exact causes of failure. Information collected from gathered data is significant for making recommendation and conclusions.
When investigating an incident involving equipment failure, the first job is to preserve the physical evidence. The instrumentation and control settings and the actual reading before the failure happen should be fully documented for the investigating team. In addition, the operating and process data, approved standard operating (SOP) and standard maintenance procedure (SMP), Copies of log books, work packages, work orders, work permits, and maintenance records; eq should be preserved.
Some methods of gathering information include:
Conducting interviews/collecting statements – Interviews must be fact finding and not fault finding. Preparing questions before the interview is essential to ensure that all necessary information is obtained.
Interviews should be conducted, preferably in person, with those people who are most familiar with the problem. Although preparing for the interview is important, it should not delay prompt contact with participants and witnesses. The first interview may consist solely of hearing their narrative. A second, more‐detailed interview can be arranged, if needed. The interviewer should always consider the interviewee’s objectivity and frame of reference.
Reviewing records: Review of relevant documents or portions of documents and reference their use in support of the root cause analysis.
Acquiring related information: Some additional information that an evaluator should consider when analyzing the causes include:
Evaluating the need for laboratory tests, such as destructive/nondestructive failure analysis.
Viewing physical layout of system, component, or work area; developing layout sketches of the area; and taking photographs to better understand the condition.
Determining if operating experience information exists for similar events at other facilities.
Reviewing equipment supplier and manufacturer records to determine whether correspondence has been received addressing this problem.
Interviews
For critical incidents, all key personnel involved must be interviewed to get a complete picture of the incident. Individuals having direct or indirect knowledge that could help clarify the case should also be interviewed.
Questions to Ask
What happened?
Where did it happen?
When did it happen?
What changed?
Who was involved?
Why did it happen?
What is the impact?
How can recurrence be prevented?
Analyze Sequence of Events
The sequence of event helps in finding out which cause has first triggered the incident. This helps in organizing the information and establishes relationship between the event and incident.
Design Review
It is essential to clearly understand the design parameters and specifications of the systems associated with an event or equipment failure. Unless the investigator understands precisely what the machine or production system was designed to do and its inherent limitations, it is impossible to isolate the root cause of a problem or event. The data obtained from a design review provide a baseline or reference, which is needed to fully investigate and resolve plant problems.
The objective of the design review is to determine whether the machine is running within acceptable operating envelope. The condition of the machine and the process condition are being investigated. For example, a centrifugal pump may be designed to deliver 1OOO m3/h of water having a discharge Pressure of 20 kg/cm2. If it is operated beyond this point, then the power will increase and due to running beyond design limit vibration may go up. The review should establish the acceptable operating envelope, or range, that the machine or system can tolerate without a measurable deviation from design performance. Evaluating variations in process parameters, such as pressures flow rate, and temperature, is an effective means of confirming their impact on the production system.
Operating and Maintenance Manuals
O&M manuals are one of the best sources of information. In most cases, these documents provide specific recommendations for proper operation and maintenance of the machine, equipment, or system. In addition, most of these manuals provide specific troubleshooting guides that point out many of the common problems that may occur. A thorough review of these documents is essential before beginning the RCA. The information provided in these manuals is essential to effective resolution of plant problems.
Operating Procedures and Practices
This part of the application and maintenance review consists of evaluating the standard operating procedures and the actual operating practices. Most production areas maintain some historical data that track its performance and practices. These records may consist of log books, reports, or computer data. These data should be reviewed to determine the actual production practices that are used to operate the machine or system being investigated.
This part of the evaluation should determine if the SOPs were understood and followed before and during the incident or event. The normal tendency of operators is to shortcut procedures, which is a common reason for many problems. In addition, unclear procedures lead to misunderstanding and misuse. Therefore, the investigation must fully evaluate the actual practices that the production team uses to operate the machine or system.
Maintenance History
A thorough review of the maintenance history associated with the machine or system is essential to the RCFA process. The primary details that are needed include frequency and types of repair, frequency and types of preventive maintenance, failure history, and any other facts that will help in the investigation.
Operating Envelope
Evaluating the actual operating envelope of the production system associated with the investigated event is more difficult. The best approach is to determine all variables and limits used in normal production. For example, define the full range of operating speeds, flow rates, incoming product variations, and the like normally associated with the system. In variable‐speed applications, determine the minimum and maximum ramp rates used by the operators.
Maintenance Procedures and Practices
A complete evaluation of the standard maintenance procedures and actual practices should be conducted. The procedures should be compared with maintenance requirements defined by both the design review and the vendor’s O&M manuals. Actual maintenance practices can be determined in the same manner as described earlier or by visual observation of similar repairs. This task should determine if the SMPs are followed consistently by all maintenance personnel assigned
