pressure rating pressure rating 4094347496 (Mechanical) (OP) 31 Jul 12 20:07 can somebody explain me what is difference between ANSI 150 and ANSI 300 pressure rating in gate valve???? RE: pressure rating micalbrch (Mechanical) 1 Aug 12 06:12 Perhaps the flanges, 150 lbs and 300 lbs? RE: pressure rating 4094347496 (Mechanical) (OP) 1 Aug 12 08:59 yes the flanges,what is difference RE: pressure rating micalbrch (Mechanical) 1 Aug 12 09:10 Diameters and numbers of holes. Google "150 300 lbs ANSI flange". You find all dimensions in the internet. RE: pressure rating zdas04 (Mechanical) 1 Aug 12 10:12 Look at ASME B16.5 for flange details. Bottom line is that a gate valve rated for ANSI 150 will be able to withstand less pressure than one rated for ANSI 300 (the "lb" or "lbs" designation has fallen out of favor because too many people took it for a direct indication of a numerical pressure rating, now it is "class" as in "ANSI 300 Class" which is generally rated by application engineers between 600 psig and 750 psig) David Simpson, PE MuleShoe Engineering "Belief" is the acceptance of an hypotheses in the absence of data. "Prejudice" is having an opinion not supported by the preponderance of the data. "Knowledge" is only found through the accumulation and analysis of data. RE: pressure rating SNORGY (Mechanical) 1 Aug 12 15:13 Depending on the material group numbers involved your numbers will be different. For SA 105 flanges at 100 F, the corresponding pressure rating is 285 psig for 150# ANSI class ant 740 psig for 300# ANSI class. RE: pressure rating arash807 (Mechanical) 9 Aug 12 02:00 ANSI has 6 major rating classes as follow: 150-300-600-900-1500-2500(psi) these numbers represent the pressure and temperature rating.one thing which should be kept in mind is that these are nominal pressure classes. for example class 150# can bear more than 150 psi. ASME B16.34 have the exact working pressure and temperature for each material. regards Arash RE: pressure rating zdas04 (Mechanical) 9 Aug 12 10:17 I have to ask, did you read the thread, or just read the question and assume that not a single one of the over 1 million eng-tips.com members could possibly know the answer so you just skipped to the respond panel? David Simpson, PE MuleShoe Engineering "Belief" is the acceptance of an hypotheses in the absence of data. "Prejudice" is having an opinion not supported by the preponderance of the data. "Knowledge" is only found through the accumulation and analysis of data. RE: pressure rating arash807 (Mechanical) 9 Aug 12 11:00 Dear zdas04 I am not sure if your last post is related to me.if so I should say of course I have read the it. is there any thing wrong here? regards Arash RE: pressure rating gerhardl (Mechanical) 10 Aug 12 04:33 Hello 4094347496: Your question asks generally for the 'difference' between ANSI150 and 300 classifications, and then seemingly you want to know the difference between flanges (and building lengt?, topwork? other?). I presume, as often is for 'open' questions, that there is a specifc problem causing you to ask the question. Perhaps you want to know if a specific valve, for a specific process, can be substituted with one of the different class, or if you should select the one or the other class for a specific application, etc. etc. If you want more precise and detailed advice it is always a good idea to give as many details as possible. This is, after all, as zdas04 says, a forum with a large number of specialists.