ML21323A102

A New Look at Design of Raw Water Piping Bowman TVA 1980

ML21323A102
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Site:	Browns Ferry
Issue date:	08/31/1980
From:	Bain W, Bowman C Tennessee Valley Authority
To:	NRC/RES/DRA
Aird, Thomas - 301 415 2442
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ML21323A100	List: ML21323A101 ML21323A102
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Download: ML21323A102 (5)

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A new look at design of raw water pip.i:ng

Extensive tests indicate that presently recognized standard m~tt,,ods for calculating pressure drops in raw water piping do not allow for required flow over a 40-yr projected operating lifetime ofthe,pipi_ng.

Changes in the recommended design practices are sugg~sted

By CHARLES F. BOWMAN and WILLIAMS. BAIN, Tennessee Valley Authority

During preoperational testing of the raw cooling water system at TVA's Browns Ferry nuclear plant during the summer of 1976, it was found that certain heat exchangers were not receiving their de sign water flow rates. Sections of the car bon steel piping which supply water to these components were removed and were found to have a buildup of material on the interior which impeded the water flow. An analysis of the samples indi Figure 1. Sample of piping from Kingston cated that iron as Fe20 3 was the major Steam Plant shows formation of deposit constituent of the deposit. The buildup of iron oxide was attributed to oxidation of Figure 2. Average reduction in pipe diameter as a function of years of service

• the pipe interior by common corrosion of for pipelines with normally flowing or stagnant water; : * *,

• steel piping by aerated river water. A study was undertaken to determine the

• Sample taken from a.nor:nallyitagnan;li~e pervasiveness of this problem in the TV A system and to develop recommended

- practices to mitigate its effects in the l~ _i design of future power plants. 0.6

- Sampling program Approximately 50 sections of carbon 0.5 steel raw water piping were removed WC-22 **

from nine different TV A steam plants. ~ ~ WC-f6 *..... ~ 0.4..

Both normally stagnant and normally

flowing piping systems as well as both qi E: 0.3 vertical and horizontal runs of pipe were 'o 0 sampled..s

0.

In virtually every case, the primary mech "'

0

anism was found to be corrosion of the..._

steel piping by aerated river water and 0 SNP-1

0./

redeposition of the corrosion products. a

• The problem was found to a significant degree at all plants that were sampled. 0 5 15 20 25 30 35 40 The result is random pitting in the pipe wall and the formation of a tubercle over Service years each pit as shown in Figure 1.

A measured length of each piping sample was sealed at one end and filled with water. The volume of water contained in the sample was compared with the origi nal volume as calculated from the nomi nal dimensions of a new pipe. The per-cent volume occupied by the deposit rep resents the average loss in pipe cross,,/'......

sectional area and was related to an : -~ 1 : 5 average decrease in pipe diameter. This..

0.....,, average diameter reduction as a function.....

V of years of service is shown on Figure 2.. " -- -. ~

~-...... ~_,*~

• . In addition, the deposit in each sample ---~ :':. -.. ~

was removed and analyzed for various constituents as presented in Table 1. Figure 3. Pictures of three samples of pipe removed from the same pipeline indicate the large variations that occurred in deposits.

From the scatter of data it can be seen

POWER ENGIN EERI NG / AU GUS T 1980 73 RAW WATER PIPING r al>le 1. Analysis of samples taken from deposits in raw water piping.

Sample Norn. Flow System Sample Age Average * % Deposit Analysis Comments on t ID Site Diam, In. Condition Taken From (Years) Diam Red, In. Fe 2 0 3 Si0 2 s Mn0 2 Appearance or Use

! C-1 Colbert 3 Continuous Boiler feed pump 22.2 0.273 82.9 NA 0.3 NA Large, brittle Un it 1 cooling water tubercles supply ("1 G -1 Gallatin 3 Continuous Ash sluice 17.8 0. 167 88. 1 NA 0.8 NA Large, brittle ~ -- -

Unit 3 supply line tubercles JS-2 John Sevier 3 Stagnant Fire protection 17.7 0.070 75.8 NA 0.5 2.2 Thin, brown _deposit Unit 1 line K-2 Kingston 3 Stagnant Fire protection 18.2 0.133 81.4 NA 3.3 NA Large, brittle Unit 1 line tubercles WB -2 Watts Bar 3 Nearly Alternate supply 34.1 0.314 84.4 NA 1.0 NA Large, brittle Unit C continuous to backiet tubercles WC-1 Widows Creek 4 Stagnant Fire hose 24.7 0.198 13.4 NA 2.3 NA Large, brittle Unit 6 supply line tubercles WC-2 Widows Creek 3 Continuous Ash hopper 23.8 0.218 38.6 NA 0. 6 NA Large, brittle Unit 3 supply line tubercles WC-4 Widows Creek 21/2 Continuous Ash hopper 12.1 0.054 90.4 NA 0.5 NA Small, hard tubercles Unit 8 supply line SNP-1 Sequoyah 4 Continuous Construction 2.0 0.096 87.5 NA 0.4 NA Small, hard tubercles const. piping water line

BFNP-1 Browns Ferry 21/2 Continuous Discharge core 5.0 0. 163 NA NA NA NA Large, brittle Unit 2 spray room coder tubercles WC -10 Widows Creek 2 Continuous Boiler feed 25 0.226 80.0 7.0 0.7 1. 6 Rust/mud appearance Unit4 pump piping 0.4 in. tubercles WC-11 Widows Creek 2 Continuous Boiler feed 25 0.230 72.5 7.0 0.4 1. 9 Heavy buildup Unit 4 pump pipinQ WC-12 Widows Creek 21/2 Continuous Bottom sluice 251/4 0.258 77.8 5.0 0.4 1.5 Sch. 80 pipe. Unit 2 line Light buildup of

tubercles with varicolored deposit WC-13 Widows Creek 21/2 Continuous Bottom sluice 25 0.115 77.9 7.0 0.3 2.4 Sch. 80 pipe, very Unit 2 line small buildup,

0.2 in. tubercles

......... WC -16 Widows Creek 4. Continuous H2 cooler 17 0.405 90.0.6.0 0. 1 3.0 Large amt. of buildup ;

Unit 7 cooling water Some tuber. tubercles r -.

3/4-1 in. high t )

CU-1 Cumberland 2 Continuous Pulverizer oil 5 0.096 88. 5 8.0 0.4 1.8 Mild corrosion, very cool inQ water few tubercles

~-

: CU-2 Cumberland 2 Stagnant Raw service 5 0.162 88.9 8.0 0.6 1.5 Reddish deposits, water

• widely scattered tubercles, some 0.4 in. in height CU-4 Cumberland 4 Continuous Oil cooler 5 0.183 85. 2 9.0 0. 5 1.4 Mild buildup of

• cooling water tubercles, 0.2-0.25 in. in height, some tuber -

des briQht oranqe CU -5 Cumber land 6 Continuous Sluice 5 0.110 74.0 21.0 0.6 2.0 High Si0 2 level, water supply orange tubercles :

throughout, 0.5 to 1 in. in height CU-6 Cumberland 2 Continuous Cooling water 5 0.080 81.2 17.0 0.4 2.7 High Si0 2 level,

to vac. priming mild corrosion pumps except for a few 0.3 -0.5 in. tubercles

CU -7 Cumberland 4 Continuous Coo ling water 5 0.106 89.0 9.0 0.4 1.9 Orangeish interior to vacuum pump most tubercles 0.2-0.25 in.. some 0.5 in.

CU-8 Cumberland 6 Continuous Cooling water 5 0.150 78.0 14.0 0.3 1to pyrite hold-streaked; some. 5 Muddy appearance,

ing bin 0.5 in. tubercles JS -3*

• John Sevier 2 Stagnant Fire protection 23 0.242 85.6 6.0 1.0 1.0 Flaky deposits, Unit 1 system ( 1.3)

• large tubercles, 0.4 in. in hei ht

JS-4 John Sevier 2 Stagnant Fire protection 23 0.277 91.0 6.0 1. 3 0.6 Flaky deposits, darker Unit 2 system (0.8)* than JS -3, some tubercles 0.6 in.

JS -5 John Sev ier 3 Stagnant Fire protection 23 0.177 85.6 6.0 0.7 1.3 0.5 in. tubercles system (1.0)*

WB -3 Watts Bar 4 Continuous Makeup to slag 35** 0.148 93.7 4.0 0.3 1.0 Relatively even Unit C chamber buildup, some

tubercles 3/4 in he ight in.

WB-4 Watts Bar 6 Co n t inuous Supply to ash 35** 0. 150 92.5 5.0 0.4 1. 2 SeeWB -3 Unit C quencher nozzles

74 POWER ENGINEERING/ AUGU S T 1980

. *,. Sample Norn. Flow System Sample Age Average % "Deposit Analysis Comments on ID Site Diam, In. Condition Taken From (Years) Diam Red, In. Fe 2 O 3 SiO 2 s MnO 2 Appearance or Use WB-5 Watts Bar 2 Continuous Cooling water to 35** 0.206 89.7 5.0 0. 5 1.2 Large number of Unit C boiler feed pump small tubercles WB _-6 Watts Bar 4 Continuous Makeup to slag 33** 0.152 81.8 8.0 0.3 1.5 See WB-3 Unit D chamber

WB-7 Watts Bar 6 Continuous Supply to ash 33** 0.311 90.0 7.0 0.8 1.3 See WB -3, more Unit D quencher nozzles pronounced tubercles WC-21 Widows Creek 3 Nearly Water supply to 13.75 0.259 65.0 20.1 3.7 amples removed than WB-3 Unit 8 continuous pulverizers from linP. whP.rP.

WC-22 Widows Creek 3 Nearly Water supply to 13.75 0.440 79. 1 6.9 2.4 pressure drop tests Unit 8 continuous pulverizers were oerformed. All WC-23 Widows Creek 3 Nearly Water supply to 13.75 0.326 81.0 8.1 2.4 samples had a large Unit 8 continuous pulverizers amount of buildup.

WC-24 Widows Creek 3 Nearly Water supply to 13.75 0.594 56.3 27.4 5. 2 High SiO 2 levels in Unit 8 continuous eulverizers WC-21 and WC -24 K-7 Kingston 6 Nearly 23 0.169 81.8 5.4 1.3 Unit 7 stagnant

K-8 Kingston 6 Nearly { f;c, pm<~foa 23 0.098 79.4 4.8 1 1 { Oaly a =*II *=*II Unit 7 stagnant line with a

• deposit but very large K-9 Kingston 6 Nearly very small 23 0.101 80.2 3.4 (2 in. in height) Unit 7 stagnant flow spaced. Vertical line. continuous 0.8 tubercles randomly

K-10 Kingston 6 Nearly 23 0. 163 90.3 4. 2 0. 9 Unit 7 sta nant G-2 Gallatin 8 Stagnant Fire protection 19.5 0.227 78.2 9.9 1.9 1.5 Units 3 & 4 header G-3 Gallatin 8 Stagnant See G-2 19.5 0.313 74.8 10.3 1.8 1.6 { '-9' aumbe,of Un its 3 & 4 large tubercles -

G-4 Gallatin 8 Stagnant See G-2 19.5 0. 280 82.6 8.3 2.5 1.4 1 to 11/4 in. in he ight.

Units 3 & 4 Reddish deposit.

G-5 Gallat in 8 Stagnant. See G-2 19.5 0.359 75.5 8.2 2. 2 1.4 Units3 & 4 NA - Not Available.

• Values indicated in parentheses indicate amount of MnO 2 found in John Sevier $amples only. ~

. * *Watts Bar was removed from service for a number of years so that these ages may not be t he effective age.

that age is not the only parameter which observed data, an approach was devel was installed adjacent to the sections of influences corrosion product buildup. oped to estimate a 40-year design value piping where pressure drop measure Large variations in buildup can be seen of diameter reduction from the available ments were taken. Taps were installed in for piping removed from a given site at a data. Samples which were found to have the lines to allow pressure drop measure given age and in some cases large varia high levels of buildup were discarded ments to be made and mercury manome tions can be seen from samples removed where justified. ters were used to measure the pressure from a single pipeline, as indicated by the The largest value of diameter reduction drops across the orifice and each section three views in Figure 3 of a pipe from remaining after discarding all possible of piping. Samples removed from each Widows Creek steam plant. It was found data, 0.40 in., was selected as the 40- test line were analyzed to determine the that the average buildup in 8-in.-diam year design value. Although the. ap percent volume reduction of the pipe inte samples taken at the Gallatin steam plant proach is somewhat speculative, it is felt rior due to the corrosion product buildup.

and 6-in.-diam samples taken at the King that the result is conservative enough to It was found that the samples removed ston steam plant was approximately the be a design value. There may be some from the 3-in. test line at Widows Creek same as the buildup in the 2-in., 3-in., isolated instances where buildup will be had a substantial amount of buildup on and 4-in.-diam samples taken at the John so excessive that pipe replacement may the interior, made up of iron oxide and Sevier and W idows Creek steam plants. be required. silicon oxide, whereas the samples re Buildup does not appear to be dependent moved from the 6-in. line at Kingston on pipe diameter. Pressure drop tests were found to have only a small amount Large differences in the appearance and Tests were performed at the Widows of uniform buildup but had very large ran consistency of the corrosion product Creek, Kingston, and Gallatin steam domly spaced tubercles ( some ap buildup were found. In some cases, more plants to evaluate the effects of corrosion proaching 2 in. in height). The 8-in.-diam than products of corrosion were found on product buildup on pressure drop. The samples from Gallatin were found to have the pipe interior. Most of the samples had sites were selected to cover a range of a more uniform buildup than the Kingston a relatively uniform buildup ( very rough ages as well as a variety of water 6-in. line but also had large, randomly surface). However, some samples such sources. All tests were made on straight spaced tubercles. The average diameter as shown in Figure 1 had almost no aver lengths of pipe to avoid consideration of reduction of each set of samples was age buildup but had large, randomly bends. Tees were included in some of the found to be the following:

spaced isolated tube rcles. No significant piping systems tested but the pressure Average Measured differences were observed in the cor drop across the tee was neglected since Plant

• Diam Reduction roded condition of horizontal and vertical the run of the tee was always in line with Widows Creek 0.405 in.

t1 *) runs of pipes as long as the pipes were the test flow and the lateral branch was Kingston 0. 133 in.

~ completely full of raw water. always closed. Gallatin Since TV A does not have any steam An orifice inserted in a length of new pip Section A 0.270 in.

plants wh ich have been in service for 40 ing was installed in each. of the piping Section B 0.320 in.

yea rs, and due to the large scatter in the systems to measure flow rate. The orifice

POW ER ENGIN EE RING /AUGUST 1980 75

• I

• RAW WATER PIPING

The corresponding diameter reduction for For each set of data ( a unique value of hl = 820 2 (7) 0 each test line was then used with the a 1), a table of ( C,d) values was gener where a 2 is a constant, was obtained for pressure drop test data to develop ap ated which will satisfy Equation ( 3). each set of data.

propriate equations for predicting pres sure drop. The Hazen-Williams and Dar Several figures were generated in an Setting Equations ( 6) and ( 7) equal and cy equations for pressure drop were con attempt to find a correlation between solving for the friction factor, f:

sidered with each set of data being diameter reduction and C. Values of C f = a2d5 (8) treated separately and then analyzed to were assumed and corresponding values 3.11 establish a correlation to the other sets of of d were calculated for a given test using data. Predictive equations were tt:ien for Equation ( 3). A dimensionless parame-:

mulated to predict pressure drop iri car ter, d 0, was defined for use in correlating Moody presented an expression for the bon steel raw water piping after 40 years the above calculated value of d with the friction factor in fully rough flow as:

of service. measured value of diameter reduction: ~ 3.7

d. = (dNOM - dCALC) 1 / V' = 2 log1oic/d (9)

Correlation of test data The Hazen-Williams equation can be writ ~dMEAS ten in the form where E is the absolute roughness of the 85 Q1.65/d*.8655 Calculated Diameter Reduction pipe interior expressed in inches. ( Full hl = 0.2083 ( 1~) 1* Measured Diameter Reduction (4) rough flow is almost certain to exist at

( 1) design flow in old, corroded piping.) This where : where: equation can be rearranged to:

hL = head loss in feet per 100 ft of dNOM = nominal inside diameter of Eld=3.7/[101I2 11'] (10) pipe new pipe, in inches For each pressure drop test ( a unique d = pipe inside diameter in inches dCAt.c= calculated inside diameter of value of a 2) values off were calculated C = roughness factor pipe using Equation ( 3) for different assumed inside diameters Q = flow rate in gpm diameter reduction corre using Equation ( 8). Equation ( 1 O) was form sponding to the percent vol-used to calculate Eld. Using the assumed A least squares curve fit of the ume reduction measured, in values of d, the corresponding values of E hL = a1Q1.s5 ( 2) inches were calculated.

where a 1 is a constant, was obtained for d

• as a function of C for all the pressure In the same manner as was used for the each set of data. Equations ( 1) and (2) drop tests is shown on Figure 4. The Hazen-Williams equation, various curves were set equal to solve for d : smallest variation of calculated diameter were generated in an attempt to establish reduction I measured diameter reduction a correlation based on the pressure drop d = [ (0.2083/a1) ( 1~) 1.85] 1/4.8655 occurs at a value of C of approximately tests. The best correlation was found 57 at a value of d* equal to 2. from a plot of E vs d*, shown in Figure 5.

(3) Using a slightly more conservative value The smallest variation in E appears to of C equal to 55 and a diameter reduction occur at a value of d

• equal to 1.0 to 1.2 equal to twice that measured, the Hazen where E = 0.9 to 0.8 in.

Williams equation becomes Using a value of E = 0.9 in. and a calcu 0.63Q1.85 (5) lated diameter reduction equal to the hl = (d - 2 ~d )4.6655 NOM MEAS measured value of diameter reduction

The Darcy equation can be written ( for a 18 pipe length of 100 ft) in the form

~ 7 hl = 3.11 fQ2 /d 5 (6) 5. 0 i5

~ where hL, Q, and d are the same as

~6---+----+-+-+-6-H--#1------i defined previously and f is the friction lg factor. A least squares curve fit of the Cl)

~ 5 f---t----t-<e--f-:!~'-7">-r---; form

• I

~4---+------r--,--~

~

Cl)

~31----t----<Jf-f-:trn#~-='-i Figure 4. ( left) Relationship between rough 0 ness factor and the ratio of calculated diame

~ ter reduction to measured diameter reduction

~2r---t---ffj~-+----t--~ 0 ( for Hazen-Williams equation) is shown for all.s

pressure drop tests. c_i0. 02.____.__.....__.____,_ _ _._~

ci u 0 0.5 /.0 1.5 2.0 2.5 3.0 u Figure 5. ( right) Relationship between abso lute roughness of pipe interior and ratio of cal d*, calculated diam. reduction/

culated reduction to measured diameter reshown for all measured diam. reduction 40 60 80 JOO duction (for Darcy equation) is.

pressure drop tests

• 76 POWER ENGINEERING / AUGUST 1980

Figure 6. ( right) Comparison of measured and predicted pressure drops for Widows Creek 3-in. line. cu 40f:---........i""1l'cy.-iWll,~~~~'4---t----:-.d~d'-t---i Q.

Rgure 7. ( below) Comparison of measured and predicted pressure drops for Kingston plant 6-in. line. ~ 301----:...::='--'1:..:..'..'.!=~C!!!!--+-,,,.@~7"'-i,!+---I---I 8

Rgure 8. ( below right) Comparison of measured and predicted pres ;:

sure drops for Gallatin plant 8-in. line. ' 20 l----+-----+--4-..,;L-~-+---+ --t-----i

~ IO 1---+-:;;;;...-J-,,,,"-==--+---+--t---t---t- - -; "'

"tJ 0 Cl>

t Flowrate, gpm

• Measured data, measured Section I

-- Hazen-Williams with C =55 and diam. =nom.diam.-211D >

• Measured data,

--- Darcy with :=0.9in. and diam. =nom.diam. -11D measured

• Measured data, Section2

-*- Hazen-Williams withC=IOOanddiam. =nom. diam. 2 5 -- Hazen-Williams with 12~-~-~-~-~-~--~~ C =55 and

C>

10 t 20 l-r...-il---+--+,,--~---11---+r--+----i

..... Q. ~

0 8 0 6 0

..... 4.....

'.,,~ "'

~ "' 2 ~ 51---1--t--+~IF..,,.l,m~--t--:--t----1 "tJ 0 "tJ

0

t 150 200 250 300 350 400 450 £ ~OOL--"==4CO=::........iL-..6CXJ........._____,__EXXJ_._____.__l_(XXJ....____.

Flowrote, gpm Flowrate, gpm

( d * = 1 ), the Darcy equation becomes per 100 ft of pipe) in piping after 40 Therefore, for more conservative calcula hl = 3.11 fQ2/(dNOM - MMEAS) 5 (11) years of service is: tions, the modified Hazen-Williams equa hl=3.11fQ2/(dNOM-0.4)5 (14) tion should be used.

where Impact on design f ={210910 [ ( 4. 1) ( dNOM - t.dMEAS) l }- 2 where: The results of this study should have a (12) f= [210910[(4.1) (dNOM-0.4)JJ-2 profound impact on the design of future (15) raw water piping systems, since the pres Predicting pressure drop At reasonable velocities, the modified sure drops calculated by methods rec Figures 6, 7, and 8 show the raw data Hazen-Williams equation consistently ommended herein are significantly great taken for various pressure drop tests predicts values of pressure drop greater er than those which would be calculated along with curves representing different than the modified Darcy equation when by presently recognized standard meth methods of calculating pressure drop. Equations ( 13) and ( 14) are used. This ods. For example, for a new pipe design Extrapolating the equations to predict is apparently because the large diameter velocity of 4 fps, the pressure drop calcu pressure drop in piping after 40 years of reduction projected after 40 years is dou lated by the methods recommended service reduces to establishing a value of bled in Equation ( 13) but not doubled in herein in 100 ft of straight 3-in. and 8-in.

diameter reduction expected after 40 Equation ( 14). The equations reverse in line would be approximately 1-2 and 4 years of service. Based on the results of severity at higher flow rates but as pipe times, respectively, that calculated by the sampling program, this value is 0.4 in. diameter increases this transition velocity the Hazen-Williams formula with the com as indicated above. also increases so that in large diameter monly accepted C value of 100. Alter Substituting these values into Equation piping with practical velocities, the modi nately stated, a 3-in. line sized by con

( 5) the Hazen-Williams equation to cal fied Hazen-Williams equation always pre ventional means to pass 95 gpm will be culate pressure drop ( head loss per 100 dicts higher values of pressure drop than capable of passing only 25 gpm with the ft of pipe) in piping after 40 years of the modified Darcy equation. same available pressure drop, or an 8-in.

service is: Note that as diameter increases, the val line sized to pass 1000 gpm will pass ue of dd and f [from Equation ( 15) J only approximately 450 gpm at the end h =. 0.63O 185 (13) decrease. Since both of these values of its 40-year life.

L (dNOM - 0.8)*-8655 decrease, the modified Darcy head loss It should be noted that these results 0 prediction decreases more rapidly than apply only to friction losses and should Similarly, substituting the 0.4 in. value of would be seen based on diameter innot be applied to form losses. END diameter reduction into equations ( 11 ) crease alone. This is in contrast to the and ( 12), the resultant Darcy equation constant C factor incorporated in the to calculate pressure drop (head

• loss modified Hazen-Williams equation.

POWER ENGINEERING / AUGUST 1980 77