Can a safety valve be equipped with a manual valve?
Thread Content
Can hand valves be installed before and after the safety valve? Under normal conditions, the manual valve is locked in the open position; it is only closed during maintenance
If there are relevant regulations, I remember it seems that it’s not allowed, but I’m not sure.
The rule is that it’s not allowed, as there is a concern that it might affect the operation of the safety valve. However, most manufacturers, especially those dealing with pressure vessels that contain toxic or hazardous substances, install manual valves to ensure safety; otherwise, it would be impossible to disassemble, inspect, or service the safety valve, which in turn affects production
It is generally not allowed to install valves, but in special situations (such as calibration or maintenance), valves can be installed. However, during production, they must be kept fully open, with a lead seal in place to ensure this state is maintained. Our unit has been using it this way.
It wasn’t allowed before, but later (in 2000? ) After that, they asked to add it; anyway, we did add it
It should be installed; otherwise, the safety valve cannot be serviced online
It would be prohibited according to design safety specifications; however, due to requirements from companies such as Sinopec for regular calibration, a valve is generally installed at the inlet of the safety valve. If it leads to a flare system, another valve is also required after the valve, but this one needs to be kept in an open position.
It is indeed possible; nowadays, many newly designed projects include a manual valve in front of the safety valve for online maintenance or replacement of the safety valve. I also think this is necessary, as it contributes to safer production.
Some of ours have it and some don’t; those that do have it must be fully sealed with lead seals.
A safety valve can be equipped with a manual valve, but the prerequisite for this is to have a backup safety valve; in other words, two safety valves are used in parallel. In such cases, it is possible to install a manual valve and keep it sealed with a lock in an open position. This practice is quite common abroad, as it meets both the requirements of long-term production and safety considerations.
The rule states that it’s not allowed, but in practice it seems that they are added anyway; however, the valve that is added must remain open at all times. Here, we require that the valve in front of the safety valve must remain open at all times, be sealed with a lead seal, and have a sign indicating that it is to stay open. And monthly inspection records are required.
This issue has been discussed before; please make use of the search function on the forum: http://bbs.hcbbs.com/viewthread.php?tid=123903&highlight=%B0%B2%C8%AB%B7%A7
The requirements for installing safety valves are as follows: 1. Safety valves should be installed vertically, and they should be placed in the gas space above the liquid level of the pressure vessel, or on a pipe connected to the gas space of the pressure vessel. 2. The cross-sectional area of the connecting fitting between the pressure vessel and the safety valve must not be smaller than that of the safety valve’s inlet; moreover, such connecting pipe should be as short and straight as possible. 3. When two or more safety valves are installed on a connection port of a pressure vessel, the area at the inlet of that connection port shall be at least equal to the total cross-sectional area of the inlets of these safety valves. 4. It is generally not advisable to install stop valves between the safety valve and the pressure vessel. To enable online calibration of safety valves, a burst disc device can be installed between the safety valve and the pressure vessel. For pressure vessels containing media with extremely high, high, or moderate toxicity, flammable media, corrosive or viscous media, or valuable media, in order to facilitate the cleaning and replacement of safety valves, a shut-off valve may be installed between the safety valve (rupture disc device) and the pressure vessel, provided that it is approved by the technical responsible person in charge of pressure vessel safety at the operating unit and that reliable preventive measures are put in place. During the normal operation of the pressure vessel, the stop valve must remain fully open (sealed or locked). The design and diameter of the stop valve must not interfere with the safe discharge function of the safety valve. 5. The installation location of the safety valve should facilitate inspection and maintenance.
The current standards allow for this; gate valves are commonly used, but they must be fully open and sealed with lead seals, and the upstream and downstream manual valves must not be operated while the device is in operation
In our factory, some units are equipped with manual valves to facilitate shutdown and maintenance; others do not have such valves
Currently, domestic design institutes install both a front valve and a rear valve on safety valves, which has both advantages and disadvantages. The advantage is that if the safety valve fails to return to its original position after activating, the front valve can be closed, which facilitates maintenance. The downside is that after maintenance, the front valve or the rear valve is often neglected. However, foreign designs generally do not have front and rear valves; this might be because foreign designers place a high priority on safety, always giving it top priority. My suggestion is that safety valves can be installed both at the front and back, but labels should be placed on them or records kept regularly to ensure that production can continue always under safe conditions.
The CLG is designed to be added, but the manual valve must be sealed with lead
It can be installed, and it seems that the petrochemical industry even issued a regulation requiring its installation
Some of the safety valves in our workshop are equipped with hand valves while others are not. Hand valves are generally installed on those handling particularly hazardous substances. For safety valves that are installed side by side, one in use and one as a backup, hand valves are also provided for each of them. The hand valves attached to safety valves must be clearly marked with the warning “Do not close””