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Process Safety

Process Safety by Dennis Hendershot, principal process safety specialist, Chilworth Technology Inc.

Dennis Hendershot is a principal process safety specialist for Chilworth Technology Inc. He spent more than 35 years with Rohm & Haas Co. He has served on a number of subcommittees of AIChE’s Center for Chemical Process Safety, including those for inherently safer design and hazard evaluation techniques. He authored the chapter on inherently safer design in “Guidelines for Engineering Design for Process Safety” and coauthor of “Inherently Safety Chemical Processes: A Life Cycle Approach.” He also gives courses on inherently safer design for the Mary K. O’Connor Process Safety Center at Texas A&M University.

Why is the diameter size of a pressure safety valve outlet line bigger than the inlet line?
Why is the diameter size of a pressure safety valve outlet line bigger than the inlet line?
Category: Process Safety

What are recommended color-code markings?
What are the recommended color-code markings for a box over the filling point of hydrochloric acid and caustic soda?
Category: Process Safety

Are there standards that ensure valves are kept open or closed as needed?
I would like to know the reqirements to define a CSC, CSO, LC or LO valve. Is there any standard or guideline for this definition?
Category: Process Safety

How do you design a vessel to withstand explosions?
One of pharmaceutical industry is building hydrogenation room. In that room there are 14 reactors of small capacity. These reactors' capacity vary from 500 ml- 5 liters. These hydrogenators are operating a150 bar pressure. Now the question is what should be the thickness of the wall to sustain the overpressure generated by explosion? We have done a risk analysis study in which overpressure generated by explosion is 1 bar maximum.

Kindly tell me the basis for that thickness of the wall.
Category: Process Safety

Process Safety: What is the flash point of Reagent Alcohol?
I am looking for a reliable table that shows the flash point of 3A alcohol (Reagent Alcohol).
Category: Process Safety

Is There a Danger With Water Spray Inside Heat Exchangers?
We have flue gas heat exchangers for thermal oil, which has around a 400 degree Fahrenheit flash point and a chamber temperature around 700 degrees Fahrenheit. Standard insurance recommendations and NFPA (6-64) call for automatic water spray fire protection inside the heat exchanger. The theory is that the water spray, when discharged, will contact refractory, flashing to steam -- aiding the fire control for fires resulting from leaking/damaged HTF piping. However, we have management team members that are so worried about false trip and cold thermal stress to the refractory that systems are kept manual -- and may never be actuated, even in a fire situation. Do you know of loss experience data concerning water spray inside heat exchangers that can support use of water spray (or not). We manufacture OSB (oriented strand board) and factories do not have steady supply of steam for fire protection in HEs and HEs are so large that CO2 system costs are prohibitive.
Category: Process Safety

Enhance your Risk Assessment Skills
Process Hazard Analysis are essential for both designing and running a chemical plant safely and developing PHA is a major task for Process Safety Engineers. Which are the main Congresses/Conferences/Trainings where a Process Safety Engineer could enhance his risk assessment skills?
Category: Process Safety

Static electricity references
I am researching the issue of the incidence of fires caused by static electricity in chemical plants. How big of a problem is this? Would you be able to direct me to sources for data on fires and their causes, and methods used by chemical plants to minimize the risk of fires caused by static electricity?
Category: Process Safety

Layering problem in oil storage tanks
Due to processing different types of crude oils at a petroleum refinery, the density of ATF (Aviation Turbine Fuel) produced varies wildly resulting in layering in storage tanks. This is not acceptable and there is apprehension that if a jet nozzle is used in the storage tank and is subjected to circulation, the electro static charge will accumulate (considering low conductivity of ATF) and would be unsafe. Do you experience such problems? If so, how you prevent or correct the layering problem? What method and precautions are taken? Please confirm whether use of a jet mixer in the tank for ATF circulation is allowed.
Category: Process Safety

Oxygen expolsion cause
We have an oxygen plant that produces liquid oxygen and separates it from nitrogen by distillation. All of these processes are inside a box that is called a cold box. When the consumer plant had a shutdown, an explosion happened in the cold box. Can help me to find the reason of the explosion or lead me to experts in the field?
Category: Process Safety

PRV design
I want to design a PRV and size the outlet line of the PRV, which goes to a drain header. Is there a method to do it? The maximum operating pressure in the pipe line is 70 psig.
Category: Process Safety

Color coding for pipes
What is the color code for compressed air distribution lines, and also for vacuum distribution lines? Is there a color code for shutoff valves for compressed systems and for vacuum systems (i.e. laboratories, schools and hospitals)?
Category: Process Safety

Handling liquid sulfur trioxide
We are handling liquid Sulfur trioxide. we have kept around 4.8 tons in storage for 4 months. We have had a very heavy monsoon for 3 months and have also encountered floods in our area. Due to this we have lapsed on temperature control and have found that the sulfur trioxide has solidified and has formed needle shaped (like glass wool) on the top of the horizontal storage tank as seen through sight glass. Heating facility is available with thermic fluid through the jacket. There is no stirring facility available. The tank is connected to scrubber and there is no vent line to atmosphere. Please suggest the best process by which we can liquiy the sulfur troxide.
Category: Process Safety