Re: hygdrogen embrittlement Eko,
My name is Chris Jones of Materials Performance Technologies (www.matperf.com). I have been involved with ultrasonic examination of three ammonia plants and one oil refinery for inspections for high temperature hydrogen attack. I have found hydrogen damage to varying severity levels in one HT shift vessel, two LT shift vessels, converter areas, two methanators, 1 secondary reformer and even mild damage in 1 desulphurising unit of an ammonia plant.
I have found extensive damage in associated pipe work in these plants. I have found the damage in parent material, weld metal and heat affected zone regions. I have found damage in forgings and in heat affected zones of weld repairs in cast elbows.
In all cases the pressure equipment had the potential for hydrogen embrittlement according to the most recent Nelson curves of API941 and the material of construction was in all cases carbon half molybdenum grade materials. The reason for the relatively recent known susceptibility to hydrogen damage was associated with awareness provided by the recent changes to the Nelson curves in relation to carbon half molybdenum material 1997 - API941.
The ultrasonic methods I employ (backscatter and a combination of velocity ratio and attenuation testing methods) are suitable for detection of hydrogen damage and in many situations I can provide an indication of the severity of the damage. The problem I find with procedures that I have developed which attempt to classify damage is that hydrogen damage occurs differently for different materials. Factors such as steel cleanliness dictate how damage will manifest in various materials.
I have published at the International Conference on Pressure Vessel Technoliogies (ICPVT 9) and soon intend to publish again devulging many of the things I have learnt since my original encounters with HTHA.
If you are intending to undertake inspection I can provide advice on where to look and how to look for the damage.
: I (My company) have a problem with hydrogen embrittlement at BFW-Synthesis ammonia exchanger, and I need newest information about Nelson curve. Please give me some information about it.
: Best regards