Goetze 851 Mode D'emploi page 12

Safety valves without bellows and without gastight cap ( Fig. c)
In addition, in the case of safety valves without bellows and without gastight cap,
the entire upper part can be unscrewed from the housing using appropriate tools
and any residue removed from the seat and the seat sealing.
Prior to removal make sure that the safety valve is not under pressure.
The response pressure of the safety valve is not altered through the reassembly of
the upper part in the housing.
Safety valve with metal bellows (Fig. d)
In the case safety valves with metal bellows the upper part is not to be separated
from the housing, because otherwise tightness is no longer guaranteed in the event
of backpressure occurring.
Safety valves with gas-tight cap ( Fig. f) or gastight lifting ( Fig. g)
On safety valves with gas-tight cap or gastight lifting lever, the top part may not be
separated from the housing as this compromises gas tightness. However, if the top
part does have to be unscrewed for a repair, it should be ensured that the tension
on the spring is released before dismantling. You should also check before dismant-
ling the valve whether there is any medium in the cap and if so, what it is. Potential
risk of chemical burns or poisoning.
Lifting for maintenance purposes
In the case of safety valves with a lifting device it is recommended, and in certain
plant-specific cases even stipulated that the valves from time to time must be made
to blow-off by lifting the seal off the seat, in order to assure the correct functioning
of the safety valve. This ist why they can be made to open at the latest as from an
operating pressure of  85% of the response pressure. The lifting device is not to
be operated when in a pressure-free state. In steam generating equipment, testing
the ease of movement of safety valves must be carried at least every 4 weeks
in compliance with TRD 601. Safety valves are the ultimate safety device for the
tank or system. They must be able to prevent impermissible overpressure even
when all other upstream control and monitoring equipment fail. To ensure these
functional characteristics safety valves require regular and recurring maintenance.
The maintenance intervals are determined be the operator in dependence of the
operating conditions.
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Dismantling the fi tting
In addition to the general installation instructions it must be ensured that the
system is made pressure free prior to disassembly of the safety valve.
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Repairs
Repair work on safety valves is only to be carried out by Goetze KG Armaturen or by
officially approved specialist workshops authorized by Goetze KG Armaturen using
original spare parts only.
Assembly and maintenance instructions - 851/451, 852/452/352, 652, 861/461, 420, 460 www.goetze-armaturen.de