K
I would like to know if its essential to have a bypass with flow orifice on the lube oil overhead or rundown tank filling line.And if its not there what are the advantages or disadvantages in terms of machine reliability.
M
maint
please i have question about your topic
why the lube oil tank level take the the actual level from top of tank by inch.
Thank You
why the lube oil tank level take the the actual level from top of tank by inch.
Thank You
K
Kolindrekar
sorry I didn't get your question. Can you put it in other words? It confusing "actual level from the top of tank by inch"
S
Seen
i am sorry nobody answer i think this reason for lube oil drain: if you have Heat exchanger inside the tanks the leak will drain inside tank and to easy detect the leak. i hope this answer i hopeful with others thanks
GE-design heavy duty gas turbines usually use the bottom of the top of the L.O. Tank (i.e., the "ceiling" of the tank) as the reference point for measuring the level in the tank, and then measure to the top of the L.O. The tank conditions (Full, Half Full, Empty, Alarm, etc.) are all relative to the level of L.O. from the bottom of the top of the tank.
The usual method of measuring an oil tank level is with some kind of "dipstick", but when the turbine is running there is a lot of turbulence in the tank and this method isn't very reliable or repeatable.
Also, sometimes the dipstick is a piece of wood, and that wood can be any kind of wood or even a piece or metal or pipe, and can have been used for many different "dipping" applications, or be covered with dirt. (People will do some very unusual things when trying to determine a L.O. tank level in an emergency, which is when they usually pay attention to the tank level, <b>after</b> a Low Level alarm has been annunciated. They will usually grab the first "stick" they can find and then find the first opening they can find in the top of the tank and "dip the stick" into the L.O. And, then when they go to the L.O. Tank system drawing (the Piping Schematic, or P&ID) they will usually find the level is measured from the bottom of the top of the tank. Which just infuriates them!)
Look, when something is being measured the point of reference can be any point. In this case, the designers chose to use the bottom of the top of the tank as the reference, and measure to the top of the liquid level in the tank.
So, if this doesn't suit the needs of the site, then all that need be done is to use a clean and dedicated dipstick inserted until it touches the bottom of the tank, and make a mark on the stick at the bottom of the top of the tank. Then make marks at the distances shown on the Piping Schematic Drawing for Full, Half Full, Empty, Alarm, etc. measuring down from the mark made at the bottom of the top of the tank.
This stick can then be used in the future to "stick" the tank (from the same entry/opening!) and determine the level measuring from the bottom of the tank to the top of the wet mark on the stick. The stick should be cleaned (wiped dry) after each use, and stored in a clean, dry environment, and probably wiped clean again before any reinsertion.
Of course this method will not work very well when the unit is running, again, because there is a lot of turbulence in the tank with all the L.O. pumps off and the turbine shut off. But, a really motivated crew will establish a level in the tank (say Full) and then start the turbine and tank another measurement with the stick, say on the opposite side of the stick used for the "quiet" measurement. And that will be the "running" measurement which corresponds to Full. And then make marks at the distances below that mark for Half Full, Empty, Alarm, and so on.
All of this should be done with the L.O. at a relatively warm temperature, because as we all know, oil expands with heat.
One site uses a plexiglass "tube" for measuring the L.O. Tank level. They had a rubber cork on a string attached to the top of the tube and had made the appropriate marks on the tube as above. They would lower the tube slowly into the tank, allowing it to touch the bottom of the tank, then plug the top of the tube with the rubber cork (the cork was smoothed to match the diameter of the tube), and withdraw the tube carefully and vertically noting the level in the tube. This helped with repeatablility issues when the turbine was running and there was lots of turbulence in the L.O. tank.
There are probably other variations. Some sites use differential pressure measurements, and that can be done after the level from the bottom of the tank is established relative to the level from the bottom of the top of the tank. But, all of this involves forethought and planning, so that this can be done before the L.O. Tank Level Low alarm is annunciated and people start scrambling to determine the actual level in the tank.
Perhaps otised can shed some light on the precise reason why the bottom of the top of the tank was chosen as the reference point.
The usual method of measuring an oil tank level is with some kind of "dipstick", but when the turbine is running there is a lot of turbulence in the tank and this method isn't very reliable or repeatable.
Also, sometimes the dipstick is a piece of wood, and that wood can be any kind of wood or even a piece or metal or pipe, and can have been used for many different "dipping" applications, or be covered with dirt. (People will do some very unusual things when trying to determine a L.O. tank level in an emergency, which is when they usually pay attention to the tank level, <b>after</b> a Low Level alarm has been annunciated. They will usually grab the first "stick" they can find and then find the first opening they can find in the top of the tank and "dip the stick" into the L.O. And, then when they go to the L.O. Tank system drawing (the Piping Schematic, or P&ID) they will usually find the level is measured from the bottom of the top of the tank. Which just infuriates them!)
Look, when something is being measured the point of reference can be any point. In this case, the designers chose to use the bottom of the top of the tank as the reference, and measure to the top of the liquid level in the tank.
So, if this doesn't suit the needs of the site, then all that need be done is to use a clean and dedicated dipstick inserted until it touches the bottom of the tank, and make a mark on the stick at the bottom of the top of the tank. Then make marks at the distances shown on the Piping Schematic Drawing for Full, Half Full, Empty, Alarm, etc. measuring down from the mark made at the bottom of the top of the tank.
This stick can then be used in the future to "stick" the tank (from the same entry/opening!) and determine the level measuring from the bottom of the tank to the top of the wet mark on the stick. The stick should be cleaned (wiped dry) after each use, and stored in a clean, dry environment, and probably wiped clean again before any reinsertion.
Of course this method will not work very well when the unit is running, again, because there is a lot of turbulence in the tank with all the L.O. pumps off and the turbine shut off. But, a really motivated crew will establish a level in the tank (say Full) and then start the turbine and tank another measurement with the stick, say on the opposite side of the stick used for the "quiet" measurement. And that will be the "running" measurement which corresponds to Full. And then make marks at the distances below that mark for Half Full, Empty, Alarm, and so on.
All of this should be done with the L.O. at a relatively warm temperature, because as we all know, oil expands with heat.
One site uses a plexiglass "tube" for measuring the L.O. Tank level. They had a rubber cork on a string attached to the top of the tube and had made the appropriate marks on the tube as above. They would lower the tube slowly into the tank, allowing it to touch the bottom of the tank, then plug the top of the tube with the rubber cork (the cork was smoothed to match the diameter of the tube), and withdraw the tube carefully and vertically noting the level in the tube. This helped with repeatablility issues when the turbine was running and there was lots of turbulence in the L.O. tank.
There are probably other variations. Some sites use differential pressure measurements, and that can be done after the level from the bottom of the tank is established relative to the level from the bottom of the top of the tank. But, all of this involves forethought and planning, so that this can be done before the L.O. Tank Level Low alarm is annunciated and people start scrambling to determine the actual level in the tank.
Perhaps otised can shed some light on the precise reason why the bottom of the top of the tank was chosen as the reference point.
Sorry - I plead ignorance on this one. I was a controls engineer on the Speedtronic controls in the Mark I, Mark II and Mark IV period, but reference point for full LO tank is not something I ever needed to know. I had to interface with the level switches, but the settings were done by the LO systems engineers.
Hey; it was worth a try. We all have some unrelated trivia stored in our heads which can be useful from time to time.
At any rate, we're not really answering the original post. I didn't really understand the post anyway.
Kolindrekar, from what I can discern from your post, you are asking for some kind of analysis of adding a second filling line with an orifice. But, you haven't explained the problem, real or perceived, that you are trying to solve or prevent. You haven't provided enough information about the system you want to implement.
It's been said many times before: When you own the unit and it's no longer under any warranty, you are free to make any changes you can take responsibility for. If you can justify any changes you want to make, then you are free to do so. As long as you understand that you are responsible for any consequences.
It's that simple. If you work out that the change solves a problem, real or perceived, and you feel you have analyzed all the consequences and the change still meets your requirements, you own the unit and can make whatever changes you see fit.
At any rate, we're not really answering the original post. I didn't really understand the post anyway.
Kolindrekar, from what I can discern from your post, you are asking for some kind of analysis of adding a second filling line with an orifice. But, you haven't explained the problem, real or perceived, that you are trying to solve or prevent. You haven't provided enough information about the system you want to implement.
It's been said many times before: When you own the unit and it's no longer under any warranty, you are free to make any changes you can take responsibility for. If you can justify any changes you want to make, then you are free to do so. As long as you understand that you are responsible for any consequences.
It's that simple. If you work out that the change solves a problem, real or perceived, and you feel you have analyzed all the consequences and the change still meets your requirements, you own the unit and can make whatever changes you see fit.
K
Kolindrekar
Hi CSA
Thanks for your comments.
Actually my post is about Lube oil rundown tank. Run down tank supplies oil to the bearings in the event of lube oil pump failure (mostly due to power failure or so). Rundown tank is filled after lube oil pump start prior to start up the compressor. In fact run down tank level is one of the start permissive and it must be full.
Now my question is about filling line. Once the run down tank is full the oil inside remain stagnant and over a period the temperature of that will be equal to ambient temperature and could be as low as 10 deg.(depend upon the region and climatic conditions)
So in the event of lube oil pump failure oil from the rundown will be supplied to the bearings.
such a low temperature it may give thermal shock to bearings. So is it advisable? or what could be the other impacts?
Thanks for your comments.
Actually my post is about Lube oil rundown tank. Run down tank supplies oil to the bearings in the event of lube oil pump failure (mostly due to power failure or so). Rundown tank is filled after lube oil pump start prior to start up the compressor. In fact run down tank level is one of the start permissive and it must be full.
Now my question is about filling line. Once the run down tank is full the oil inside remain stagnant and over a period the temperature of that will be equal to ambient temperature and could be as low as 10 deg.(depend upon the region and climatic conditions)
So in the event of lube oil pump failure oil from the rundown will be supplied to the bearings.
such a low temperature it may give thermal shock to bearings. So is it advisable? or what could be the other impacts?
So, what you were really asking in your original post was about adding a "drain line" with a small orifice to have a continuous flow of oil out of the rundown tank, which would mean that warmer oil would replace the oil in the tank to maintain the level, in an effort to keep the tank temperature above ambient.
I've never considered the thermal stress caused by "suddenly" introducing lube oil at a lower temperature to bearings at a high temperature. I would have to think the designers of the system have considered this and have deemed it not to be a problem. But, sometimes things like this do get overlooked.
I would think the larger problem would be that suddenly introducing oil of a lower temperature, with a higher viscosity, would cause elevated vibration levels which would be of greater concern than thermal stresses.
Rather than adding this line, how about considering using a combination of insulation and the same kind of heating wiring used on pipes in cold climates. It's relatively inexpensive; it's "flexible"; it runs on "low" voltage (110/220 VAC). I've seen some very good "calculators" on some of the manufacturer's websites which might be used to calculate how much of this heating line would be necessary to maintain a desired temperature. Also, the sellers of this kind of heating wiring could be contacted to assist with calculating the amount of wiring needed to maintain a certain temperature.
You would be heating the outside of the tank; no heat exchanger inside the tank. It would be a relatively small current requirement. It could have a thermostat for on/off based on temperature.
Again, if you own the machine you are free to make whatever changes you are willing to take responsibility for. This modification seems fairly innocuous, but this is a "safety" system (the L.O. Rundown tank) so any change to the piping should be carefully considered.
I've seen insulated rundown tanks, but I don't recall if they were "heated". I imagine in some very cold climes (Canada; Alaska) they were but I wasn't involved with commissioning the compressors. I just needed the 'Rundown Tank Level Normal' indication for a start-check permissive for the turbine!
I've never considered the thermal stress caused by "suddenly" introducing lube oil at a lower temperature to bearings at a high temperature. I would have to think the designers of the system have considered this and have deemed it not to be a problem. But, sometimes things like this do get overlooked.
I would think the larger problem would be that suddenly introducing oil of a lower temperature, with a higher viscosity, would cause elevated vibration levels which would be of greater concern than thermal stresses.
Rather than adding this line, how about considering using a combination of insulation and the same kind of heating wiring used on pipes in cold climates. It's relatively inexpensive; it's "flexible"; it runs on "low" voltage (110/220 VAC). I've seen some very good "calculators" on some of the manufacturer's websites which might be used to calculate how much of this heating line would be necessary to maintain a desired temperature. Also, the sellers of this kind of heating wiring could be contacted to assist with calculating the amount of wiring needed to maintain a certain temperature.
You would be heating the outside of the tank; no heat exchanger inside the tank. It would be a relatively small current requirement. It could have a thermostat for on/off based on temperature.
Again, if you own the machine you are free to make whatever changes you are willing to take responsibility for. This modification seems fairly innocuous, but this is a "safety" system (the L.O. Rundown tank) so any change to the piping should be carefully considered.
I've seen insulated rundown tanks, but I don't recall if they were "heated". I imagine in some very cold climes (Canada; Alaska) they were but I wasn't involved with commissioning the compressors. I just needed the 'Rundown Tank Level Normal' indication for a start-check permissive for the turbine!
C
curt wuollet
It may chill the bearings, but it's much better than the alternatives. And I'm not even a turbine jockey.
Regards,
cww
Regards,
cww
H
Habib
I saw always the lube rundown tank with continuous overflow line to keep the oil temperature suitable for lubrication and fresh.
While line I saw two types.
1. With NRV to supply oil from rundown tank to machine. While filling is done by separate line with orifice, while one bypass line is there to fill up quickly at the time of startup. In normal condition this start up valve remain closed.
2. with NRV to supply oil from rundown tank to machine with built in orifice for continuous flow and overflow from rundown tank to reservoir tank. While bypass line is there to fill up rundown quickly during start up.
In both cases purpose is same ,there is not any big difference .
The orifice can be a separate line or built in in the NRV for continuous flow.
While line I saw two types.
1. With NRV to supply oil from rundown tank to machine. While filling is done by separate line with orifice, while one bypass line is there to fill up quickly at the time of startup. In normal condition this start up valve remain closed.
2. with NRV to supply oil from rundown tank to machine with built in orifice for continuous flow and overflow from rundown tank to reservoir tank. While bypass line is there to fill up rundown quickly during start up.
In both cases purpose is same ,there is not any big difference .
The orifice can be a separate line or built in in the NRV for continuous flow.
