Regarding the design pressure for boundary conditions, operating pressure, intrinsic safety, operating conditions, and misoperations – how do people make decisions regarding these aspects?
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Regarding the design pressure (temperature) and operating pressure (temperature) of boundary conditions, intrinsic safety, operating conditions and misoperations, how do people make their choices? As title: 1. How is the boundary operating pressure determined between upstream and downstream units? Should I select the downstream backpressure + pipeline pressure drop? So, for the pressure at the boundaries of upstream and downstream operations, must it be higher on the upstream side than on the downstream side? So, with a constant flow velocity in the gas-phase medium pipeline, should it be designed with a smaller diameter upstream (where the pressure is high) and a larger diameter downstream (where the pressure is lower and expansion occurs), in a trumpet shape? 2. How is the design pressure at the boundary determined between upstream and downstream units? Should the upstream pump shutdown pressure/upstream tank safety valve pressure be selected? If understood in this way, then since the acidic water high-pressure tank for hydrogenation supplies sulfur under its own pressure, wouldn’t the design pressure of the pipeline need to be determined based on the safety valve of that high-pressure tank? There is a pipeline leading to the fuel gas at the compressor outlet; does this mean that the design pressure of the fuel gas pipeline needs to be increased to the pressure of the compressor outlet safety valve? Only by doing the above can intrinsic safety be ensured. 3. How should intrinsic safety be understood? Intrinsic safety requires preventing human error, equipment failures (such as valve plates falling off and closing), and environmental factors (such as earthquake conditions?) ) If intrinsically safe means absolute safety, then should the design pressure of the flare line be increased to the set pressure of the safety valve of the highest-pressure compressor? Manager Discussion Group
1. The operating pressure at the boundary is usually determined by process requirements and the mutual influence of upstream and downstream equipment. The downstream back pressure plus the pipeline pressure drop can be used to determine this value, ensuring smooth flow of the fluid. It is not necessarily required that the upstream pressure be higher than the downstream pressure; this depends on the specific process and the properties of the fluid. If there is a gas-phase medium, the shape of the pipeline may need to take into account the distribution of pressure and flow velocity to ensure effective fluid transfer. 2. The design pressure for the boundary is usually determined by the highest pressure that may be encountered, which is typically the maximum operating pressure upstream or the setting pressure of the safety valve. Indeed, as you mentioned, the design pressure of high-pressure tanks should take into account the pressure of their safety valves to ensure safety. In the case where the compressor outlet is connected to the fuel gas pipeline, it is indeed necessary to increase the design pressure of the fuel gas pipeline to match the compressor’s maximum safe pressure release value. 3. Intrinsic safety refers to minimizing the likelihood and impact of accidents through design and process control. This includes preventing human error, equipment failures, and resilience to environmental changes such as earthquakes. Intrinsic safety does not mean absolute safety, but its purpose is to minimize risks as much as possible. The design pressure of the flare system should indeed match the highest pressure that may be encountered in the system, to ensure its safe operation in emergency situations. .
Also, the design temperature of the reflux tank at the top of the tower is generally low, with a design/operating temperature of 80/40°C; yet low-pressure steam at around 180°C is used for purging. How should this be understood?
The design temperature of the tower top reflux drum is low, but the use of high-temperature steam for purging may be intended to meet specific process requirements. For example, in some chemical processing processes, high-temperature steam can be used to remove residues or impurities from tanks, facilitate the circulation of materials, or prevent them from solidifying. Although the temperature of the purge steam is much higher than the designed and operating temperature of the tank, control measures are usually in place to ensure safe operation, such as adjusting the steam flow and pressure, using heat exchangers to cool down the steam, or setting specific times and conditions for the purge process. Furthermore, this situation is taken into account during system design, with appropriate materials and thicknesses used to withstand short-term high temperatures and prevent equipment damage. In summary, the purpose and methods of using high-temperature steam purging should be determined comprehensively based on specific process requirements, safety assessments, and system design. .
The design temperature and pressure define the maximum conditions for normal operation; the design temperature and pressure of the equipment are not determined by these start-up and shutdown conditions, but such conditions must be taken into account in the equipment’s design.
Intrinsic safety means addressing the error-prone aspects at the source in order to prevent harm that may result from errors; it is also about comprehensively analyzing the purpose of such measures
The design was not carefully considered; it should be designed in accordance with the principle of intrinsically safe design
It’s not that it hasn’t been thought through; the key is to know what constitutes thorough consideration
Often, it’s not possible to meet all the requirements at the same time, which results in raising the low pressure to high pressure, thereby doubling the investment cost