AIR TANK BOMB(Engine compartment temps)
- Thread starter patrick flowers
- Start date
> Jim,
> The pressure in the tank will vary with the
> temperature in the tank.
> Correct?
> Andy M
> 75 PB
>
>
Yes. Even tho the plastic has some insulating
properties, prolonged exposure to a temperature
variation will affect the air temp in the tank. As
the ambient temp outside goes up, the temp inside the
tank will go up. The plastic will loose integrity and
the air pressure inside will go up. Somewhere, soon,
the two will cross and ????.
Jim 3
75PB MN
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> The pressure in the tank will vary with the
> temperature in the tank.
> Correct?
> Andy M
> 75 PB
>
>
Yes. Even tho the plastic has some insulating
properties, prolonged exposure to a temperature
variation will affect the air temp in the tank. As
the ambient temp outside goes up, the temp inside the
tank will go up. The plastic will loose integrity and
the air pressure inside will go up. Somewhere, soon,
the two will cross and ????.
Jim 3
75PB MN
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>tank will go up. The plastic will loose integrity and
>the air pressure inside will go up. Somewhere, soon,
>the two will cross and ????.
As Tom pointed out, the cost of a new tank is pretty small when compared to
the potential risk of a plastic tank failure. The risk of damage from
failure is somewhat smaller with the plastic tank because PVC normally will
split as the failure mechanism (no shrapnel) although this isn't a
guarantee. Secondly, the mass of a given volume of PVC is much smaller than
an equivalent amount of steel (the normal exploding tank source of
shrapnel) so there's less kinetic energy involved. Still it can be
dangerous (even deadly) if it fails.
If you're going to make a PVC air tank, you need to install an over
pressure valve. This will allow venting of excess pressure as temps go up
in the compartment or where the tank is mounted.
Henry
>the air pressure inside will go up. Somewhere, soon,
>the two will cross and ????.
As Tom pointed out, the cost of a new tank is pretty small when compared to
the potential risk of a plastic tank failure. The risk of damage from
failure is somewhat smaller with the plastic tank because PVC normally will
split as the failure mechanism (no shrapnel) although this isn't a
guarantee. Secondly, the mass of a given volume of PVC is much smaller than
an equivalent amount of steel (the normal exploding tank source of
shrapnel) so there's less kinetic energy involved. Still it can be
dangerous (even deadly) if it fails.
If you're going to make a PVC air tank, you need to install an over
pressure valve. This will allow venting of excess pressure as temps go up
in the compartment or where the tank is mounted.
Henry
> As Tom pointed out, the cost of a new tank is pretty
> small when compared to
> the potential risk of a plastic tank failure.
Henry,
We agree 100%.
Jim 3
75PB MN
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> small when compared to
> the potential risk of a plastic tank failure.
Henry,
We agree 100%.
Jim 3
75PB MN
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Rick,
Don't worry about the 14.7, it works on both sides of the tank so it
cancels out. Your pressure gauge just shows the pressure differential,
which is what we're concerned about here.
Patrick
>
> I assume the pressures are absolute, not "gauge" (eg: "psig"). (Add 14
> and small change psi to your gauge pressure, right?) And I also assume that
> the temperatures are in degrees Kelvin?
> Or am I assuming too much? I'm not an engineer, just a techie. Any of
> you number-crunchers able to enlighten me?
- --
Patrick Flowers
Mailto
atrick
The GMC Motorhome Page
http://www.gmcmotorhome.com
Don't worry about the 14.7, it works on both sides of the tank so it
cancels out. Your pressure gauge just shows the pressure differential,
which is what we're concerned about here.
Patrick
>
> I assume the pressures are absolute, not "gauge" (eg: "psig"). (Add 14
> and small change psi to your gauge pressure, right?) And I also assume that
> the temperatures are in degrees Kelvin?
> Or am I assuming too much? I'm not an engineer, just a techie. Any of
> you number-crunchers able to enlighten me?
- --
Patrick Flowers
Mailto
atrickThe GMC Motorhome Page
http://www.gmcmotorhome.com
>When using that formula to calculate
> pressure change vs.
> temperature, what units does one use?
The formula uses degrees farenheit for temperature and
pounds per square inch for pressure.
Jim
75PB MN
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> pressure change vs.
> temperature, what units does one use?
The formula uses degrees farenheit for temperature and
pounds per square inch for pressure.
Jim
75PB MN
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> Jim,
> I assume the pressures are absolute, not "gauge"
> (eg: "psig").
Rick,
It doesn't matter if the pressure is psig or psia.
All the formula does is point out that the temperature
causes an increase in pressure. The main point we
were trying to make was that as the ambient
temperature increases, the pressure increases. It had
already been pointed out by someone else that as the
ambient temp increases the integrity of the pvc
decreases. Using his numbers and doing a little math
using the formula will point out that the pipe will
probably fail at a much lower temperature than
expected. To use the pipe as a temporary reservoir
would probably be fine, but we would not recommend it
for a working reservoir.
Jim
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> I assume the pressures are absolute, not "gauge"
> (eg: "psig").
Rick,
It doesn't matter if the pressure is psig or psia.
All the formula does is point out that the temperature
causes an increase in pressure. The main point we
were trying to make was that as the ambient
temperature increases, the pressure increases. It had
already been pointed out by someone else that as the
ambient temp increases the integrity of the pvc
decreases. Using his numbers and doing a little math
using the formula will point out that the pipe will
probably fail at a much lower temperature than
expected. To use the pipe as a temporary reservoir
would probably be fine, but we would not recommend it
for a working reservoir.
Jim
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