Dear All;
B31.1 and B31.3 code recommends the use of bending pipes in power and petrochemical plants. in our project, the contractor use this technique by HFIB to avoid the use of elbows and minimize the weld joints, and of course in order to earn money.
My problem is that the contractor avoids making mechanical and metallurgical qualification tests to try this method. I have not found any publications on the Internet that deal with the impact of bending on the mechanical, creep resistance, corrosion resistance and others characteristics.
Can someone help me to prove to our contractor about the bending in the ASME B31 Codes are not convincing especially for low and high alloy steels
HIGH FREQUENCY INDUCTION BENDING OF PIPES
HIGH FREQUENCY INDUCTION BENDING OF PIPES
MECHRI ABDEL GHANI
mechri1973@yahoo.fr
mechri1973@yahoo.fr
Re: HIGH FREQUENCY INDUCTION BENDING OF PIPES
Against which code piping has been designed? If it is B31.3 then what is the fluid category? You may provide the pressure temperature conditions and the service of your piping.
Also tell me the material of construction of piping in ASTM.
Also tell me the material of construction of piping in ASTM.
Re: HIGH FREQUENCY INDUCTION BENDING OF PIPES
Induction bending is the now a leading manufacturing technique for piping bends and is being used extensively in all industries.
This has been proved that a piping bend made with high frequency induction bending withstands a hydro-burst test as compared to the straight pipe or elbow of the same material and thickness.
You may proceed with your query as follows:
1. Contractor has to provide you a qualified procedure for high frequency induction bending that must include the whole process along with specified process parameters like temperature as this is the key parameter involved in induction bending process. The procedure must be qualified through subsequent mechanical and metallurgical tests.
2. If your contractor meets all the above requirements then the second step is that he must follow the guidelines of applicable ASTM standard for manufacturing of piping bend. For carbon steel and low alloy steels, ASTM A234 governs.
3. The owner's specifications (your specifications) shall include everything if you have allowed for making of bends instead of elbows in process or power piping. According to my experience, piping bends are least preferred in process and power piping although code ASME B31 allows it and modern manufacturing techniques are in place. However, in B31.3 high pressure piping, it has been clearly mentioned that impact test is mandatory to be carried out on a sample out of final material. Owner's specifications may include additional requirements also just to ensure the mechanical / metallurgical properties of the final product. You may see supplementary requirements in relevant ASTM standard against which bends are being manufactured.
4.Contractor must state that against which standard bends are being manufactured. What are the inspections being carried out etc. Like piping bends are extensively used in transportation pipelines for which ASME/ANSI B16.49 governs but valid for ASME B31.4, 31.8 and 31.11 only. It is not applicable for B31.1 or 31.3 (power and process piping).
To cut the long story short, I would say that the bending operation for low or high alloy steels if carried against a controlled procedure would not cause major mechanical or metallurgical impacts on the piping material. However, stated requirements in B31 codes (like for high pressure K piping), and in relevant ASTM for checking the mechanical properties must be met.
This has been proved that a piping bend made with high frequency induction bending withstands a hydro-burst test as compared to the straight pipe or elbow of the same material and thickness.
You may proceed with your query as follows:
1. Contractor has to provide you a qualified procedure for high frequency induction bending that must include the whole process along with specified process parameters like temperature as this is the key parameter involved in induction bending process. The procedure must be qualified through subsequent mechanical and metallurgical tests.
2. If your contractor meets all the above requirements then the second step is that he must follow the guidelines of applicable ASTM standard for manufacturing of piping bend. For carbon steel and low alloy steels, ASTM A234 governs.
3. The owner's specifications (your specifications) shall include everything if you have allowed for making of bends instead of elbows in process or power piping. According to my experience, piping bends are least preferred in process and power piping although code ASME B31 allows it and modern manufacturing techniques are in place. However, in B31.3 high pressure piping, it has been clearly mentioned that impact test is mandatory to be carried out on a sample out of final material. Owner's specifications may include additional requirements also just to ensure the mechanical / metallurgical properties of the final product. You may see supplementary requirements in relevant ASTM standard against which bends are being manufactured.
4.Contractor must state that against which standard bends are being manufactured. What are the inspections being carried out etc. Like piping bends are extensively used in transportation pipelines for which ASME/ANSI B16.49 governs but valid for ASME B31.4, 31.8 and 31.11 only. It is not applicable for B31.1 or 31.3 (power and process piping).
To cut the long story short, I would say that the bending operation for low or high alloy steels if carried against a controlled procedure would not cause major mechanical or metallurgical impacts on the piping material. However, stated requirements in B31 codes (like for high pressure K piping), and in relevant ASTM for checking the mechanical properties must be met.
Re: HIGH FREQUENCY INDUCTION BENDING OF PIPES
Mechri,
I would be late in relying to this thread. Anyway still adding some comments:
1. HFIB is widely used as an economical solution for carbon steels and stainless steel materials.
2. To the best of my knowledge, HFIB for low alloy steels is only preferred under certain special situations like large diameter or large wall thickness when bends are not readily available.
3. For Cr-Mo steels, if steel is quenched and tempered then after HFIB an air quenching from austenite temperature and tempering must be done. However, if normalized steel is subjected to HFIB then the steel has to be normalized after this operation with cooling in still air.
4. HFIB for ferritic steels and with Cr % above 5% like in case of P5 and P9 piping material special care must be adopted.
5. HFIB requires special qualification procedure which must be mentioned by the Client. Normally, three test bends for each material are recommended to be made by the Contractor and shall be tested in Client's approved / suggested laboratory.
6. Qualification shall be made by conducting all mechanical tests and non-destrictive examinations as specified in the applicable materials specification (ASTM or equivalent).
7. For low alloy steels, it is recommended to carry out micro-structural analysis also in order to verify absence of any micro cracks in the material.
If you want to seek any clarification in this regard, you are welcome.
I would be late in relying to this thread. Anyway still adding some comments:
1. HFIB is widely used as an economical solution for carbon steels and stainless steel materials.
2. To the best of my knowledge, HFIB for low alloy steels is only preferred under certain special situations like large diameter or large wall thickness when bends are not readily available.
3. For Cr-Mo steels, if steel is quenched and tempered then after HFIB an air quenching from austenite temperature and tempering must be done. However, if normalized steel is subjected to HFIB then the steel has to be normalized after this operation with cooling in still air.
4. HFIB for ferritic steels and with Cr % above 5% like in case of P5 and P9 piping material special care must be adopted.
5. HFIB requires special qualification procedure which must be mentioned by the Client. Normally, three test bends for each material are recommended to be made by the Contractor and shall be tested in Client's approved / suggested laboratory.
6. Qualification shall be made by conducting all mechanical tests and non-destrictive examinations as specified in the applicable materials specification (ASTM or equivalent).
7. For low alloy steels, it is recommended to carry out micro-structural analysis also in order to verify absence of any micro cracks in the material.
If you want to seek any clarification in this regard, you are welcome.