SU1756819A1 - Method of determining dust permeability of textile materials - Google Patents

Description

There is a known direct method for determining dust resistance, according to which dust permeability is estimated by the weight of the sample, through which a certain amount of air with known dust is passed through for a certain time with a prescribed pressure drop.

 The disadvantage of this method is the impossibility of determining the duration and dynamics of the process of retaining dust by a sample. Furthermore, the method does not take into account the force effect of the air flow on the structure of the test specimen, which is essential, especially for deformable textile materials, and affects the objectivity of the results.

The purpose of the invention is to increase the objectivity of the results of the determination.

The goal is achieved by the fact that the method of determining the dust permeability of textile materials, which consists in passing a dust-air mixture through a sample at a certain pressure drop for a given time interval, determining the amount of dust deposited on the sample, and estimating dust penetration through it. A control sample of the same material is air at a given pressure, and the value of the drop in pressure DRE of the air on the control sample is determined; through the test sample, the air mixture is carried out at the same pressure as that of the control sample, and the amount of dust deposited on the test sample is determined by the magnitude of the pressure drop on it, and the dust permeability index is calculated by the formula

P-K, APt (t),

1L At V AD.1

At

Dere

where P is dust permeability, m2 / m3-s;

K - coefficient taking into account the type and concentration of dust in the dust-air mixture, m2 / m; ;

At is the specified time interval for the experiment, s;

APt (t) is the change in the current value of the pressure drop on a controlled sample as a result of exposure to it by a dust-air mixture under a certain pressure drop, mm et.ed .;

Dre - pressure drop on a controlled sample as a result of exposure

airflow under a certain pressure drop, mm water.s.s, and the specified time interval for dust-air mixture to pass through it

The sample is determined experimentally as the smallest time for filling the samples of the same material with dust at the same predetermined pressure.

Figure 1 shows schematically an installation for the implementation of the proposed method; in fig. 2 - choke circuit; in fig. 3 is a wiring diagram for analog reference elements.

The installation is a camera.

1, consisting of two pneumatic isolated compartments 2 and 3 from each other. Pneumatic insulation is carried out by wall A. For ease of insertion of the material 5 gz chamber 1 last can be performed

detachable along the line of location of the material 5.

Each compartment has in the upper part of the channel for the supply of compressed air (or dust-air mixture of a given concentration), and in the lower part - adjustable throttles 6,7. In addition, each compartment contains pressure sensors of 8.9 and 10.11 located on opposite sides of the test specimen.

The proposed method is implemented as follows.

The test sample is placed in chamber 1, with each compartment 2 and 3 being divided into two parts by the sample: the upper

and lower. Compressed air under a certain pressure drop is supplied to the upper part of compartment 2 on a control sample.

The magnitude of the overpressure PBX is recorded by sensor 8. Using adjustable throttle 6, it is achieved that the Roych pressure in the lower part of compartment 2 is equal to 0.6 PBX. The value of Pvyh1 register sensor 9. Then the air is turned off. The throttle resistance 7 is set equal to the resistance of the throttle 6. The last operation is carried out by sequential switching on the chokes 6 and 7 (Fig. 2). After adjusting the throttles 6, it is turned out of compartment 2. Then the throttle 7 is turned out of compartment 3. The chokes are turned on in series, as shown in FIG. 2. Adjust the resistances of the throttles 7 so that the output signal

Pvyh was 0.5 RVH. In this case, the resistances of the chokes 6 and 7 are equal.

After adjusting the throttles 6 and 7, they are installed in the appropriate compartments 2 and 3, and the installation is ready for operation.

The outputs of the sensors 9-11 are connected to the inputs of the analog elements 12 and 13 of the comparison, the outputs of which are connected to the inputs of the recorders 14 and 15. In the case of using pneumatic comparison elements, for example, type PGES 3 of the USEMPA system, there is no need for sensors 9-11. In this case, it is necessary to pneumatically connect the inlet chambers of the comparison elements with the corresponding parts of compartments 2 and 3 using flexible hoses.

Compressed air is supplied to the upper part of compartment 2. Under the same pressure for a predetermined time interval, a dusty air mixture of a given concentration is applied to the sample under investigation at the upper part of compartment 3. The pressure drop value ДРэ Рвх-Рвых1 (compartment 2) on the control sample is almost constant and characterizes the pneumatic resistance Re of the material under study. Magnitude

Re

ARZ SI

where QI is the compressed air flow through the sample.

The magnitude of the pressure drop of the Drag Pvc-Pout2 (compartment 3) is variable and depends on the properties of the test sample, the type of dust, its concentration, etc.

Magnitude

R (t) Oz (t)

where Q2 is the variable flow rate of compressed air, the value of which depends on the current dust permeability of the test specimen.

On the other hand

Q2

in

R3-R6

Q2

 in

RT + R

where Re and R are respectively pneumatic resistances of chokes 6 and 7. Then

Rvyh1-VK

Re

-

 GBH

R3 + R6 R Rv PB

RT + R RT -H Re

0

five

0

five

0

five

Therefore, with Re R7 const, Pbyx2 and Pout1 are only functions of the pneumatic resistances of the textile material.

PBbixi f (R3) const;

PBbix2 f (RT) var.

Thus, at the output of the comparison element 12, a signal is obtained which characterizes the time variation of the pneumatic resistance RT (t) of the textile material caused by exposure to it by a dust-air mixture.

The pressure drop of A Fe on the control sample when exposed to air flow is determined as follows

And Re Rvh-Rvyh1 S01Sh.

The pressure drop on the test sample during exposure to the dust-air mixture is P (t) Pox-Pebix2 (trvar.

The change in pressure drop on the test sample as a result of exposure to it with a dusty air mixture is

A P (t) A Pi (t) -A Рэ Рвх-Рвых2 (1) -Рвх + Рвых2 Рвых1 Рвых2 (т.).

The value of A P (t) is the variable component of the pressure drop across the sample, which characterizes its ability to pass dust.

In order to normalize the index of dust permeability of a textile material, the value of P is expressed as follows.

TT J AP (t) To DRT (O.-Re At DRE AtARE

K At

(DRTS-p

. L R.

AR:

The process of changing the value of DTA (t,) Pout1-Pout2 (1) is recorded, for example, using an oscilloscope 13. For this, the value is converted into an electrical signal. The maximum experiment time is determined by the moment when the output signal of the comparison element 13 becomes equal to PBX, since at Pout2, the textile material loses its ability to pass dust. This time point is recorded using comparator 15.

Studying the waveform of the change in APT (t). one can trace the dynamics of change in dust permeability of tested textile materials.

As a result of preliminary passage of air through a control sample of a textile material under a certain pressure drop and determination of the size of the ERA characterizing the pneumatic resistance Re of the sample, information is obtained on the force effect of the air flow on the structure of the textile material. If a textile material is made of soft, pliable yarns, then its structure will change more as a result of exposure to air flow than that of a textile material produced from rigid yarns. A change in the structure of a textile material also leads to a change in its dust permeability. Consequently, these operations allow the value of A Re (or R3) of a textile material to determine the effect of the air flow on its structure and to take this effect into account when evaluating dust permeability using the formula

p-k-rAEL ii

And A11DR b

since a pt is the sum of two quantities

DRT ARE-ARP.

where DRP - component, due to the properties of the textile material,

those. reflects the ability of yarn, textile material to hold (pass) dust.

Thus, the value of P characterizes the ability of a textile material to pass dust, due not only to interstitial gaps, but also to adhesion properties.

The proposed method allows to evaluate the properties of a textile material without taking into account the specific dimensions of the test specimen.

Example. The test sample of the material is placed in chamber 1. The sample area of the material is 100 cm2.

Compressed air under pressure mm Vog.st. (103 Pa) is supplied to Branch 2. The chokes 6 and 7 are tuned in accordance with the described procedure. As a result of setting the chokes 6 and 7, we get a PW1 of 60 mm water column. One time after the start of the passage of soot through the sample, the pressure of Reix2 became equal to 17 mm of water column.

Thus, the value of A re Ryugrovy1 40 mm water column., And the value of A RT (with c) -Pin-Ptykh21I100-17 83 mm water column.

The K factor for carbon black concentrations of 50 mg / cm is assumed to be 17 m / m3.

Get

GT - K. (D ° 1 s-r1

11 At (DRE;

The maximum test time is determined by the time of the change in the current value of the pressure drop on the control sample as a result of exposure to it.

dust-air mixture under a certain pressure drop D Pt. If, as a result of the test, the value of APt ceases to change (increase), then the textile material ceases to leak dust and the test must be stopped. Consequently, by the time of the change in the value of APt, it is possible to determine the appropriate time for the test.

Claims (1)

Invention Formula The method for determining the dust permeability of textile materials, which consists in passing a dust-air mixture at a certain pressure drop over a test sample for a given time interval, determining the amount of dust deposited on the sample, and estimating dust penetration from it, in order to increase objectivity of the determination results, air is preliminarily passed through a control sample of the same material at a given pressure and the value of the air pressure drop is determined on the control sample, passing the dust-air mixture through the test sample is carried out at the same pressure value as through the control sample, and the amount of dust deposited on the test sample the sample is determined by the value of the pressure drop over it, and the coefficient of permeability is calculated by the formula 40 P K g APt (t) 11 At L AREJ where P is dust permeability, m2 / m3 s; K - coefficient taking into account the type and concentration of dust in the dust-air mixture, m / m, At is the specified time interval for the experiment, s; D Pt (0 change the current value pressure drop on the test sample when exposed to a dusty mixture under certain pressure drop, mm waters Art. Dre is the pressure drop over the reference sample when exposed to the air flow under a certain pressure drop, mm water line, And the time interval for the passage of dust-air mixture through the test The sample is determined experimentally by the dust of the control sample at as the smallest time value at the same predetermined pressure. St / th ra r fadyx, {| one 4-H Fig / L breathing FIG. 2 PQX Pi / Light Air II mixture + B J AGH