Gas / Propane Generators

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fayc11

Member
Location
plymouth ma
Good Morning,

I have (2) NATURAL GAS Caterpillar generators (G3512) 555KW / 208volts

These Generators will also run on propane, KW drops down to 380KW / 208volts

My problem is they won't run on propane.

(2) 1,000 gallon propane tanks in the ground, vaporizer has been replaced twicedue to being outside and weather conditions etc...

When I switch from natural gas to propane, the (1) incoming 2" pipeline starts to frost up, the 2 engines start to rev up and down.

The (1) 2" pipe comes into the building and branches off to feed thegenerators. Each of the engines has their own factory installed regulator.

There is also regulator out at the vaporizer.
Any direction, advice greatly appreciated.
Thank You
 
gadfly56

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
fayc11 said:
Good Morning,

I have (2) NATURAL GAS Caterpillar generators (G3512) 555KW / 208volts

These Generators will also run on propane, KW drops down to 380KW / 208volts

My problem is they won't run on propane.

(2) 1,000 gallon propane tanks in the ground, vaporizer has been replaced twicedue to being outside and weather conditions etc...

When I switch from natural gas to propane, the (1) incoming 2" pipeline starts to frost up, the 2 engines start to rev up and down.

The (1) 2" pipe comes into the building and branches off to feed thegenerators. Each of the engines has their own factory installed regulator.

There is also regulator out at the vaporizer.
Any direction, advice greatly appreciated.
Thank You
Click to expand...

IIRC, when you switch you have to change the orifice/regulator size for generators. This is the same for a variety of propane/NG appliances. I would guess you need a second set of regulators for the propane.
 
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bsmith8691

Member
Location
Ellington, CT
How far are the generators from the fuel source? How many bends? Hunting ( revving up and down)is normally indicative of fuel/air mixture being off. I have spent many years on installing and servicing generators. The 2" line feeding 2 generators doesn't seem adequate as evidenced by the line freezing. That tells me that the draw on that line is extremely high. What is the required water column v.s. the incoming water column? This will also predicate pipe size.

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gadfly56

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
Leaving aside any regulator issues, if the lines are frosting up after the vaporizers, that means the vaporizers are too small. You need more of them or larger ones.
 
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GoldDigger

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Location
Placerville, CA, USA
Occupation
Retired PV System Designer
gadfly56 said:
Leaving aside any regulator issues, if the lines are frosting up after the vaporizers, that means the vaporizers are too small. You need more of them or larger ones.
Click to expand...
And if they are frosting up before the vaporizers, you are not actually supplying liquid to the vaporizers.

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GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
bsmith8691 said:
I forgot to ask......what is the conversion method to go from ng to lp? On most generators, the orifice needs to changed.

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Click to expand...
Typically two things get changed:

1. The orifice(s) in the generator carburetor,
2. The input pressure regulator setting (may be part of generator or external to it.)

In other words, the pressure at which LPG vapor is supplied to the engine will be different from the corresponding NG pressure.
 
Last edited:
kwired

kwired

Electron manager
Location
NE Nebraska
fayc11 said:
Good Morning,

I have (2) NATURAL GAS Caterpillar generators (G3512) 555KW / 208volts

These Generators will also run on propane, KW drops down to 380KW / 208volts

My problem is they won't run on propane.

(2) 1,000 gallon propane tanks in the ground, vaporizer has been replaced twicedue to being outside and weather conditions etc...

When I switch from natural gas to propane, the (1) incoming 2" pipeline starts to frost up, the 2 engines start to rev up and down.

The (1) 2" pipe comes into the building and branches off to feed thegenerators. Each of the engines has their own factory installed regulator.

There is also regulator out at the vaporizer.
Any direction, advice greatly appreciated.
Thank You
Click to expand...
I agree you likely have orifice/regulator issues, possibly failure to change/adjust something when switching fuel type. Output rating is usually higher on same unit when supplied with LP than it is for NG, but you stated it was higher for NG.
 
F

fayc11

Member
Location
plymouth ma

Name plate on Generator... NaturalGas 555kw, Liquid Propane 363kw,

The High Pressure Natural Gas line feeds into one end of the generator engine,has its separate solenoids, it’s on separate regulators etc...

The Liquid Propane Line feeds in on the other end of the generator engine andit has its own separate solenoids, it’s on separate regulators etc...

Caterpillar has told me that it can switch over to propane if we were everrunning and we lost the natural gas line? I would know that because it’s neverrun on propane since the beginning.

The propane line frosts up after the vaporizer

I had a mechanical / plumbing engineer look at it, hesuggested electric vaporizer? Remove the regulators from the generator enginesand just have one regulator out at the vaporizer?
I don’t think Caterpillar will go along with removingregulators from the engine.

If I looked at this backwards…
I got a Cat Generator, runs on propane, 363kw output with propane fuel
What size pipe line needed to feed the engine fora 363kw output?
What size Vaporizer is needed?
The regulator out at the vaporizer is set for? Psi?
The regulator at the engine is set for? Psi?
Is a mechanical / plumbing engineer the best one to call?
Is a Caterpillarengineer the best one to call, (I tried thatand got no where)

 
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