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Testing to support safe design of batteries and electrical power backup facilities particularly to satisfy UL9540a ed.4

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Develop critical safety data for inclusion in SDS documents

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Evaluate electrical cables to demonstrate reliability and identify defects or degradation
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Analysis and testing to identify and prevent unwanted hydraulic pressure transients in process piping
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Fauske & Associates fulfills the requirements of ISO/IEC 17025:2017 in the field of Testing

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Fauske & Associates fulfills the requirements of ISO 9001:2015
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Evaluate your process to identify combustible dust hazards and perform dust explosion testing
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On-site safety studies can help identify explosibility and chemical reaction hazards so that appropriate testing, simulations, or calculations are identified to support safe scale up
DIERS Methodology
Design emergency pressure relief systems to mitigate the consequences of unwanted chemical reactivity and account for two-phase flow using the right tools and methods
Deflagrations (Dust/Vapor/Gas)

Properly size pressure relief vents to protect your processes from dust, vapor, and gas explosions

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Pressure relief sizing is just the first step and it is critical to safely handle the effluent discharge from an overpressure event

FATE™ & Facility Modeling

FATE (Facility Flow, Aerosol, Thermal, and Explosion) is a flexible, fast-running code developed and maintained by Fauske and Associates under an ASME NQA-1 compliant QA program.

Mechanical, Piping, and Electrical
Engineering and testing to support safe plant operations and develop solutions to problems in heat transfer, fluid, flow, and electric power systems
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Testing and consulting on the explosion risks associated with devices and processes which use or produce hydrogen
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Our Nuclear Services Group is recognized for comprehensive evaluations to help commercial nuclear power plants operate efficiently and stay compliant
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Safety analysis to underpin decomissioning process at facilities which have produced or used radioactive nuclear materials
Adiabatic Safety Calorimeters (ARSST and VSP2)

Low thermal inertial adiabatic calorimeters specially designed to provide directly scalable data that are critical to safe process design

Other Lab Equipment and Parts for the DSC/ARC/ARSST/VSP2 Calorimeters

Products and equipment for the process safety or process development laboratory


Software for emergency relief system design to ensure safe processing of reactive chemicals, including consideration of two-phase flow and runaway chemical reactions


Facility modeling software mechanistically tracks transport of heat, gasses, vapors, and aerosols for safety analysis of multi-room facilities


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With over 40 years of industry expertise, we have a wealth of process safety knowledge to share.

Recent Posts

Replacing Complex Two-Fluid Models With A Simple Model 

Posted by Fauske & Associates on 01.08.18

Replacing Complex Two-Fluid Models With A Simple Model That Has No Adjustable Parameters and That is Agreeable With Experimental Data Including Both Non-Equilibrium and Equilibrium Flashing Flows

By: Hans K. Fauske, D. Sc., Regent Advisor, Fauske & Associates, LLC (FAI)

In contrast to the two-fluid models that require numerous assumptions and the corresponding closure equations, the Simple Model can be stated as:

Equation 1(1)

where G (kg m-2 s-1) is the Non-Equilibrium or Equilibrium two-phase flow rate including the effects of subcooling (GSC), Y is the dimensionless independent variable ranging from 0 to 1 and G0 and G1 are the corresponding asymptotic flow rate limits. For all specified stagnation conditions (subcooled liquid, saturated liquid and liquid-vapor mixtures) and flow geometries (nozzle, short and long), the easy to estimate G values in the region between the known asymptotic limits with no arbitrary adjustable parameters are in remarkable agreement with available experimental data. The nozzle constant area length L is the key parameter and values (Y) leading to non-equilibrium and equilibrium flashing flows is provided by (Fauske, 1985, 2017).


An example is illustrated below the agreement of the simple model is consistently good for all inlet quality (Xo) conditions, where Gc is the dimensionless mass flux, defined as G/√Poρo, and quoting Sozzi and Sutherland (1975), stagnation quality (Xo) in the vessel upstream of the nozzle is based on the density in the vessel and the stagnation pressure (Po):

Equation 2(2)

when the liquid is subcooled, vf >1/ρ and, consequently Eq. 2 results in Xo < 0 as a negative quality.

It should be noted that the short nozzle No. 2 (D = 12.7 mm and L/D = 1) non-equilibrium data by Sozzi and Sutherland (1975) have provided difficulties in predicting especially with two-fluid modelling which required empirical adjustment to fit the test results (Levy, 1993).

For more information or to discuss two-phase flow concerns, contact Kris Fauske at 630-887-5213,


Hans K. Fauske, 1983, "Flashing Flows Or: Some Practical Guidelines for Emergency Releases," Plant/Operations Progress, July, 1985.

Hans K. Fauske, 2017, "Further Clarification of Non-Equilibrium and Equilibrium Flashing Flows Through TOP Located Relief Valves (SRVs)," Process Safety News, Summer 2017, Volume 24, Number 3.

Solomon Levy, 1999, "Two-Phase Flow in Complex Systems," A Wiley Interscience Publication, 1999.

Sozzi, G. L. and Sutherland, W. A., 1975, "Critical Flow of Saturated and Subcooled Water at High Pressure," Report NEDO-13418, General Electric Company, San Jose, Ca (July).



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