Typically for an in-service vessel failure you have two paths regarding determination of the cause of failure. One path is where the vessel fails in a catastrophic manner resulting in damage to plant equipment and personnel injury. For this type of failure, an outside agency in normally informed and conducts the investigation into the cause of failure. The method for determining the cause of failure is mentioned below.
For an in-service vessel failure (where you have no personnel injuries) the documents for review would be shift logs related to operating history, maintenance records and information on the construction of the vessel. What was the code of construction for this in-service vessel? How were repairs performed?
Evidence is investigated by actual hands-on evaluation of the failed vessel or applicable sections of the vessel in the as-failed condition. Normally, a team of cross-functional experts is assembled to conduct a proper root cause analysis investigation. The team usually consists of operating, maintenance, pressure vessel engineering and material/metallurgical engineering expertise to evaluate all forensic evidence to establish one or more root causes.
Thanks for your response,In-service vessel had catastrophic manner with personnel injury, What are the steps need to be taken to find out cause of failure? The code of construction is unknown and vessel had repair before.
What criteria need to be taken into account to approach the cause of failure?
pardiss2523;
Is your failed vessel located in a region where boilers and pressure vessels are subject to regulation? If so, because of injuries sustained from the vessel failure you need to contact the authorities that regulate pressure vessels in your jurisdiction.
If there is no regulatory body for pressure vessels, I would contact the insurer of the vessel. Do you know the insurance carrier? Most boiler/machinery insurance providers have access to providing expertise for forensic services.
The main thing is to not disturb the vessel failure until proper authorities can investigate or your insurance company sends out investigators.
To emphasize a points made by metengr. If the remnants of the failed vessel haven't been moved do everything you can not to move or distribute them until you get some expert advice and the jurisdictional authority on site. If for some reason they absolutely have to be moved get photographs of every piece in their respective location after failure. Make sure you save every piece. In your photographs try to get any marks or scars on anything generated by the incident.
Don't allow anything to touch the failure surfaces.
Interview the operators as soon as possible. This helps keeping them from forming a group opinion.
Isolate any records of operational conditions for the vessel, especially 96 hrs prior to the incident. This needs to be longer if there were operational problems. If you have shift logs these need to be copied or isolated now.
If there is any possibility of litigation get a metallurgical forensic group involved if at all possible as soon as possible. You will need their help as there always seems to be a parallel universe surrounding every catastrophic failure.
If using an outside entity to perform failure analysis, establish "chain of custody" documentation for transfer of parts for examination.
Photograph, Photograph, Photograph! Include date and times of photos and photographer.
Obtain all repair/maintenance data.
Research all test/inspection data on the vessel. Establish dates of inspections.
Research all original design criteria. Research any change in process during original operation until failure.
Assuming there will be a plaintiff, the plaintiff's attorney will be entitled to everthing you have during the Discovery process, assuming in USA or other countries having similar legal processes.
Thanks for your useful infprmation you provided me guys, I really appreciate you, Refer to Unclesyd suggestion regarding involving metallurgical forensic group, what are roles of group, what should they do exactly,like type of examination, for helping the investigation?
A Metallurgical Forensic Group or any named group that is able to evaluate the failure analytically from a materials point of view. Essentially what they do is take the metal from the failure do a PMI, determine failure mode, locate the origin of the failure, a full metallurgical analysis of the metal and determine the root cause failure. The reason for stating group is you have to have someone who has the expertise either in house or on call and equipment to do the evaluation. They can do the complete analysis or do the analytical work for say an in house group.
If your site has a metallurgical or materials group they can probably do the job, but you state that there were injuries. If there is litigation I assure you that the plaintiff will have such a group.
You need to verify that the material is what you are assuming it to be. Depending on the mode of failure the specific material can have a big influence.
As an example if the failure originated in or near a weld the material determines what the weld metal has to be along with any required post welding heat treatment.
Another is using the composition of the material plus the hardness will determine if the vessel is suitable for the service conditions experienced.
Depending on the failure mode it can eliminate a lot of second guessing latter.
To me it's just nice to really know as I've seen too many material screw ups.
