|Applying Reliability Based Decision Making to ITM Frequency|
Issue 89: Applying Reliability Based Decision Making to ITM Frequency
By Amanda Kimball
Many National Fire Protection Association (NFPA) fire protection system standards contain requirements for periodic inspection, testing, and maintenance (ITM) including NFPA 251, NFPA 72,2 and others. These are often historical requirements that are not based on ITM data or on observed deficiencies. As NFPA develops new documents that involve integrated systems, such as NFPA 4,3 the need for a more data based approach to standardized ITM frequencies will be important. Further, in the case of water based systems, the required resources associated with testing are increasing at a rapid rate.
Fire protection systems normally operate in standby mode and become active in emergency conditions. Failures are not detected until the system is operated. Regular testing is intended to verify the operational condition of the equipment.
Currently, testing of fire pumps generates field data. However, this data is not collected in a standardized manner. The Fire Protection Research Foundation published a report entitled Fire Pump Field Data Collection and Analysis.4 This project was undertaken with the belief that a collective set of standardized data could provide a scientific basis for optimum testing frequencies of the equipment to be included in NFPA 25.
Based on the field data that was available, the objective of this project underwent changes over the course of its completion. Ultimately, the project collected and analyzed fire pump field data from a number of sources and established a framework to collect data for long term future efforts. The collected data was analyzed for the following: how well and how frequently the tests provide evidence of existing or developing problems, the reliability of fire pumps (i.e. what is the expected impairment time for fire pumps), and the effect of test frequency on the reliability of fire pumps (i.e. what is the expected impairment time for fire pumps tested weekly, monthly, and yearly).
In order to establish the relationship between pump test frequency and the mean time to failure, more data is needed. However, an important outcome from the analysis of the existing data was that reliability decreased when fire pumps (both electric and diesel)were tested monthly as opposed to weekly.
The main recommendations from the project were related to long term data collection: setting up and maintaining a permanent data collection web site, developing a solicitation plan for users, and developing data collection forms for other water based system components (e.g. valves and pressure regulating devices).
Additionally on the topic of ITM frequencies, the Foundation held a workshop in July of 20125 on applying reliability based decision making to ITM frequency for fire protection systems and equipment. The objective of the workshop was to gather feedback from participants on developing a generalized approach to ITM frequency, including obtaining, organizing, and analyzing the data, as well as developing ITM frequency decisions.
During the discussion at the workshop, participants noted several issues that should be considered by a generalized approach. Poor management of change was stated as one of drivers of failures, and its consideration in ITM frequency approach was deemed necessary.
Many participants felt that human and environmental factors also need to be included in the approach. Specifically, qualifications of personnel performing ITM activities is a key element of concern, one which currently depends on the system. The workshop further supported one of the learning points from the fire pump project, that in many cases there is an opportunity to collect good data, but it needs to be standardized in order to analyze and draw conclusions on ITM frequency.
A couple of groups also noted that the definition of failure needs to be clear as this will drive the data collection format. Participants expressed the additional need to consider non-fire scenario failures. It was also noted that in some cases, testing can impact performance when equipment is not put back into service after the testing. Good design (i.e. sensors) could address this.
Through these activities, the Foundation realized that developing a generalized approach for reliability based ITM frequencies for all fire protection systems may not be possible due to the complexities of the systems. However, a need still exists for research on the topic of reliability based ITM, a need which was further highlighted in a workshop held by the Foundation in December of 2013.6 This workshop focused on the issue of design evaluations – if they should be required and what code or standard should require these evaluations. The participants of the 2013 workshop agreed that the frequency of the design evaluations needed to be risk/reliability based.
The Foundation is currently working on an effort to focus on reliability based ITM frequencies of water based systems. Following the completion of this effort and based on its results, the approach could possibly be expanded to other systems as well.
Amanda Kimball is with the Fire Protection Research Foundation
3rd Quarter 2013 – Fire Protection Inspection, Testing, and Maintenance and Building Fire Risk – Francisco Joglar, Ph.D
4th Quarter 2012 -- Bridging Installation Standards and Fire Protection Engineering – Kathleen Almand, P.E., FSFPE
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