Tianchen Design Institute releases the pressure through blast discs into the atmosphere – is this safe?
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This post was last edited by liu530014416 on 2022-12-1 11:53. Dear teachers, the process involves vacuum distillation; it was designed in Germany for the first time. Tianchen simply translated the PID parameters. The operating pressure of this process is -70 kPa, and the temperature is 180°C. The entry of air into the system can lead to an explosion; the burst pressure of the rupture disc is 0.19 Mpa, and it is a reverse-burst type of rupture disc. During the maintenance over these two days, the tower was heated with water, and steam was introduced more rapidly; as a result, the pressure in the tower rose to 40 Kpa, which caused the rupture disc to deform. It did not explode, but the deformation broke the wire used for indicating the pressure level on the rupture disc. Tianchen Design has directed the vent directly to the atmosphere. What if, during normal operation, a rupture disc fails and air is drawn in? Although a nitrogen supplementation pipeline was designed, with a diameter of DN25 and a pressure of 50 kPa, a flow-limiting orifice was installed on the pipeline; however, during the punching tests, the amount of nitrogen delivered was insufficient and the speed was too low. The deformed rupture disc appears to be a single piece of metal, and it doesn’t seem likely to leak. In Shandong, we also have distillation units designed in Canada; they didn’t include rupture disks, and we don’t understand why the Germans included such disks in their designs. Question: 1. Can a safety valve with a setting pressure of 0.19 Mpa be installed on top of the burst disc? 2. Can this vent be connected to a nitrogen-sealed storage tank designed for a pressure of 0.3 Mpa?
1. Safety valves and burst discs can be used together, depending on the specifications. Since safety valves may experience internal leakage, we generally use them in series with rupture disks, and a pressure gauge is required between them. 2. The theory is acceptable; it is necessary to consider whether the operating pressure exceeds the design pressure of 300 kPa for the tank
Some reactors are also equipped with rupture discs to release gas directly to the atmosphere; since the volume of gas that needs to be released is too large, safety valves cannot be used. Could it be directed to a flare stack instead?
Negative pressure allows the use of no rupture disc. Can your system experience a sudden increase in pressure if the burst disc is not installed?
The use of a rupture disc in such cases is intended to address the situation where the pressure drops below the operating negative pressure, causing the tank to be under suction. However, the outlet side of the rupture disc should be connected to a nitrogen supply; this way, when the rupture disc bursts under negative pressure, sufficient nitrogen flows in, and it does not come into contact with air during bursting under positive pressure. Therefore, it is necessary to know what the backpressure on the outlet side of the rupture disc is, that is, the pressure of the nitrogen supply. A safety valve is not necessary; after the rupture disc fails under negative pressure, a safety valve does not provide a proper seal, allowing air to enter and it may also cause the container to become overpressured.
What to do with pressure-relief containers without rupture discs? There must be requirements regarding the design pressure and negative pressure resistance of containers; otherwise, a rupture disc would not be installed
There is no need to worry about deflation issues, as the equipment design allows it to operate in a complete vacuum
The design is fine; the key issue is that negative pressure should not cause suffocation； After blasting, nitrogen should be supplied promptly ； No safety valve is required.....
The design pressure of the equipment is based on operation under \"full vacuum\" conditions, so there is no need to worry about deflation. Moreover, the original poster has explicitly stated that \"air entering the system can cause an explosion,\" which means that the main purpose of introducing nitrogen through the flow control orifice plates is to prevent the formation of an explosive mixture when air gets in. For vacuum distillation systems, the installation of a positive pressure safety valve (or a combination of a safety valve and a rupture disc) is generally done in consideration of accident scenarios such as fires or excessive heat input to the reboiler at the bottom of the tower. If the pipeline from the vapor phase at the top of the tower to the atmospheric leg of the vacuum system is unobstructed or the valve is set to “CSO”, a positive pressure safety valve is generally not required.
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