【Weekly Topic】Discussion on whether a valve should be installed in front of the safety valve (third week of June)
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The last edit to this post was made by zxf760718 on 2015-6-15 at 11:01. In June, some companies begin their annual maintenance work due to a weak market; one task that must generally be carried out at this time is the calibration of safety valves. Most equipment can be shut down for the calibration of safety valves during system maintenance. However, in the case of utility systems, tasks such as system purging are also required during maintenance; if the maintenance time is relatively short, it is not possible to shut down the equipment, and thus the safety valves cannot be removed. To test the safety valve, some people say that the problem can be solved by adding another valve in front of it, right? However, in accordance with the relevant requirements of the \"Regulations on the Safety Inspection of Pressure Vessels,\" it is not recommended to install a valve in front of the safety valve for systems that are non-toxic, have low pressure, and low temperature. This leads to this week’s topic: This week’s topic: Can valves be installed on all safety valves beforehand? Why? We welcome everyone to actively participate in the 【Collection of Essential Knowledge for the Machinery Forum】 http://bbs.hcbbs.com/thread-1389197-1-1.html. Topics for each week and daily questions are being sought (prizes available for participation) http://bbs.hcbbs.com/thread-1373282-1-1.html
Personally, I think it’s fine. All the safety valves in our factory are equipped with valves, and this is done to facilitate maintenance – it makes it easier to remove them for testing or repair, and it also serves as a means of isolation. The relevant requirements in the \"Regulations on the Safety Supervision of Pressure Vessels\" should take into account the potential safety risks associated with valves being closed or getting stuck; this is just my personal opinion though.
This is extremely necessary; as mentioned on the second floor, when there is a leak in the safety valve or when it needs to be inspected and calibrated, isolation can be carried out； It is only necessary to exercise strict control over the installation of the front valve during the production process; if needed, special records can be kept or appropriate warning signs can be installed, such as “Do Not Operate” and “Always Open”!
Personally, I think it’s not possible. A safety valve is installed to prevent explosions in the pipeline as well as accidents involving people and equipment, which could occur due to excessive pressure inside the pipeline. When the pressure inside the pipeline exceeds the set value of the safety valve, it will activate to release pressure. If a valve is installed in front of the safety valve, once this valve closes, the safety valve loses contact with the piping system and cannot operate when pressure increases in the pipes, which could lead to serious accidents. Therefore, no other valves should be installed in front of the safety valve. **The standards set requirements: The Regulations on Safety Technical Inspection of Steam Boilers stipulate that: Article 137 The safety valve shall be installed vertically, at the highest point of the boiler drum (shell) or the header. No steam extraction pipes or valves shall be installed between the safety valve and the boiler drum (shell), or between the safety valve and the header.
Safety valves are basically equipped with manual valves; the primary purpose is to maintain a constant pressure during production, and the second purpose is to facilitate maintenance. If the safety valve leaks internally or fails to return to its original position after activating, and if there is no isolation valve, it will inevitably affect production; operations must be halted for repairs, resulting in significant losses. Therefore, I believe a manual valve must be installed in front of the safety valve; proper daily maintenance is essential – the manual valve must be kept fully open, sealed with lead seals, and inspected before signing off.
It seems fine; this is all done to facilitate maintenance – it makes testing and repairs easier, and it also serves as a means of isolation. However, proper management is necessary in daily operations: the manual valves must be fully opened, and checks must be carried out with corresponding signatures.
If a spare safety valve is available, an isolation valve should be installed to allow the safety valve that needs to be inspected to be removed while under pressure. If there is no spare safety valve, and the system must be drained when maintenance is required, then installing isolation valves becomes meaningless; in fact, such valves increase the risk. When the safety valve needs to be maintained or calibrated, personnel on site tend to avoid draining the system and instead simply close the isolation valves, allowing the system to continue operating under pressure, which is very dangerous.
It can be added; when changing the safety setting, it can be turned off and then manual pressure relief can be adjusted. If it has dual safety valves, they will all be added
It is very necessary to install a manual valve in front of the safety valve. When the safety valve needs to be repaired or calibrated, if there is no manual valve, how should leaks or overdue inspections of the safety valve be dealt with?； To prevent accidental operation of the manual valve, it can be sealed with a lead seal!
This post was last edited by zxf760718 on 2015-6-15 10:53