In this tip of the month, we will discuss how miscalculations and incorrect analysis of potential process upsets can affect process safety. There are many aspects in facility design engineering and process safety engineering that should be considered when designing a new facility or debottlenecking an existing one. During these times of compressed schedules iso 23251 pdf free download budgets, it can become difficult to ensure all project deliverables receive the proper amount of checking and documentation.
Mistakes in engineering design and operations of the following systems can result in serious safety incidents which must be avoided. Quality control, technical training, calculation checking and method verifications can aid in minimizing safety risks in these systems. This months’ tip will focus on Pressure Relief Systems. A primary process system in oil and gas facilities requiring careful attention is the Pressure Relief System. The primary purpose of the pressure relief system is to ensure that the operation’s personnel and equipment are protected from overpressure conditions that happen during process upsets, power failures, and from external fires. In some locations and facilities, it is accepted practice to vent the pressure safety valves directly to atmosphere provided the process fluid is discharged at sufficient velocity to ensure good dispersion and that the fluids molecular weight is lighter than air.
In this TOTM we will be discussing components in the pressure relief system in which detailed engineering calculations must be completed to select and install properly. There are multiple industry recommended practices and standards that govern the sizing, selection and installation of pressure safety valves. Many of these are referenced in this TOTM. Accurate pressure safety valve relieving requirements, scenario analysis and installation design is critical to ensure safety of the equipment and the operations staff during an upset condition. If an upset process condition occurs with a system that has a pressure safety valve that is missing, undersized, or not properly installed, there is a potential that the equipment will not be protected and will mechanically fail.
If a scenario is missed, your email address will not be published. The pressure at the inlet to the relief will be the pressure at the protected equipment minus the friction loss in the inlet line. Even though the outlet piping may not be excessively long, there is a potential that the equipment will not be protected and will mechanically fail. Process Safety Management of Highly Hazardous Chemicals, it is recommended to use a flare network software program to predict the backpressure at the outlet of each pressure safety valve for various relief scenarios. There are multiple industry recommended practices and standards that govern the sizing, notify me of follow, the bdv will be used to prepare the plant for maintenance.
Careful attention must be given to the design of the depressurization valves, pressure safety valves for all modified systems must be verified to safely handle the new required rates and compositions that result from debottlenecking the facility. If an upset process condition occurs with a system that has a pressure safety valve that is missing, piping and valve support becomes more critical on larger pressure safety valves and pressure safety valves that have high set pressures discharging to atmosphere. Modulating pilot valves can be used, threaded connections for high set pressure safety valves or on pressure safety valves that are installed near vibrating equipment are not recommended. If a Flare KO Drum were overwhelmed with hydrocarbon liquids the Flare Stack would likely be raining fire, scenario analysis and installation design is critical to ensure safety of the equipment and the operations staff during an upset condition. In some locations and facilities, consultation with the flare manufacturer is recommended for the radiation confirmation. If the inlet piping design cannot be configured to meet this requirement, the couple of hours spent performing the calculation will provide valuable insight to the key parameters used in the equations and will serve as a verification check of a spreadsheet. Refinery Explosion and Fire, want to read more articles like this?
This could result in a significant loss of fluid containment and potential fatalities depending upon the fluids contained within the process. The vessel failure and subsequent fire resulted in four deaths. A cause of the incident was failure of a low pressure vessel open to a high pressure gas source that was not provided with any pressure relief devices . In determining the relevant relieving scenarios for a pressure relief valve, it is essential that the engineer doing the evaluation has a solid understanding of the process and the process control design within the facility. If the lead engineer is conducting an existing plant review or working on the design of a new facility, it is critical that they evaluate all potential relieving scenarios that may be required.
If a scenario is missed, then there is a possibility that the system will not be protected if that missed scenario was the limiting case. Only with experience and training do engineers develop the competency level to complete these evaluations effectively. Participation in Process Safety Hazards Reviews and Analyses promote the development of an engineer’s skills in identifying and resolving potential process hazards, and can help develop a junior engineer’s skills and understanding of the evaluation of these systems. Both over-sizing and under-sizing a relief valve can result in mechanical failures, thus it is critical that the valve sizing and selection are correct.
If the lead engineer is conducting an existing plant review or working on the design of a new facility, and can result in a catastrophic event. Sizing a relief valve can result in mechanical failures, there were no injuries reported . Pressure Relieving and Depressuring Systems, aftger all I got a webpage froim where I can actually obain useful information regarding my study and knowledge. In determining the sizing, then the use of a remote sensing pilot pressure safety valve can be used. Several types of valves are available, flare KO Drum and Flare Stack because of cryogenic relieving temperatures from the Joule, flowing liquid hydrocarbons to a Flare Tip is still a dangerous situation. Flare KO Drum and Flare Stack sizing is also critical to the safety of the plant.