The following example is based on a tube diameter of 8.5mm.

The intended use of the tubular heaters contributes to the surface load calculations and to the life span

 

P = Surface loading W/cm²
P = Rated output
Lb=Heated length in c.m.
s = Circumference i.e. 8.5mm
diameter  = 2.67 (D x PI)

 

Medium	Max. medium temperature	Max. tube surface load (W/cm2)	TM* 1.4541	TM* 1.4571	TM* 1.4435	RMW* 1.4828	TM* 1.4876
Water
Circulating water	100	10	X		-	-	X
Distilled water	100	8	-	X	-	-	X
Industrial water	60	4.0-6.0	-	-	-	-	X
Steam generation	100	5	-	X	X	-	X
Oils
Heavy oil	100	0.8 - 1	-	-	-	-	-
Lubricating oil	40	1	-	-	-	-	-
Hydraulic oil	40	0.8 - 1.5	-	-	-	-	-
Heating oil light EL	20	4	-	-	-	-	-
Thermal oil	250	3	X	-	-	-	-
Other liquids
Photographic developer	40	5	-	X	X	-	-
Milk	50	1	X	-	-	-	-
Caustic Soda	100	2	-	-	-	-	X
Acids (thin)	100	2	-	X	X	-	X
Lyes (thin)	100	4	-	X	X	-	X
Phosphating bath	90	3	-	X	-	-	-
P 3-Degreasing	60	4	-	-	-	-	-
Burnishing bath	-	2	X	-	-	-	-
Carbonic acid	20	3	-	-	-	-	-
Diphyl	350	1.5	-	X	-	-	-
Frying Fat	200	4	X	-	-	-	-
Glycerin	110	3	-	-	-	-	-
Salt melting	400	2	-	X	-	-	-
Lead bath	500	4	X	-	-	-	-
Trie	80	1.5	-	-	-	-	-
Wax	60	1	-	-	-	-	-
Tar	150	1	-	-	-	-	-
Air
De-frosting	-	1	X	-	-	-	-
Grill heating element	-	4.0-6.0	-	-	-	X	X
Still air	-	1.0-6.0	X	-	-	X	X
Moving air	-	-	-	-	-	-	-
Speed: 3 m/s	-	5.5	-	-	-	-	-
Speed: 6 m/s	200	7	-	-	-	-	-
Speed: 10 m/s	200	10	-	-	-	-	-
Speed: 10 m/s	200	4	-	-	-	-	-
Radiating heat	450	3.0-5.0	X	-	-	X	X
Air conditioning	-	0.5 - 3	X	-	-	X	X
Circulation air (dry)	300	2.0-4.0	X	-	-	X	X
Solids
Aluminium (cast.)	400	8	X	-	-	-	-
Charcoal igniting	-	3.5	-	-	-	X	-
Metal (poured into slots)	-	6	X	-	-	-	-
Sawdust igniting	-	3.5	-	-	-	X	-
Sand	200	1.5	X	-	-	X	X
Stone (night storage)	600	2	-	-	-	X	X
Rollers	300	2.5	-	-	-	X	X

*TM = Tube material