ASME Comments

The ASME VIII-1 code book is a curious combination of design experience mixed with theory, often in surprising or confusing ways. We have had to examine some sections in considerable depth, and have posted some of our comments here.

NOTE: Only ASME can make interpretations on the ASME VIII-1 code. The articles in this section are for information purposes only.

	Dual Certified Vessels for Low Temperature Service Many older carbon steel vessels do not meet modern code rules for low temperature service. The service history on these vessels is good resulting in an attitude that the current code rules are too restrictive.
	Use of Type (3) welds in ASME Pressure Vessel Design Table UW-12 provides 8 types of welds with appropriate efficiencies to use when differing levels of radiography is applied. Confusion exists when trying to determine if a single welded circ weld in a small vessel is type 1 or type 3. Our answer...
	External Pressure External pressure (vacuum) calculations are more complex than internal pressure calculations. Once jackets or other sources of pressure are added the difficulty increases.
	F&D Head Stress Stress formulas for flanged and dished heads can not be traced back to theory. The stresses found in the knuckles of F&D heads can be surprisingly high, exceeding VIII-2 allowables...
	Loads on Flanges ASME VIII-1 Appendix 2 provides a method of sizing flanges. The calculations use three loads - HT, HG & HD and two operating conditions - seating and operating. What are these loads...
	Nozzle Area Replacement Rules The area replacement rules in the ASME code books have always interested me: You can cut a hole in a vessel as long as the nozzle attached to it replaces the lost area. How is this rational...
	Use of 44w in Pressure Vessels There are many misunderstanding and changes in opinion on whether Canadian grade 44w (or CS-G40.21 44W) material is allowed into code pressure vessels...
	Weld Efficiencies Weld efficiencies are one of the true black holes of the ASME VIII-1 code book. UW-11, UW-12, UW-11(a)(5)(b)... The ideas of this section are simple, but the presentation is anything but...
	Lethal Service - Quick Guide Requirements for lethal service are scattered through VIII-1, the code cases and the interpretations. We collected all these requirements in one place.
	Unlisted Materials Requirements for lethal service are scattered through VIII-1, the code cases and the interpretations. We collected all these requirements in one place.
	Flanged and Flued Expansion Joints ASME VIII-1 mandatory Appendix 5 provides guidelines for the design of flanged and flued expansion joints, but does not provide methods of calculating the stresses, fatigue life or spring rate.
	The Three Pen Method of Self-Checking Work An irony of this computer era is that a code calculation and a drawing can be prepared by the same person on the same computer, but all the information on the drawing needs to be hand entered.
	Hand Calculations - How To and How Not To We at PVEng use hand calculations when we do not have a program or spreadsheet or when we want to create a spreadsheet and need verification.
	Using the ASME VIII-1 Nozzle F Factor (UG-37) The stresses around a nozzle located in a cylindrical shell are not the same in all directions. If a non-round nozzle is oriented in the correct direction, ASME allows us to take advantage of this.