Steam is the most popular heat transfer media. When steam is used for heating purpose, latent heat is transferred and phase of steam changes from vapor to liquid. The liquid formed after steam heating is called as condensate. The condensate formed after steam condensation is having good amount of specific heat and DM water. Condensate must be collected back to Boiler for water and energy conservation. For transferring of condensate from one location to other condensate transfer pump is used. There can be various types of condensate transfer pump which can be used for this purpose, Lets discuss few condensate transfer pump :-
- Mechanical condensate transfer system
- Instrument based condensate transfer system.
- Electrical pump driven condensate transfer system
1 Mechanical condensate transfer system
Mechanical condensate transfer system consist of condensate collection vessel or reservoir for condensate collection with air vent and overflow line, Two check valves for direction control of condensate, Float arrangement for water level control in pressurized power pumping unit, Motive steam arrangement and depressurizing vent as shown in fig-1.
Condensate is collected in reservoir and due to gravity it travels to pressurized pumping unit, Pressurized pumping unit consist of two NRVs, condensate is collected through first NRV while second NRV restricts condensate line back pressure in pressurized pumping unit. As the condensate level increases float fitted will move upwards and opens motive steam to enter into pressurized pumping unit. As the pressure increases in the pressurized pumping unit, Condensat starts traveling though second trap while first trap restricts pressure to release to condensate collection vessel, When Condensate gets empty out, float will go down and stop steam supply to the pressurized pumping unit, depressurizing vent releases pressure and makes system ready for next operation. The capacity of this system depends on the motive steam pressure and size of the pressurized pumping unit.
2 Instrument Based condensate transfer system,
Instrument based condensate transfer system consist of condensate collection vessel or reservoir for condensate collection with air vent and overflow line, Two check valves for direction control of condensate, Level transmitter and controller for water level control in pressurized power pumping unit, Motive steam arrangement and depressurizing vent as shown in fig-2.
Here also, Condensate is collected in reservoir and due to gravity it travels to pressurized pumping unit, Pressurized pumping unit consist of two NRVs, condensate is collected through first NRV while second NRV restricts condensate line back pressure in pressurized pumping unit. As the condensate level increases Level transmitter senses the level of condensate in pressurized pumping unit and controller opens steam supply . As the pressure increases in the pressurized pumping unit, Condensate starts traveling though second trap while first trap restricts pressure to release to condensate collection vessel, When Condensate gets empty out, Level of the condensate will go down with level transmitter showing minimum reading and stop steam supply to the pressurized pumping unit, depressurizing vent releases pressure and makes system ready for next operation. The capacity of this system depends on the motive steam pressure and size of the pressurized pumping unit.
3. Electrical pump driven condensate transfer system, Electrical pump based condensate system is very simple system with reservoir with level transmitter and centrifugal pump arrangement as shown in fig 3, Condensate is collected in the reservoir and flows to the centrifugal pump, Pump operate based on the level of reservoir and pumps condensate. In this type of condensate transfer system, static head needs to be maintained to avoid churning or prevent vaporizing of liquid inside pump,
Which is the best Condensate transfer pump
Condensate transferring with steam as motive energy either in Mechanical or instrument condensate transferring pump are best option to consider. Because steam consumed in the transferring process is not wasted and recycled backed to heat network. Mechanical condensate system has advantage over instrument condensate system as it having electric free operation and can be used in hazardous area. Electrical energy is utilized in electrical condensate transfer pump and if it is used in hazardous area instrument cost increases therefore electrical condensate system is now becoming obsolete.
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