Jafar 4493 Руководство по эксплуатации - Страница 10
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Fig.10 The movement of the valve flap in the standard version
The above Fig.10 shows the standard version of eccentric butterfly valves with the JFR GRAY gearbox. The
standard movement that opens the flap is clockwise. In contrast, the permanently marked arrow on the valve flap
pivots shows the movement that closes the flap (counter clockwise). This is the optimal movement that increases
the service life of the valve components. Irrespective of the requirement for a straight piping run at least 3×DN
long between the valve outer flange face and the piping bend (alternatively, the designed valve can be replaced
with one of a higher pressure rating), to minimise the localised flow acceleration and interruption by the piping
bend. The valve shall be installed with the centreline of the valve closure pivot shaft perpendicular to the vertical
line of the piping bend so that the valve closure drive shaft centreline is aligned with the piping bend plane. While
the valve is being closed or opened, the medium is at its maximum flow rate and entrains the contamination settled
in the neighbouring part of the pipeline. The valve installation shown in Fig. 10 additionally extends the service
life and operating reliability even with media loaded with contaminants which by their weight tend to settle down
in the piping. A consequence of this is that the deposits can be entrained from the upstream of the valve by the
maximum possible flow passing the bottom part of the valve closure during the opening operation (Fig. 11). Apart
from normal flow deflection by the piping bend, the liquid flow applies a high strain in the low-pressure valve
area. This in turn causes the valve to operate with difficulties.
When designing the installation, consider that the horizontal orientation of the valve closure pivot shafts is the best
for operating performance and reliability:
1.
the weight of the pivot shafts and the closure rests on both bearings;
2.
the load at the bearing of the face end of the shaft is decreased,
3.
valve life is increased, particularly when the liquid contains solids the particles of which tend to settle at
the bottom of the pipe.
OPERATING MANUAL
Fig. 11. Correct valve flap orientation
07-2022
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