Gas Header Pressure Balance

How many kilometers long is a DN50 line that adds 12 m³? What is the size of the original line that basically parallels the new line? Can you reroute the short GT inlet lines so they are near to each other along the main header, thereby minimizing the pressure differences? (The graphic isn't very clear, but lots of drawings seem to be grayed out on CR4.)

My bad..

it was 12 % not 12 m3.

Then the original header looks like DN150 (or maybe DN125). In either case, I don't think a DN50 supplemental line will help much.

DN150 reduces to DN100..

I can't tell you if your balancing header solution will remedy the situation the way you intend without a bit more info.

Here is the way I would approach your situation...

1) Are the fuel valves for turbines 3 & 4 modulating or wide open? If they are modulating, then increasing the supply pressure would be a waste.

2) If the valves are not modulating what is the supply pressure? (also what is the approx gas demand for each turbine?)

A side note to 1... I have helped out a plant with a similar situation. In that situation, the turbine's fuel valve was wide open and the operators and management didn't like the situation (a trip in another unit would cause a spike in gas pressure and likely overspeed/trip the still running one... that was their thought anyhow). The solution was to simply reduce the supply TEMPERATURE of the gas, and hence the viscosity was reduced just enough to allow the valve to modulate and give them back control.

So this would lead to question 3) Is your goal to increase power output or just maintain control?

Instead of adding a new circuit for potential leaks, why not move the supply point to the center of the two turbin manifolds? This will act to stabilize the pressure differential between the two manifods. Since the CNG flow wil be equal, on both manifolds, you have the additional advantage of having a spare regulator.

I looked at the drawing (the link you provided is clear).

The drawing is amateurish and poses some questions:

Why there are to reducers shown on some places:

DN150 to 100 on one line shows a reducer (I thing tha is what you draw(??), and just a normal connection from DN150 to DN 100 going to another reducer from 100 to 80 towards GT-4 while nothing is shown for the GT-3 except the mention that the pipe becomes DN80..?

Instead of Zigzaging the line drawing, just make a straight line and print the length (Approx) of each branch on the side of the line. Show all the reducers with symboles or omit them all otherwise we are confused about what the symbole really means!

The balancing line of DN50 might help but I can't say how much. It is not really possible unless you provide the length of the pipings for each branch.

You might be better off extending the DN150 so that the branching, down stream is more symetrical. Make sure that the compressors are providing enough volume of gas to suit the number of turbines running at the same time.

You could place back pressure regulators in the inlet of each compressor so that the pressure is the header is uniform and balance the loads, so that they take uniform quantities from the headers. It needs decoupled pressure control loops to work optimally

Seasons greetings to all,

Referring to the post there is a whole slew of information required before a sensible answer can be given:

1. What are the flow rates to each turbine at full rate.
2. As asked by another contributor what are the lengths of the various sections of pipe.
3. How big is the pressure difference between the compressors. If it's more than a few psi the pipework is undersized. The pressure drop at full load from compressor outlet to turbine inlet should not exceed about 65psi.
4. How are the turbines configured as to load sharing. If turbine 1 is the covers the base and the others provide top up and standby then the pressure at T1 must be lower than at say T4 otherwise there would be no flow to use the pressure difference. If they are set up in the reverse order the pressure difference would be much less.