How to detect inboard seal failure in multiple Plan 54

[MarceloRS]

We are planning to install one Plan 54 unit dedicated to eight mechanical seals in a Diesel Hydrotreating Unit, but we don't know how to detect the inboard seal failure. Does anybody have similar experience with this?

 

[JJPellin]

We have a similar situation with a set of four Vacuum Tower Bottoms pumps. All four pumps have pressurized double seals that are supplied with gland oil from a common system. We need to know if the inner seal leaks because any gas oil that leaks into the bottoms stream will end up in our cokers. Since gas oil is worth perhaps $20US per barrel more than VTB, any leakage into the process is very expensive. At the inlet to each seal we have an orifice sized to pass the amount of flow that the seal manufacture indicated we need. On the outlet from the seal back to the gland oil system we have a flow meter and a needle valve. The needle valve is adjusted to hold 30 psi positive pressure in the seals (above seal chamber pressure). If the inner seal starts to leak, the pressure in between the seals will drop and the outgoing flow will drop. If the operators pinch down on the needle valve to restore the pressure between the seals, the outgoing flow will drop even further indicating that the additional flow must be leaking into the process. If it was desirable to automate the process, a low pressure alarm could alert you if the pressure between the seals were to drop

 

[Milkboy]

Maybe you are to far down the line for this but you could consider a thermocouple on the Inboard Stationary Seal Ring which would record seal face operating temps and then in the event of a total failure the temp would drop off to meet the pump product pressure in that area.

*maybe* there could be a difference in temps which could be compared across the 8 pumps.
i.e. A 'leaky' seal will have a lower temperature at the face

HTH

-
Milkboy