Seal open and seal close!
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Recently, while studying the process flow diagrams, I found that all the safety valves, rupture discs, and root valves were sealed with lead seals. Valves with lead seals are rare; I have only seen them on flow restriction orifice plates. Has everyone seen where sealed shut and sealed open are used?
Opening and closing lead seals are measures for safety management. A lead-sealed closed valve means that the valve, which is sealed with lead, is closed. \"Car seal open\" means that the valve which was sealed with a lead seal is now open. Valves that are sealed with seals (just like those used for instrument calibration) generally cannot have their status changed arbitrarily; if such a change occurs, the seal will be damaged, and it is necessary to keep relevant records and re-seal the valve.
There’s no need to talk about things that can be found online with just a quick search; it’s obvious that the person above copied it from the internet. I hope everyone can share the devices on which they have seen lead seals being opened and closed.
LZ has provided a fairly comprehensive summary. All I’ve seen are safety valves and burst discs, which were sealed using lead seals； It seems that it isn’t really used very often.
Actually, I mainly want to know where lead seals are used and what the basis for their use is I hope someone knowledgeable can provide an answer.
Most of the valve devices I have come across were sealed with lead seals; they are mainly root valves for safety accessories in pressure vessels； According to the old version of the Safety Regulations, no valves are allowed to be installed between the safety accessories and the equipment interfaces. However, after years of actual operation, this requirement is not feasible in the equipment and pipelines of some production facilities ； A continuous production process cannot be halted due to the regular calibration of a safety accessory; therefore, the current approach has been adopted, whereby a root valve can be installed on such accessories, but it must remain in an open position and be sealed with a lead seal. I’ve never dealt with valves that are sealed with lead seals; I’m wondering if they were installed due to requirements of the process/instrument control system Personal opinion, for reference only!
A lot has been said upstairs; the lead seals I’ve come across were on the boiler feed water pumps. What is connected to it behind is a flow-limiting orifice plate, leading to the steam drum. I’ve never understood what his seal is for; I hope someone can explain to me its purpose.
Based on what you’ve described, this lead-sealed valve should be on a bypass pipeline (? ), its function can be understood as follows: under normal conditions, the \"flow control orifice plate\" is not used, and the boiler feed pump supplies water to the steam drum at a normal flow rate; therefore, this valve is normally in a closed state (sealed with lead) ； It is opened in an abnormal state, causing the water that should enter the steam drum at a normal flow rate to be reduced in volume after passing through a flow limiter.
My pump outlet also has a control valve; using it is more convenient than using a flow-limiting orifice plate.
There is an issue with the adjustment range of the control valve; perhaps the flow-limiting range of the orifice plate falls outside this adjustment range? ! Perhaps a calculation using the flow restriction orifice plate can lead to a conclusion? After all, the designer must surely have their own design concepts!
I understand: generally, the outlet of a pump has a flow rate limit to prevent cavitation. Therefore, when the flow rate is very low, using a throttling version helps to stabilize the flow at the pump outlet while also reducing the circulation volume.