Gas Turbine Drain Pressure 2

[choack]

Hi,

I just want to ask if there is a chance to have a pressurized gas exiting drain lines of gas turbines?

I'm suspecting turbine casing and the enclosure skid drains.




Christopher Kenneth Choa

 

[racookpe1978]

Well of course it is possible.

Gas pressure builds up inside the compressor staging of the CT (combustion turbine compressor) to 6 to 11 atmospheres pressure - depending on the size and age of your compressor's design. older units could not get to the pressures newer ones do, smaller units won't get as high a pressure as larger units with larger (more) compressor blades.

There are drains (normally shut of course) off of the bottom of the compressor casing at several points. All of these drain points will be pressurized under operation, if there was water (fuel ?) in the casing that water will come out when the drain valve is opened after startup. Once bled dry, there shouldn't be more water coming out unless you are running inlet (cooling) water spray that is not fully evaporating .

There will likely be drain valves under the casing so the power turbine can be drained as well. Possible sources of fluids are un-burned fuel, water spray if you're not running, rain water into an open turbine casing under repair, possibly water coming back down the exhaust stack if you were not running the past day or so. Could be a lube oil leak through a bad bearing seal that sprays into the drained area.

Once the

 

[rmw]

I hope I never encounter a combustion turbine that has any gas build up in the compressor stages.

But it is possible, because downstream of the compressor comes the burner stages, and there are drains of various types associated with the burner equipment especially if it is a dual fuel unit. Is it? If so, the liquid drain line can emit some gas while the liquid manifold is being purged. Normally this is piped to a drain some distance from the turbine.

Another comment is that if you have gas at your skid drains, you may have a gas leak somewhere inside the skid. Be careful.

rmw

 

[racookpe1978]

Now, worse case condition, and one that IS deadly, is a cross-connected pipe between the gas supply (which is pressurized obviously) and some drain line. Unlikely - the fuel piping and ignition piping and rotor cooling air pipes are fabricated so they can't get shouldn't be able to be hooked up wrong - but it has happened when re-assembly is wrong.

Or when re-assembly is "forced" by an over-enthusiastic millwright.

If pressurized liquid is coming out I'd suspect the backup fuel piping or cut-out valves to the backup liquid fuel are leaking. The original poster has not defined his problem (what is his operating conditions are nor what fluid nor when the problem occurs nor for how long it happens.