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Finned Tube Products
 Armstrong/Chemtec has been making finned tubing for 25 years
and incorporating finned tubes into our heat transfer equipment for more than 40
years. As with all our products, our excellent heat transfer background which
combines our own in-house research information with the knowledge base of HTRI and HTFS
allows us to accurately design and develop finned tube products which are unparalleled in
the process industry. Currently we manufacture welded helically finned tubing (WHF)
and longitudinally finned tubing (LFT). Our finned tubing is incorporated into
several specific products including tank suction heaters, line heaters, and tank internal
heaters. We manufacture finned tubing and all these types of finned tube equipment
at each of our three locations in the USA, Singapore and Scotland.
Advantages of Armstrong/Chemtec Finned Tubes
Finned tubes are able to even out the heat transfer between the inside of the tube and
the outside. When the heat transfer coefficient on the outside of the tube is
significantly lower than the heat transfer coefficient on the inside of the tube, there is
a major advantage to incorporate fins on the outside tube surface to take full advantage
of the high heat transfer rate on the inside of the tube.
A good example is the frequently encountered situation of heating viscous oil outside a
tube with steam condensing on the inside of the tubes. The internal steam
coefficient may be 1500 Btu/hr-ft2-F
or more and the outside coefficient only 20 or 25. By using a finned tube with eight
times as much surface on the outside of the tube, the total length of the tube required
for heating the viscous oil can be reduced by one-sixth. Similar gains are obtained
when heating gases with steam where the external coefficient of the gas to tube is only
10-20.
All of our finned tubes feature WELDED FINS. Welding is necessary to prevent
deterioration in a finned tube's ability to transfer heat that results from a rising
contact resistance between fin and pipe. If fins are wrapped or embedded, thermal
cycling will loosen the fin (increasing contact resistance) and cause a loss in the finned
tube's heat transfer capability. Armstrong/Chemtec heaters
do not lose capacity with age.
Armstrong/Chemtec's long background in application of both
electric heat and fintube heat transfer come together when electrical resistance elements
are finned. Since the coefficient of heat transfer is very high between the interior
resistance coil and the element's external metallic sheath, it is ideal to incorporate the
two technologies. Armstrong's
Electrofin
Heaters and withdrawable stab-in electric tank heaters fall
into this category with unique application to process heat transfer.
Tank Heaters
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Horizontal
In-Tank Heater
These heaters are typically supplied with multiple pipes with welded helical fins.
Due to the compact surface, much larger amounts of heat can be added to the tank
contents than when using bare tube coils of comparable area. |
Bayonet
type Stab-in Tank Heater
For installation in side entering tank nozzle. Bayonet heaters are usually single
pipe, with fins to allow good natural convection circulation of the fluid being heated.
These heaters are available in many metals, including stainless steels. |
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Coil Type
Stab-in Tank Heater
This type heater is installed through a side entering tank nozzle and differs from the
bayonet type in that usually more pipes or tubes than one are used, requiring a tubesheet
or bonnet or continuous coil to allow for usually lower flow of heating medium. Fins
are helical to allow unimpeded natural convection. |
Vertical
Cluster In-Tank Heater
This type heater can be supplied in many metals but it usually steel or stainless steel
and is used to provide very large amounts of surface in a relatively confined space.
These heaters can be either steam or heat transfer oil heated. By placing
several of these heaters around the intake of a suction heater, very high viscosity fluids
can be pumped through a suction heater, where otherwise they might not flow well enough to
insure normal suction heater operation. |
Electric
Tank Heaters
 
When steam or heat transfer oils are not available
on site, Armstrong/Chemtec can
 supply electric heated tank
heaters. We manufacture these stab-in type heaters in two different types: (1)
with elements that are removable while the tank is filled with product, and (2) with
elements that can only be removed if the tank is empty. Our electric tank heaters
have the same welded fins and robust construction as our steam heated units. These
heaters can be supplied with normal NEMA 4 terminal boxes or with
explosion-proof terminal boxes to allow use in hazardous areas.
Controls can be provided separate from the heater or integral (inside
the heater's terminal box).
Suction & Line Heaters
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Suction heaters are normally installed in a tank side nozzle
and used to heat up relatively large flows of viscous materials using steam, hot water, or
other heating fluid passing through the tubes. These heaters normally have low shell
side pressure drops to minimize NPSH problems in pumps. For very high viscosity
fluids, consult us for methods of reducing intake viscosity. Main uses of this type
heater include bunker C and other heavy fuel oils, asphalt, lube oil additives, molasses,
caustic, etc. |
Line heaters resemble suction heaters with an enclosed end so
that the heater can be installed outside the tank. This permits addition of an
external valve between the tank and the heater to allow servicing the heater without
pumping down the tank. |
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