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gas turbine fuel nozzle pressure test
pressure requirement of gas turbine fuel nozzle pressure test

Dear Sirs,

During schedule combustion inspection test of GE FRAME 9 E gas turbine, what must be the value of pressure upto with duel fuel nozzle must be tested for, same is applicable to single fuel nozzle , need to confirm.

This is not really a controls-related problem, but, because when the unit is re-started if there are any higher-than-normal exhaust temperature spreads it usually gets blamed on the control system.

We'll try to help. (I'll never understand how can it be the control system when nothing was changed in the control system, but combustion hardware was removed and replaced, but management and the mechanical department will *always* blame spreads on the control system!)

If you have a GE Frame 9E gas turbine packaged and sold by GE, then you will have a set of service manuals that will describe the testing of the dual fuel nozzles.

In my experience, during Combustion Inspections, fuel nozzles are not normally tested unless there is some reason to suspect problems, or unless there is an attempt being made to flow-test the nozzles to try to match them to try to reduce exhaust temperature spreads.

The latter requires some constant pressure media (usually air or distillate (diesel) fuel, and a means of reasonably accurately measuring the flow-rate of both with some degree of repeatability. I've seen some interesting set-ups which weren't very sophisticated but yielded some good results when properly executed, reducing exhaust temperature spreads significantly. (Of course, this does require extra fuel nozzles to mix and match to try to achieve a well-matched set.)

The biggest thing to pay attention to is proper re-assembly and good visual inspection of components, including any dimensional checks against new components (it's always a good idea to check a set of new components for dimensions, record them, and use them as references for inspections).

Dear Sir,

Thanks for your valuable suggessions,

i just need to confirm flow test of fuel nozzles to be conducted if flow difference across nozzles be > 10%

Flow Variation across nozzles should be less than 2% for Liquid circuits for DLN nozzles. this can be achieved only through a precision flow testing bench for calibration.

I work as a Gas Turbine Fuel Nozzle Technician in a Dubai based Gas Turbine Fuel Nozzle Over haul Facility.

Out of my experience I can say that in Calibration of the nozzles, historically a flow range tolerance of 5% for a set of fuel nozzles has been acceptable in this industry, but for Fr 9E Fuel ports, we need to attain much tighter tolerance .i.e. less than 2%

we need to flow test individually the following spares and calibrate these spares to bring them below 2% except for Atomizing cones which flow variation of 5% is acceptable.

a) Gas tips
b) Liquid tips
c) Atomizing cones

After Flow Testing and Calibrating of above spares (individually), we need to rebuild the tips to the nozzle body by applying proper torque and a Comprehensive flow test on the fuel nozzle gas paths, fuel paths and Atomizing paths has to be performed on assembled condition and calibrate it to OEM Spec. This has to be done in order to minimize the exhaust spread and for Optimum Combustion.

Apart from this, it is not advisable to reuse the consumable items such as gaskets, lock plates & O rings, once the fuel nozzles are dismantled for overhaul it has to replace with new ones.

Ultrasonic chemical cleaning and ultrasonic raw water rinsing is recommended on all the spares which cannot be opened such as fuel cartridges and atomizing cones. this will allow you to reuse the same spares for long period.

For any further technical clarifications contact me. My cell number is 00971 50 2548904


Dear Mr Jais,

Thanks for more details on subject, it will be helpful to us indeed.


Do you know how to test flow the DLN-1 system fuel nozzles?



Most sites send their fuel nozzles out for refurbishment and flow-testing. Qualified shops will have the proper equipment and test procedures.

Be aware that if you find blockages in the secondary/tertiary fuel nozzle orifices of the secondary fuel nozzles that most of them have to be disassembled by "un-welding" welded joints and then welding them back together again. And hoping they don't come apart when the turbine is at rated speed (which has happened). That's another reason why it's a good idea to develop a good relationship with a qualified shop in the region where you're located and send the nozzles out for inspection, repair, refurbishment and flow-testing.

Some things are better out-sourced.

Having said that, if you're trying to understand what a shop does or you want to try to perform your own testing look in the Parts List section of the Service Manuals provided with the turbine and auxiliaries and find the fuel nozzle section and then find the drawings of the fuel nozzles (primary and secondary). Usually, in the upper right-hand corner of one of the sheets is some information which can be used by someone knowledgeable in flow-testing and with the proper equipment to test the nozzles. Some site spend a LOT of money putting together a test set-up for flow-testing nozzles and having a couple of their maintenance technicians get trained to perform fuel nozzle testing. It's not inexpensive, but it can be very helpful.

I've even seen a write-up a few years back in one of the Maintenance volumes of the Service Manuals which described a test rig and test procedure for DLN-I fuel nozzles, but I think that's no longer provided (it was in the early days of DLN-I combustion systems--before the OEM figured out they could make a lot of money on refurbishment and testing of fuel nozzles).

Finally, if you're interested in something other than a typical flow-test which measures the flow-rate through the nozzles at a particular pressure, please describe what it is you're trying to do.

Dear Sir,

We had a GE Frame 9E machine with Dual Fuel Nozzles. We wish to carry out flow test of these nozzles at our Fuel Nozzle testing skid supplied by M/s GE.

The test skid have Liquid Fuel and Gas fuel test skids and having Pressure and Flow rate instrumentation for both fuels.

Since, I'm new and we haven't any detailed procedure for calibration of Dual Fuel Nozzle. I request if you have the testing and calibration procedure, may please share.

Deepak Kumar


There is some very good information about flow-testing of nozzles provided in the responses above.

You do not really "calibrate" fuel nozzles. All you do is test the flow-rate through the assembled fuel nozzle (liquid side and gas side) and note the flow-rate. You want to put in a set of nozzles with the lowest flow-rate deviation from one another, AND when the nozzles are installed you try to put the nozzles with the highest flow-rate deviation the farthest apart from one another, so as to minimize exhaust temperature spreads that might result after the new nozzles are installed.

Some sites find that having nozzles that have no more than a total of 5% flow-rate deviation from one another work fine. Others find that a flow-rate deviation of 2% or less work better, and others are fine with 10% deviation (which used to be the OEM standard for a set of new fuel nozzles).

If the nozzles have been removed from a unit that was experiencing high exhaust temperature spreads or starting problems, using the test "bench" or "skid" can usually help to identify what was the cause of the problem (choking (plugging); enlarged passages caused by wear of the orifice/opening; loose internal assembly; loose external assembly; etc.).

But, one doesn't really calibrate individual fuel nozzles. During testing of re-assembled or refurbished nozzles leaks or assembly problems may be apparent that can be fixed before the nozzles are installed in the unit. But, there's no "adjustment" that can be made to orifice sizes (well, if they're too small then they could probably be enlarged--if you have the proper equipment to do so; but if they're too large then it would require welding them closed and re-drilling the opening to the desired size (this is for circular orifices)).

The Operations & Service Manuals which were provided with the unit should have information in the Maintenance section, where they had drawings of a typical flow test "bench." You could also contact GE to ask if they have instructions for the operation of the equipment they provided. Lastly, as suggested in a previous response to this thread you will probably find in the 'Notes' section of the fuel nozzle drawing in the Parts List section of the manuals provided with the unit, or provided with the nozzles if you have purchased a set from a vendor (or the OEM) some information regarding expected flow-rates and possible testing information. Also, if you have purchased a set of nozzles from a vendor (or the OEM) they probably came with a certificate or some kind of documentation that listed the results of flow-rate testing, and that document may have some detailed information about the pressures and other criteria used for the testing.

Again, when "bench-testing" fuel nozzles, you are primarily looking for a good spray pattern (even spray) and the flow-rate of each nozzle. To obtain the flow-rate it will be necessary to use a consistent pressure for each nozzle; I don't think it needs to be the exact pressure the nozzles will experience in the machine (tens of barg), but it has to be consistent. As you gain more experience with the equipment and the procedures you will develop your own test procedures and criteria.

The 'Notes' section of most parts drawings in the Parts List section of the manuals provided with the unit usually have LOTS of very useful information about clearances and testing, when applicable. Never overlook the 'Notes' section of parts drawings when working with parts, whether it be replacing or ordering parts, or testing parts.

Hope this helps! I would imagine that different test equipment would have different operating instructions, so anything you might obtain from another site with similar equipment might be directly applicable and would have to be modified for your specific equipment. Again, please contact GE for detailed instructions for your skid. Be prepared to provide the part number of the skid when asking for information to speed up the process (as much as it can be sped up...!).

Hello Deepak,

You have conventional or DLN-1 combustion?