Jwong Generallly, Threaded connections should not be used where severe erosion, correosion, shock or vibration are likely to occur or at temperatures over 925 deg F. For limitations in sizes for use of threaded connections, please refer to 56.30 - 20 (c) Table for pressure and temperature limitationos. Generally, Socket weld connnections should not be used where severe erosion, corrosion are likely to occur. For limitations in use of socket weld connections, please refer to ANSI B 16.11 Table 56.60 (1b) & Fig 127.4.4C in ANSI B 31.1. Socket weld limitations for Class 1 & Class 2 service restrictions appear in 56.70-15 (c) & 15 (d) & 56.50-105 for low temperature service. Restrictions in use of socket welds for drains and by-pass connections should conform to bore dia, shoulder thickenss, socket depth should conform to ANSI B 16.11. Trust this helps you in design and use of socket weld or threaded coonections for your application. C.V.Srinivasan Nishi Engineers Pvt Ltd India April 1, 2007 E-mail: nishi@vsnl.com >Are there any rules regarding the use of socket welds versus >threaded connections for different services? I have heard >some people not using threaded connections in sour service >and caustic service. Since both have crevices, what would >be the advantage of socket welds? I have a laundry list of >services and I am supposed to say whether socket welds or >threaded connections are allowed. > >Thank you very much.