Stain aging on A-212 Gr. B carbon steel

[hcjulien]

Hi,

after reading API 571, I've found the section no. 4.2.4 talking about Strain Aging especially on old vintage carbon steel.

I need to rerate a pressure vessel containing butane built in 1955 with SA-212 Gr. B, cold formed, No PWHT and working between -25F and 100F at 250 PSIG. Cracks has been found during the history of the pressure vessel (1990 & 1997, no crack has been found in 2006).

Do I need to worry about strain aging (reduction in ductility and toughness), especially when the pressure vessel is working at low temperature?

Thanks in advance,

hcjulien

 

[metengr]

hcjulien;
Strain aging in pressure vessels and boiler pressure parts fabricated of SA 212 steel plate is difficult to quantify by general characterization. I would be very concerned with low fracture toughness with this material under the service conditions you provided versus strain aging. EPRI Fossil Repair applications is also concerned with low fracture toughness of these vintage plate steels used in lower mud drums and in steam drums of boilers because of concerns related to pressure testing at only ambient temperature. At service temperatures above 250 deg F, there is adequate fracture toughness, but this provides you no benefit.

With that said, if you are looking to re-rate the vessel, what I would do is one of the following;

use API/ASME 579 to evaluate brittle fracture behavior at your stated service temperature range and/or

remove a material sample and evaluate the chemcial composition and fracture toughness properties.

In addition, I would perform extensive nondestructive testing (NDT) of the shell seam and girth welds and surrounding base material thickness as part of the re-rate procedure. Despite the intrusive nature of removing a sample for evaluation, this will help to better quantify and defend the vessel re-rate for service.