Anonymous
I have been following this thread and find a lot of credibility in both point of views. I worked for Fluor for over twenty five years and ABB for ten years plus seven years for world class fabricators (not to mention several smaller fabricators when I was younger). Ive also been part owner of two smaller code fabrication shops. Additionally, I have been a member of the ASME Code since 1966 and have been a member of several committees (I’m a Registered Professional Mechanical Engineer). I have also been a member of delayed coking excellence committees for several refineries. In my career I have been involved in over twenty five delayed coking projects from grass roots to repair and replacement. I have also been involved in field fab coke drums as well as shipment of some of the first SHI coke drums to Baytown. In all the coke drums I have been involved, not one has failed from a fabrication error. The first coke drums I designed are still in operation; however, they operate on an 18 hour cycle and I have to admit that this is less severe than a twelve hour cycle.
Initially, the coke drum licensors did not specify much fabrication parameters or QA/QC requirements. Lately, because of the number of delayed coking projects, every licensor wants to get a leg up by controlling their design and guarantees. However, at no time is a fabricator expected to provide any other guarantee than a mechanical design and fabrication guarantee; just as an engineering company does not provide a process guarantee for a unit.
All of you might ask why none of the coke drums I designed have failed; the main reasons are:
1. I specify the materials, allowable microalloys, J factor if I specify 2.25 Cr,
2. The specifications applicable to the design
3. The welding requirements and consumables that I specify
4. The NDT requirements that I specify for every step of fabrication
5. The most important aspect is the skirt attachment
Neither the ASME Code, the licensor, nor the fabricator can substitute engineering, design and fabrication experience. One of the major problems that I have encountered, is the lack of experience in writing specifications and providing the fabricators the requirements to ensure the quality and long life of the product. What I have run into, is that most engineers now require a go by or they do not know what to do. Its not their fault as much as is the computer age. In their opinion, if is not on a screen it can not be right. Technically, (running numbers to the tenth decimal point) they are very sharp and they are all willing to learn; but again, the fabricator can only provide what the engineer requires and specify; it does not matter if is JSW, Kobe, Sumitomo, Belleli, ATB or anybody else. A fabricator is not going to add additional procedures if is going to cost money and increase his overall bid price. Nothing is free. I have to stress that no matter what, the fabricator is only going to quote and fabricate what the purchaser specifies.
One last point, it is my opinion that an LC Finer or a Hydrocracker is more complex to fabricate and specify than a delayed coker. There are more design and fabrication parameters to consider than the coke drums. Both are extremely severe and as you mention coke drums are in cyclic service, but one involves potential catastrophic results in case of failure where the other will typically only cause major localized problems.
Thanks to both for your valued information and participation