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Vacuum Gauge Relocation
Vacuum gauge/manometer is located far from mist eliminator

In frame 6B, 30 MW machine vacuum gauge/manometer is used for monitoring vacuum of main lube oil tank of gas turbine. This meter is currently mounted on the accessory compartment wall outside the compartment. But it is located little far from mist eliminator and is not visible while standing in front of mist eliminator and maintaining vacuum. Currently length of tubing from MOT to vacuum gauge is about 2-3 meters.

I asked instrument engineer to relocate the gauge nearer to the Mist eliminator by extending its tubing from MOT. But he said that it is not feasible because it will be a more distance for proper measurement of vacuum through manometer and vacuum will not be measured correctly.

Is it correct?
if it is correct then what is permissible distance?
and is there any other solution to this?

1 out of 1 members thought this post was helpful...

Really? An instrument engineer said that?

That is incorrect. In fact, a long run of small tubing will affect the reading more than if the gauge/manometer was mounted directly on the Mist Eliminator.

Get another gauge/manometer, put a tee in the tubing, and mount the new gauge/manometer on the Mist Eliminator near the throttle valve. That way the operators can see the gauge on the Accessory Compartment door without having to climb on the Mist Eliminator (it's all about operator convenience, anyway).

The operators would actually prefer a pressure/vacuum or differential pressure transmitter connected to the turbine control system so they could occasionally see the value on the HMI without having to leave their chair in the air conditioned Control Room....

thanks a lot..

i am confused with line
Long run of small tube
does it mean long time use of small (in length) tubing from MOT to gauge?
also the role of tee is confusing?


Apparently, I didn't properly understand the TLA (Three-Letter Acronym) MOT, mistaking it for the Mist (Eliminator) Oil Tank.

A long run of tubing can adversely affect the reading of a gauge, especially when we're taking about very low pressures/vacuum readings. Losses in the run can cause sudden changes in pressure to not seem as sharp, and can also cause a drop in the reading at the gauge. I was thinking the gauge/manometer was connected to some tap on the Mist Eliminator--not the Main Oil Tank. So, I was suggesting putting a tubing tee on the tubing coming out of the Mist Eliminator and adding a local gauge/manometer on the Mist Eliminator.

You can add a tubing tee to the existing tubing between the existing gauge/manometer and run a length of tubing over to the Mist Eliminator and mount a gauge/manometer where it's easier to see on the Mist Eliminator. I recommend tubing on the order of 3/8" or so (sorry; I don't have my metric converter for tubing sizes at this writing). Also, the tubing run should be pitched (sloped) back toward the tee, and the tubing tee should be below the existing gauge/manometer so that any condensation (oil vapors do condense!) will run back to the Main Oil Tank and not into the existing gauge/manometer.

Sorry for any confusion. (It greatly helps me, and probably others, when people explain the first usage of any acronym; it only has to be explained once in the thread (at the first usage).)

Completely agree with CSA.

In addition generate a MOC and install one vacuum transmitter and watch from control room.

Do not tap the tube elsewhere than MOT.