LITTLE P.ENG. FOR ENGINEERING CONSULTANCY SERVICES

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

Most threaded joints in ASME B31.3 piping systems are made with taper threads in accordance with ASME B 1.20.1. Figure 5.1 shows a taper thread. These threaded joints are generally acceptable for Normal Fluid Service and Category D Fluid Service. Paragraph 314.1(a) states that threaded joints should be avoided in any service where crevice corrosion, severe erosion, or cyclic load may occur. Cyclic loading is not defined and this limitation is rather unclear, because all syste

Flanges are discussed in previous post (ASME B31.3 Limitations on Flanges). Additional requirements for flanged joints are provided in para. 312 of ASME B31.3. These discuss conditions where flanges with different strengths are bolted together. This can involve two flanges of the same or different materials or with different ratings, or a nonmctallic and metallic flange bolted together. In both cases, precautions are required to avoid overloading the weaker flange. In additio

Welded joints are covered by para. 311 and are required to follow the ASME B31.3 rules for fabrication and examination. In addition, the following specific rules are also provided. Weld backing rings are generally permitted to be left in. However, if the resulting crevice would be detrimental (e.g., subject to corrosion, vibration, or severe cyclic conditions), para. 311.2.3 recommends removing the ring and grinding the internal joint face smooth. Split-backing rings are proh

Requirements for bolting are provided in para. 309. Listed bolting is acceptable. The only relevant component standards are ASME Bl.l, Unified Inch Screw Threads (UNand UNR Thread Form). ASME B 18.2.1, Square and Hex Bolts and Screws (inch series), and ASME B 18.2.2, Square and Hex Nuts (inch series). Table A-2 in ASME B31.3, Appendix A provides listed boiling material specifications. Unlisted bolting (i.e., not listed in Table A-2) are subject to the requirements of para. 30