wT 1255/12
Page 13
10
Installation and Putting into Service Regulations
Piston valves can be installed into the pipe system in any given orientation. The preferred
flow direction, however, should be taken into consideration in this context.
This series of piston valves is equipped with a pressure compensated piston and
therefore does not show any piston pump effect.
In order to protect against impurities and damage, the connections of the valves are
covered. We recommend removal of these covers only prior to installation.
The spindle of the valve must be protected against dirt in order to avoid premature wear
and tear of the trapezoid thread.
Valves with welding ends may generally be welded into a pipework by means of fusing
welding procedures. In this context, the welding and quality requirements and their norms
are to be complied with. As a consequence, welding may only be carried out by qualified
personnel. The safety regulations of the plant operator and/or the plant manufacturer are
also to be complied with.
Installation of valves with flange ends may only be carried out by qualified personnel in
accordance with EN 1591. It must in this case be observed that no additional tension is
exerted on the valve, such as for example as the result of selecting a too large distance
between the to be bolted flanges.
Should the pipe and the valve be insulated, then insulation should only reach up to the
body-side top flange. This ensures accessibility of the bonnet securing nuts and allows
for the valve body to remain in the pipe during repair and maintenance work, necessitating
only the removal of the bonnet.
Following installation and prior to putting into service, it must be ensured that solids and
impurities, which are not part of the medium, have been removed from the pipeline
system and/or from the facility. A pressure and a function test must be carried out prior
to putting into operation
When opening the valve, care should be taken to ensure that, after having reached the
end position, the handwheel must be again turned clockwise between ½ to a full rotation
in order to avoid jamming of the piston in the body.
Prior to putting into service of valves in steam pipes, proper condensate draining must
be ensured in order to avoid steam hammer hazards. In extreme cases, a steam hammer
may lead to breaking of the valve. Rapid increases in temperature and pressure are to be
avoided during all operation phases (start – operation – shutting down).
The maximum permissible test pressure is 1.1 x PN if the piston valve is in a closed state.
The valve must be open when testing the pipe pressure (1.5 x PN).