Liquid Fuel System Articles

I have seen some articles (for example CCJonline and there are other sites), about water cooled check valve increases the reliability of transfer to liquid fuel when needed.

Are these articles talk about the LF system that has re-circulation and benefited from water cooled check valve?

or are they talking about the system that didn't have re-circulation? because from my understanding they are ways to prevent coking.

1-re circulation
2-water cooled check valve or 3 way valve

but I think if you use water cooled valve without re circulation, you will have a problem which is flow divider binding

In our power plant we use distillate oil. We have 3 way valve, but not water cooled but an ordinary one. We have re-circulation system. Please if anything (Idea) can be added to this system to please share it here.

we have also nitrogen to purge the liquid fuel. but my question when do we used the nitrogen and why nitrogen (I know it is inert gas), but would it be really bad if purged with air?

* please if there are important information that are really necessary to know when studying the system, please share it here. I have a fairly good knowledge about the system though

* If any issue regarding the liquid fuel system that needs to be research, please write it here.

I do have a day job, and it's keeping me quite busy these days. I don't get paid for this gig at, and when I have time I write (some members of my family think I spend too much of my non-work time on

You would have to contact the author of the trade journal articles to get clarification on the circumstances of their writing(s).

Liquid fuel check valve- and three-way valve problems are most usually attributed to non-use--meaning the units are run infrequently on liquid fuel, and when they are (run on liquid fuel) the weakest link in the system are the check- and associated three-way valves. And because when the units are run on liquid fuel there are usually problems, plant management usually don't want to operate very often on liquid fuel--which just makes the problem(s) worse.

The high temperatures in the turbine compartments of F-class units helps to contribute to coking of the liquid fuel which isn't purged from the lines, which results in choking of the check- and three-way valves.

In my personal opinion, it's not logical to think liquid fuel systems can be operated once or twice or even thrice a year for brief periods of time and be expected to be reliable back-ups in the event of loss of gas fuel. There are simply too many moving parts (check valves and three-way valves) located in high-temperature areas which subject the "waiting" liquid fuel in the lines to the effects of high temperature (coking and varnishing). There are some very elaborate liquid fuel recirculation systems which, apparently, have proven to be very effective in increasing the reliability of liquid fuel as a back-up to gas fuel. And, from what I've heard (anecdotally), the water-cooled valves have been very effective, also--at least they haven't increased the problems associated with the valves they replace. There are a LOT of components in the liquid fuel system which aren't controlled by the Speedtronic turbine control system but which must all work as designed and applied in order for the liquid fuel system to be reliable, and when these components aren't regularly exercised and used they suffer intermittent failures and cause liquid fuel systems to be deemed unreliable. When, in fact, it's the lack of operation/exercise that causes the unreliability. There are hundreds of liquid fuel-only GE-design heavy duty gas turbines that run very reliably simply because they only operate with liquid fuel and the components in the system work reliably and as designed. I know of some dual fuel GE-design heavy duty gas turbines that operate primarily on liquid fuel and infrequently on gas fuel and those units are very reliable--again, because the liquid fuel system components are regularly used.

I believe GE recommends at least weekly periodic operation on liquid fuel, and in my personal opinion if liquid fuel is critical to the reliability of the power plant then even that's too long between operation. That's why recirculation systems are more important when liquid fuel system reliability is critical, especially when liquid fuel operation isn't very frequent.

As for nitrogen purging, that's another attempt at removing the liquid fuel from the system to prevent coking (and choking)--but removing the liquid fuel from the lines makes a quick change-over from gas fuel to liquid fuel not so quick.

If liquid fuel operation is critical, a good recirculation system--coupled with frequent liquid fuel operation--is very important. But, that also increases the complexity of the unit auxiliaries and control system.

Lastly, when you really stop and consider that most dual fuel GE-design F-class heavy duty gas turbines use DLN combustion systems to reduce emissions when operating on gas fuel and that when operating on liquid fuel the combustion is primarily diffusion-flame combustion a quick, or relatively quick, change-over from gas- to liquid fuel is a pretty amazing feat all by itself (I'm speaking of a bumpless change-over, or transfer). And, many units require water injection to reduce emissions when operating on liquid fuel, and that's just another level of complexity--and more check- and three-way valves, too!--which makes "quick" gas-to-liquid fuel changeovers even more problematic. (A lot of sites in some parts of the world just don't turn on the water injection system, or if it trips (as it usually does) during a transfer they just don't re-start it.)

Really, these dual-fuel units are marvels of engineering--but they need to be properly operated. Just because they are capable of certain operating conditions doesn't mean they will operate reliably at any time they are called on--and if they are called on infrequently to operate in certain modes, then they just don't seem to do so without a lot of auxiliary equipment and maintenance. Which means more cost, which means more money.

Plant management needs to take the time to understand the complexity of the liquid fuel system and auxiliaries, and if liquid fuel operation is critical to plant operation they need to plan accordingly for regular and frequent change-overs to keep everything in working order. And consider recirculation systems--and possible replacement of OEM-provided check- and three-way valves. The likelihood of plant management enlightening themselves is next to nil, and they don't always rely on their technical staff recommendations. So, a good technical staff leader will have to put together spreadsheets with clear numbers to show the effects of infrequent liquid fuel operation with the effects of regular, periodic liquid fuel operation on reliability and availability--using monetary figures.

I have to get back to my day job--which pays.
Thank you dear CSA,
I really want to thank you for your time and effort. you always elaborate on the topics and never give a short answer.

I wish you all the best.