27-28 Watlow v2 10/9/09 13:29 Page 28
industry equipment
rhombus4
In most tubing systems, additional components like pumps,
components create the biggest heat
losses, and their geometry is in most
valves or other equipment are integrated which create
cases considerably unsymmetrical
which makes efficient heating
particular challenges for uniform tempering. These
extremely difficult. Sufficient heating
components create the biggest heat losses, and their
of these particular components
however, is of great importance,
geometry is in most cases considerably unsymmetrical
because condensation and
precipitation take preferentially place
which makes efficient heating extremely difficult
in these areas. This is due to the
significantly different thermal
properties of these components
compared to common tube sections.
voltages. Core of this so called Pump temperature controller and In these cases simple wrapping with
/ Gas Line heating system is a heater semiconductor power switch. heat trace does not lead to the
jacket made from fibreglass enforced Optionally, the control units can be desired results, so that a specific
silicone material with backside connected to a PC. This allows adjustment of the heating element to
insulation and snap fasteners or configuration and data logging with a the component becomes necessary.
velcro for easy assembly and HMI software package. Pump/ Gas Such an adjustment is not only
disassembly. With this design, time- Line heaters are available in different limited to the geometry of the heater
consuming wrapping of heat trace diameters, lengths and geometries as jacket, but also must consider heat
around the tubing and subsequent a standard. Also elbows, flanges and losses in these locations. This
insulation becomes redundant. T-sections can be covered and requires an adaption of power and
Moreover, each heating jacket is heated with standard jackets. By power density of the heater jacket to
equipped with plugs that ensure easy choosing suitable heater jackets, a the specific thermal conditions.
connection between the individual full covered heating of the complete
heating jackets and to the control tubing will be achieved. Especially at valves, much higher
unit. For temperature measurement, heat losses occur compared to
thermocouples or RTDs can be In most tubing systems, additional common tube sections which make a
attached to the heating elements. components like pumps, valves or higher power input per surface unit
other equipment are integrated which necessary. In some cases it is
The system is completed by a control create particular challenges for required to equip the heating jacket
unit, equipped with a PID uniform tempering. These with an additional temperature sensor
and to operate it in a separate
control loop. This becomes
particularly necessary when the
thermal properties of the valve are
significantly different than the rest of
the tubing system.
It ensures desired temperatures and
prevention of condensation even in
tubing systems with sections of
highly different thermal properties.
Another feature of these heating
systems is the accurate distribution
of heating power. This can be
achieved on one hand by adapting
watt density to the specific
requirement, on the other hand by
temperature control of the heaters.
This, together with the insulation of
the heating jacket, leads to energy
savings because only the amount of
actually required power is brought
into the thermal system.
28 www.compoundsemiconductor.net September 2009
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