4 replies to this topic

[bdabhi]

As majority oil & gas industries are using gas turbine for process requirement & this turbo machinery need special attention at the given course of interval based on contenous operation hours or equevalent operation hours , Can any body help to find EOH of Gas turbine.As it is known to me that formula is avaiable based on number of machine trips.Thanks in advance.

[Art Montemayor]

bdabhi:

What is it EXACTLY that you are looking for? "Equivalent Operation Hours" is a term that is new to me, after a lot of years in engineering. I've installed and operated these machines and know that there are a variety of reasons for a gas turbine "trip" - and most of them are not due to the turbine, but to external causes. Therefore, there is no reason for a manufacturer to predict or develop a so-called "formula" for determining what you call an "EOH". Different gas turbine applications call for different risk analysis and a trip out is just one risk. How is it known to you about an "EOH" and the "formula"?

What is the purpose or reason for your query? Obviously you have a concern. Perhaps if you just come out and level with us, telling us that concern, we can help you.

[Zauberberg]

Basically you are asking for turbine operational availability, which is a function of total equipment downtime (per year), and total time (one year). This formula is:

Operational Availability = [Up-time]/[Total time]

Up-time is the total time minus total downtime which includes equipment trips as well.

For more info, go through: http://www.weibull.c...vailability.htm
Also:

http://www.weibull.c...reliability.htm
http://www.weibull.c...tainability.htm

[kkala]

An alumina plant Project (1990) had considered 2 NG turbines of 16 MW each and required "operational availability" = 96% each. The meaning was that each of them could produce 0.96*8760*16=134554 MWh/year; assumed "operational availability" was not the precise term to use. Nevertheless Equivalent Operation Hours (EOH) were probably 0.96*8760=8410 h/y for each NG turbine. And operational availability would be a bit higher than 96% for one gas turbine (see post by Zauberberg).
Loss of 4% of yearly production was due to limited capacity or shutdowns of NG turbine, for any reason caused within the relevant power plant. External reasons were not considered, e.g. loss of NG supply (assumed 24 hours/y max).
As concluded from other cases, this "operating factor" of 96% (another name of it) would be almost same, if diesel was used instead of NG (natural gas). Other fuels could affect it.
Besides different NG turbine models of same capacity can have different "operating factors". This is also assumed for NG turbines of different capacity.

Edited by kkala, 06 March 2011 - 04:35 PM.

[bdabhi]

As Gas turbine maintanence is recommended by OEM based on Equvivalent operation hours(EOH). This EOH is calculated based on normal operatiion hours & number of trips machine had.As each trip is considered to be equal to reduction in normal operation hours because trip adds more stess in turbine metarllurgy resluting in reduction in normal operation hours.Maintance schedule of turbine is designed based on stress genereted in materllury of turbines.
For Example if maintainence shedule is fixed at 4000 EOH means whether is contineous runnnig of 4000 hrs at full load or reduction of contenous runnnig hours less than 4000 hours due to trips to reach as same stress level.

regards