I am suggesting a translation for you, thoughts and some links.
However, the sentences you posted are terribly jumbled up, and you need the correct source text to carry out the translation.
My entry here does in no way support any translation attempt of the sentences you quoted.

ensuring/taking into account/observing adequate allocation/provisioning/of gas supplies

other options: I favor "supplies" (plural)
ensure/ensuring/taking into account/considering adequate gas supply (gas supplies)
ensuring adequately calculated/dimensioned gas supply(gas supplies)
ensuring the amount of supplied gas /ensuring the gas feed is at an adequate level
ensuring sufficient amount/allocation.provisioning of (supplied) gas

Okay, here's a translation based on some context that works. I found your sentence, slightly different at its beginning, but only as a fragment:


maybe your context from a book quoted below:
http://www.gleich-lesen.de/Oldenbourg Industrieverlag / Vulk...
Kapitel: Einsatz einer Mikro-Gasturbine zur Prozesswärmeerzeugung 10.92 EUR - 8 Seite(n)
Seite:43
...e durch den Anlagenbetrieb unbeeinflusste, möglichst kühle Frischluftzufuhr sowie eine ausreichende Dimensionierung der Gasversorgung zu achten. Auch spielt die Verfügbarkeit der Anlagen bezüglich des wirtschaftlichen Einsatzes eine ...

Personally, I am not happy with "sufficient dimensioning of (the) gas supply/supplied gas" - although dimensioning can often be found as a translation for "Dimensionierung".

I would rather go with something like

adequately calculated/dimensioned gas supply
or, because the idea here is, in my opinion,

to make sure the amount of supplied gas /gas feed is at an adequate level

http://www.rheinzink.co.uk/200.aspx

Compared to the all-inclusive gutter calculation, which was applicable up until now, as of July 2001, bracket-mounted and interior roof drainage systems must be dimensioned for sufficient sizing by means of an hydraulic calculation.

German:
http://www.rheinzink.de/197.aspx

One can translate it probably with "ensuring sufficient amount of (supplied) gas / gas supplies

different text, good context:
http://www.hornglass.com/gas.php
Beheizungsausrüstung für Erdgas


Die gesamte Gasversorgungsausrüstung wird auf modernen CAD-Stationen geplant. Spezielle Rechenprogramme unterstützen bei der Auslegung und Dimensionierung der Gasversorgung. Auf Grund der langjährigen Erfahrung verwendet HORN nur sehr zuverlässige und dauerhafte Komponenten von speziellen Herstellern. Die einzelnen Stationen werden fertig vormontiert und auf Funktion getestet, um somit fehlerhafte und zeitraubende Montagearbeiten auf der Baustelle zu vermeiden.









--------------------------------------------------
Note added at 2 hrs (2011-03-13 05:11:03 GMT)
--------------------------------------------------

correction for other options above:
ensuring sufficient amount/allocation/provisioning of (supplied) gas


--------------------------------------------------
Note added at 3 hrs (2011-03-13 05:48:26 GMT)
--------------------------------------------------

OPTION 2:

Although "Versorgung" means supplies/supply, the author of your text could have the sufficient size of the gas tubes or adequate/required room/space/dimensions for the gas tubes in mind.

It could be solved as:

"...ensuring the tubes are of sufficient size to provide a supply of gas to meet the requirements of volume (and pressure) at the point of use"

or, only regarding the size of the system:
ensuring the size of the gas supply system is sufficient (to meet the requirements.... - not really necessary add-on)

"ensuring gas tubes (tubes supplying gas) are of sufficient size"

or, for the required space/room for (dimensions of) the gas supply system/gas tubes:
"ensuring/provisioning adequate space for the gas tubes (gas supply system)

It's hard to say because I don't really know if it's the required volume of supplied gas that's important in your text or the required space for the tubes or the adequate space for the gas system.

So, the first solution above (option 2) is somewhat of a compromise, including all ideas (see also the link below):

http://www.copper.org/applications/fuelgas/rg-systemchoice.h...
In either of the above systems, the tube must be of sufficient size to provide a supply of gas to meet the requirements of volume and pressure at the point of use.

--------------------------------------------------
Note added at 3 hrs (2011-03-13 05:56:27 GMT)
--------------------------------------------------

PS: of course, in the text you quoted, there is no way to be sure. You need a correct version of the source text. So, at this point, none of my suggestions can or should be used for any of your sentences. My suggestions simply deal with various possible translations of "Dimensionierung der Gasversorgung" for various contexts which I supplied myself.

--------------------------------------------------
Note added at 3 hrs (2011-03-13 06:06:02 GMT)
--------------------------------------------------

corr of one of my sentences above:
It's hard to say because I don't really know if it's the required volume of supplied gas that's important in your text or the required size of the tubes or the adequate space for the gas system.