How Are Plastic Plugs Made?

Small End Caps: Formed as a single, integral piece.

Large and Medium End Caps: Formed after initial splicing-this is the most widely used method, and the requirements specified in relevant standards primarily apply to this category.

Extra-Large End Caps: Due to requirements related to transportation, clearance, and other factors, these are formed in segments (petals) which are subsequently welded together to form the complete cap.

For dished end caps, splicing should be avoided in the knuckle radius (r) region, as this area is prone to wall thinning and high stress concentrations.

Regarding splicing, the orientation of weld seams is restricted to radial and circumferential directions only. However, this specific requirement may eventually be waived for large-scale end caps. There are specific requirements regarding the spacing of splices: the distance must be greater than 3δ (where δ represents the wall thickness) and not less than 100 mm. (The Heat-Affected Zone-HAZ-of a weld constitutes a high-stress region, and the chemical composition within this zone may undergo degradation due to thermal effects. Therefore, it is essential to avoid placing splices within this high-stress zone; the extent of this zone is directly related to the material thickness. Based on practical experience, the stress decay length-i.e., the distance required for stress to dissipate-is determined to be greater than 3δ but not less than 100 mm.) However, due to the unique characteristics and specific constraints of refrigeration equipment, strictly adhering to this particular requirement can often be challenging.