Start/stop sequence for dry gas seals in pumps
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At present, dry gas seals for pumps mainly come in two structures: double-end face and series type. Double-end face: Composed of two stages of dry gas seals, it represents a true dry gas seal. The flushing scheme is 74; the pressure of the sealing gas is higher than that in the pump chamber, allowing a small amount of nitrogen to enter the pump chamber. The air intake volume is related to factors such as shaft diameter and rotational speed. To use this structure for sealing, it is necessary that the gas pressure be higher than the pressure in the sealing chamber, and that a small amount of nitrogen be allowed to enter the medium. So it isn’t used much. Series dry gas seal: It consists of a mechanical seal and a dry gas seal connected in series; the flushing scheme is 72+75/76. 75 is mainly used for media that are not easily volatile, and it comes with a liquid storage tank to collect the medium that leaks from the first-stage seal. 76 is mainly used for volatile media and media with leaks in the primary seal, which are directly sent to the flare. Start-up and shutdown procedure: For double-ended systems, nitrogen should be introduced first, followed by the use of tank pumps; otherwise, the medium will leak into the seals, resulting in seal failure. Subsequently, the standby pump can be used normally or the pump can be started; in standby mode, a small amount of nitrogen is injected into the pump chamber. In series sealing, nitrogen is introduced first to the pump. Driving can then be resumed, as the sealed gas will not be injected into the pump chamber.
Thank you for sharing. I haven’t had any practical experience in this area, so it’s indeed not easy to understand
Thank you for sharing. When putting the dry gas seal into use, attention must be paid to the sequence
Thank you for sharing. Dry gas seals can easily cause pump cavitation
Some of our clients here also use dry gas seals, and the results are quite good :)
No! The series-connected seal operates at a nitrogen pressure of 0.07 Mpa; I’ve never heard of any case of evacuation occurring due to the use of dry gas seals
You’ll know for sure after giving it a try. The one-time investment isn’t high compared to 52; it’s easy to maintain, convenient to use, keeps the work area clean and environmentally friendly, and performs even better with hydrocarbon-based media!
Well, once you’re used to the operation, it’s fine; subsequent maintenance is simple
There is a question: since the series dry gas seal consists of a mechanical seal plus a dry gas seal, is the inner seal a mechanical seal or a dry gas seal? If the inner seal is a mechanical seal, and leaks from the inner seal are sealed by an external dry gas seal, then isn’t it more economical to use two mechanical seals in series, rather than using just one? After all, when there is a significant leak from the inner seal, a sealing tank is used to collect the leaked material; in order to prevent further leakage, gas from the external seal must flow into this sealing tank, which causes the tank to bubble continuously. It’s better to simply use two mechanical seals in series ； If the internal seal is a dry gas seal, and the medium inside the pump must not be contaminated by gases, then the pressure of the sealing gas used in the dry gas seal cannot be higher than that inside the pump; otherwise, the medium inside the pump will leak into the dry gas seal, thereby damaging it. In general, are series-connected dry gas seals less economical and reliable compared to series-connected mechanical seals?