This study (currently in process) is being carried out on the test rig developed for ASHRAE RP-1327 at the Danish Technological Institute (DTI) in Aarhus, Denmark. This information produced by this study will further the understanding of two-phase pressure drop and flow in risers and should lead us to better designs with this critical part of ammonia piping systems.
ARF funded a research project based on the conducting of a Quantitative Risk Analysis (QRA) for various ammonia dispersion methods (release to atmosphere, flaring, scrubbing, water diffusion tank). The results of the study were presented in a workshop session at the 2013 IIAR Conference and in a technical paper at the 2014 IIAR Conference.
The objective of the project was to determine the effectiveness of different methods of mitigating ammonia releases through a pressure relief device in an ammonia refrigeration system. A literature review was conducted and among the methods discovered, five were selected for further study and include: discharge into a tank containing standing water, discharge into the atmosphere, discharge into a flare, discharge into a wet scrubber, and an emergency pressure control system. All the methods were compared applying quantitative risk analysis where failure rates of each system were combined with ammonia dispersion modeling and with the monetized health effects of a system’s failure to contain an ammonia release. It was determined that the ammonia release height had the greatest influence on the downwind cost impact relative to the other variables, including weather conditions and release from multiple sources. While the discharge into a tank containing standing water was determined to have the lowest failure rate, the other discharge methods can be designed to have comparable failure rates and comparable release consequent cost. The emergency pressure control system, now required by codes, used in conjunction with the other ammonia release mitigation systems, was determined to be very effective. (2014 IIAR Technical Paper Presentation)
In 2007, IIAR revised its recommended practice for replacing pressure relief valves on industrial ammonia refrigeration systems (Section 6.6.3 of Bulletin 110). In addition to the prescriptive five year relief valve replacement interval, the revisions to Bulletin 110 added an alternative replacement method based on an evaluation of in-service relief valve life using appropriate testing and data analysis methods. This paper describes the results of a research project that aimed to validate guidelines for the postmortem testing of relief valves. The purpose of the data collected by post-mortem testing is intended to support the alternative path to determine the service life of relief valves following their removal from the system prior to their disposal (i.e. post-mortem). The testing procedure and data gathering methods described in this paper are intended for relief valves that have not discharged during their in-service life. A test rig suitable for post-mortem testing of relief valves was designed, constructed, and proof-tested. The function of the experimental rig was established by testing a range of alternative relief valves that included high and low set pressures; high and low capacities; as well as both new and used relief valves. The draft test procedure was modified using the information gathered during the rig proof-test. The results of this project include a relief valve test rig design and corresponding test procedures suitable for data collection by post-mortem testing of relief valves. (2011 IIAR Technical Paper Presentation)
A second project was funded by ARF to develop an accompanying statistical analysis software tool. The researcher produced a final report on the statistical method along with the “SRVCalc” software package. The test method and software is now in beta testing with two end users.
Extension of ASME exemption curves has been accomplished by consistent application of old and new ASME fracture mechanics concepts originally intended for pressure vessels. It is recognized that materials produced by modern means may be deserving of greater credit for toughness and reassignment to different traditional curves or even new curves may be in order. Where there is impact toughness data, the mean temperature in the transition region may be estimated and new exemption curves developed. Procedures described were used to adjust exemption curves for thickness where pipe wall is less than the normal Charpy specimen width. (2009 IIAR Technical Paper Presentation)