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Moá i töông quan giöõ a taà n suaá t "SPM" vaø
ñoä nhôù t dung dòch cps coù taù c duï n g cho
theù p AI51 3 1 6L hoaë c nhöï a PP hoaë c PP11.
Ñöôø n g oá n g ñaå y
Khi maø beà maë t dung dòch bôm trong beå huù t cao hôn coá t cuû a beå
chöù a thì seõ xuaá t hieä n moä t doø n g chaû y khoâ n g kieå m soaù t ñöôï c töø beå
huù t sang beå chöù a .
Ñeå traù n h hieä n töôï n g naø y thì aù p löï c ñaà u ñaå y phaû i lôù n hôn ít nhaá t
0,3 bar so vôù i aù p löï c cuû a ñaà u huù t , trong tröôø n g hôï p löu löôï n g nhoû
thì ñoä cheâ n h aù p phaû i laø 0,5 bar.
Trong tröôø n g hôï p khoâ n g ñaù p öù n g ñöôï c caù c ñieå u kieä n treâ n thì caà n
thieá t phaû i laé p ñaë t moä t van ñeå taï o ra aù p löï c ngöôï c hoaë c toá t hôn heá t
laø khoaù chaë t oá n g ñaà u ñaå y ñeå traù n h hieä u öù n g siphoâ n g (H.10).
H. 10
Sai
Hieä u öù n g siphong khoâ n g theå
kieå m soaù t ñöôï c löu löôï n g
Wrong
Siphoning Uncontrollable flow rate.
Sai
Khoâ n g coù van taï o aù p ngöôï c , doø n g löu
löôï n g trong oá n g "A" keù o dung dòch töø
thuø n g chöù a maø khoâ n g kieå m soaù t ñöôï c
Wrong
Failing a back pressure valve, the flow in
pipeline "A" draws the product from the
tank in an uncontrolled way
Van xaû aù p
Bôm ñònh löôï n g maø n g cô hoï c phaû i laé p theâ m moä t van xaû aù p ;
moä t aù p löï c cao hôn aù p löï c laø m vieä c toá i ña cuû a maø n g seõ laø m
hoû n g cô caá u maø n g.
Van an toaø n caà n ari ñöôï c laé p ñaë t ngay sau ñaà u ñaå y cuû a bôm,
l
taá t nhieâ n laø tröôù c van ñoù n g ngaé t .
AÙ p löï c van (aù p löï c ñaë t ) khoâ n g vöôï t quaù aù p löï c lôù n nhaá t cuû a bôm
l
Baû n g E
Taà n suaá t / phuù t Ñoä nhôù t (cps) Max nhoù m A
S.P.M.
cps max execution "A"
36
1000
50
800
70
300
95
150
115
50
155
10
Discharge line
When the free surface of the liquid in the suction side tank is
above discharge-side tank level, an uncontrollable flow from the
suction side tank to the discharge side tank will occur.
To prevent this natural passage of liquid, the discharge pressure
must always be at least 0,3 Kg/cmq, higher than the suction
pressure, in case of small flow rates 0,5 Kg/cmq
If for any reason this condition cannot be complied with the plant it
is necessary to create a backpressure by means of a suitable
valve, or better to highten the discharge pipe so as to prevent the
siphoning effect (fig. 10).
Relief valve
Mechanical diaphragm metering pumps absolutely need the
installation of a relief valve; a pressure higher than the rating
plate value would break the mechanism.
The safety valve has to be installed immediately after the dis-
l
charge connection, anyhow before the on-off valve.
The relief valve setting (set pressure) must not exceed the pump
l
max. pressure value.
Table E
Relationship between strokes per minute
"SPM" and viscosity of the liquid "cp",
valid for AISI 316L or PP.11 pump heads.
VAN TAÏ O AÙ P LÖÏ C NGÖÔÏ C
BACKPRESSURE VALVE
ÑAÀ U CHAÂ M
INJECTION NOZZLE
2
Laé p ñaë t
ñuù n g
Right
Laé p ñaë t
ñuù n g
Right
9
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