solid particles or media with physical and chemical properties similar to clean water. The medium temperature ranges from ‑20℃ to 160℃, and the maximum allowable inlet pressure is ≤0.59 MPa.

Example of model designation: DG46‑50×6. DG stands for boiler feed pump; 46 refers to the design flow rate in m³/h; 50 denotes single‑stage head in meters; 6 indicates the number of impeller stages. The total head of the pump can be adjusted by changing the number of stages.

Ⅰ. Key Selection Points

Flow Rate and Head

Parameters shall be determined according to the rated boiler feed‑water flow and total system pressure drop. The total head covers boiler working pressure, pipeline friction loss, local resistance and safety margin. Insufficient head can be compensated by increasing impeller stages. Flow rate is determined by the impeller hydraulic model and cannot be changed merely by adding or removing stages.

Performance range: flow 3.75‑300 m³/h, head 69‑1050 m, power 4‑1250 kW.

Medium Temperature and Suction Conditions

Standard version is applicable for feed‑water ≤105℃; sub‑high‑pressure version is suitable for 160℃ high‑temperature de‑oxidized water. For high‑temperature working conditions, verify shaft‑seal cooling and bearing heat dissipation configuration. Keep inlet pressure below 0.6 MPa to avoid cavitation risk.

Wetted‑part Materials

For conventional boiler feed‑water: cast‑iron pump casing plus carbon‑steel shaft, cost‑effective solution.

For de‑oxidized water and slightly corrosive service: stainless‑steel impeller and wear ring to reduce corrosion and erosion. Specify medium temperature and water quality when placing orders to prevent wear‑ring damage caused by high‑temperature corrosion.

Shaft Seal Types

Packing seal: low‑cost, permits minor water dripping, suitable for medium‑and‑small‑size boilers with intermittent operation.

Mechanical seal: extremely low leakage, preferred for thermal power and waste‑heat boilers operating 24 hours continuously.

Axial‑force Structure

Standard DG pumps adopt balance disc to counteract axial force with good spare‑part interchangeability. For long‑term non‑stop operation, DGP self‑balanced structure is optional to reduce balance‑disc wear failures.

Motor and Rotational Speed

Most units adopt high‑speed configuration of 2900 r/min. For high‑power and high‑pressure conditions, check motor protection class and matched coupling to fit on‑site power supply conditions.

Selection note: Inlet and outlet flanges have different pressure ratings. The discharge flange bears high pressure with higher rating than suction flange. Matching pipe flanges shall be selected separately and must not be mixed‑used.

Ⅱ. Main Application Scenarios

Industrial Boiler Water Supply

Water supply and make‑up water for gas‑fired, biomass‑fired and coal‑fired industrial steam boilers of medium‑low and sub‑high pressure. This is the primary application of DG pumps, widely used in boiler rooms of factories, printing‑and‑dyeing plants and food‑processing enterprises.

Thermal Power and Waste‑heat Power Generation

Boiler feed‑water systems for small thermal units, steel‑industry and chemical‑industry waste‑heat power stations. Adaptable to header‑type and unit‑type feed‑water processes to realize continuous and stable water supply.

Central Heating Plants

High‑temperature hot‑water boosting and system water make‑up for central‑heating boiler houses.

Other Extended Working Conditions

High‑pressure clean‑water transportation in factories and high‑head water supply for high‑rise buildings. With modified materials and seals, it can convey non‑corrosive high‑temperature liquids similar to clean water. Not applicable for media containing solid particles or strong corrosive substances.

Ⅲ. Operation Notes

The conveyed medium must be de‑oxidized to mitigate oxidation and erosion of impellers and wear rings.

This pump is of horizontal segmented construction. Tightening quality of tie bolts directly affects sealing performance. Keep good alignment during maintenance and assembly.

Prohibit long‑time operation under low‑flow no‑load condition, to prevent excessive temperature rise and shaft‑seal damage.