Q & A > Question Details
we are going to set up 1 MMTPA Naphtha hydrotreater in our refinery. Naphtha hydrotrater consist of vertical cylindrical Naphtha charge heater. The charge heater has two pass and each pass contain 32 nos of vertical tube. Our charge heater is in construction stage. For checking mechanical integrity of weld joints in tubes we are going to carry out hydrotest of tubes after placing tubes inside firebox. Also charge heater is part of reactor circuit. Any lumps of water will damage hydrotreater catalyst.
1) How should we remove water and debris from tubes after hydrotest as our tubes are vertical?
2) Are there any alternative methods to check weld integrity instead of hydrotest?
I know one option is pigging but we are not going to do it because of cost.
10/06/2009 A: Mike Watson, Tube Tech International Ltd, mike.watson@tubetech.com
1) All the water can be removed easily using a series of cheap and cheerful soft, oversized water absorbent swabs (pigs).Use these until they exit the furnace tube in a relatively dry state.The remaining moisture can be dried using hot air dryers over a period of 2 hours.
2) Hydrotest on new tubes is fine, just not when they possibly have a layer of coke, however thin. Intel pigs are available for 5" plus diameter tubes but they don't as yet inspect the welds that well on the bends. As an alternative you could, providing physical access is available, use hand held ultrasonic inspection tools. Gamma ray is another more costly option.
3) As a suggestion its worth considering designing in our mechanical online decoking system to negate fouling and improve level of future inspection.
08/06/2009 A: Virendra Kapoor, Petroleum Refining Consultants, vkkapoor9@yahoo.com
It is necessary to make the reaction section dry before loading the catalyst. Standard procedures of hydrotest, water removal and drydown are available and recommended by the licensors
08/06/2009 A: keith bowers, B and B Consulting, kebowers47@gmail.com
100% x-ray photos and evaluation of each weld joint will verify weld integrity--but not 'system' integrity.
What method does the process licensor recommend?
The integrity of the entire reactor circuit should be proven before catalyst is loaded. This is usually done in sections to keep volumes small.
08/06/2009 A: Eric Vetters, ProCorr Consulting Services, ewvetters@yahoo.com
You can hydrotest and dry out before you load catalyst into your reactor which will reduce your risk. Dry out would be through a normal gas recirculation procedure with routine draining of water from low points.
I believe that 100% x-ray of welds is an alternative to hydrotest, but that is likely to be more expensive than pigging to remove water. I'm not sure how effective pigging will be at removing water. Check with your inspection department on what your codes allow in lieu of hydrotrest.
08/06/2009 A: Hubert Mueller, Bayernoil, guhumueller@web.de
X-raying the welds is not a real alternative, but may be tolerated by the authorities. Normally flushing the tubes with high velocity water is used to clean them from debris but I would add a x-ray check of the bottom elbows to be sure. The remaining water will be vaporized during the dryout procedure of the furnace and the reactor circuit. If you have condensate or demineralized water available, you could flush the tubes after the pressure test with this clean water and you will not get any salt layers at the bottom of the lower elbows.