Pressure Vessel Charpy Impact Tests

There are plenty of articles that describe conditions that need to be satisfied for a pressure vessel component to be exempt from impact testing; however, very few that summarize the ASME Code requirements if the component needs to be impact tested. This article is an attempt to summarize the ASME Section VIII, Division 1 requirements of paragraph UG-84 applicable to pressure vessel components made from SA 516 Gr 70.

Each set of test specimens to be impact tested shall consist of three specimens of Charpy V-notch type conforming to Figure 1 shown here:

Figure 1: Simple Beam Impact Test Specimens (Charpy Type Test)

The standard (10 mm x 10 mm) specimens, when obtainable, shall be used for nominal thickness of 7/16 in. or greater.

When the specimen width along the notch is at least 8 mm, the impact test temperature may be set warmer than the MDMT by an amount shown in Table 1.

Table 1: Impact Test Temperature Differential

When the specimen width along the notch is less than 8 mm, or the thickness is less than 7/16 in, the impact test temperature shall be lower than that indicated in Table 1 by the amount shown in Table 2.

Table 2: Charpy Impact Test Temperature Reduction below MDMT

The applicable minimum energy requirement for all specimen sizes shall be that shown in Figure 2, multiplied by the ratio of the actual specimen width along the notch to the width of a full size (10 mm x 10 mm) specimen.

Figure 2: Charpy V-notch Impact Test Requirements for Full Size Specimens for Carbon and Low Alloy Steels, Having a Specified Minimum Tensile Strength of Less than 95 ksi

When the average value of the three specimens equals or exceeds the minimum value permitted for a single specimen and the value for more than one specimen is below the required average value, a retest of three additional specimen shall be made.

Similarly, when the value for one specimen is below the minimum value permitted for a single specimen, a retest of three additional specimen shall be made.

The value of each of these retest specimens shall equal or exceed the required average value.

Reference: ASME Section VIII, Division 1 - Edition 2019