4.3 Determination of the acceptable stress

The value of acceptable stress k is equal to the value of acceptable lower scatter band �20% from the obtained mean value of residual creep strength for the adopted time tep and temperature Tep. It is calculated from the following formula:

$$\mathbf{k} = \mathbf{0}.8 \mathbf{R}\_{\mathrm{Ze/Te/te}}.$$

The obtained values of acceptable stress k for the adopted levels of temperature Tep = 530, 540°C, and times te = 10,000, 30,000, 50,000, and 100,000 h of further service are provided in Table 4.

#### Figure 13.

Temporary residual creep strength of the material of test elbow and circumferential welded joint made of 14MoV6–3 steel after 200,000 h service at 530°C under creep conditions.


#### Table 3.

Residual creep strength for the adopted levels of temperature Tep = 530, 540°C, and times tep = 10,000, 30,000, 50,000, and 100,000 h of further service of the materials of test elbow made of 14MoV6–3 steel after 200,000 h service under creep conditions.


Table 4.

Determined values of acceptable stress k for the adopted levels of temperature Tep and times te of further service for the material of test primary steam pipeline component made of 14MoV6–3 steel after 200,000 h service under creep conditions

### 4.4 Definition of parameters of further service

The parameters of further service are defined to be the same as the previous ones. To calculate the required minimum wall thickness, in addition to pressure pep and temperature Tep of the component, it is also necessary to define its nominal outside diameter DOut, nominal wall thickness gn, design pressure po, operating pressure of further service pe, and construction weakening coefficient z. The required values are summarised in Table 5.
