A Step by Step Guide to Estimate Ammonia Releases and Reporting

Development of a “leak calculation tool” to aid end users in determining the quantity and/or rate of a release for reporting purposes. 

CFD Simulation of Ammonia Dispersion within a Machinery Room

To further understand the effectiveness of various emergency ventilation designs and emergency ventilation rates for controlling the flammability hazard associated with accidental ammonia releases in machinery rooms, IIAR and NRF commissioned a study intended to provide a technical basis for potential updates to the emergency ventilation recommendations and requirements in IIAR-2, Standard for the Safe Design of Closed-Circuit Ammonia Refrigeration Systems. The study used computational fluid dynamics (CFD) to quantitatively evaluate the performance of various emergency ventilation designs and emergency ventilation rates for controlling the flammability hazard during ammonia releases in machinery rooms. The study was limited to two machinery room configurations (small and large) and five ventilation system designs. Furthermore, it was limited to ammonia releases from full-bore failures of ¾" lines containing high temperature, high pressure liquid; low temperature, high pressure liquid; and high pressure vapor; all at specified temperatures and pressures. A wide range of emergency ventilation rates were considered in addition to a range of leak location/direction combinations. In total, approximately 2000 CFD simulations were performed. Emergency ventilation performance was quantitatively evaluated based on the system’s ability to limit the size of the flammable ammonia/air cloud during a leak. 

IIAR members can access by searching the elibrary. 

Non-members can access the report by purchasing it in the IIAR Store. 

CFD Simulation of an Ammonia Dispersion within Refrigerated Spaces

Historically, ammonia detection has been required by IIAR-2 as well as the model codes, however, specific guidance on the appropriate number and placement of ammonia detectors for a given type and size of space was not given. Applying Computational Fluid Dynamics (CFD) analysis to answer a number of questions related to the appropriate number and placement of detectors in various types of refrigerated spaces was the object of the study. Principal Researcher, William Greulich, of Kensington Consulting conducted the research and delivered the results of the work in 2020 with a well received technical paper and presentation at the IIAR annual conference.

The results of the study were used by the Standards Committee to determine if there was merit in requiring additional detectors beyond the minimum requirement of one in every room with ammonia equipment. The study showed that having additional detectors would indeed reduce detection time, however, the reduction was small enough that it was determined that the addition of more than one detector in each room would not be justified. For example, an additional detector on average would reduce detection time by only a few minutes in a large room. Adding more detectors would only reduce response time by a few seconds. It was concluded that the actual leak response (action taken by either plant personnel or in some cases automatic system reaction) would not be significantly improved by the addition of detectors. In summary, the Safety Committee used the study to reinforce the requirements that are already included in IIAR-2 and made no new requirements for additional detectors.

The study also showed that detector placement is not extremely critical, but that placement can influence response time. The study is referenced in the latest IIAR-2 informative Appendix A to aid people with complying with the requirement that detectors be “mounted in a position where ammonia from a leak is expected to accumulate”.

2020 IIAR Technical Paper Presentation: CFD Simulation of NH3 Release and Detection in Refrigerated Spaces (Results of the IIAR/NRF Research Project) - Author: William Greulich, Kensington ConsultingIIAR Members can access Technical Paper information for free through the IIAR online elibrary

Development of a Mechanical Insulation Installation Guideline for Refrigeration Applications
 
Mechanical (pipe, tank, and equipment) insulation is a critical contributor to energy efficiency and process control in cold applications. Water and water vapor intrusion into these insulation systems is their main failure mechanism. The resistance of the insulation system to water is controlled by the materials used and the quality of the installation. Water resistance of the insulation and vapor retarder materials is well understood but the impact of joints and terminations in these materials and the role installation plays in the water resistance of the insulation system has not been well studied.

The Principal Investigator (PI), Gordon Hart, of Artek Engineering visited 20 refrigerated facilities in 14 states to examine insulation removal and new insulation installation at older facilities, as well as insulation installation at newly constructed facilities. The project has resulted in a number of recommended installation processes and joint treatments for insulation systems which, if followed, will increase the resistance of insulation systems to water vapor intrusion thus improving their lifespan.

Results of this project can be found in the IIAR Publication - Guideline for Installing Insulation on Ammonia Refrigeration Systems

Optimum Pipe Sizing

The objective of this research was to revisit the economic sizing methodology, originally proposed by Genereaux and subsequently transplanted into the industrial refrigeration industry by Richards, in order to update and expand the recommended pipe sizing tables included in the IIAR Piping Handbook.  A primary aim of this project is to provide a computer-based analysis tool that will allow users to explore optimum pipe sizing based on input data that includes: piping system capital cost information, system energy cost data, piping system life expectancy, and refrigeration system operating efficiency information. 

Results of the research project have been included in the 2019 IIAR Refrigeration Piping Handbook.

Analysis and Correlation of Data from ASHRAE RP-1327 (Flow in Two-Phase Ammonia Risers)Tests: Conducted with 2” and 4” pipes. 
As a contributor to the ASHRAE research project RP-1327, which measured pressure drop in 2” and 4” ammonia wet suction risers, IIAR/NRF was given access to the data taken during the project. The RP-1327 data, originally taken at the Danish Technologic Institute (DTI) in Aarhus, Denmark, was used in a NRF-funded research project to develop an accurate method for predicting pressure drop and properly designing ammonia suction risers.

Dr. John Thome, of JJ Cooling Innovation in Switzerland, was selected as the Principal Investigator for the project and successfully delivered a calculation method to determine void fraction and pressure drop in ammonia two-phase upward flow based on the DTI data. The results of this work were presented by Dr. Thome at the 2019 annual conference. The new calculation method was then incorporated into a software design tool written by Morten Stovrup of Danfoss, a member of the Project Monitoring Subcommittee (PMS). The information from the study is also included as a new manual calculation method in the latest edition of the Piping Handbook.

2019 Technical Paper Presentation - Prediction of Void Fraction and Pressure Drops in Vertical Ammonia Risers - Author: John R. Thome, DPhil, École Polytechnique Fédérale de Lausanne
IIAR Members can access Technical Paper information for free through the IIAR online elibrary

Influence of P-Trap vs 90 degree Elbow Inlet on Two-Phase Pressure Drop in Vertical Suction Risers
Approval Date: 6/18/2013

This study was carried out on the test rig developed for ASHRAE RP-1327 at the Danish Technological Institute (DTI) in Aarhus, Denmark. The information produced by this study has furthered 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.   

NRF funded a research project based on the conducting a Quantitative Risk Analysis (QRA) for various ammonia dispersion methods (release to atmosphere, flaring, scrubbing, water diffusion tank).

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. 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.

2014 IIAR Technical Paper Presentation - Comparison of Various Methods of Mitigating Over Pressure Induced Release Events Involving Ammonia Refrigeration Using Quantitative Risk Analysis  - Authors: Donald Fenton and Tyler Hodges
IIAR Members can access Technical Paper information for free through the IIAR online elibrary

Comparison of Various Methods of Mitigating Over Pressure Induced Release Events Involving Ammonia Refrigeration Using Quantitative Risk Analysis
Approval Date: 6/22/2013

2019 IIAR Technical Paper Presentation - Predictive CFD Modelling of Condensation-induced Water Hammer in Two-phase Ammonia Systems - Authors: Chidambaram (Chidu) Narayanan, DSc and Lane Loyko
IIAR Members can access Technical Paper information for free through the IIAR online elibrary

Development and Validation of a Bench Test Procedure for Post-Mortem Testing of Safety Relief Valves (SRV) and Development of Statistical Analysis Software Tool 
Approval Date: 7/28/2009

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 - Development and Validation of a Bench Test Procedure for Post Mortem Testing of Relief Valves - Authors:  T. B. Jekel, M. Claas,  D. T. Reindl
IIAR Members can access Technical Paper information for free through the IIAR online elibrary

Comparison of Various Methods of Mitigating Over Pressure Induced Release Events Involving Ammonia Refrigeration Using Quantitative Risk Analysis
Approval Date: 12/20/2007

 Joint ASME-NRF Research Project: Impact Testing Exemption Curves for Low Temperature Operation of Pressure Piping.  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 - Impact Testing Exemption Curves for Low Temperature Operation of Pressure Piping - Author: Martin Prager
IIAR Members can access Technical Paper information for free through the IIAR online elibrary

NRF Research Project Programs

NRF Research Project Proposal Form