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recommended that operators purge the HTF system with
nitrogen and lower the system's temperature to less than
100°C before opening. Performing these steps removes
the most significant hazard altogether by removing hot
volatile organics as a possible exposure. If these steps
are not tenable for one reason or the other, operators can
be provided with proper ventilation in the environment if
the system is indoors, personal protective equipment and
training to perform tasks quickly and effectively.
The key for minimizing both exposure and emissions is
to operate the HTF in a strictly controlled closed system.
When the heat-transfer system is operated in this manner,
the risk of fluid release and any potential exposures
are minimized. Maintenance and routine events, filling
and draining, are the major points of exposure for operators.
A few of the additional routine tasks that should
have developed procedures and safety considerations
are outlined below:
* Maintaining or exchanging equipment on the process
side of heat exchangers
* Cleaning pump strainer and/or the side-stream filter
* Replacing the sealing of a pump
* Exchanging a defective instrument or valve on the
HTF loop
* Replacement of gaskets on flanges
* Cleaning or removal of fluid from equipment, such
as the expansion vessel that needs to be inspected by
manual entry and HTF sampling for routine analysis
The best way to minimize exposure risk is to ensure your
system is properly designed. The procedures for that system
should be standardized and captured in formal documentation.
Also, personal protective equipment (PPE)
and proper training should be provided for operators of
the system. All of these safety considerations should align
with your facility's regional and national requirements. PPE
is the last line of defense against exposures for operators.
Facilities should consider all other aspects of the hierarchy
of controls as they develop their system design. By the end,
facilities should have a closed system that only presents
hazards to operators when opened hot. As such, facilities
can employ procedural, administrative and PPE controls
to further minimize any risk of exposure. Suggested PPE
for an HTF system includes gloves, long sleeves, goggles
and chemical-resistant footwear. It is also recommended
that operators don additional protection for the eyes and
skin using chemically resistant aprons and face shields.
System design & maintenance
" Applying appropriate constructive and design measures,
in combination with organizational measures, can
also lead to permanently technically tight plant(s). Apart
from the human and technological factors, the organizational
structure for safety measures also plays a key role
when it comes to plant safety " [8].
Heat-transfer systems, when designed and maintained
properly, are low-cost, low-exposure and low-maintenance
systems to have on an industrial site. Scheduling
of maintenance events can vary from user to user, but it is
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generally recommended that systems are sampled every
12 months and that system inspections occur according
to technical and regulatory requirements. System inspections
may result in the need to perform system maintenance.
Primary outcomes of system inspections, and the
resulting maintenance activities, are highlighted below.
For the maintenance scenarios, operators should always
consider their own procedures first. Operators
should also be cognizant of requirements laid out by
their national and regional authorities when developing
or adapting procedures.
Filling and draining. Prior to unloading the contents
of a bulk container, it should be properly positioned for
safe access, centered in front of an unloading dock, and
within spill containment areas. If bulk-container heating
is required during unloading, which is typically performed
with pressurized steam, it is important not to exceed the
maximum allowable pressure rating of the bulk container.
The maximum allowable pressure of the bulk container
can vary and should be referenced before unloading.
HTF systems are normally filled from the bottom to the
top. This technique is employed to prevent aeration of
the fluid. While filling, top vent(s) on the system should
be opened for displacement of the vapors from the system
to a predetermined and predictable location. During
the filling process, it is recommended to have person
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