My customer has some swab tanks that were manufactured in 1953; they are made of rolled 1/2-inch plate A283C; the tank is 84 in. in diameter and is rated for 100-psi service. The question is given the following conditions does this tank meet NACE MR0175? According to Section A2.1.6 the requirement that all rolled or deformed material must be stress relieved and have a hardness of 22 HRC max. The problem is we cannot or have no documentation as it relates to the heat treat of the plate post welding. yet when tested the material meets the A283C requirements and the hardness are in the 120-127 HB. Ultrasonic testing as part of a corrosion survey on the tank was performed and all was in order. Engineering approval was granted on the status of the vessel as a pressure vessel under the ABSA (Alberta Boilers Safety Association). This tank is 52 years old, is in excellent condition, and the customer wants to have more current documents on the tank as it relates to its status as an ABSA pressure vessel and it’s NACE MR0175. With all this information can a determination be made that this material in its current state is suitable as a material that qualifies as a NACE MR0175/ISO 15156-compliant material? Using the long life, performance, and the mechanical data gathered can this determination be made? If so, can these criteria be used to establish a basis for performing future work on this exact style of tank?
The ISO 15156 Maintenance Panel cannot advise on the suitability of this tank for use in sour service.
It is the responsibility of the equipment user to assess the suitability of the material and to ensure compliance with NACE MR0175 / ISO 15156.
Consideration of the following could contribute to any evaluation of suitability you undertake:-
For some equipment NACE MR0175/ISO 15156-2, Table 1 allows the equipment user to categorize equipment as a “Permitted exclusion” where the operating pressure does not exceed 0.45 MPa (65 psi).
NACE MR0175/ISO 15156-1, Clause 6 and in particular 6.2 d) offer some guidance on the fitness for purpose evaluation of materials in existing equipment.
This question is in relation to NACE MR0175/ISO 15156-1 Clause 6
Reference: ISO 15156 Maintenance Panel Inquiry #2005-31
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