API 653 Refresher Course

POINTS TO RECALL (DAY 1)

1. API 570 Code is applicable for inspection, repairs, alteration and re-rating of in-service , metallic piping.

2. ASME B 31.3 piping is used for construction of new piping installation.

3. Revised edition and addenda of API and ASME Codes may be used from beginning with date of issue. But they become mandatory from 6 months after issue date.

4. Table A-1B of B 31.3 Code gives weld joint quality factor for manufactured pipes. The factor can be increased for Electric Fusion welded pipes by conducting additional radiography (spot or full) as per Table 302.3.4.

5. Minimum required thickness (tm) for a pipe of outside diameter (D), made from material having safe stress (S) and subjected to internal pressure (P) is given by:

where E = weld joint factor

Y = material co-efficient (Table 304.1.1)

C = corrosion and other allowances

6. Maximum allowable internal pressure for a pipe for given metal thickness is worked out by substituting nett thickness in Barlow formula and calculating the required internal Pressure (P).

(Nett thickness = Available Thickness Corrosion Allowance)

7. Thickness of a permanent blank for the pipe is given by:

Where, dg = the inside diameter of gasket

8.Hydrostatic Test pr = 1.5 Design pr x stress ratio

Stress ratio is ratio of material stress at test temp to the stress at design temp. Stress ratio is always greater than or equal to 1.

9. Pneumatic test pr = 1.1 x Design pr

During pneumatic test a pressure relief valve (with set pr 1.1 x Test pr.) shall be installed. Pressurization should be in steps. Initially, pressure shall be slowly increased to 25 psi or 50% of test pressure (whichever is lower). Check for leakage, if any, and correct them.

Thereafter, the pressure shall be increased in steps up to the full pressure. Inspection shall be carried out at Design Pressure.

10. Hydrostatic test is preferred over Pneumatic test. The butt joints where Hydro or Pneumatic test can not be performed, 100% RT or UT may be done on butt welds, and PT or MT may be done on other welds (branch welds, fillet welds, etc.) as alternative to Leak testing.

11.If temperature thickness combination falls on or above the material curve (Fig. 323.22), impact testing is NOT required. (If below the curve impact testing is required)

12. For impact testing 3 specimen are required. If the average of 3 specimen > = Required Average and Value of only one specimen is less than average but more than minimum for one specimen Accept

13. If average of 3 specimen > = Minimum for one specimen and

a. Value of one specimen is less than average and also less than minimum for one specimen Retest

b. Value of two specimen is less than average Retest

After retest, all specimen must have value > = Average Value14. Table 330.1.1 gives required and recommended pre-heat temperature. Recommendation becomes requirement if ambient temp is < 0 C.

15. In dissimilar pipe joints higher temperature of the two is to be used for pre-heating.

16. PWHT Table (331.1.1) gives temperature range, minimum time and maximum hardness values. Hardness survey shall be done for 10% samples for furnace PWHT, and 100% for local PWHT.

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