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Good afternoon
I am reviewing the requirements of SAE J 524, specifically the performance tests/Pressure proof test. I have a long (20years) experience testing under API stds, which are similar in spirit to ASTM. Membrane stress for the test is limited to a given percent of SMYS (60% typically) and following Barlow's equation you derive pressure proof test. Additionally this pressure can be capped to a given value (ASTM A53, ASTM A450, API, etc). This test basically verifies that the pipe is watertight.
SAE philosophy seems a bit different since defines pressure proof test from UTS (Burst Pressure), and it is quite confusing IMHO if I try to follow the nested requirements that stem from the references SAE Standards. Any advise from someone with experience on SAE J524 pressure proof test will be welcomed.
Here is what I understand from the standards:
At the beginning SAE J524 states that all tests will be performed in accordance with SAE J1677. In the case of Test 8.8, Pressure Proof Test, is performed by agreement between purchaser and producer. It indicates that "allowable unit stress of material = 140 MPa - 80% om SMYS".
When referring to SAE J1677 the test is described as:
The tube shall be tested to two times its calculated 4:1 reference working pressure... Test pressures shall be determined by the following formula derivative of SAE J1065 Reference Working Pressures for Steel Hydraulic Tubing. In the formula pressure is related to Minimum Tensile Strength. When SMYS/UTS is below 50% additional formulas are provided that INDEED refer to "allowable fiber stress", however this is not the case for SAE J524 where SMYS/UTS ratio is 55%. In addition SAE J1065 lists "working pressures" for some OD/thickness combinations.
Going through calculations things do not add up very well. Taking a std pipe 1/2" OD 1.24 mm thickness these are the values from tables/calculations:
Table 2 in J1065 (for J524) lists 18.8 MPa working pressure. Calculation gives 16.8 MPa. Checking results for other combinations (results are coincidental), I must ASSUME a typo (not a nice thing when defining test pressures). Going to J1677, 2x16.8 gives 33.7 MPa. I may INFER membrane stress form Eq. and this gives me 155 MPa membrane stress... Above 140 MPa.
EDIT: for this same pipe ASTM A179/A210 require 7 MPa of test pressure. ASTM A53 a similar value, both way off values above 30 MPa from different SAE calculations....
My apologies for the long introduction, but I cannot see how to unravel these apparently conflicting requirements in an unambiguous way. Any guidance is welcomed.
Thanks!
I am reviewing the requirements of SAE J 524, specifically the performance tests/Pressure proof test. I have a long (20years) experience testing under API stds, which are similar in spirit to ASTM. Membrane stress for the test is limited to a given percent of SMYS (60% typically) and following Barlow's equation you derive pressure proof test. Additionally this pressure can be capped to a given value (ASTM A53, ASTM A450, API, etc). This test basically verifies that the pipe is watertight.
SAE philosophy seems a bit different since defines pressure proof test from UTS (Burst Pressure), and it is quite confusing IMHO if I try to follow the nested requirements that stem from the references SAE Standards. Any advise from someone with experience on SAE J524 pressure proof test will be welcomed.
Here is what I understand from the standards:
At the beginning SAE J524 states that all tests will be performed in accordance with SAE J1677. In the case of Test 8.8, Pressure Proof Test, is performed by agreement between purchaser and producer. It indicates that "allowable unit stress of material = 140 MPa - 80% om SMYS".
When referring to SAE J1677 the test is described as:
The tube shall be tested to two times its calculated 4:1 reference working pressure... Test pressures shall be determined by the following formula derivative of SAE J1065 Reference Working Pressures for Steel Hydraulic Tubing. In the formula pressure is related to Minimum Tensile Strength. When SMYS/UTS is below 50% additional formulas are provided that INDEED refer to "allowable fiber stress", however this is not the case for SAE J524 where SMYS/UTS ratio is 55%. In addition SAE J1065 lists "working pressures" for some OD/thickness combinations.
Going through calculations things do not add up very well. Taking a std pipe 1/2" OD 1.24 mm thickness these are the values from tables/calculations:
Table 2 in J1065 (for J524) lists 18.8 MPa working pressure. Calculation gives 16.8 MPa. Checking results for other combinations (results are coincidental), I must ASSUME a typo (not a nice thing when defining test pressures). Going to J1677, 2x16.8 gives 33.7 MPa. I may INFER membrane stress form Eq. and this gives me 155 MPa membrane stress... Above 140 MPa.
EDIT: for this same pipe ASTM A179/A210 require 7 MPa of test pressure. ASTM A53 a similar value, both way off values above 30 MPa from different SAE calculations....
My apologies for the long introduction, but I cannot see how to unravel these apparently conflicting requirements in an unambiguous way. Any guidance is welcomed.
Thanks!
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