Arnab For Pressure Test : Test at Ambient temperature conditions (Room Temperature conditions). You have to apply appropriate design pressure vs design service temperature correction factor as per ASA B 31.3 or ASME code or any design code for the hydro test set pressure (Test pressure for the design pressure / temp for the particular material wiil vary and a correction factor as per table given has to be applied for the H.T set pressure at Room temperature conditions) Low Alloy steel exhibits is susceptible for NDT (Nil Ductility Transition) variation at low temp. Avoid testing at too low or too high a temperature for low alloy steel. If you are located in a cold temperature area, you may have to slightly heat to get to Room Temperature conditions for testing. Trust this helps you. C.V.Srinivasan Nishi Engineers Pvt Ltd India Sept 16, 2006 E-mail: nishi@vsnl.com to >Is there any chart available for minimum pressurisation >temperatures of various grades of Low alloy steel?

Arnab Krish had answered partially to your question - if that is the question. If your question is related to start up temperature for high pressure reactor of low alloy steel (subjected to long term exposure at high temperature and re-start condition after a shut down), you have to take the temper embrittlement factor for temperature. Here also, raising slowly till a steady state temperature of +20-30 deg centigrade higher than room temperature (Room temperature in tropical countries like India is normal 30 - 35 deg centigrade) is reached above normal room temperature condition is suggested. If the vessel is in a too cold country with ambient temperature at sub zero, naturally you have to take additional precaution not to heat up too rapidly after a shut down. If the alloy chemistry is known, you can roughly work out the NDT-T (Nil-Ductility Transition Temperature) and then re-start the vessel with gradual heating in slow stages to avoid the problem of temper embrittled condition. Basic guide-line thumb rule: Never subject a material (especially low alloy steel) after prolonged exposure to high temperature of > 25000 - 75,000 hrs to drastic temperature excesses. Re-start of such vessel / piping, made of low alloy steel, after a shut down should be done only by gradual heating and watching. Do not subject to drastic changes in temperature cycling during re-start up of the plant. Trust this helps you C.V.Srinivasan Nishi Engineers Pvt Ltd India Oct 11,2006 E-mail: nishi@vsnl.com >I think arnab is talking about start-up of high pressure >reactor after the shutdown to avoid temper embrittlement in >hydrogen charged vessel. >For MPT we have to check the X-Factor and J-Factor which >will depends on alloy composition and heat treatment >followed.I dont think any standard chart will be available >for the same because each manufacturer will follow his own >standard way of manufacutring. > >regards, >krish