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Installation and putting into operation of the BNA…EX bypass
level indicator, heated, double-walled version, in explosion risk
areas
The bypass tube is also available in a heated, double-walled version, in which the
bypass tube is surrounded by a second tube (heating jacket). A heat-carrying medium, heated
liquid or heated steam can be pumped through the resulting double-mantle space through two
connections. Stainless material qualities in accordance with the AD specification sheets are used
for the higher temperatures to which this construction is exposed.
To eliminate the risk of explosion caused by the heating system, the following
requirements apply to operation of the heating system and the heat-carrying medium:
1. The temperature of the heat-carrying medium must not exceed 80% of the ignition temperature
of the stored material.
2. The equipment operator must ensure, by means of constant monitoring and operational checks,
that the ignition temperature listed under item 1 is not exceeded. These monitoring and
checking activities must also take temperature dynamics resulting from chemical reactions into
consideration. For example, maintenance of the permissible temperature level can be ensured
on the basis of saturated steam pressure or the boiling point of a liquid.
