	Applies To
	Product(s):	AutoPIPE Vessel
	Version(s):	45.00.03.001
	Date:	March 2025
	Area:	Air Cooler
	Original Author:	Bentley Technical Support Group

Problem:

How AutoPIPE Vessel calculates ligament efficiency of multidiameter holes in plates (Plug cover)?

Answer:

he ligament efficiency for the Bonnet/Plug Cover is calculated in accordance with ASME Section VIII, Division 1, paragraph 13-6. For membrane stresses (em), the calculation follows the guidelines specified in paragraph 13-6(a). Please refer to the code reference below for further details.

The ligament efficiency for bending loads (eb) is calculated in accordance with ASME Section VIII, Division 1, paragraph 13-6(b). Please refer to the code reference below for further details.

Scenario 1:

Input:

Output:

The nominal diameter of the plug (DN) is calculated as the tube's outside diameter plus 1/8 inch.
Therefore, DN = 31.75 mm + 1/8" (3.175 mm) = 34.925 mm. With this DN value (34.925 mm)

Now we have value of DN (34.925mm) and according to Aerorefrigerants (Creusot Loire) volume-1 chapter-3 d Cylindrical Plugs Joints, we can calculate the value of d0 and d1.

Note: These values are hard coded in the software and can not be changed.

For a nominal diameter (DN) of 34.925 mm, the value of do is 43 mm. And d1 always remains same as DN that is 34.925mm.

According to ASME Section VIII, Division 1, paragraph 13-6(a), equation 2, Dem is calculated to be 35.35 mm. Similarly, as per equation 1 of the same section, em is determined to be 0.443.

See below calculation for Ligament Efficiency in case of bending loads (eb):

Values of em (0.443) and eb (0.426) is matching with the report.