Carbolite Work Tube End Seals - Manual (Page 8)

MS76 – 1.00
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3.2 Use of probes/thermocouple entry
Any metal object used to probe into the furnace tube while the furnace is connected
to the supply must be earthed (grounded). This applies in particular to metal
sheathed thermocouples, where the sheaths must be earthed. The refractory material
of the work tube becomes partly conducting at high temperatures, and the electric
potential inside the tube can be at any value between zero and the supply voltage.
Unearthed probes can cause serious electric shock.
3.3 Pressure
Work tubes are not intended to accept high internal pressure. When gas seals or similar fittings are
in use, the gas pressure should be restricted to a maximum of 0.2 bar (3 psi). A pressure of
approximately half of that should normally be sufficient to achieve the desired gas flow rate. The
customer must ensure that the exhaust path from the tube is not blocked, so that excess pressure
does not occur.
A suitably regulated air supply should always be used.
It is recommended that a pressure relief system should be used to avoid an over pressurisation of
the work tube.
A sealed work tube should not be heated from cold due to the pressure build up
during the heating process. Only seal the work tube once furnace and tube are at
temperature.
3.4 Operator safety
Drop hazards – Care must be taken when fitting and removing the end seals from the work tube.
Products should be used for professional use only and the end users work place risk assessment
should consider appropriate safety procedures.
Surface temperature – If the end seals are used with a horizontal tube furnace
using the correct tube plugs or radiation shields, it is unlikely that the end seals will
reach a temperature that will pose a risk to the end user. If the tube furnace is used
in a vertical orientation there is potential for the top end seal to exceed the
recommended limit for hot surfaces that are easily touched.
Vacuum – When used under full vacuum a maximum pressure of 1bar will be acting
on the work tube. When applying vacuum to a thin wall section quartz tube, safety
glasses should be worn in the unlikely event that the work tube fails under vacuum
pressure.
Viton O ring – Silicone ‘O’ rings are used and supplied as standard. If using Viton
‘O’ rings care must be taken to avoid exposing the Viton to temperatures that could
cause the Viton to burn. At high temperatures, or in a fire, fluoroelastomers
decompose, and may release hydrogen fluoride. Any residue must be handled using
protective equipment.
Pinch hazard – Care must be taken when fitting the screw fit clamp to the end seals to avoid
possible pinch/cut hazards. Sharp edges caused by misuse or accidental damage of the product
must be dealt with accordingly.
Quartz tube – due to the fragile nature of quartz tubes extra care should be taken to avoid over
tightening of the end seals on a quartz tube. As a precaution when fitting to a quartz tube, suitable
eye and hand protection should be used.