The tubes of condenser

 

Basic specifications

The tubes of condenser are typically used in various types of power stations (e.g. thermal, nuclear power station etc.) These special tubes are used in a tertiary circle of power stations in which they are serve to flow cold water into the condenser. See pic. 1.
 

 
The condenser is a heat exchanger in which vapor is condensed on the tubes of condenser which are cooled down by cold water. The vapor is driven into the condenser from the last level of a steam turbine. Condensation heat is taken away into a cooling tower by the cooling water.
Cooling water is water which takes heat, released during condensation of vapor, away from the condenser. Cooling water is cooled down in a cooling tower and then it is returned to the condenser. Due to the volume of cooling water, the cooling tower belongs to the biggest, although not the most complicated, devices in a power plant.

Basic specifications

  • Cooling water temperature (input)
  • Cooling water temperature (output) 
  • Condenser pressure
  • Output to volume ratio
  • Warming of cooling water
15 - 25 °C
26 - 35 °C
0,45 kPa
3,2 m3/s
approx.11 °C

The tubes of condenser

Condenser tubes are used to supply cooling water into the condenser. They can be of two chemical compositions. They are either brass tubes of condenser based on zinc or bronze tubes of condenser based on nickel. Division Kovohutě Čelákovice produces brass tubes of condenser based on zinc with three chemical compositions - CuZn28AlSnMn, CuZn28Sn1As and CuZn20Al2As. At the time being division Kovohutě Čelákovice is trying to produce CuNi10Fe1Mn.


Usage

Condenser brasses are designated for production of tubes of condenser extruded in a cold process. The alloy CuZn28AlSnMn is characteristic for its resistance against corrosion caused by fresh water and water from the sea. Also the other condenser brass CuZn20Al2As (and CuZn28Sn1As) produced by Kovohutě Čelákovice, a.s. has high corrosion resistance, especially against de-zincing. All three alloys are used for tubes of condenser in thermal power stations.
 

Chemical composition

Element [%] Cu Al As Fe Mn Ni P Pb Sn Zn
Min. 69,0 0,6  0,02 - 0,1 - - - 0,6 scrap
Max. 72,0 1,5 0,06 0,07 0,5 0,1 0,01 0,05 1,5
  
Element [%] Cu Al Sn Al + Sn Mn Ni Pb total Zn
Min. 69,0 0,6 0,6 - 0,1 till 1% is
calculated
 as Cu
- - scrap
Max. 72,0 1,5 1,5 2,7 0,5 0,1 0,4
  
Element [%] Cu Al As Fe Mn Ni P Pb Zn
Min. 76,0 1,8 0,02 - - - - - scrap
Max. 79,0 2,3 0,06 0,07 0,1 0,1 0,01 0,05
  

Alloy

EN

ČSN

DIN 17660

ASTM

BS

CuZn28AlSnMn

-

423239

-

-

-

CuZn28Sn1As

CuZn28Sn1As

-

CuZn28Sn1

C44300

CZ 111

CuZn20Al2As

CuZn20Al2As

-

CuZn20Al2

C68700

CZ 110

  
Properties of condenser alloy

Tubes of condenser have high corrosion resistance, are capable of deep draw (see table of tensile properties), dispose of good firmness in high temperatures. They have also good chemical stability and do not suffer from corrosion cracks. Condenser alloys can contain also small amount of tin or manganese. A small addition of arsenic improves characteristics too. Even these alloys must however be protected against corrosion, for example by undervoltage

Alloy 

Tensile properties

Rm
[MPa] 
Rp0,2
[MPa] min
Expansion
A [%] min 
Hardness 
[%] min
Treatment
CuZn28Sn1As 360 140 45 30 R360
320 100 55 30 R320
CuZn28AlSnMn 304-373 78 45 - 42 3239.15
343-422 108-196 40 - 42 3239.26
CuZn20Al2As 390 150 45 30 R390
340 120 55 30 R340


 
Quality control

Tubes of condenser produced by KOVOHUTĚ HOLDING DT, a.s. tested by a 100-percent non-destructive electromagnetic method using Defektomat CP 2.842 made by Institut Dr. Foerster which belongs to world top NDT testing materials. The device offers big resolution of surface and internal imperfections of the tested material. Defektomat is equipped with a microprocessor with a graphic card which makes it possible to display the output voltage signal in various evaluation modes in time including impedance scheme.
The software is designed in line with international standards 9000 which makes it possible to set up all configuration parameters well and evaluate and protocol measurement results.
It is possible to set up Defektomat in standard quality and also in a version with higher surface quality according to an order or requirements of the customer. A test protocol is prepared and archived for every tested batch - order of tube of condenser - including all configuration parameters and responsibilities of defectoscopic personnel during testing and evaluation.
Qualification and certification of NDT employees is in line with relevant articles of the defectoscopy center and it is based on an internationally respected system EN 473.
Quality of tubes of condenser is monitored in the whole process of production from melting to expedition. Chemical composition of every cast is analyzed by X-ray quantometer ARL. Also in all following production operations - warm forming, rolling, and cold melting - is quality of tubes of condenser checked gradually. All important parameters such as chemical composition, dimensions, mechanical values, metallurgy, metallography, extended tests, NTD surface tests, test of internal tension, hardness etc.
The whole quality process is defined and documented in relevant controlling, production and technological processes and in relevant regulations as a part of quality standard ISO 9002.
 

Current production assortment

At the time being KOVOHUTĚ HOLDING DT, a.s. is able to produce sizes from diameter and wall thickness 14 x 1 mm to diameter and wall thickness 30 x 3 mm.