steam condenser types, function, condenser vacuum, importance in power plant , air ingress prevention,fouling

1. Condenser
WAQAR AHMED
HUBCO POWER PLANT

2. Contents
 Introduction
 Types
 Condenser vacuum
 Function of condenser
 Tube materials
 Importance
 Leak test methods
 Cleaning of tubes

3. Introduction
A steam condenser is a closed vessel which is maintained at low pressure, (lesser than
atmospheric pressure). The condenser acts as a heat exchanger where exchange of
heat occurs between steam and cold circulating water. In this system, heat rejection at
atmospheric temperature takes place by condensing exhaust steam from prime mover.
The condensate can be reused as feed water to the boiler. The steam turbine
condenser is located under
LP turbine.

4. Types of Steam Condensers
The steam condensers are broadly classified into two types:
 Jet condensers (or mixing type condensers). In jet condensers there is
direct contact between the exhaust steam and cooling water.
 Surface condensers (or non-mixing type condensers). In surface
condensers, there is no direct contact between the exhaust steam and the
cooling water.

5. Jet Condenser
In jet condensers, the cooling water is
sprayed on the exhaust steam and
there is direct contact between the
exhaust steam and cooling water.
The process of condensation is very fast
and efficient, but here cooling water
and condensed steam are mixed up.
The condensate then cannot be reused
as feed water to the boilers.

6. Surface Condenser
In surface condensers, there is no direct contact between the exhaust steam and the
cooling water. The
exhausted steam from the LP
turbines is condensed by
passing over tubes containing
water from the cooling system.

7. Surface Condenser
These tubes are usually made of stainless steel, copper alloys, or titanium depending on
several selection criteria (such as thermal conductivity or corrosion resistance).
Titanium condenser tubes are usually the best technical choice, however titanium is
very expensive material and the use of titanium condenser tubes is associated with very
high initial costs. In general, there are two types of surface condensers:
 water-cooled surface condenser
 air-cooled surface condenser

8. Condenser vacuum
For water-cooled surface condensers, the shell's internal vacuum is most
commonly supplied and maintained by an external ejector system. Such an
ejector system uses steam as the motive fluid to remove any non-condensible
gases that may be present in the surface condenser.
Motor driven mechanical vacuum pump such as the liquid ring type, are also
popular for this service.

9. Why vacuum is necessary
 To pull out non condensable gases/air
 Make faster the process of condensation otherwise the gases will react ,
can cause of serious material fatigue & tubes failure.
 To achieve the process/plant efficiency.
 To pull the low pressure steam.
 To change the phase steam to water rapidly.
 To prevent the turbine back pressure.
 To protect the tubes failure.

10. Sources of air ingress
 Atmospheric relief valves
 Rapture disks
 LP heaters / re-heater
 Drain valves
 Turbine seals
 Condenser expansion bellow
 From ejector lines
 Instruments /sight glasses
 Valve stems/bonnets
 Hot well man hole covers
 Piping weld joints
 Condensate pump seals

11. Effects of air ingress
 Efficiency of condenser decreases
 Condensation process will slow
 Failure to remove non condense able gases , that may cause of corrosion
or material failure
 Lower heat transfer properties
 Unconscious temperature occur in turbine last stages
 Pressure can generates on last stages
 Rotor blades can effected

12. Function of Condenser
 Create the vacuum for condensing steam
 Removing dissolved noncondensable gases from steam
 Change the phase, steam to condensate
 Re use the demin water
 Providing a barrier between condensate and non treated cooling water
 Providing a barrier against the air ingress
 Preventing excessive back pressure to turbine
 Serving as a drain receptacle ,receiving vapors & condensate from many exchanger, from valve
leak off
 Facility of storage and makeup water

13. Condenser tube materials
 Copper base alloy (ASTM B111 , B543)
 Stainless steel (ASTM A213, A249, A268, A269, B268)
 Titanium (ASTM B338 , Gr1&2)
 Carbon steel (ASTM A179, A214)

14. Why condenser is
important in power plant

15. Why condenser is important
 Can get Maximum steam energy
 For Rankine cycle
 High vacuum can obtained easily
 increases of plant efficiency
 Reuse of condensate water
 Saving of Water treatment plant cost
 Power saving

16. Condenser Leak Test Methods
 Hydro testing
 Soap test
 Electronic device test

17. Hydro testing
 Take permit and open the water box covers.
 Check the oxygen level in confined space.
 Fill the shell with water until all tubes get dip in water
 Insert the fluorescent powder in water and mix it well.
 Give some time to penetrate the water in cracks.
 Check tube sheet from both sides, if any water leak find then mark and plug both end of tube
 After it , use the fluorescent light to detect leak(off other light while using F.light)
 The fluorescent light identify the minor leaks, then plug the tube both ends.
 After all , drain the water and close the covers.
 Check housekeeping , return permit .
 Fill the box up sheet.

18. Soap testing
 Take permit and open the water box covers.
 Check oxygen level in confined space.
 Clean the tube and tube sheet.
 Start the ejector / vacuum pump for vacuum , because we need vacuum .
 Use rubber gloves and Prepare the soap water & mix well to obtain the bubbles.
 Put the soap bubbles to the tube ends and check the bubbles is cracking or not, because if the
bubbles are cracking it means the tube is sucking air, and that particular tube is leak.
 Identify the leak tube and install plugs on both ends.
 After all check housekeeping and close covers.

19. Electronic tube detector
 Take permit and open water box covers
 Check the oxygen level in confined space.
 Start the ejector for vacuum.
 Use electronic device on the end of every tube.
 Check the air passing, when air passing in tube it means tube sucking air, and that tube is leaking.
 Identify the tubes and plug it.
 Update the tube sheet check list.

20. Eddy current
Eddy current testing uses electromagnetic induction to identify defects in tubing. A probe is inserted into
the tube and pushed through the entire length of the tube. Eddy currents are generated by the
electromagnetic coils in the probe and monitored simultaneously by measuring probe electrical impedance.

21. Fouling
Fouled condenser tubes cause significant economic
problems for power station operation.
Reduced heat transfer capability results in a higher
backpressure in the condenser and less efficient
turbine performance , requiring increased fuel or
even limiting generation capacity .
A second serious concern is that condenser tube
leaks commonly occur as a consequence of fouling.

22. Types of fouling
Condenser tube fouling is mostly a tube interior concern, generally into the
categories
 Microbiological
 Scale
 Deposition
 Corrosion
 Tube sheet plug gage

23. Fouling prevention
Steps can be taken to significantly reduce the possibility of condenser tube
fouling .incoming water may be treated for particular removal by the use of
settling ponds or by filtration.
The chemical dosing system can reduce the fouling effect (to improve water
quality).
The travelling mesh can prevent from fouling.
Mechanical system of sponge ball can also be use to prevent the tube fouling.

24. Condenser tube cleaning
Condenser tube cleaning can occur:
 With steel rod
When just debris on tube ends then we can use steel rod.
 Pressurized water gun:
When tubes are fouling , pressurized water gun will remove the accumulated debris
internally.

25. Any Question??

26. Thank You