SAPAG Monovar 8P AN - Fluid Control Services
SAPAG Monovar 8P AN - Fluid Control Services
SAPAG Monovar 8P AN - Fluid Control Services
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<strong>Control</strong> valve<br />
MONOVAR ®<br />
A 65-61 A
<strong>Control</strong> valve MONOVAR ®<br />
2<br />
■ Extremely simple design<br />
(patented)<br />
■ Excellent cavitation<br />
characteristics<br />
■ Sensitive to small variations<br />
opening over entire travel<br />
■ No fluctuations induced<br />
in flow<br />
■ Manual or automatic control<br />
■ Mesures of flow<br />
■ Small size<br />
Operating principle<br />
The simplicity of the MONOVAR ®<br />
design is apparent from the Figure as<br />
shown.<br />
Conception<br />
Components are simply two circular<br />
perforated plates, and an annular<br />
body (1) mounted between pipe<br />
flanges. Plate (2) is fixed. Plate (3) on<br />
the upstream side is free to slide up and<br />
Advantages<br />
The energy given up by a fluid when it<br />
flows through a valve often causes a<br />
moderate to large distrubance in the<br />
flow.<br />
Examples are : flow fluctuations liable to<br />
cause vibration of the pipework, potentially<br />
damaging cavitation bubbles (i.e.<br />
fluid vapour bubbles), and noise. Noise<br />
may be due to turbulence or the sudden,<br />
explosive collapse of cavitation bubbles.<br />
In MONOVAR ® valves, energy dissipation<br />
is controlled by the dozens of<br />
evenly distributed jets into which the<br />
perforated plates divide the flow. This<br />
means that distribution effects are considerably<br />
reduced, as described below :<br />
MONOVAR ® automatic or manually<br />
operated control valves have been specially<br />
designed by <strong>SAPAG</strong> for really<br />
heavy duty pipe-flow situations.<br />
Their essential sturdiness springs for the<br />
large number of small jets into which the<br />
incident flow is divided to create the<br />
requisite throttling effect.<br />
The jets are evenly distributed over<br />
the flowsection of the pipe and the<br />
uniform, small-jet configuration thus<br />
achieved is highly effective in suppressing<br />
such operating hazards as<br />
down. In the fully open position the orifices<br />
in the plates coincide. The fully closed<br />
position is obtained by displacing<br />
the mobile plate (3) through a (very<br />
short) distance equal to one orifice in<br />
diameter.<br />
Under normal flow control conditions,<br />
the position is intermediate, with the<br />
orifices in the fixed plate only partly<br />
blocked off by those of the mobile<br />
plate. The latter may be positioned by<br />
hand or by a valve actuator piloted<br />
automatically by a control device<br />
choice.<br />
• Flow fluctuations are reduced because<br />
jet energy and the scale of jet-induced<br />
turbulence are low. Diminished also is<br />
the distance through which any disturbances<br />
present propagate downstream.<br />
Consequently, devices such as flow<br />
meters may be placed much closer to<br />
the control valve than is normally the<br />
case.<br />
• MONOVAR ® control valves have<br />
cavitation inception figures which are<br />
more favourable than those of conventional<br />
valves.<br />
• Fully developed cavitation does not<br />
constitute a hazard with MONOVAR ®<br />
valves since the cavities occur solely in<br />
the fluid and not in the immediate<br />
vicinity of the valve's vital parts. This<br />
vibration, cavitation damage, pressure<br />
fluctuations and noise.<br />
These unique features, together with the<br />
wide range of construction materials<br />
make, MONOVAR ® valves an automatic<br />
choice in all severe industrial and<br />
water-supply situations requiring fluid<br />
flow control or of some associated characteristic,<br />
e.g. pressure, temperature<br />
and level.<br />
3 1<br />
2<br />
situation compares favourably with that<br />
of conventional valves where cavitation<br />
is frequently observed on the flow<br />
restrictor, seat and trunnion pivot.<br />
Further, vapour cavities do not form<br />
when MONOVAR ® valves are properly<br />
resulting in greatly reduced risk of<br />
pressure oscillation.<br />
A final point for operational reliability :<br />
MONOVAR ® valves have no natural<br />
tendency to open or close.
This section gives a brief rundown on<br />
the hydraulic design data and selection<br />
criteria for MONOVAR ® control valves.<br />
The data come from measurements<br />
made on the <strong>SAPAG</strong> valve-rigs, from<br />
experience gained on <strong>SAPAG</strong> turbine<br />
test installations, and from feedback<br />
from MONOVAR ® users in the industry<br />
and in the water resources field.<br />
Head loss<br />
The pressure drop caused by flow<br />
through MONOVAR ® valves is written<br />
as :<br />
V 2<br />
∆H = k 2g<br />
∆H : the pressure drop in water column<br />
metres at a given valve opening,<br />
k : the (dimensionless) head loss<br />
coefficient at the same valve<br />
opening,<br />
V : the velocity of the liquid in metres<br />
per second computed on the<br />
basis of the nominal flow-section<br />
of the valve,<br />
g : gravitional acceleration in metres<br />
per second squared.<br />
The figure below shows an example<br />
curve of k values for maximum perforated<br />
area of the MONOVAR ® plates.<br />
Headloss coefficient / per cent valve opening<br />
k<br />
1000<br />
100<br />
10<br />
10 20 40 60 80 100<br />
% valve opening<br />
Specific flow<br />
Specific flow is defined as the flow passing<br />
through a one metre dia. MONOVAR ®,<br />
which causes a head loss equal to one<br />
metre head of flowing liquid. Specific<br />
flow q may be written in terms of head<br />
11<br />
loss as :<br />
Q<br />
q =<br />
11<br />
D 2∆H q : specific flow in m<br />
11 3/s at a given<br />
valve opening,<br />
Q : the total flow passing through the<br />
valve in m 3/s,<br />
∆H : the head loss in water column<br />
metres liquid at the same valve<br />
opening,<br />
D : is the nominal MONOVAR ®<br />
diameter in metres.<br />
The figure below shows how q 11 varies<br />
with valve opening at constant<br />
headloss.<br />
Nota that q 11 may be expressed in terms of the<br />
head loss coefficient as :<br />
In the fully open position, the specific q 11 of a<br />
MONOVAR ® valve with maximum perforated<br />
area installed in a pipe whose diameter is equal<br />
to the nominal diameter of the valve is 1,3 m 3/s.<br />
The specific flow value drops to 0,95 m 3/s for<br />
an end-mounted valve. :<br />
100<br />
80<br />
60<br />
40<br />
20<br />
2 g<br />
q 11= 8 k<br />
Typical flow characteristics<br />
Flow %<br />
10<br />
10 20 40 60 80 100<br />
% valve opening<br />
MONOVAR ®<br />
Hydraulic characteritics<br />
Cavitation<br />
The flow-path contractions, sudden<br />
expansions and changes of direction<br />
encountered by a fluid as it passes<br />
through a valve mounted in a pipe tend<br />
to create - frequently via so-called flow<br />
separation effects - a considerable<br />
reduction in the local pressure. If the<br />
pressure reduction is such that the absolute<br />
pressure falls below the vapour<br />
pressure of the liquid, then the liquid<br />
boils and individual vapour bubles or<br />
bubble-producing vapour cavities<br />
appear in the liquid. This phenomenon<br />
is called cavitation.<br />
The tendency of a valve to cavitate is<br />
usually characterized by a cavitation<br />
number defined as :<br />
P 2 – P V<br />
= P1 – P 2<br />
P 1 : absolute upstream pressure measured<br />
in pratice one pipe diameter<br />
above the valve,<br />
P 2 : absolute pressure measured 10<br />
pipe diameters below the valve<br />
and corrected for friction losses<br />
between points 1 and 2,<br />
P V : vapour pressure of the liquid at the<br />
operating temperature.<br />
These pressure values are generally expressed<br />
as metres head of liquid. Some valve manufacturers<br />
utilize a cavitation number defined as :<br />
P 1 – P 2<br />
K = P1 – P V<br />
with the same notations. Simple algebra shows<br />
that the two numbers are related by<br />
1 1- K<br />
K = 1+ et = K<br />
For a given valve opening various<br />
values of are established by the<br />
manufacturer corresponding to various<br />
degrees of cavitation. Also defined for a<br />
given valve is how the values vary<br />
with opening.<br />
These values may be plotted in the form<br />
of so-called "required sigma" curves<br />
which indicate the degree of cavitation<br />
risk which will be encountered by users<br />
of the manufacturer's valve<br />
3
<strong>Control</strong> valve MONOVAR ®<br />
An example of MONOVAR ® cavitation<br />
curves in shown in the figure below for<br />
a given perforated area.<br />
To determine to what extent cavitation<br />
will occur with a given valve under given<br />
operating conditions, the manufacturer's<br />
required sigma curves should be compared<br />
with curves representating the available<br />
cavitation number which it is normally<br />
the user's responsability to establish.<br />
Both sets of curves are similarity to the<br />
available and required NPSH of a pump.<br />
4<br />
q 11<br />
The available cavitation number should<br />
be computed for all operating regimes<br />
which the valve is likely to meet with.<br />
The formula is as before, namely :<br />
P 2 – P V<br />
= P1 – P 2<br />
in which subscripts 1 and 2 refer to<br />
points such as 1 and 2 in the figure at<br />
the bottom of the page.<br />
Example of MONOVAR ® cavitation curves in terms of specific flow and cavitation number<br />
Area 1 Excellent<br />
Area 3 Operation possible with some risk<br />
Area 2 Acceptable Area 4 Forbiden area<br />
4 3 2 1<br />
Graphic method of determining available<br />
sigma<br />
The available cavitation figures may be<br />
calculated quite simply by graphic means.<br />
The example calculation shown in the<br />
Figure below is based on flow between<br />
tanks at different levels. The figure depicts<br />
the connecting pipe and included control<br />
valve and, to the right, a head versus flow<br />
chart. Pressures are expressed here as<br />
heads of flowing liquid because this is the<br />
usual procedure. However, variables H 1,<br />
H 2, H V have the same basic meanings as<br />
P 1, P 2,P V cited above, e.g., Hv is the<br />
vapour pressure of the flowing liquid<br />
expressed in metres head of that liquid.<br />
Vertical a b c d conveniently depicts the<br />
head loss components at the maximum<br />
value of discharge Q.<br />
The head losses above and below the<br />
1<br />
2<br />
H 1<br />
H 2<br />
0<br />
– (H a – H v )<br />
H<br />
valve are ab and cd respectively. The intermediate<br />
distance bc, i.e. (H1 - H2) represents<br />
the head loss which may be throttled<br />
out by the valve. The (quadratic) curves<br />
leading down to b and up to c show how<br />
head is lost by friction effects along the two<br />
lengths of pipe.<br />
Ha, the head at point a, corresponds to the<br />
pressure at the surface of the upper tank,<br />
I.e. atmospheric. Having drawn out the<br />
essentials of the figure thus far, it only<br />
remains to add a further horizontal line<br />
labelled e. This should be drawn at a distance<br />
equal to (Ha - HV) below the zerohead<br />
axis.<br />
The numerator (P2 - PV) of the sigma<br />
expression is represented by the length ce,<br />
which is evidently equivalent to H2 + Ha -<br />
HV, the denominator being bc. The desired<br />
sigma cavitation number is therefore<br />
ce/bc.<br />
Example calculation of avaiable <br />
Head H in metres flowing vs florate Q<br />
Vertical abcde corresponds to maximum flow rate<br />
a<br />
b<br />
c<br />
d<br />
e<br />
Q<br />
Q<br />
Operating limits<br />
Temperature<br />
MONOVAR ® valves made from the<br />
standard materials should not be operated<br />
outside the temperature range<br />
0 to 80° C. Seal effectiveness may be<br />
maintained up to 200° C by using special<br />
seal material.<br />
Elastomer and plastomer seals cater to<br />
low temperatures down to - 50° C.<br />
The temperature limits above are only<br />
approximate and depend on fluid and<br />
operating pressure, notably from the<br />
standpoint of cavitation risk.<br />
Pressure<br />
NP 64 : ND 100<br />
NP 40 : ND 150<br />
NP 25 : ND 200 to 600<br />
NP 16 : ND 700 to 800<br />
NP 10 : ND 900 to 1500<br />
Applications<br />
Fields of application of MONOVAR ®<br />
control valves include those set out below.<br />
Operating conditions are extremely<br />
severe in many instances. Prime control<br />
variables include flow-rate, pressure,<br />
temperature, level and concentration.<br />
Essential application characteristics are<br />
shown in parentheses after each application<br />
cited :<br />
• Water supply systems (reliability,<br />
pressure, cavitation),<br />
• Industrial flow, cooling and mixing<br />
systems (cavitation, sensitivity, pressure,<br />
reliability),<br />
• Head works of water treatment plant<br />
(reduced civil works, cavitation,<br />
reliability),<br />
• Flow relief for pump and turbine units<br />
(cavitation),<br />
• Water intake at the foot of a dam<br />
(reduced civil works, aeration, reliability),<br />
• Laboratory test-rigs (sensitivity,<br />
absence of disturbances).
MONOVAR ® flow and cavitation characteristics<br />
are shown in fig. beside in<br />
terms of specific flow q 11 in m 3/s.<br />
Q : m 3/s<br />
D : m<br />
∆H : mC liquide<br />
Q<br />
q =<br />
11<br />
D 2∆H P 2 – P V<br />
= P1 – P 2<br />
P 1 – P 2<br />
K = P1 – P V<br />
Characteristîc curves of MONOVAR ® valves.<br />
The 3 curves on the right-hand delineate the 4 cavitation<br />
areas shown in figure page 3.<br />
The figure does not apply to valves discharging to<br />
atmosphare.<br />
MONOVAR ® diameter choice<br />
1. Input data<br />
Liquid<br />
• Flowrate odjustable between ........ Q and Q'<br />
• Range of absolute upstream pressure .......... P 1 and P' 1<br />
• Range of absolute downstream pressure ...... P 2 and P’ 2<br />
• Available MONOVAR ® thorottling range ..... ∆H and ∆H’<br />
• Vapour pressure of liquid at operating<br />
temperature .............................................. P V<br />
• Nominal diameter of pipe ......................... D<br />
2. Firt computation stage<br />
Q Q’<br />
q =<br />
11<br />
D 2 and q’ =<br />
11<br />
∆H<br />
D 2 compute<br />
∆H’<br />
• if q’ 11 1.3, the MONOVAR ® diameter will be less than<br />
or equal to D.<br />
• if q’ 11 1.3 the MONOVAR ® diameter will be greater<br />
than D, and the new valve should be<br />
chosen so that q’ 11 1.3.<br />
3. Second computation stage<br />
P2 – PV P’ 2 – PV = ‘ =<br />
P1 – P2 P1 – P’ 2<br />
If points (q11, ) are situated in cavitation region 1 (excellent)<br />
in fig. 6, then there is no risk of cavitation and the<br />
MONOVAR ® diameter initially assumed may be selected - or<br />
even diminished.<br />
If points (, q11) are situated in regions 2 or 3 (acceptable<br />
or possible), the effective cavitation risk will depend on operating<br />
life and it may be necessary to choose a larger<br />
MONOVAR ® .<br />
MONOVAR ®<br />
<strong>Monovar</strong> ® flow and cavitation characteristics<br />
q 11<br />
1<br />
0.5<br />
Area 4 Area 3 Area 2 Area 1<br />
100 80 60 40 20 0 0.5 1 1.5<br />
Example numerics<br />
water<br />
0.67<br />
0.5 0.4<br />
Q = 0.150 m 3/s Q’ = 0.250 m 3/s<br />
P 1 = 50 mCE P’ 1 = 48 mCE<br />
P 2 = 25 mCE P’ 2 = 28 mCE<br />
∆H = 25 mCE ∆H’ = 20 mCE<br />
P V<br />
= 0.2 mCE<br />
D = 0.3 m<br />
N.B. : The appearance of a contraction expansion wili modify<br />
the MONOVAR ®'s specifications. Please consult us if this occurs.<br />
0.15 0.25<br />
q =<br />
11<br />
0.3 2 = 0.33 q’ =<br />
11<br />
25<br />
0.3 2 = 0.62<br />
20<br />
0.62 1.3 : the MONOVAR ® will therefore have a<br />
dia. 0.3 m.<br />
25 – 0.2 28 – 0.2<br />
= 50 – 25 = 0.99 ‘ = 48 – 28 = 1.39<br />
As both points lie in region 1, a 0.3 m dia. MONOVAR ®<br />
may be chosen. If D were reduced to 0.25 m, then<br />
q 11 = 0.48 q’ 11 = 0.89<br />
and the valve would be subject to cavitation in certain cases.<br />
K<br />
5
<strong>Control</strong> valve MONOVAR ®<br />
Valve dimensions<br />
6<br />
C<br />
DN Actuator(1) A(4) B C(3) D(3) E(3) d N(2)<br />
100 M 162 60 250 390 – 7 8 11<br />
100 E 162 60 383 480 290 7 32<br />
150 M 220 80 250 516 – 11 12 20<br />
150 E 220 80 383 580 320 11 38<br />
200 M 290 80 250 587 – 15 15.5 35<br />
200 E 290 80 383 645 350 15 46<br />
250 M 350 84 315 727 – 18 19 56<br />
250 E 350 84 475 795 377 18 80<br />
300 M 400 95 400 757 – 22 11.5 79<br />
Weight<br />
daN<br />
300 E 400 95 475 850 400 22 106<br />
400 M 516 110 500 943 – 29 15 148<br />
400 E 516 110 400 1 160 602 29 215<br />
500 E and M 593 150 580 1 720 900 36 480<br />
600 E and M 695 160 580 1 840 960 43 560<br />
700 E and M 810 160 580 1 920 1 010 50 600<br />
800 E and M 917 160 580 2 040 1 060 58 700<br />
900 E and M 1 017 160 580 2 150 1 120 65 800<br />
1 000 E and M 1 124 160 580 2 280 1 170 72 900<br />
1 200 E and M 1 344 160 580 2 460 1 280 87 1 100<br />
1 400 E and M 1 552 160 580 2 670 1 380 102 1 400<br />
1 500 E and M 1 660 160 580 2 770 1 440 109 1 700<br />
Dimenssions in mm, weights in kg - Dimensions and weights are given as a guide<br />
D<br />
DIA<br />
A B<br />
(1) M : Manual actuator (2) Number of turns closing by manual actuator<br />
E : Electric actuator (3) Dimensions in mm<br />
E and M : Electric actuator + manual control (4) Insertion between flanges according to NFE 29 201 PN 10, 16 or 25 or<br />
via reduction gear <strong>AN</strong>SI 150 Ibs.<br />
C<br />
d<br />
E<br />
D
Valve actuators<br />
MONOVAR ® control valves may be<br />
controlled manually (handwheel with<br />
micrometer position indicator) or by<br />
electrically or pneumatically powered<br />
valve-actuators. Information on the<br />
large range of actuator possibilities is<br />
available on request.<br />
Materials<br />
of construction<br />
Standard materials are as follows :<br />
• Body : FGS 500-7 nodular cast iron<br />
• Fixed plate : FGS 700-2 nodular cast<br />
iron or 13 % Cr stainless steel (Z20 C13)<br />
• Moving plate : FGS 500-7 nodular<br />
cast iron or 13 % Cr stainless steel<br />
(Z20 C13)<br />
• Support : FGS 500-7 nodular cast iron<br />
• Stem : 13 % Cr stainless steel<br />
• Flange and stem seals : 70 Shorehardness<br />
Perbunan<br />
Other construction materials are available<br />
on request to suit particular operating<br />
conditions.<br />
Assembly<br />
MONOVAR ® valves may be mounted<br />
between pipe flanges with the aid of tierods,<br />
which ensure correct alignment.<br />
They may also be mounted at the end of<br />
a pipe. To facilitate mounting and<br />
disassembly, sliding flanges or sleeves<br />
are recommended.<br />
The valves may be installed in both vertical<br />
and horizontal pipes. In vertical<br />
pipes the flow should preferably be<br />
downwards. Valves mounted horizontally<br />
should be placed with the actuator<br />
upwards to make proper use of the<br />
drain orifice, which will then be situated<br />
on the underside.<br />
MONOVAR ®<br />
Other related<br />
products and services<br />
Safety and flow control equipment :<br />
• Flow controler and meter MODUVAR ®,<br />
• Diaphragms,<br />
• Relief valves,<br />
• Butterfly valves,<br />
• Clasar non-return check valves,<br />
• Globe valves.<br />
MONOVAR ® DN 1200<br />
Water adduction in Riyadh<br />
(Saoudi Arabia)<br />
Terminal Dam (California)<br />
ND40’ (1000 mm)<br />
7<br />
- 02/00 - 2000 - <strong>SAPAG</strong> Industrial Valves reserves the right to modify at any time the characteristics of the materials presented.<br />
CFAG<br />
PILE OU FACE ➤ GROUPE
2, RUE DU MARAIS - 80400 HAM - FR<strong>AN</strong>CE<br />
TÉL. 33 (0)3 23 81 43 00 - FAX 33 (0)3 23 81 18 69<br />
HEAD OFFICE : AVENUE BROSSOLETTE - 59280 ARMENTIÈRES - FR<strong>AN</strong>CE<br />
TÉL. 33 (0)3 20 10 55 00 - FAX 33 (0)3 20 10 56 00