ASME B31.3 Limitations on Miscellaneous Joints


ASME B31.3 Limitations on Miscellaneous Joints

Caulked and soldered joints are only permitted in Category D Fluid Service. Caulked joints are further limited to a maximum temperature of 93°C (200°F), and provisions are required to prevent disengagement of the joints and resist the effects of longitudinal forces due to internal pressure. With soldered joints, the low melting point of solder is to be considered where possible exposure to fire or elevated temperature is involved.

Brazed and braze-welded joints are permitted to be used in Normal Fluid Service. However, they are required to be safeguarded in fluid services that are flammable, toxic, or damaging to human tissue (see Section 2.5). They are prohibited from use under severe cyclic conditions, and the melting point of the brazing alloys is to be considered where possible exposure to fire is involved.

For other joints, such as bell-type and packed joints, the separation of the joint must be prevented by a means that has sufficient strength to withstand the anticipated conditions of service. Pressure tends to pull these joints apart. Furthermore, if the fluid service is flammable, toxic, or damaging to human tissues, or exposed to temperatures in the creep range, joint separation must be prevented by mechanical or welded interlocks. Friction within the joint or use of external anchors is not sufficient. However, joints in which the mechanical strength is developed by crimping a Female part onto a pipe or tube (e.g., Victaulic Pressfit) do qualify as having a mechanical interlock.

There are provisions that restrict mechanical joints and bell-and-gland-type joints in severe cyclic service. However, since severe cyclic service only applies to those components with a stress exceeding 80% of the allowable displacement stress, it is highly unlikely that these joints would be in severe cyclic service. #Little_PEng.

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