SOCKOLET 12"-8"X 1 1/2" 3000+ FOR PIPE 1 1/2" SCHED. 160 1

I'm not sure if you have an answer to your question yet, but I might be able to help somewhat. I'm going strictly from memory since I don't have a copy of ASTM B16.11, nor MSS-SP-97 in front of me. MSS-SP-97 gives all the necessary information for installing O-Let type fittings. ASME B16.11 has a chart correlating ratings and schedules of pipe. Typically 3000# is for Sch 80 pipe, 6000# is for Sch 160 pipe and 9000# is for Sch XXS pipe. However, a schedule 160 pipe can be used on a 3000# class O-Let, but the designer must ensure that the code calculations are verified for your given design conditions. There are only a few manufacturers of O-Let fittings here in the states that can help you out with your code calculations, that is if you don't have the necessary information at your disposal. First and formats, you will need who the manufacturer of the O-Let as well as a MTR from the manufacturer as well as all of the design conditions.
I hope that this helps you out.