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Other important considerations for dosing pumps in ex-zones
Page 20
9.4
Installation, hydraulic
WARNING
•
Dosing pumps used in ex-zones must be fitted with an appropriate safety relief valve
on the output side of the dosing pump (serves to protect against overheating resulting
from overloading and arcing due to interruption of drive components as a result of
overloading.)
•
Piston dosing pumps are designed for use in temperature class T3. The pumps can be
used in T4 if they are fitted with an additional flow controller on the output side (serves
to protect against a rise in temperature resulting from dry running) or with an
appropriate temperature controller.
•
Similarly, dosing pumps whose diaphragm is driven hydraulically must be fitted with a
temperature or flow controller for use in T4. (The internal relief valve protects against
overheating in the event of extended operation.) Without this protection, temperature
class T3 is applicable.
•
With different temperature classes being available for different components, the
possible application of the entire pump corresponds to the component with the lowest
temperature class.
•
Combustible media may only be extracted using stainless steel dosing heads. In
exceptional circumstances, where stainless steel is not available, PTFE with carbon
can also be used. Our TT designs are manufactured from this conductive synthetic
material. The operator should take special care in this instance due to reduced
mechanical stability.
•
Piston dosing pumps may not be used for combustible media. Where it is impossible to
avoid the use of piston pumps, additional control measures should be implemented to
ensure the required level of safety. This includes flow controller + piston leakage
controller, and an additional temperature controller on the dosing head for media with
critical friction characteristics.
•
Hydraulic diaphragm pumps are perfectly suitable, however it is compulsory to have
those whose construction includes diaphragm-rupture controller Ex "i" and flow
controller.
•
Diaphragm pumps with mechanically linked diaphragm, e.g. Zt. MTMa..., TZMa...,
Sigma's S1Ba..., S2BaHM..., S3Ba: no additional measures are required, although it is
essential to use the construction with diaphragm-rupture indicator, in the Ex "i"
construction.
•
Installations in ex-zones must be checked by a "recognised qualified" person.
•
The following applies to all dosing pumps when metering combustible media: Start up
and drain only under the supervision of an appropriately qualified person.
•
Observe the relevant national directives with regard to installation!
ProMinent
ProMinent
®
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