DI PIPES



 GUIDELINES FOR FACTORY INSPECTION OF DI pipes (IS 8329-2000)

Marking:

Each pipe shall have as cast or stamped or legibly and indelibly painted on it with the following appropriate marks:

  1. Indication of the source of manufacturer.
  2. The nominal diameter.
  3. Class reference.
  4. The last two digits of the year of manufacture.
  5. The non-standard length of the pipe if specially ordered.
  6. Where applicable, an indication of length over which the pipe is suitable for cutting on the site.
  7. A short white line at the spigot end of each pipe with push-on joint in sizes DN 700 and above to indicate the major axis of the spigot.
  8. The pipes may also marked with standard mark.

Classification of Pipes as K7, K8, K9 , K10, K12 depends on service condition and manufacturing process.

The class designation shall comprise of:

a) a prefix K.

b) a whole number used for thickness class designation, this is the selected coefficient inserted into the equation  e = K (0.5 + 0.001 DN)

The value of K will depend on the following service conditions .

Nominal Dia (mm)

Water Main

Sewers

Gas Mains

80-300

K9 to K12

K7-K12

K9-K12

350 – 600

K8-K10

K7-K10

K9-K10

700 -2000

K7-K10

K7-K10

K9-K10

2. Sampling

2.a) Scale of sampling and criteria for acceptance for dimensional requirement , mass and straightness of pipes. ( As per IS 11606- 1986).

Lot Size

Sample Size

Acceptance Number

Up to 50

8

0

51 to 100

13

1

101 to 150

20

1

151 to 300

32

2

301 and  above

50

3

2.b) Sampling for Mechanical Test ( Tensile Strength,% of Elongation &  Brinell Hardeness )

DN (mm)

Maximum Batch Size (Pipes)

80 – 250

200

300 -600

100

700-1000

60

1100-1400

40

1600-2000

30

All pipes shall be test  for hydrostatic test .

Physical Measurements

  1. Internal Diameter
  2. Length  ( Tolerance ± 100 mm )
  3. Wall Thickness   ( e)

e =K * (0.5+0.001DN)

Where e – wall thickness , mm

DN – Nominal Diameter , mm

The tolerance on wall thickness (e)  shall be as below:

Sl No

Dimensions

Tolerance (mm)

1)

Wall thickness (e) up to 6 mm

-1.3

2)

Wall thickness(e) above 6 mm

-(1.3 + 0.001 DN)

k- Whole Number Coefficient ( K7, K8, K9 ,K10, K12)

  1. External Diameter  - Tolerances as per Table 7 of IS 8329-2000
  2. Ovality – 100*( A1-A2)/(A1+A2)

Where A1- Maximum Axis, A2- Minimum Axis of the pipe cross section .

        Tolerances per Table 8  and Table9 of IS 83292000

  1. Coating ( External Protection)

e.1) Zinc Coating

The main dry film thickness of finishing layer shall not be less than 70µm with nowhere 50 µm.

The external coating was done with bitumen over zinc (Internal certificate required ).

e.2) Cement Mortar Lining  thickness.

The surface of the cement mortar lining shall be uniformly smooth . Only isolated grains of sand are allowed to appear on the surface of the lining.

Thickness of the Lining:

DN (mm)

         Thickness  (mm)

Maximum Crack width/ Radial Displacement

 

Nominal Value

Tolerance

 

80 to 300

3

-1.5

0/8

350 to 600

5

-2.0

1/0

700 to 1200

6

-2.5

1/2

1400 - 2000

9

-3.0

1/5

e.3) Bituminious Coating

The mean thickness of the coating shall not be less than 70µm and minimum thickness thickness shall not be less than 50 µm.

Hydrostatic Tests

All pipes shall be tested hydrostatically at a pressure shall be applied internally and shall be steadily maintained for a persiod of 10 secs. The pipe shall withstand the pressure test and shall not show any sign of leakage , sweating or other defects of any kind.

for DN

80 to 300

p = 0.05 * (K+1)^2

for DN

350 to 600

p = 0.05 * (K)^2

for DN

700 to 1000

p = 0.05 * (K-1)^2

for DN

1100 to 2000

p = 0.05 * (K-2)^2

Mechanical Test

Tensile Test

Test Specimen

A test bar shall be machined from each sample to be representative of the metal at the mid-thickness of the sample, with a cylindrical part having the diameters given in table below.

The test bars shall have a gauge length at least five times the nominal test bar diameter. The ends of the test bars shall be such that they will fit the testing machine.

Two methods of measuring the tensile strength may be used at the manufacturer’s option:

 Method A -- Machine the test bar to its nominal diameter *lo percent, measure the actual diameter before the test with an accuracy of 0.01 mm and use this measured diameter to calculate the cross-sectional area and the tensile strength;

Method B - Machine the test bar to its nominal area S, within a specified tolerance on diameter and use the nominal area to calculate the tensile strength.

The thickness of sample and diameter

Casting Thickness (mm)

Test Bar, Method A , Nominal dia (mm)

Test Bar , Method B

 

 

Nominal Area (mm^2)

Nominal Dia (mm)

Tolerance Diameter (mm)

Centrifugally Cast Pipes:

 

 

 

 

- less than 6

2.5

5.0

2.52

0.01

6 up to but not including  8

3.5

10.0

3.57

0.02

8 up to but not including 12

5.0

20.0

5.05

0.02

12 and over

6.0

30.0

6.18

0.03

- Test Results of Tensile Strength and Minimum Elongation Test are as given below:

Nominal Dia (DN) mm

Minimum Tensile Strength (MPa)

Minimum Elongation at Break, %

80-1000

420

10

1100-2000

420

7

% Elongation = ((l2-l1)/l1)*100

Where l2- Final Elongated Length , l1- Initial gauge length

Brinell Hardness Test

Brinell Hardness shall not  exceed 230 HB on the external un machined surface when tested in accordance with IS 1500.

Brinell Hardness  (HBW) =  0.102 * 2*F /( ( π *D) * (D-(D2-d2)^0.5 ))

Where, D- Diameter of the ball, in mm

F- Test Force in N

d- Mean dia of indentation = (d1+d2)/2  in mm

d1, d2 – Indentation dia measured at 90 deg in mm

h- Depth of indentation (mm) = (D-(D2-d2)^0.5 )/2

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