API Plan 13
API Plan 13
(OP)
Hi All,
Quick question..vertical pump does not have back wear rings and balance holes due to high suction pressure..we need full discharge pressure in the seal chamber to maintain the API (30%) vapour pressure margin..I am suggesting API Plan 13 to right choice, however, would you open up the throat bush from 0.010" to 0.025", as we are trying to reduce the pressure drop as much as possible?
One seal vendor stated that the plan 13 flow is not as efficient as the plan 11 as it is directed towards the face etc. He said use a close clearance throat bush and have a plan 14..so we would have a pressure drop across the throat bush going into the seal chamber..there would now be a flow through the plan 11 piping and then the total flow, Plan 11 + Throat bushing flow, would be going back to the suction in the plan 13..does this make any sense? Is this preferable?
Quick question..vertical pump does not have back wear rings and balance holes due to high suction pressure..we need full discharge pressure in the seal chamber to maintain the API (30%) vapour pressure margin..I am suggesting API Plan 13 to right choice, however, would you open up the throat bush from 0.010" to 0.025", as we are trying to reduce the pressure drop as much as possible?
One seal vendor stated that the plan 13 flow is not as efficient as the plan 11 as it is directed towards the face etc. He said use a close clearance throat bush and have a plan 14..so we would have a pressure drop across the throat bush going into the seal chamber..there would now be a flow through the plan 11 piping and then the total flow, Plan 11 + Throat bushing flow, would be going back to the suction in the plan 13..does this make any sense? Is this preferable?





RE: API Plan 13
Use a plan 14, with the 11 connection in the seal chamber. Locate the connection so that it flushes directly across the seal faces.
Small plan 13 orifice, larger plan 11 orifice. Do not change throat bushing clearance, if it is a carbon bearing it can "wash out" or have accelerated wear.
RE: API Plan 13
This has been discussed in other threads in the mechanical seal forum including the one I have attached as a link.
Johnny Pellin
RE: API Plan 13
The last comment in the thread you referencing is the following:
"If the pump is a verticasl turbine style model, than a plan 13 is really all you need. A plan 11 in that situation would provide zero flow as the respective pressures (discharge and seal chamber) would be equal."
That is my question..how are we going with a 14 when the pressure between the throat bush and the impeller, no back wears or balance holes, is full discharge..isnt 13 the only option?
Sorry..I am novice when it comes to this..please dont get frustrated:)
RE: API Plan 13
RE: API Plan 13
You are correct. If the seal chamber must be at full discharge pressure, then you will have no flow through the Plan 11 line. I am assuming that you would be close to discharge, but could still have some differential, even if it was only a pound or two.
If you must have full discharge pressure, then a Plan 13 is all you need. If the pressure drop across the bushing would be a problem, then groove it or drill in bypass holes to allow flow to bypass the bushing
Johnny Pellin
RE: API Plan 13
Thanks very much for the info! Appreciate all the help!
RE: API Plan 13
RE: API Plan 13
I would be much more concerned about how long it takes the vapor pocket at the top of the seal chamber to dissipate. Since the seal faces are probably very close to the high point, the seal faces will be running dry until this area is flooded. Once again, no harm may occur if the bubble is small and is forced out quickly.
It is better to be safe than sorry. Place the vent at the high point and vent the seal liquid full before starting.
Johnny Pellin