PERFORMANCE M E T E R I N G DEVICE ( P M D ) FOR CONVEYERS

W I T H VARYING ANGLE OF I N C L I N A T I O N

Ya. S. K r a v c h e n k o , M. B. B e r e n b o i m , a n d T. S, K r a v c h u k

UDC 622.6a7 : 621.867

For measuring the throughput of a belt conveyer, the most widely used devices are electronic meters with strain gauges. The throughput is taken as the product of the weight of the load by its rate of motion [1.2].

Tensometric balances involve great difficulties owing to the complex technology required to prepare the strain gauges and the conditions for their use. The use of such a balance on a conveyer requires the construction of a special measurement platform and the reconstruction of the roller bearings.

To measure the throughput of a conveyer with a variable angle of inclination, we must introduce corrective elements to the instrument: this leads to additional construction and design complications in the tensometric

balance unit.

At the UkrNIIproekt Institute, in developing a performance metering device for conveyers with variable angle of inclination, we based it on the principle that the instantaneous throughput is proportional to the power consumed by the motor. The device designed for the ~RG 400/1000 rotor excavator is applicable to a dumping-arm conveyer.

We can assume that the power consumed by the conveyer motor is related to the throughput by the foUowing

expression [3, 4]:

I . l o L ( qo + qolW'cos~ 1.1QL(a,~cosaS:sln~) ~_ , (i)

Prot -- ~" ~'d Tin ' 3,6 ~ r. d r, m

where v is the belt speed, L the belt length, q~ the weight per meter of belt (lower section), ct~ is the weight per meter of belt (upper section), w' is the coefficient of resistance to motion, a is the angle of inclination of the con- veyer, rid is the efficiency of the drive, Vm is the efficiency of the motor, Q is the instantaneous throughput of the conveyer, and wkt is the coefficient of resistance to motion of the material.

For a belt conveyer in its working range,

w" = win= w; r,m=const; ~Td=--const.

We are putting

1 1 1 I. - = q'o + q ; = q ~.': -r. d ~m

Then the total operative power consumed by the motor is

Ptot = cvqw cos a + cq Q (r~ cos a + sin ~t). (2)

Since the angle of inclination of the I~RG 400/1000 excavator's dumping conveyer may vary from + 7 to -3" , we can put cos a ~ 1. Then Eq. (2) reduces to the simpler form

t~ot = cvqw § cc: O (w 4- sin ~) = Pzdl~- Pmeful,

where cvqw = Pidle is the power consumed to move the conveyer without load (th e idle power), and

cclQ(w i sin a ) = Puseful

is the useful power expended on moving the load. Hence

Q _ Ptot - -~dle (3) cc~ (w • sin a)

UkrNIIproekt, I~iev. Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Bkopaemykh, No. 2, pp. 109-114, March-April, 1967. Original article submitted November 24, 1968.

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r

Fig. 1. PMD system for horizontal conveyer, ( A P - active power monitor).

On the other hand,

Ptot" = 3U/l:ot

Therefore

Equation (3) was taken as the basis for our design.

Let us examine the particuiar case of a horizontal conveyer, when a = 0, while the denominator cclw is constant. Let us c a d i t I/k. Then Eq. (3) becomes

q = k (Ptot -- Pidle)- (4)

Obviously

aUhl ~ %eful= 3W=ef=c~ ;=' where U is the motor voltage, I idle is the motor current when there is no load on the belt, Iuseful is the motor current expended on moving the load, ql is the phase difference between U and I id le , and ~2 is the phase difference between U and Iuseful. Then

cos ? -~ 3U ( / id le COS,, +/usefulCOS ~) . (5)

/>tot --- q d l e Q _-- 3UlidlCOW, + ...~. (6)

Q = 3k (U/ to t cos V -- U~dlpS ?a) (7)

o r

0 = akU(/mt cos ~ - ~d~S v,). (8)

Thus, for the case when the conveyer is horizontal, the instantaneous throughput is direct ly proportional to /he difference between Ptot and Pidle and the constant coeff icient lL Figure 1 shows a system for solving Eq. (8). The id le power is compensated for by a voltage U s taken from resistance R F

The id le power is regulated when there is no load on the belt. In this case the voltage at the output of the power sensor wil l be proportional to the idle power, Uv -- Pidle- If we regulate Us so that U s = Uz, then Uz = 0. Consequently on further change of UT (with a load on the belt) ,

U, = U7 -- Us -- Ptot - - P i d l ~ Q"

In the case when the conveyer is at an angle to the horizontal ( i .e., when vr ~= 0), the relation between the instantaneous throughput and the power is

Q = 3U(/rn r cos ~- I id l~OS r /~ot ~ d l e OCt t t~ ::[: sin =) = ccl (~ + sin =) ( 9 )

Consequently a device for monitoring the throughput of a conveyer working with variable angle of incRnation must effect both the operation of algebraic summation, (Ptot - Pidle), (w i sin a) , and that of division,

P to t - - P idte. "cci (~ + sin =)

To find G, the weight of rock transferred by the conveyer in t ime t t - t z (shift, day, etc.), we integrate Eq. (9):

t~

O = ~' P t o t - - Pidledt" (10) J col (w + sin =) t=

Write a l l the terms in F.q. (i0) as equivalent voltages

Ptot --/~dl~ mU2; sin= --- Us;

then Eq. (10) can be written

G=m f tt

U= ~•

w_--U~,

d t. (li)

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u.

%,

Fig. 2. Function circuit: 1, 3) algebraic summation unit; 2) power sensor; 4, 5) division units; 6) transformation unit; 7) integration unit.

' C ' 3 To maim 2 Tm-~

I I C5"

I EU- !

| I ,..jK"~, D 1 iC . , ~l/~Si , I . .l= r~Rs ~C~,~ I

i __ '

SS-1 1 I

Fig. 3. Line diagram of apparatus: 1) division unit; 2) transformation unit; 3) integra- tion device; 4) voltage stabilizer; IAS) inclination-angle sensor; MPM) magnetic power monitor.

where m is a proporr/onality coefficient.

A functional circuit for realizing Eq. (11) is shown in Fig. 2.

Block 1 effects algebraic summation of voltage U4 and voltage Us = n Uc~ sin cr obtained from the output of the incl inat ion-angle sensor (IAS) which consists of a BD-501 A selsyn operating in transformer conditions (U a is the supply voltage of the IAS and n is the transformation ratio of the selsyn). Blocks 4 and 6 effect division of Uz by Us, which is accomplished with the aid of an autocompomator [4]. The quotient k, - Q is converted to an e l ec - t r ical magnitude in block 6 which consists of a contactless selsyn of type BD-501 A built into a potentiometer [5],

Figure 3 is a line diagram of the PMD. The division unit (Block 1) consists of parts of an ~PV-01 electronic potentiometer [6] - an ~U-109 amplifier with output to an RD-09 reversible motor and a sl ide wire R s with a scale. The output of the division unit is the position of the slider on P-s, which gives the instantaneous value of the throughput:

/>tot - Pzdle Q= ccI (ru + sin =1

The voltage Uou t _-- Q is taken from the selsyn rotor SS-1 built into the potentiometer and is fed to the inte- grating unit (Block 3). which is an ordinary electrical-energy meter. The meter is rewound so as to ensure match- ing of the load resistance of the SS-1 selsyn, which is the current winding of the meter. To match the current and

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voltage phases in the meter, the voltage U on the voltage winding is fed via a phase-shifting bridge P, sRtCtC 0. The

whole measuring circuit is supplied via a voRage stabilizer (Block 4).

A pilot model of the device has undergone industrial tests, has been calibrated, and is now in experimental use on the rotor excavator of the Lebedinsk quarry of the KMA-rud Combine. Little engineering work was required

in iustalling and connecting up the device, so that the conveyer did not have to be shut down for long. An incli-

nation-angle sensor was attached to the dumping arm, and the MPM was connected complete to the conveyer

motor [7].

Since Eqs. (3) and (11) contain quantities wlRch depend on tbe conveyer parameters, the device must be

adjusted before being calibrated. This operation consisted in determining the supply voltage U a of the IAS at

which the value of a scale division would not vary when the conveyer inclination was altered, i.e.,

V = = ~ = const w h e n = - - vat, (12)

s

where a is the value of a scale division, and s is the number of turns of the meter when a volume V of rock passes through the conveyer."

If we take an arbitrary value U~ for the supply voltage of the I.AS, for a > O, we get

t2 t~

I U2(t) d r = mt a s'= = rat , U," + nU=' stn= U, + all'= sin = U2 (0 at . (13)

t~ t=

However, V a ,~ as~:

~g

V = = a s = = m I ff tt

U= (t) U4 + nU= sin a.

at. (14)

To find U a we divide E q , (13) by Eq. (14) and solve for Ua:

u.= , [ < /'l sift ct L $=

. ] (U, + n U = s in =) - U, .

If the conveyer is horizontal, c~ = 0, and the meter reading does not depend on Uct:

G

V~ = as~ = -~4 ; U' ( t) dt and a~ soV~ t~

(16)

Here V 0 is the volume of rock discharged at a = 0, and s a is the number of turns of the meter during the discharge

of volume V 0.

Knowing Vet, the volume discharged in a rime At = tz--t I during which the conveyer is operating with angle of inclination a , and having found a from Eq. (16), we can evaluate

If= (17) $=== a

Substituting Eq. (17) into Eq. (15), we can determine the required supply voltage U a of the IAS.

In adjusting the device, the arm is first set in a horizontal position, and with an arbitrarily chosen value of

U 4 we dump a cone of volume V 0. reading the number of turns of the meter s 0, and use r~l. (16) to find the value of a division a, For greater accuracy, the experiment is repeated several times and the mean value any found. Then with a known angle o~ and an arbitrarily chosen value of U a, a cone of volume V,, is dumped, the number of turns

of the meter, s~, is read off, and the required number of turns is determined:

* It is convenient to adjust the device from the volume of rock passing through the conveyer, rather than from the

mass, because the latter is difficult to measure.

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v~ aav

Substituting the value found into Eq. (15), we find the required value of the supply voltage to the IAS, Ucc

The value of U 4 is found from the condition that the scale should be used to its fullest extent. If U 4 is large,

the device can operate only at the beginning part of the scale, and the sensitivity will be low; if U 4 is small, com-

pensation of the voltage at the amplifier is incomplete and the divider unit cannot work.

If there is only a small variation (8-590) in the density of the excavated rock, the device can be used to esti-

mate the volume of broken and unbroken ground transported by the conveyer in a given time (shift, day, hour), i.e.,

the device can be used to monitor the throughput of the assemblage.

According to the parameter in question, we vary only the calibrating coefficient

6: V p . V w. r 1 ~ ~ ; G2 ~ - - , a3-- ,

$ 8 8

where G, Vp, V w are the weight and volume of the broken ground and the volume of unbroken ground, and a I, a z,

a s are the calibration coefficients.

Since the rock worked at the Lebedinsk quarry has a uniform density (chalk - 1.8 tons/m s, clay - 1.85 tons per mS), from the readings of our device we can find the volume of soil removed. In this case, the device is ca l i -

brated from the volume of unbroken ground:

Vw. a 3 - -

$

where Vw. is the volume of ground in the untouched mass according to survey measurements, and a s is the value of

a division on the meter in terms of the volume of ground in the untouched mass.

First experimental operation of the device has afforded satisfactory accuracy of measurement. The volume of ground removed in 12 shifts, according to the device, was V~v =31,140 mS; the volume removed according to

survey measurements was V w = 31,500 m s. The relative error was thus

k= Vw-- V' w ,100~ = 1 , 1 4 ~ . Vw.

Because of the ease with which this device is installed and connected up, we recommend it not only as a source of operational information for the engineer, but also as a measuring instrument for comparing the operation

of different machines.

LITERATURE CITED

1. V.I . Pechuk and L. Ya. Nagornyi, Electronic Strain-Gauge Weight-Measuring Devices, Avtomatika t Pribo-

rostoeuie, No. 4 (1961). 2. T.S. Kravchuk and ~. P. Semagina, Selecting a Principle for Measuring the Weight Throughput of a Rotor

Excavator, In Symposium: Experience of Modernization and Automation of Excavators and Rotor Machines

[in Russian], Moscow., TsNIIT~Iuglya (1966). 3. S. IL Mairnin and V. A. Mursdn, Consumption of Electrical Power by Conveyers, Topics in Mine Transport

[in Russian] (1954). 4. A.O. Spivakovskii and N. F. Rudenko, Underground Transport Machinery [in Russian], Moscow., Mashgiz

(1949). B. Ya. S. Kravchenko and T. S. Kravchuk, Experience in the Operation of the ~PV-01 Potentiometer as a Di-

viding Device, Priborostroenie, No. 6 (1964). 6. A.V. Erofeev, Electronic Monitoring and Comrol Devices for Thermal Processes [in Russian], Moscow., Gos-

energoizdat (1956). q. S.A. Ginzburg, A Magnetic Power Transducer [in Russian], Tr. TsnigL, Moscow, Gosenergoizdat (1957).

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