Combustible Dust Testing

Laboratory testing to quantify dust explosion and reactivity hazards

Safety Data Sheets

Develop critical safety data for inclusion in SDS documents

Gas and Vapor

Laboratory testing to quantify explosion hazards for vapor and gas mixtures

Classification of hazardous materials subject to shipping and storage regulations
Testing and consulting on the explosion risks associated with devices and processes which use or produce hydrogen
Safety Data Sheets

Develop critical safety data for inclusion in SDS documents

Thermal Stability

Safe storage or processing requires an understanding of the possible hazards associated with sensitivity to variations in temperature

Adiabatic Calorimetry
Data demonstrate the consequences of process upsets, such as failed equipment or improper procedures, and guide mitigation strategies including Emergency Relief System (ERS) design
Reaction Calorimetry
Data yield heat and gas removal requirements to control the desired process chemistry
Battery Safety

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

Safety Data Sheets

Develop critical safety data for inclusion in SDS documents

Cable Testing
Evaluate electrical cables to demonstrate reliability and identify defects or degradation
Equipment Qualification (EQ)
Testing and analysis to ensure that critical equipment will operate under adverse environmental conditions
Water Hammer
Analysis and testing to identify and prevent unwanted hydraulic pressure transients in process piping
Acoustic Vibration
Identify and eliminate potential sources of unwanted vibration in piping and structural systems
Gas & Air Intrusion
Analysis and testing to identify and prevent intrusion of gas or air in piping systems
ISO/IEC 17025:2017

Fauske & Associates fulfills the requirements of ISO/IEC 17025:2017 in the field of Testing

ISO 9001:2015
Fauske & Associates fulfills the requirements of ISO 9001:2015
Dust Hazards Analysis
Evaluate your process to identify combustible dust hazards and perform dust explosion testing
On-Site Risk Management
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

Effluent Handling

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
Hydrogen Safety
Testing and consulting on the explosion risks associated with devices and processes which use or produce hydrogen
Thermal Hydraulics
Testing and analysis to ensure that critical equipment will operate under adverse environmental conditions
Nuclear Safety
Our Nuclear Services Group is recognized for comprehensive evaluations to help commercial nuclear power plants operate efficiently and stay compliant
Radioactive Waste
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


Our highly experienced team keeps you up-to-date on the latest process safety developments.

Process Safety Newsletter

Stay informed with our quarterly Process Safety Newsletters sharing topical articles and practical advice.


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

Published March 26, 2019

Should Set Point For Pressure Relieving Device Be Equivalent to Design Pressure?

By Himanshu Chichra, Principal Process Safety Engineer and host of ‘Process Safety and Risk Blog’ []

This blog is focusing on the general practice sometimes followed in industry related to the set point of Pressure Relief Devices of process equipment. Many times during process hazard analysis (PHA), I have come across a general philosophy of keeping the set point of the reactor's pressure relieving devices equivalent to its design pressure. This might be adequate for a non-reactive system. But the question is, is it adequate for a reactive system?

Here, the reactive system is one where there are hazards due to a chemical reaction, including the possibility of decomposition or polymerization or some side reaction, etc. We know based on normal kinetics that the rate of reaction is directly proportional to the temperature which in turn is proportional to pressure. In simple terms, it is said that the rate of a chemical reaction doubles with every 10 deg C rise in the reaction temperature. Hence it can be said that:

Higher set pressure leads to a correspondingly higher "set" temperature (i.e. the relieving temperature). This, in turn, leads to a higher rate of reaction which results in higher self-heating or higher temperature rise rate (dT/dt i.e. deg C/min) and a higher pressure generation rate (dP/dt i.e. bar/min). This is very important because for a chemically reactive system the required pressure relief area depends directly on the self-heating and pressure rise rates at the relief conditions.

Referring to the below composite graph for the methanol and acetic anhydride reaction (from an adiabatic calorimetry test), we see that at a given set pressure the corresponding temperature value can be obtained from the graph of pressure versus temperature. For example if the set pressure is 20 psi (about 35 psia) then the set temperature is about 99 deg C. Based on that set temperature, the temperature rise rate can be obtained from the plot of self-heat rate (dT/dt), giving a value of about 20 deg C/min in this illustration. The data show that the temperature rise rate increases exponentially with increasing temperature, and the system pressure rise rate must follow. Notice that if the set pressure is higher, say 35 psig (about 50 psia) then the set temperature is about 110 deg C and the corresponding self-heat rate is about 34 deg C/min. The implication is that at the higher set pressure the reaction rate is higher and the required pressure relief (vent) area is therefore larger.

composite graph methanol acetic anyhydride in VSP2 

Recall we have discussed T2 laboratories in my previous blog post, [], where the process was to batch load three different reactants, heat them to 99 deg C, start the agitator and continue heating to the process temperature. There was a provision of cooling water for reactor mass cooling and the reactor was provided with a 4" rupture disc with a set point of 400 psig. But on the day of the incident, cooling system failure resulted in runaway of the desired reaction, which further led to a second undesired exothermic reaction. The set-point of Rupture Disc was too high which led to an even higher temperature before the opening of the rupture disc. Higher temperature resulted in an increased rate of reaction and the 4" rupture disc was not sufficient for the required relieving rate causing the explosion. With lab trials, it was proved that the same 4" rupture disc with a set point of 75 psig would likely have been sufficient to relieve and prevent the reactor explosion.

This should make it clear that if a pressure relieving device is set at a lower pressure for a chemically reactive system, the size of the pressure relieving device will be smaller as compared to the size of a relieving device set at high pressure for the same system.

Thanks for reading the post. Let me know if you have any comments or queries on Also, you can share topics which you would like to learn about and I can consider these topics for my future blog posts.

Mr. Chichra is a guest blogger with whom Fauske & Associates, LLC (FAI) has recently worked to support customers in India. Read more of his posts related to process safety at [] and subscribe to FAI's blog to never miss out on any new process safety content.

Subscribe Now

Sign up for our newsletter to Get all the latest information

Share this article

Find more resources articles