Surface cracks in piping - is it allowed ?
We have ordered pipe after API 5L Gr.B. The pipe we have received from an east european manufacturer has surface cracks which we have detected with the use of MPI. The cracks vary in length from a couple of mm up to 50cm, and in depth from 0.1 to 0.4mm...
we now know we have had a reducing (oxidising) atmosphere in the heater under operation which has given rise to the formation of the oxide layer on the tube surface. Which, after we shut the heater down, has resulted in PASCC.........if only we had known before we shitdown, we could have...
Cracks have been confirmed as resulting from polythionic SCC. All tubes are now scrapped and new tubes are being sourced. Cracks are on the OD of the tubes. We have always prevented PASCC on the inside by soda washing, as we knew the situation could arise. We were unfortunately unaware of a...
Which is the correct standard to use for specifying buttwelding return type piping components(180 deg elbows)? ASME lists 2 standards as far as i can see:
ASME B16.28 - wrought steel buttwelding short radius elbows and returns
ASME B16.9 - factory made wrought buttwelding fittings (std. lists...
The possibility of thermal fatigue is already being investigated by performing replica of the tube external surfaces. We will receive results back in the coming days.
The external spiral patterns have a pitch approximately equal to the pipe diameter of 5" NB.
We have a fired heater open for inspection and have observed spiral patterns on the outside of the 5Cr heater tubes in the radiant zone. The patterns can be seen with the naked eye, but cannot be felt. The tubes are of seamless construction. These patterns have not been seen at previous...
Anybody aware of any NDT method that can be used to test for the presence of polythionic acid stress corrosion cracking in heatr pipes in a fired heater ? Are there any methods that can be used to give a 100% picture of the status of the pipes whilst they are mounted in the heater? I know you...
The coating is some form of epoxy paint. I'm not sure that a lengthened vacuum test would be enough to make the paint fail ? In accordance with API 650 we are talking about a partial vacuum of 3-5psi.
That is what we normally do but we are soon approaching winter and the plan for coating after test would put us into winter with subsequent problems with minimum coating temperatures and longer curing times. Therefore the sub-contractor has requested to coat the tank bottom now while we have...
Not sure if i'm in the right forum here (it's not a pressure vessel type question) but i'll ask the question anyway. We have a number of large atmospheric storage tanks (50-80m dia) that we inspect on a 15 -20yr basis. After repairing the tank bottoms all welds are vacuum tested before coating...
Thanks for the reply. We have done some previous repairs on vessels that have had high hydrogen levels where we have preheated the vessel at 250-300degC (390-570F) for approx 16hrs. I was wondering that with lower concentration levels of hydrogen the preheating time could be less. The whole 10m...
We have to do some welding on the inside of an existing pressure vessel that has been in service where there has been hydrogen sulfide in the product. Knowing the problems that can arise through hydrogen cracking after welding, are there guidelines for how long the vessel needs to be warmed up...
We have both 5Cr and 9Cr piping material specifications. ASME B16.48 (steel line blanks) only lists forged material for 5Cr, and no 9Cr material is listed. The forged material is listed i presume because forgings are less susceptible to laminations than plate material. What type of material...
Thanks for the reply. On checking the website out, one of our mechanical engineers informed me that we actually have bought a copy of PVElite but doesn't reckon it can calculate appendix 13 vessels without having a load of supplementary hand calculations as well. I presume from the name of the...
Hi,
Anybody know of or have experience with calculation software for ASME VIII appendix 13 pressure vessels - vessels of non-circular cross section ??
Specifically we have some air coolers with a rectangular section headerbox, with dividing plates that we would like to control ?
Thanks.
