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Average wall thickness
Posted: 18 Aug 2010, 06:47
by Ahmedfromkuwait
In Fired heater tubes are specified by "average wall thickness" & not by nominal thickness. In case we have to procure the heater tubes & to check whether it conforms wrt average wall or not, how we should proceed?
thanks
Ahmed
Re: Average wall thickness
Posted: 18 Aug 2010, 07:42
by arcpro
Exchanger tubings is normally supplied on the basis of nominal diameter and the minimum or average wall thickness.
Nominal diameter is equal to the O.D of the tube and average wall thickness is with +/- tolerance. This tolerance varies with type of tube material, diameter, applicable material standard, fabrication technique etc.
Just specify the O.D and minimum wall thickness to the supplier. Remember, minimum wall thickness is always with + tolerance only.
Re: Average wall thickness
Posted: 18 Aug 2010, 08:21
by ashfaqanwer
What's the applicable material standard for the tubes you want to procure?
Re: Average wall thickness
Posted: 18 Aug 2010, 23:39
by mechcolor
You must have a calculated thickness from API 530.
Lets say the thickness comes out to be 10 mm. Take out the mill tolerance, minimum thickness would be 10 * 0.875 = 8.75 mm
Specify tube O.D and minimum wall thickness 8.75 to your suppliers. Or you may mention average wall thickness 10 with +/- 12.5% tolerance.