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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

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