Combustible Dust Testing

Laboratory testing to quantify dust explosion & reactivity hazards

Flammable Gas & Vapor Testing

Laboratory testing to quantify explosion hazards for vapor and gas mixtures

Chemical Reactivity Testing

Laboratory testing to quantify reactive chemical hazards, including the possibility of material incompatibility, instability, and runaway chemical reactions

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 safety handle the effluent discharge from an overpressure event

Thermal Stability

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

UN-DOT

Classification of hazardous materials subject to shipping and storage regulations

Safety Data Sheets

Develop critical safety data for inclusion in SDS documents

Biological

Model transport of airborne virus aerosols to guide safe operations and ventilation upgrades

Radioactive

Model transport of contamination for source term and leak path factor analysis

Fire Analysis

Model transport of heat and smoke for fire analysis

Flammable or Toxic Gas

transport of flammable or toxic gas during a process upset

OSS consulting, adiabatic & reaction calorimetry and consulting

Onsite safety studies can help identify explosibility and chemical reaction hazards so that appropriate testing, simulations, or calculations are identified to support safe scale up

Mechanical, Piping, and Electrical

Engineering and testing to support safe plant operations and develop solutions to problems in heat transfer, fluid flow, electric power systems

Battery Safety

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

Hydrogen Safety

Testing and consulting on the explosion risks associated with devices and processes which use or produce hydrogen

Spent Fuel

Safety analysis for packaging, transport, and storage of spent nuclear fuel

Decommissioning, Decontamination and Remediation (DD&R)

Safety analysis to underpin decommissioning process at facilities which have produced or used radioactive nuclear materials

Laboratory Testing & Software Capabilities

Bespoke testing and modeling services to validate analysis of DD&R processes

Nuclear Overview

Our Nuclear Services Group is recognized for comprehensive evaluations to help commercial nuclear power plants operate efficiently and stay compliant.

Severe Accident Analysis and Risk Assessment

Expert analysis of possible risk and consequences from nuclear plant accidents

Thermal Hydraulics

Testing and analysis to ensure that critical equipment will operate under adverse environmental conditions

Environmental Qualification (EQ) and Equipment Survivability (ES)

Testing and analysis to ensure that critical equipment will operate under adverse environmental conditions

Laboratory Testing & Software Capabilities

Testing and modeling services to support resolution of emergent safety issues at a power plant

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 (DSC/ARC supplies, CPA, C80, Super Stirrer)

Products and equipment for the process safety or process development laboratory

FERST

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

FATE

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

Blog

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.

Resources

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

Recent Posts

Pressure Relief Evaluation for Monomer Storage Tanks

Posted by The Fauske Team on 09.25.13

By Hans K. Fauske, DSc, Regent Advisor, Fauske & Associates, LLC

two phaseflowIntroduction - Thermal initiation of monomers due to fire exposure presents an interesting problem in vent sizing in order not to exceed the allowable overpressure. For large atmospheric vessels the potential occurrence of sufficient liquid swell resulting in two-phase flow is of special importance. Since little or no overpressures (< 0.1 psi) can be accommodated in many cases of interest the vent area augmentation due to two-phase flow is to the first order proportional to (Untitled 1) where pl and pg are the liquid and vapor densities, respectively. It is also of interest to note that for many monomers significant thermal initiation coincides closely with the normal boiling point of the monomer, resulting in a chemical induced self-heat rate of the same order as the equivalent volumetric heating rate due to the fire exposure. Examples of such behavior include monomers like styrene, butyl acrylate, ethyl acrylate, etc.

Fire Exposure Only - For fire exposure heating only and a freeboard of about 10%, Fauske (1986) has demonstrated that for non-foamy systems the vent requirement can be based upon all vapor venting independent of available overpressure. The basis for this argument is the absence of vapor generation throughout the bulk of the liquid and the liquid swell is due entirely to the wall boiling two-phase boundary layer associated with the fire heating. While the recirculation velocity (uc) resulting from the wall boiling two-phase boundary layer can exceed the terminal bubble rise velocity which is typically of the order of 0, significant vapor carry-under and hence significant liquid swell, is prevented by static head effects. The increasing subcooling of the liquid as the vapor bubble are dragged under by the recirculating flow results in rapid condensation and collapse of the vapor bubbles (Fauske et al., 1986). This behavior is confirmed by relevant fire simulation experiments and practical industry experience (Fauske et al., 1986).

Fire Exposure and Chemical Heating - The above observation can be extended to include chemical heating as follows. Again, the absence of significant vapor generation throughout the bulk of the liquid is assured by the static head effect if the following inequality is satisfied
A Practical ApproachEq 1(1)

where tchem describe the image is the chemical self-heat rate, Φ oCm 1 is the subcooled temperature gradient due to the liquid static head, and describe the image m min 1 is the average liquid recirculation velocity as a result of the wall boiling two-phase boundary layer density effect. Considering typical values for Φ and describe the image of about 20cm 1 and 10 describe the image, respectively, chemical self-heat rates well below about describe the image should assure the absence of volumetric boiling as the bulk of the liquid will remain subcooled. As a result of the liquid recirculation, the sensible heating produced in the bulk liquid from the chemical reaction is largely transferred to the wall two-phase boundary layer in the form of latent heat.

Design Example - Consider an API-650 uninsulated vessel (12’ diameter x 18’ 55 ss vertical on grade) with a 15,000 gallon capacity containing styrene exposed to fire. The volumetric heating rate due to fire exposure is 130min 1, the adiabatic chemical heating rate at a relief set pressure of 0.13 psig is 190cmin 1 (note that this value is much smaller than that required by Ineq. 1), resulting in a combined heating rate of about 320cmin 1. The maximum allowable venting pressure is 0.19 psig.

For this example, considering bulk volumetric boiling resulting in flashing two-phase venting (the DIERS methodology) requires a vent area of about 2,390in2, allowing for an overpressure of 0.06 psi. However, since Ineq. 1 is clearly satisfied in this case the vent area can be estimated from
A Practical ApproachEq 2(2)
where A (m2) is the ideal vent area, V (m3) is the volume of reactant, P (psig) is the relief set pressure and T describe the image is the combined heating rate from fire exposure and chemical heating at the relief set temperature. Setting V = 56.8describe the image, P = 0.13 psig and describe the image = describe the image, results in A = 0.2describe the image or 312describe the image. Equation 2 is based upon all vapor venting and provides a practical approach to pressure relief evaluation for monomer storage tanks exposed to fire and undergoing chemical heating as well.

Reference
Fauske, Hans K. et al., 1986, “Emergency Relief Vent Sizing for Fire Emergencies Involving Liquid-Filled Atmospheric Storage Vessels,” Plant/Operations Progress, Vol. 5, No. 4, October 1986.

Emergency Relief Vent Sizing for Fire Emergencies Involving Liquid-Filled Atmospheric Storage Vessels

For further information or assistance with your process safety testing, please call +1630-323-8750, info@fauske.com

 

Topics: process safety, relief venting, vent sizing, Two phase flow, pressure relief sizing, chemical, testing

cta-bg.jpg

Is My Dust Combustible?

A Flowchart To Help You Decide
Download Now