4Pipes
Mechanical
- Aug 21, 2004
- 161
A look around any old refinery will show that B31.3 pipe branches, with and without reinforcement, in Cl 150 and Cl 300 systems have been operating for years even in quite onerous conditions.
Q1. The current practice among many large contractors is to specify fittings, reducing tees, weldolets etc for all branches in sweet, non-corrosive, non-cyclic, non-vibrating service, even though they are well within the scope B31.3 branches. Reducing sifs value might be one reason but not for all branches. Is it just a case of everybody becoming conservative. Nobody seems to know why. Does anybody know ? For offshore API RP 14E gives an example branch table that is based on fittings. Cost of failure offshore is high which is a good reason for the extra cost. However, what about more cost sensitive on-shore projects ?
Q2. Assuming correct weld procedure, correct calcs, correct PWHT and correct venting of reinforcement, are there any specific reasons why reinforced and unreinforced branches could not be used for sour service. I know they are preferred and add a margin of safety, but is there a definite "yes - no" code type reason for not using B31.3 branches. eg. Hydrogen blistering for wet sour service ?
(Materials being considered for all above are all basic API 5L and equivalent).
Many thanks
Q1. The current practice among many large contractors is to specify fittings, reducing tees, weldolets etc for all branches in sweet, non-corrosive, non-cyclic, non-vibrating service, even though they are well within the scope B31.3 branches. Reducing sifs value might be one reason but not for all branches. Is it just a case of everybody becoming conservative. Nobody seems to know why. Does anybody know ? For offshore API RP 14E gives an example branch table that is based on fittings. Cost of failure offshore is high which is a good reason for the extra cost. However, what about more cost sensitive on-shore projects ?
Q2. Assuming correct weld procedure, correct calcs, correct PWHT and correct venting of reinforcement, are there any specific reasons why reinforced and unreinforced branches could not be used for sour service. I know they are preferred and add a margin of safety, but is there a definite "yes - no" code type reason for not using B31.3 branches. eg. Hydrogen blistering for wet sour service ?
(Materials being considered for all above are all basic API 5L and equivalent).
Many thanks
