Moisture Separator Reheater - Balcke-Dürr Energietechnik Gmbh

Special publication 

a 60e 

Moisture Separator Reheater 

W. Bruckmann and M. Kienböck 

VGB Kraftwerkstechnik 04/1984 

pages 271 to 281

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RANGE OF PRODUCTS AND SERVICES 

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erection and commissioning of: 

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separators 

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Moisture Separator Reheaters 

W. Bruckmann and M. Kienböck 

Abstract 


With the commencement of construction of 

light water reactors (LWRs) it became necessary, 

because of the steam condition to provide 

Moisture Separators and Reheaters 

(MSRs) for saturated steam turbines. In a brief 

chronological summary the various stages of 

development are compared based on the designs 

and specific performance data and the 

advantages and disadvantages are contrasted. 

This paper describes cyclone separators and 

plate separators as well as plain tube reheaters 

and finned tube elements in many different arrangements. 

Kurzfassung 

Authors 

Wasserabscheider- 

Zwischenüberhitzer 

Mit dem Beginn des Baues von Leichtwasserreaktoren 

(LWR) entstand (aufgrund des 

Dampfzustandes) der Bedarf für Wasserabscheider 

und Zwischenüberhitzer (WAZÜ) für 

Sattdampfturbinen. In einem kurzen chronologischen 

Abriss werden die verschiedenen Entwicklungsstufen 

konstruktiv und mit ihren spezifischen 

Leistungsdaten gegenübergestellt 

und die Vor- und Nachteile herausgearbeitet. 

Es werden Zyklonabscheider und Prallplattenabscheider 

sowie Glattrohrüberhitzer und Rippenrohrkonstruktionen 

in jeweils verschiedenster 

Anordnung beschrieben. 

Dipl.-Ing. (FH) W. Bruckmann 

Dipl.-Ing. M. Kienböck 

Balcke-Dürr AG 

Ratingen/Germany 

Introduction 

Moisture separators and reheaters, referred to 

below as MSRs, are normally installed between 

the HP and the LP turbines in nuclear power 

plants to increase efficiency and to avoid damage 

to the LP turbine ( F i g u r e 1 ) . 

The MSRs cannot be bypassed owing to the 

fact that they are arranged between the HP 

and the LP turbines. This results in a direct 

influence on the availability of the turbosets. 

The load behaviour of the MSRs is determined 

directly by the turbines and as a result 

of possible intercept valve test cases and the 

switching on and off of the reheaters during 

operation, the MSRs are subjected to more 

complex operating conditions and greater 

load change speeds than most other heat exchangers 

in a power plant. 

From various publications [2 to 4] and unfortunately 

also from own experience we are familiar 

with damage to moisture separators and 

reheaters. Damage to the MSRs is taken note 

of and publicised to a greater extent than damage 

to other heat exchangers because of their 

direct influence on the availability of the 

whole plant. In a short chronological outline 

we would like to attempt to compare the various 

development stages with their specific 

output data and to show the advantages and 

Table 1. Types of moisture separators. 

Plant Type of separator Arrangement In 

operat. 

Obrigheim (old) Cyclone coarse 

separator with 

centrifugal main sepa- 

rator and fine separator 

Stade X 

Borssele/NL 

Mülheim-Kärlich 

Atucha/ARG 

Kalkar 

Brunsbüttel 

Unterweser 

Neckarwestheim 

Tullnerfeld/A 

Obrigheim (new) 

Gösgen-Däniken/CH 

Trillo/ES 

Philippsburg 2 

Grohnde 

Angra 2 and 3/BRA 

Cyclone separator 

with agglomerator 

connected upstream 


disadvantages. For obvious reasons we have 

limited the facts to the plants with which we 

are familiar in Germany and the plants which 

are influenced by the German market. 

Types of Moisture Separators 

The separators which we have built or designed 

are listed in Ta b l e 1 and subdivided 

into cyclone separators and chevron type separators 

according to their operating characteristics. 

Separator systems from the USA which had 

originally been proven in small plants were 

installed in the Stade, Borssele and Atucha 

plants. In all three cases the high steam velocities 

during commissioning led to vibration 

damage and complete destruction of 

these internals. The axial cyclones which had 

previously only been provided for preliminary 

separation were improved by optimising 

the blades and connecting suction devices in 

series in order to enhance these 3 plants. In 

addition, agglomerating units [7] were installed 

in the feed lines: by increasing the size 

of fine spray droplets these units displace the 

droplet spectrum to such an extent that the 

separation process can be carried out with an 

economical pressure loss. After the conversion 

of these plants residual moisture values 

Vertical 

cyclone 

Arranged 

in the 

piping 

Plate separator Pyramid 

column 

Plate separator 

Separator 

wall 

Star column 

X 

X 

X 

X 

X 

X 

X 

X 

Erec- 

ted 

X 

X 

X 

X 

X 

Under 

constr. 

X 

X 

Figure 

3 

4 

6 

7 and 8 

3


of < 0.5 % were measured downstream of the 

separator ( F i g u r e 2 ) . 

The Atucha ( F i g u r e 3 ) and Kalkar separators 

which are installed in the piping should 

be mentioned. The specific constructional 

volume of these separators is considerably 

less than that of separators installed in vessels. 

As you can see from Ta b l e 3 the specific 

constructional volume of Atucha, defined 

as m3 /MW, is only 1 ⁄ 10 of the constructional 

volume required for separators installed 

in vessels. This construction could not gain 

acceptance in Germany as a result of the pressure 

loss values and because the plate separators 

are given preference. At the moment developments 

[5] are being carried out in France 

in this direction whereby the separator is constructed 

as a multiple cyclone to reduce the 

pressure losses. 

4 

Primary circuit Secondary circuit 

Reactor 

Recirculation 

pump 

HP heater 

Moisture separator reheater 

HP turbine LP turbine Generator 

Steam generator 

Condenser 

Feedwater tank 

Feedwater pump 

LP heater Condensate pump 

Figure 1. Flow diagram of a nuclear power plant with 

pressurised water reactor. 

Table 2. Types of reheaters. 

Percentage of moisture 

at outlet separator y in % 

The disadvantages of the solution proposed 

here are that a motive steam flow of approx. 

10 % of the flow rate is required and that access 

and ease of inspection are poor compared 

to a single cyclone. 

Types of Reheaters 

1.0 

0.5 

The reheaters which we construct are vertical 

as opposed to the horizontal reheater arrangements 

applied elsewhere (USA, France). The 

condensate draining for the reheated steam 

which condenses in the pipes is simplified in 

the vertical construction compared with the 

horizontal construction as a result of the effects 

of gravity. A great deal of damage 

[2, 10] has occurred on the horizontally arranged 

MSRs as a result of a backflow of 

steam at reheater tubes under a low load and 

the subsequent subcooling of the condensate. 

Plant Bundle construction Tube No. of bundles 

per MSR 

Obrigheim (old) Header construction Plain tube 1 X 

Stade Header construction Plain tube 1 X 

Borssele/NL Header construction Plain tube 2 (2-stage) X 

From heat balance 

Derived from previous 

acceptance test measurements 

When utilising all tolerances 

0 

0 50 100 150 

Capacity in % 

Figure 2. Mean residual moisture, measurement in Stade (1973). 

The causes for this damage have been recognised 

in the meantime and proposals with regard 

to design and construction have been 

made in various publications [8, 10]. 

Our calculations and operating experience in 

connection with the vertical reheater show 

that additional measures such as: 

− graduated orifices, 

− subdivision of bundles into several passes 

connected in series with a condensate discharge 

pipe after each pass, 

− bleeding off of motive steam 

are not required for the load cases known up 

to now. 

The reheaters which we have designed are 

listed in Ta b l e 2 . Header constructions 

and tubesheet constructions are used for the 

plain tube type ( F i g u r e 4 ) . Both constructions 

function in a similar way; the reheated 

In operat. Erected Under 

construct. 

Brunsbüttel Tubesheet construction Plain tube 1 X 

Unterweser 


Tullnerfeld/A 


Tubesheet construction 




Plain tube 

Plain tube 

Plain tube 

Plain tube 

1 

1 

1 

1 

X 

X 

X 

X 

6 

6 

Unterweser (new) Tubesheet construction Plain tube 1 X 

Brunsbüttel (new) Tubesheet construction Plain tube 1 X 

Mülheim-Kärlich Tubesheet construction Fin tube 8 X 

Gösgen-Däniken/CH Tubesheet construction Fin tube 4 X 6 

Trillo/ES Tubesheet construction Fin tube 6 X 

Philippsburg 2 Tubesheet construction Fin tube 6 X 7 and 8 

Grohnde Tubesheet construction Fin tube 6 X 

Angra 2 and 3/BRA Tubesheet construction Fin tube 6 X 

Figure

22 000 

7 

3 

6 

Ø 3 200 

2 

Ø 4 500 

Drain pipe 

Figure 4. Moisture separator and reheater of the 

Unterweser Nuclear Power Plant. 

5 

1 

4 

1 Fine separator 

2 Coarse separator 

3 Reheater 

4 Turbine steam inlet 

5 Turbine steam outlet 

6 Heating steam inlet 

7 Heating steam condensate outlet 

Condensate outlet nozzle 

7 

1 

2 

3 

4 

5 

Agglomerator 

6 


1 Agglomerator 

2 Manhole 

3 1st vortex generator 

4 1st drain 

5 2nd vortex generator 

6 2nd drain 

7 HP turbine 

8 Moisture separator tank 

Figure 3. Moisture separator of the Atucha Nuclear Power Plant. 

e finned 

e plain 

j; 

5.0 

2.0 

1.0 

0.5 

0.2 

0.1 

steam condenses in the tubes and is collected 

in the lower header or the lower duct and directed 

out of the vessel whilst the 

turbine steam flows mainly in longitudinal 

flow around the bundle and is reheated in the 

process. 

As a result of the simple and distinct construction, 

this type of reheater installed in 10 plants 

of which 8 are in operation has functioned 

with practically no defects apart from damage 

to the guide shell in Unterweser. All reheaters 

of the first generation with plain tubes 

achieved better heating values than guaranteed 

but also higher pressure losses compared 

to the design data. 

e finned 

e plain 

NU plain 

8 

j finned 

j plain 

NU finned 

(apparent) 

10 

RE comparison 

4 2 5 105 2 5 106 0.05 

Figure 5. Comparison of the performance figures of fin tube and 

plain tube arrangement. 

10 3 

NU 

10 2 

5


Table 3. Comparison of technical data. 

The plain tube construction was abandoned 

because of the limitation in the admissible 

overall height of the MSRs and the high pressure 

losses and various fin tube reheaters 

were designed. The geometry of the fin tubes 

calls for a diagonal initial flow to the fin tube 

bundle. Although the area of the fin tube 

bundle is smaller than that of the plain tube 

bundle due to the larger surface area, the specific 

constructional volume of the fin tube 

reheater is larger than that of plain tube bundles 

with a longitudinal flow due to the diagonal 

flow and also the initial and exit flow 

6 

Obrigheim (old) 

Stade 

Borssele 

Mülheim-Kärlich 

Kalkar 

Operat. time approx. in 10 4 h 10 8 7 – – 7 4 4 5 – 1 4 – – – – – 

Total pressure drop 

in % of inlet pressure 

Residual moisture 

in % 

Guaranteed 

Measured 

Guaranteed 

Measured 

Specific overall volume m 2 /MW 

Velocity in the 

main separator 

Specific overall volume m 2 /MW 

Terminal 

temp. difference 

11 

Section A - B 

moisture 

separator 

10 

2.0 

1.0 

6 

12 

0.8 

0.4 

8 

– 

– 

6 

– 

0.3 

– 

3 

– 

0.8 

– 

Atucha 

Brunsbüttel 

Unterweser 


cross-sections required as a result of this. The 

main advantage lies in the lower pressure 

loss. An evaluation of the thermal advantages 

and the advantages with regard to the flow 

has been attempted in Figure 5 [6]. An efficiency 

coefficient is formed as quotient from 

the transferred thermal efficiency and the 

pump output used (pressure loss); for the 

finned heat exchanger this is by a factor of 

1.4 – 1.5 greater than for a plain tube bundle 

in a Reynold’s number range between 10 4 

and 10 6 . 

2 

– 

0.7 

– 

6 

7 

0.8 

0.3 

6 

- 

0.8 

0.3 

6 

6 

0.8 

0.3 

0.2 0.2 0.14 0.2 0.08 0.02 0.2 0.24 0.2 0.2 0.2 0.24 0.19 0.2 0.2 0.2 0.25 

m/s 21 45.5 40 45.5 30.3 40 3.8 3.7 3.9 3.9 4.7 4.0 4.0 4.0 4.0 4.0 4.0 

Guaranteed 

Measured 

C D 

5 

4 

1 

2 

6 

3 

10 

7 

reheater 

0.16 0.2 

– 40 

25 

0.55 

2-st. 

– 

– 

Tullnerfeld 

6 

– 

0.8 

– 

0.26 – – 0.2 0.15 0.2 0.2 0.35 0.26 0.27 0.25 0.25 0.25 0.4 

28.5 

– 

1 Reheater 

2 Fine separator wall 

3 Turbine steam inlet 

4 Turbine steam outlet 

5 Heating steam inlet 

6 Heating steam 

condensate outlet 

7 Coarse separator drain 

8 Fine separator drain channel 

9 Fine separator drain nozzle 

10 Vent nozzle to condensate 

collecting tank 

11 Manhole 

Section C - D 

A B 

8 

9 

Figure 6. Moisture separator and reheater in the 

Gösgen-Däniken Nuclear Power Plant. Figure 8. Installation of the reheater bundles. 

– 

– 

– 

– 

40 

40 

35 

32 

40 

32 

20 

– 


6 

6 

0.3 

0.3 

35 

35 

Gösgen-Däniken 

6 

3 

0.8 

0.5 

30 

33 

Trillo 

4.5 

– 

0.5 

– 

40 

– 

Philippsburg 2 

Grohnde 

Angra 2 and 3 

Convoy 

Instead of being compact like a plain tube 

bundle the heating surface of the fin tube 

reheater is split up into individual bundles 

because a diagonal flow is required in each 

individual bundle: these bundles are arranged 

next to one another in ring form (F i g u r e s 

7 , 8 and 9 show the installation of the reheater 

bundles in the Grohnde plant) or as a 

wall (Gösgen-Däniken F i g u r e 6 ). 

The required seals between the single tube 

bundles and to the vessel are considerably 

more costly and more complex than in the 

case of a compact bundle owing to intermittent 

operating cases and the subsequent temperature 

differences and relative motions. 

4 

– 

0.5 

– 

40 

– 

4 

– 

0.5 

– 

40 

– 

4 

– 

0.5 

– 

40 

– 

4 

– 

0.5 

– 

15 

–

Figure 7. Moisture separator and reheater in the Grohnde Nuclear Power Plant. 


7


Figure 9. Moisture separator and reheater of the Convoy Nuclear Power Plants. 

8

Figure 10. Moisture separator and reheater in the 

Obrigheim Nuclear Power Plant. 

Comparison of the Technical Data 

The technical data and the values measured 

on the different constructions in operation are 

compared in Ta b l e 3 . In summary it can be 

said that within the scope of the measuring 

accuracy both the cyclone separator with agglomerating 

unit and the plate separator yield 

a comparable amount of residual moisture. 

The advantage of the cyclone lies in the fact 

that it is insensitive to local streaks of water, 

unbalanced charging and intermittent load 

cases. The disadvantage is the approx. 1 to 

1.5 % higher pressure loss (in relation to the 

inlet pressure) with the single cyclone design. 

That means that the pressure loss is approx. 

50 % higher than that of the plate separator. 

At the same thermal efficiency and with almost 

the same space requirement the low 

pressure loss is also a point in favour of the 

fin tube reheater. The most efficient vessel is 

the MSR in the Gösgen-Däniken plant. In this 

case the pressure loss in the reheater is used to 

balance the steam flow in the moisture separator, 

whereby a total pressure loss of 3 % (in 

relation to the inlet pressure) can be 

achieved. 

New Delivery of MSRs for an 

Existing Nuclear Power Plant 

Figure 11. Deposits on the fin tubes. 

The MSRs at the Obrigheim nuclear power 

plant were exchanged after approx. 100,000 

operating hours when the fuel elements were 

replaced in 1982 because of wear. A period of 

two years elapsed between the placing of the 

order and the completion of the erection work. 

The newly delivered MSRs ( F i g u r e 1 0 ) 

were constructed in accordance with the basic 

safety concept. Access to the vessels was improved; 

all circumferential and longitudinal 

welds were kept fully accessible from the inside 

as well. 

When constructing the new MSRs an attempt 

was made to find an optimum design using 

the present possibilities and experience 

gained. It was only possible to increase the 


size of the MSRs on a limited scale because 

of the existing dimensions of the machinery 

house. The reheater outlet temperature was 

therefore kept constant, the pressure loss was 

minimised. As a result of installing the new 

separators the amount of residual moisture 

was reduced. The increase in output achieved 

as a result of these measures amounts to more 

than 1 % of the plant output. The improved 

output values were confirmed by measurements 

carried out after commissioning of the 

new MSRs. 

A problem which is also familiar from other 

projects, “the drop of several degrees in the 

reheater outlet temperature”, could be resolved 

by accurate data acquisition as well as 

long-term monitoring of data and be localised 

through tests. The temperature drop could be 

limited to 1 K by implementing a simple operational 

measure (raising the condensate 

level in the reheater condensate tank). 

Operating Experience Gained 

in the Gösgen-Däniken NPP 

Gösgen-Däniken ( F i g u r e 6 ) was the first 

plant with which we were involved in which a 

reheater with fin tubes was put into operation. 

With this construction the fine separators and 

the 4 reheater bundles are arranged horizontally 

behind one another in the form of a wall 

and the flow passes through them diagonally. 

Individual separator levels are connected to 

the reheater bundles by means of partition 

plates so that the pressure losses from the 

separator and the reheater are added together 

and the total pressure loss for the flow distribution 

over the total height is available. 

Commissioning at Gösgen-Däniken commenced 

at the end of January 1979. Towards 

the end of the commissioning work in August 

1979 deformations were noticed on several 

baffles during an inspection. Up to that point 

in time practically all the operating and test 

9


Figure 12. Fin tube. 

cases including the valve tests had been carried 

out without any difficulties and the reheater 

had been repeatedly inspected. 

The deformation of the baffles could be attributed 

to a special load point which had not 

previously been taken into account (idling at 

2 % load with reheater connected). The support 

structure for the reheater was therefore 

reconstructed when the fuel elements were replaced 

in June/July 1980. The reheater bundles 

were removed from the vessel and returned 

to the works in order to carry out the 

reconstruction. The side plates of the bundles 

were separated from the baffles and replaced 

by new side plates. In doing this the construction 

was changed in such a way that in intermittent 

load cases the relative motion occurs 

between the side wall and the baffle and not 

between the tube and baffle as was previously 

10 

the case. The whole reconstruction including 

the dismantling and installation of the bundles 

was carried out within the period of 8 weeks 

scheduled for replacing the fuel elements. 

Based on the available operating experience 

this reconstruction has proved its worth. 

When the tube bundle was removed the initial 

flow side became accessible: this cannot 

be inspected when the bundle is installed. 

Local red-brown deposits were found ( F i g - 

u r e 1 1 ) . These deposits could be removed 

without any difficulty using a steel brush. The 

other tube surfaces were covered with a thin, 

dark grey magnetic layer which had formed 

naturally as a protective layer (F i g u r e 1 2 ) 

contrary to the red-coloured foreign deposits 

which occurred locally. Part of the red-brown 

deposits was removed; analysis showed it to 

be hematite. There was no erosion whatsoever 

Figure 13. Fine separator column. Figure 14. Erection of the reheater. 

on the fins although at Gösgen-Däniken the 

separators are overloaded during intercept 

valve test cases and water is therefore entrained 

into the reheaters for short periods. 

The fin tube baffles are sometimes mounted 

on the non-finned intermediate parts and 

sometimes on the fins. Both methods have 

been proven effective. 

1300 MW Standard MSR for 

NPPs Grohnde and Philippsburg 2 

The design can be seen from Figure 7. The 

separator and the reheater are arranged above 

one another in the vessel shell. The separators 

consist of a preliminary separator (coarse separator) 

and the main separator. The steam entering 

through the lower nozzles is directed to 

the base plate in the coarse separator, where 

spray water entrained in the steam is separated 

and drawn off under the base plate. The steam 

is then redirected and flows upwards in the 

inlet channel to the fine separators. The internal 

cylinder is equipped in such a way that the 

velocity is regulated as evenly as possible over 

the cross-section of the inlet channel. 

The steam from which the spray water has 

been removed now flows to the star-shaped 

fine separator arranged in three levels above 

one another. Perforated sheets are arranged in

Air inlet 

Figure 15. Arrangement of the flow test stand. 

front of and behind the separator packs to stabilise 

the flow. The condensate in the steam is 

separated when the steam flows through the 

baffles and is directed via collecting basins 

Figure 16. Model arrangement. 

2 

Air outlet 

(displaced by 100°) 

3 4 4 3 

Model 

moisture separator 

1 Venturi duct: measurement of the air volume flow delivered 

2 Flow diversion 

3 Water injection 

4 Measurement of air distribution over the tube diameter 

and water channels into a circular torus and 

from there through a nozzle out of the vessel 

(Figure 13). 

2 

Separator elements 

16 

13 

10 

7 

4 

1 

17 

14 

11 

8 

5 

2 

18 

15 

12 

9 

6 

3 

1 


Fan 

The dried steam flows into the central interior 

space, then flows through the reheater bundles, 

installed in a circular arrangement, in 

diagonal flow, is reheated and flows to the 

outlet nozzle. The reheater is constructed in 

such a way that in all load cases compensation 

for the different thermal expansion rates between 

the reheater bundle and the vessel shell 

and between the reheater tubes and the bundle 

frame is guaranteed. F i g u r e 1 4 illustrates 

the erection of the Grohnde reheaters. 

Upper level 

Centre level 

Lower level 

Figure 17. Flow distribution over the levels of the 

fine separator column. 

0.9 1.0 1.1 

C/C,M 

11


Erosion Protection 

Great importance was attached to the fact that 

all parts which come into contact with wet 

steam have adequate erosion protection. The 

shell and the lower head in the coarse separator 

section were made of sheets clad with 

austenite. All internals such as base plate, inner 

cylinder, supporting plate of the fine separator 

were clad or made of pure austenite 

sheets. The fine separator is protected on the 

initial flow side with austenitic insulation. The 

separator baffles and the back perforated plate 

are also made of austenite. Based on previous 

operating experience [3] erosion downstream 

of the separator can be excluded as the residual 

moisture behind the main separator is less 

than 0.5 %. 

12 

Residual moisture (1 - X) in % 

0.8 

0.7 

0.6 

0.5 

0.4 

0.3 

0.2 

0.1 

GKN 

Design point 

Gösgen 

Brunsbüttel 

Theoretical 

residual moisture 

0.0 

0 1 2 3 4 5 6 7 8 

Steam velocity CD in m/s 

Figure 18. Theoretical residual moisture (1 – x) behind the separator 

as a function of the approach flow velocity (valid for a marginal 

droplet of 8 µm). 

Amplitude in mm 

1.0 

0.5 

100 % operating case Gösgen 

Entrainment level 

2.5 

10 +03 

5.0 

2.5 

10 +02 

5.0 

Tests Car ried out to Provide Proof 

of the Construction and Design 

Although operating experience was already 

available for components such as coarse separator, 

fine separator and fin tube bundle, various 

tests were carried out because of the 

altered arrangement. Some of these tests and 

the results thereof are described below as an 

example. 

Model Tests 

Model tests were carried out in order to ascertain 

the optimal construction of the coarse 

separator and to determine: 

− water distribution, 

− pressure losses, 

− amount of water stored, 

− flow distribution in the fine separator and 

reheater. 

Gösgen Jülich 

Valve test case Gösgen 80 % 

Pressure head in N/m2 0.0 

0 1000 2000 3000 

Figure 20. Amplitude over pressure head. 

Z = 10 N = 15.5 

Air 

Helium 

NU/Pr ** 0.36 

Mass value reference temperature: 

mean gas temperature 

Zukauskas, plain tubes 

Skrinska and Stasiulevicius 

Schmidt 

5.0 10 +04 2.5 5.0 10 +05 2.5 5.0 

Re 

Figure 19. Heat transfer, comparison of different measurements. 

F i g u r e 1 5 shows the arrangement of the 

test stand, F i g u r e 1 6 the plexiglass model 

(scale 1:5) with measuring equipment. The 

measured flow distribution over the separator 

column is illustrated in F i g u r e 1 7 . The 

three separator levels are shown above one another; 

the individual points each represent 6 

measuring points of one level. The max. measured 

deviation from the average velocity 

amounts to ± 10.7 %. 

Determination of the Limit of Entrainment 

of the Separator Profile 

The limit of entrainment is the velocity at which 

no droplets are entrained from the separator. 

This velocity was determined experimentally. 

The test was carried out on an original separator 

element with air-water. The values established 

with air-water, converted to the state of the 

steam compared to the operating point (100 % 

load), result in a safety margin of 90 %, or expressed 

in a different way, the flow through the 

separator can have a 1.9-fold velocity without 

droplets of water being entrained. The degree of 

separation according to Figure 18 is calculated 

for a marginal droplet size of 8 µm. The existing 

droplet spectrum is, however, not known. The 

acceptance test measurements of GKN, KKB 

and Gösgen-Däniken are entered on the theoretically 

determined graph of residual moisture. 

The residual moisture values of approx. 0.3 % 

at the design point, determined during the acceptance 

tests, are considerably below the guarantee 

value and the definible limit. The deviation 

of the measured values from the theoretical 

residual moisture value arises from the fact that 

the droplet spectrum in the steam is also made 

up of droplets which are smaller than 8 μm and 

apart from that higher steam velocities occur

locally as well as discontinuities in the water 

distribution compared to the test conditions. 

Part of the safety margin is used up by these 

deviations from the test conditions. 

Provision of Proof of Thermal Design 

When designing the first reheaters of fin tube 

construction it was found that some of the 

existing calculation documents contained 

values which deviated considerably from one 

another. 

Within the scope of an examination requested 

by BMFT, KFA Jülich carried out a test on 

fin tubes with the dimensions and pitches 

which we use to ascertain the thermal and 

flow properties. 

F i g u r e 1 9 shows the results of the heat 

transfer measurements in comparison with 

other tests; the calculation documents which 

deviated considerably were not illustrated. 

The tests were confirmed by operating experience 

gained at the Gösgen-Däniken NPP taking 

into account the existing bypasses due to 

the construction. 

Vibration Measurement on the Fin Tubes 

F i g u r e 2 0 shows the comparison of the 

amplitudes measured in the wind tunnel at 

Jülich and the measurements made during operation 

at the Gösgen-Däniken NPP. The amplitudes 

of the different tests are superimposed 

over the pressure head in this figure. 

The resonant range of the first and second 

harmonic vibrations is easily recognisable. 

The basic frequency is traversed at low pressure 

heads with practically no measurable amplitudes. 

The amplitudes calculated from the measured 

values at Gösgen-Däniken (assuming a 

simply supported beam with uniform load) 

correspond well with the amplitudes determined 

in the wind tunnel under simulated 

support conditions. The determined amplitudes 

of approx. 0.1 mm in the operating 

case and those of approx. 0.2 mm in the 

valve test case lie far below the admissible 

limit at approx. 800 MW. 

Convoy Concept 

The basic concept of the construction of the 

MSRs for the convoy plants, Figure 9, corresponds 

to the 1300 MW standard MSR. 

As the building plans have been changed the 

support has been altered from a bearing ring 

supported by link supports to a cone with ball 

and socket joints. Furthermore, the terminal 

temperature difference of the convoy plants 

has been reduced to 15 K which results in a 

larger heating surface and changed external 

dimensions. 

The MSRs for the convoy plants are being 

constructed by a consortium made up of 

Messrs. Steinmüller and Balcke-Dürr. 


References 

[ 1] Gloger, M.: Probleme der Wasserabscheidung 

in Nassdampfturbinen, BWK 22 (1970), 

S. 417 – 460. 

[ 2] Baschek, H., und Kocourek, E.: Betriebs- 

erfahrungen mit Wärmetauschern in Kernkraftwerken 

mit Leichtwasserreaktoren. VGB 

KRAFTWERKSTECHNIK 54 (1974), H. 12, 

S. 799 – 807. 

[ 3] Haas, H.: Betriebserfahrungen mit Sattdampfkreisläufen, 

Turbinen, Wasserabscheidern, 

Rohrleitungen. VGB KRAFTWERKSTECH- 

NIK 54 (1974) H. 12, S. 791 – 798. 

[ 4] Steinrück, K., Knoerzer, G. und Jaerschky, 

R.: Erste Betriebserfahrungen im Kernkraftwerk 

Isar. VGB KRAFTWERKSTECHNIK 

59 (1979), H. 1, S. 1 – 7. 

[ 5] A.I.M. – Liege: Centrales électriques modernes 

– 1981. 

[ 6] Groehn, H.G.: Jul. – 1462, Okt. 1977. 

[ 7] Kienböck, M. und Kirn, K.W.: Entwicklung 

eines Zentrifugalabscheiders mit Agglome- 

rator für Kernkraftwerke. VGB KRAFT- 

WERKSTECHNIK 55 (1975), H. 8, S. 478- 

497. 

[ 8] Schrey, H.-G. und Kern, J.: Zum Rohrreiheneffekt 

bei gasbeaufschlagten Kondensatoren. 

International Journal of Heat and Mass Transfer 

24, S. 335 – 342. 

[ 9] Kienböck, M.: Schwingungsverhalten nie- 

drigberippter Rippenrohre. VGB KRAFT- 

WERKSTECHNIK 62 (1982), H. 7, S. 584 

– 593. 

[10] Gibson, J.N.: Redesign and Replacement 

of Connecticut Yankee Moisture Separator/ 

Re-heater (MSR), Tube Bundles. ASME 

81-JPGC-PNR-2. 

13

ouR SeRViceS W o R l DWi D e 

Balcke-Dürr GmbH 

Ernst-Dietrich-Platz 2 

40882 Ratingen, Germany 

Tel.: +49 (0) 2102 1669-0 

Fax: +49 (0) 2102 1669 -617 

bdinfode@cts.spx.com 

www.balcke-duerr.com 

BRANCH OFFICE 

ROTHEMÜHLE 

Balcke-Dürr GmbH 

Wildenburger Strasse 1 

57482 Wenden, Germany 

Tel.: +49 (0) 2762 611-0 

Fax: +49 (0) 2762 611-297 

bdinform@cts.spx.com 

www.balcke-duerr.de 

Further companies in: China, Italy, Poland, South Africa, Hungary

Moisture Separator Reheater - Balcke-Dürr Energietechnik Gmbh

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