Hi all,
I am working on a HAZOP scenario regarding the rod packing seal failure of our reciprocating compressors.
We have a few recips is our LNG plant, stabilization unit. The compressors have lubricated rod packing seal. The HAZOP scenario is failure of the lubricator, loss of lubrication, accelerated packing failure to the point of excessive leakage to the distance piece.
API 618 requires a DN 40 vent connected to each distance piece, also requires the vendor to confirm this is sufficient for the seal failure (which we don’t have, the compressors are ~40 years old, probably vendor never asked at the time).
API 521 recommends modelling the clearance between the stuffing box and rod as an orifice plate. This turned out to be extremely high. To vent such a huge amount of gas a 6” vent connection is required on the distance piece. I have never seen such a huge vent connected to a recip. It seems to be overly conservative.
Now the question is that how much leakage should we expect from a failed seal? Is there any diagram to show the packing seal leakage over the time? I understand that API 521 method is correct if the entire packing rings inside the stuffing box is wiped out, but that is very unlikely, it may happen over a very long time that the seal is not inspected or maintained, but nothing that happens over the night.
Is anyone aware of a study on the rod packing seal leakage and failure in different modes?
Thank you
I am working on a HAZOP scenario regarding the rod packing seal failure of our reciprocating compressors.
We have a few recips is our LNG plant, stabilization unit. The compressors have lubricated rod packing seal. The HAZOP scenario is failure of the lubricator, loss of lubrication, accelerated packing failure to the point of excessive leakage to the distance piece.
API 618 requires a DN 40 vent connected to each distance piece, also requires the vendor to confirm this is sufficient for the seal failure (which we don’t have, the compressors are ~40 years old, probably vendor never asked at the time).
API 521 recommends modelling the clearance between the stuffing box and rod as an orifice plate. This turned out to be extremely high. To vent such a huge amount of gas a 6” vent connection is required on the distance piece. I have never seen such a huge vent connected to a recip. It seems to be overly conservative.
Now the question is that how much leakage should we expect from a failed seal? Is there any diagram to show the packing seal leakage over the time? I understand that API 521 method is correct if the entire packing rings inside the stuffing box is wiped out, but that is very unlikely, it may happen over a very long time that the seal is not inspected or maintained, but nothing that happens over the night.
Is anyone aware of a study on the rod packing seal leakage and failure in different modes?
Thank you