RU2552425C1 - Device for selection of hole size for easy detachable element of construction and its mass, designed to protect buildings and structures from explosions - Google Patents

Abstract

FIELD: blasting operations.SUBSTANCE: device for selection of the hole size for easy detachable element of construction and its mass, designed to protect buildings and structures from explosions comprises an explosive chamber, in the upper base of which there is a hole overlapped by the easy detachable element. The hole area can vary by screwing the removable rings. The detachable element overlaps the hole in the ring, over which a protective shield is fixed. The second hole is overlapped by the valve which is pressed against the hole by means of an electromagnet and opens by the spring during opening of the contacts. The pressing force of the valve and compressing the spring is set so as the total force to be equal to the allowed pressure multiplied by the area of the valve hole, i.e. ?F=Fe.m - Fpr=?Pdm Scl, where Fe.m is the force of the electromagnet pressing the valve to the hole, N/m; Fpr is force of compressing the spring, opening the valve, H:Fpr=(10÷15) gm, where g = 9.81 m/s; m is mass of the electromagnet core with the valve, kg; ?Rdm is allowable pressure drop for the model plant; Scl is the area of opening the valve, m. The easy detachable comprises a metal armoured frame with metal armoured coating and filler - lead having at the ends four fixed support tubes. In coating of the explosive object four support rods are rigidly embedded, which are telescopically inserted in the fixed support tubes of the panel. The filler is made in the form of the dispersion system air-lead, at that the lead is made in the form of crumbs, and the support rods are made elastic. Additionally, it comprises elastic-damping collapsing elements of single action, which are mounted on the support rods to the sheet-abutments through the damping base with the screws. A sleeve of single action is attached by the flange with the screws to the base coaxially to the rod, made of fragile, collapsible material such as porcelain. The space between the sleeve and the elastic part of the collapsible element is filled with construction foam, which connects the leaf springs with the sleeve of single action, forming a three-dimensional damper, which contributes to reliable fastening of the leaf springs and receives the first shock pulse.EFFECT: invention enables to improve the efficiency of protection against explosions.3 dwg

Description

The invention relates to safety systems in emergency situations and can be used for explosion protection of buildings, structures, as well as technological equipment.

The technological process of some industries is associated with the possible emission and accumulation in the production room of vapors of flammable liquids, gases or dusts, which, when mixed with air in certain concentrations, form an explosive atmosphere, such plants belong to categories A, B or E for explosive and fire hazard.

Explosion of gas, steam and dust-air mixtures causes damage to buildings and equipment. As protection of buildings from destruction in them, part of the enclosing structures is performed with easily erasable or easily destructible ones.

The closest technical solution to the claimed object is an explosion-proof device according to the patent of the Russian Federation No. 2379569 (prototype), containing a valve body, a shutter, heat insulating and explosive elements.

A disadvantage of the known solution is the relatively low reliability of operation due to the lack of comparative tests on model objects.

The objective of the claimed object is the following: according to the permissible pressure, it is necessary to select the required hole area and the permissible weight (mass) of easily erased (collapsing) enclosing devices per unit area of the enclosed opening (hole).

The technical result is an increase in the efficiency of protection of buildings, structures, as well as technological equipment from explosions by increasing the speed and reliability of operation with the help of collapsing structural elements and evaluating the effectiveness of easily resettable enclosing explosion-proof devices in emergency mode at the facility and ensuring the return of these structures to their original position after the explosion.

This is achieved by the fact that in the method of selecting the hole size for an easily ejected structural element and its mass, intended to protect buildings and structures from explosions, which consists in the explosion of vapors of a combustible liquid by igniting a combustible mixture from an electric spark of a spark plug and the parameters of the explosion are determined, and the explosive chamber is equipped with an easily erasable element, which is installed in the end part of the vessel closed by a safety shield, in parallel with the mechanical they have a pressure indicator with a toggle switch for turning on the indicator engine, and an explosive chamber with a spark plug having an ignition button is placed opposite the end part of the vessel closed by a safety shield, and the vessel is equipped with fittings for purging the explosive vessel after the experiment, and a fitting for pouring combustible liquid with the plug installed on it, they are fixed in the vessel wall above the contacts of the spark plug, while the elements involved in the test: pressure indicator, spark plug, pieces cer for pouring a combustible liquid, the fittings for purging the explosive vessel are selected by the tensile strength exceeding the strength of the studied easy-to-discharge element by at least two times, while the explosion pressure is recorded by a mechanical pressure indicator, and after each experiment, the vessel is purged with air , and the necessary concentration of the mixture of vapors with air is provided by pipetting the liquid through the nozzle, which, after pouring the liquid, is closed with a stopper, while setting such values of the hole area and the characteristics of easily ejected structures — weight and strength — are satisfied so that the condition is satisfied:

ΔP _P ≤ΔP _L ≤ΔP _D ,

where ΔP _P = P _P -P ₀ ; ΔP _L = P _L -P ₀ ; ΔР _D - permissible pressure from the condition of strength or bearing capacity of the main structures of buildings, MPa; P ₀ - atmospheric pressure, MPa; P _L - the maximum pressure on the walls during the explosion of the gas and vapor-air mixture in the vessel with an opening enclosed by an easy-to-discharge element, MPa; P _P - the maximum pressure on the walls during the explosion of the mixture in a semi-closed volume, i.e. the hole is open from the moment of ignition, MPa; at the same time, the differential pressure _{ΔР D.M} is first found for the model installation according to the following formula:

where ΔRd.n - differential pressure over the walls of the volume in natural conditions, MPa; W _H is the volume of the vessel under natural conditions, m ³ ; W _M is the volume of the explosive chamber of the model installation, m ³ ; d _cp.H , d _cp.M - the average diameter of the hole of the nature and model, respectively, and then empirically in the laboratory setting, determine the required value of K _sb and the mass of the discharged element from the condition: S _sb = Ssp / W, where Sbp is the area of the hole, m ² ; W is the volume of the explosive chamber, m ³ .

In FIG. 1 is a diagram of a device for implementing a method for selecting a hole size for an easily ejected structural member and its mass, intended to protect buildings and structures from explosions, FIG. 2 is a diagram of an easily ejected explosion-proof element; FIG. 3 is a diagram of an elastically damping collapsing element of a one-time action for an easily resettable element of an explosion-proof structure.

A device for implementing the method of selecting the hole size for an easily ejected structural member and its mass, intended to protect buildings and structures from explosions (Fig. 1), consists of an explosive chamber 1, which is a metal vessel with a volume of 500 ÷ 1000 cm ³ (wall thickness 7 ÷ 8 mm). In the upper base of the vessel there is an opening overlapped by an easily ejected element 2 of an explosion-proof design. The area of the hole can be changed by screwing in the interchangeable rings 21. The discharge element 2 overlaps the hole in the ring 21, over which the protective shield 3 is fixed. The second hole is blocked by a valve 19, which is pressed against the hole by the electromagnet 12 and opens by the spring 11 when the contacts 4 open. pressing the valve and compressing the spring is set so that the total force is equal to the permissible pressure multiplied by the area of the valve opening, i.e.:

where Fe.m - the force of the electromagnet, pressing the valve to the hole, N / m ² ; Fpr - spring compression force opening the valve, N: Fpr = (10 ÷ 15) gm, where g = 9.81 m / s ² ; m is the mass of the core of the electromagnet with the valve, kg; Scl - the area of the valve opening, m ² .

The pulling force of the electromagnet can be changed by changing the current through the rheostat 8 through the movable contact 9 of the rheostat. To measure the force of the electromagnet and the compression of the spring, a parallel device of the electromagnetic valve 6 is provided, the magnitude of the electromagnet current in which is regulated from the same rheostat 8 by switching contacts 5. For setting the required difference in the efforts of the electromagnet and the spring, there is a dynamometer 7. For the formation of a vapor-explosive mixture in the chamber vaporizer plug 18, into which the required amount of flammable liquid is introduced using a burette, and the plug is screwed so that the liquid vapor is black Without a window in the walls of the tube-evaporator fall into the chamber and, mixed with air, form an explosive mixture.

The mixture is ignited by an electric spark 20 from the induction coil 14, the ignition is turned on by the button 13. In one of the end (side) walls of the explosive chamber 1 there is an opening for the fitting 17, in which the tube from the blower 15, which is blocked by the valve 16, is fixed. The (side) wall of the blast chamber 1 has an opening for a fitting 23 for a tube 22, which is blocked by a valve 24, which serves to maintain atmospheric pressure in the chamber 1 during liquid evaporation.

The easily removable element 2 of the explosion-proof structure (Fig. 2) consists of an armored metal frame 25 with an armored metal casing 26 and a filler - lead 27. In the coating of the object 31 at the aperture 32, four support rods 28 are sealed symmetrically with respect to the axis 33, telescopically inserted into fixed nozzles - supports 30 embedded in the panel. To fix the limit position of the panel, the stop sheets 29 are welded to the ends of the support rods 28. In order to damp (soften) shock loads when the panel is returned, the filler is made in the form of a dispersed air-lead system, the lead being made in the form of crumbs, and the supporting the rods 28 are made elastic. An elastic-damping collapsing element 34 of a one-time action is attached to the abutment sheets 29.

The filler may be made in the form of spherical chips of one diameter; in the form of spherical crumbs of different diameters. The filler can be made in the form of crumbs of arbitrary shape of different diametric (maximum external, arbitrary shape, contour of the crumb) size.

The elastic-damping collapsing element 10 of a one-time action (Fig. 3) is mounted on the support rods 28 to the abutment sheets 29 by means of a damping base 35 with screws 36. To the base 35, coaxially to the rod 28, is attached by a flange 38 with screws 39 a single-acting sleeve 37 made of brittle collapsing material, such as porcelain. The elastic part of the collapsing element 34 is made in the form of leaf springs 43 facing its convex part towards the axis of the rod 28, on which there is a threaded section 40 (thread with small pitch) for fastening the clamping element 41 of the sleeve type with grooves 42 for fixing one of the ends of the sheet springs 43, the other end of which is fixed in the damping base 35 by injection molding polyurethane.

The cavity between the disposable sleeve 37 made of a brittle, collapsing material, such as porcelain, and the elastic part of the collapsing member 34 is filled with construction foam, which connects the leaf springs 43 to the disposable sleeve 37, forming a spatial damper that facilitates the secure fastening of the leaf springs 43 and takes the first shock pulse.

The assembly of the elastically damping collapsing element 34 of a single action is carried out in the following sequence. An abutment sheet 29 is welded to the rod 28, perpendicular to its axis, after which a base 35 having grooves (not shown) is fastened to it with screws 36 to install one of the ends of the leaf springs 43, which are filled with injection molded polyurethane. Then on the rod 28, a sleeve 37 is installed, made of brittle, collapsing material, which is pressed along the threaded section 40 by a clamping element 41 of the sleeve type with grooves 42 to simultaneously fix the other end of the leaf springs 43. Thus, the collapsing element 34 is ready for installation on explosion-proof panel.

Easily resettable element 2 explosion-proof design works as follows.

In an explosion inside an industrial building (not shown), the easily ejected element 2 rises from the action of the shock wave and overpressure is released through the open opening 32. After the explosion and the drop in excess pressure, dropping down, the panel closes the opening 32 and harmful substances do not enter the atmosphere. To fix the limit position of the panel, stop plates 29 are used.

Elastically damping collapsing element 34 of a single action works as follows.

When lifting the easily ejected element 2 of the explosion-proof structure from the action of the shock wave, it abuts against the clamping element 41 of the sleeve type and the thread is cut off on the threaded portion 40 of the rod 28. With the further movement of the easily ejecting element 2, the clamping element 41 destroys the sleeve 37 of a one-time action made of brittle, collapsing material, such as porcelain, and compresses the elastic elements made in the form of leaf springs 43, which, compressing from the increasing pressure of the shock wave, at a certain moment they are deceived from attaching their ends in the grooves 42 and in the base 35 and fall, freeing the way for further movement of the clamping element 41 along the rod 28 until it interacts with the damping base 35. In the case of a large (more than 5 kPa) pressure of the blast wave or the welding joint is cut off, which fastens the support rods 28 to the stop sheets 29, or the rods jam and break 28.

In order to dampen (soften) shock loads when returning an easily ejected element 2, the filler of the metal frame 25 is made in the form of a dispersed air-lead system, moreover, the lead is made in the form of a crumb, and the support rods 28 are made elastic.

Using the proposed technical solution allows the prevention of explosive objects from destruction and the reduction of harmful substances into the atmosphere during an accidental explosion.

The method of selecting the size of the hole for an easily discarded structural element and its mass, designed to protect buildings and structures from explosions, is as follows.

When designing easily resettable devices, the main task is to establish such values of the hole area (openings) and characteristics of easily resettable structures - weight and strength, so that the condition is satisfied:

where ΔP _P = P _P -P ₀ ; ΔP _L = P _L -P ₀ ; ΔР _D - permissible pressure from the condition of strength or bearing capacity of the main structures of buildings, MPa; P ₀ - atmospheric pressure, MPa; P _L - the maximum pressure on the walls during the explosion of the gas and vapor-air mixture in the vessel with an opening enclosed by an easy-to-discharge element, MPa; P _P - the maximum pressure on the walls during the explosion of the mixture in a semi-closed volume, i.e. the hole is open from the moment of ignition, MPa.

The value of ΔP _D should be determined by the calculation of the building structures for the impact of explosive loads. Moreover, ΔP _D should be considered given. With an explosion in a small chamber, the pressure on the walls of the vessel turns out to be greater than with an explosion in a large chamber with all other conditions being equal - the nature and concentration of combustible gas, the area of the hole per 1 m ^{3 of} volume, the weight of an easily discharged enclosing device per 1 m2 ^{of the} area of the hole. The influence of the scale factor becomes especially noticeable during the transition from laboratory conditions, i.e. volumes of the order of several liters, to natural conditions, for example, to the conditions of industrial premises having volumes of the order of several thousand cubic meters.

The pressure for the conditions of the explosion in industrial premises according to the experimental data obtained at the laboratory facility, can be approximately determined by the formula:

where ΔР _N - excess pressure on the walls of the volume in natural conditions, MPa; ΔР _M - excess pressure on the walls of the vessel on the model installation, MPa; W _H - the volume of the vessel (room) in natural conditions, m ³ ; W _M is the volume of the explosive chamber of the model installation, m ³ ; d _cp.H , d _cp.M - average diameter (size) of the hole of nature and model, respectively.

For the given conditions - the volume of the room W _H , the permissible pressure R _D , the nature and concentration of the explosive mixture, it is necessary to determine the required area of the hole and the mass of the easy-to-discharge element so that condition (2) is satisfied. To do this, first from relation (2) find R _D.M for the model installation:

Then empirically in a laboratory setup should determine the required value of K _sb and the mass of the discharged element from the condition:

where Sotv - hole area, m ² ; W is the volume of the explosive chamber, m ³ .

Protection of buildings with the help of easily erasable or easily destroyed devices consists in the fact that part of the enclosing structures (walls and roofs) are made weakened in comparison with the main structures, the destruction of which would lead to the complete destruction of the building. Easily erasable or easily collapsing structures include windows if window frames are filled with ordinary window glass, doors, swing gates, lampposts; constructions of asbestos-cement, aluminum and steel sheets with light insulation, special coating plates, etc.

The protective effect of easily erasable enclosing structures is that they are destroyed in the initial stage of the explosion, when the pressure of gases (explosion products) has not reached a high value and is harmless to the main (supporting) structures. Through the openings that were formed as a result of the destruction of easily ejected structures, excess volumes of gases (unburned mixture and explosion products) are forced out of the building. Due to the ejection of a certain part of the excess volumes of gas, the pressure and, consequently, the load on the main structures are reduced compared to that which would have occurred if the same mixture had exploded in a closed volume.

If the building has a sufficient number of openings fenced with easily erasable structures and their weight and strength are correctly selected, then the pressure and, accordingly, the load on the main structures can be reduced to the required values, established from the conditions of strength or bearing capacity of the main structures.

The norms established that the area of easily ejected structures should be at least 0.05 m ² per 1 m ^{3 of the} volume of the explosive room for the production of categories A and E and at least 0.03 m ² per 1 m ³ for the production of category B. The weight of the easily ejected structures should be no more than 120 kg / m ² .

Instruments and equipment used for the experiment

The installation consists of an explosive chamber 1, which is a metal vessel with a volume equal to 500 ÷ 1000 cm ³ (wall thickness 7 ÷ 8 mm). In the upper base of the vessel there is a hole overlapped by an easy-to-remove element 2. The area of the hole can be changed by screwing in the replaceable rings 21. The second hole is closed by a valve 19, which is pressed against the hole by means of an electromagnet 12 and opens by a spring 11 when the contacts open 4. The force of pressing the valve and compression the spring is set so that the total force is equal to the permissible pressure multiplied by the area of the valve opening, i.e.:

where Fe.m - the force of the electromagnet, pressing the valve to the hole, N / m ² ; Fpr - spring compression force opening the valve, N: Fpr = (10 ÷ 15) gm, where g = 9.81 m / s ² ; m is the mass of the core of the electromagnet with the valve, kg; Scl - the area of the valve opening, m ² .

The traction force of the electromagnet can be changed by changing the current through the rheostat 8. To measure the electromagnet's force and compress the spring, a parallel solenoid valve 6 is provided, the magnitude of the electromagnet current in which is regulated from the same rheostat 8 by switching contacts 5. To adjust the required difference in the efforts of the electromagnet and the spring there is a dynamometer 7.

For the formation of a vapor-air explosive mixture, the chamber has an evaporator stopper, into which the required amount of flammable liquid is introduced using a burette, and the stopper is screwed so that liquid vapors pass through the windows in the walls of the evaporator stopper into the chamber and, when mixed with air, form an explosive mixture. The volume of liquid (m ³ ) necessary for the formation of a vapor-air mixture of a given concentration in the chamber can be determined by the formula:

where W _K is the volume of the blasting chamber, m ³ ; µ _W - molecular weight of the liquid; C is the volumetric concentration of steam,%; P ₀ - atmospheric pressure, MPa; R is the universal gas constant, J / (kmol · deg); ρ _W - the density of the liquid, kg / m ³ ; T is the temperature, K.

The mixture is ignited by an electric spark 20 from the induction coil 14, the ignition is switched on by button 13.

In the side wall of the chamber there is an opening for the nozzle 17 for the tube from the blower 15, which is blocked by the valve 16. The second hole for the nozzle 23 for the tube 22, which is blocked by the valve 24, serves to maintain atmospheric pressure in the chamber during liquid evaporation.

The discharged element 2 overlaps the hole in the ring 21, over which the protective shield 3 is fixed.

The order of the experiment

1. Determination of the required specific hole area Xsb.

For the given conditions of the explosion and the given ΔР _D according to the formula (1), determine ΔР _{D · M} for the model installation:

where ΔР _N - excess pressure on the walls of the volume in natural conditions, MPa; ΔР _M - excess pressure on the walls of the vessel on the model installation, MPa; W _H - the volume of the vessel (room) in natural conditions, m ³ ; W _M is the volume of the explosive chamber of the model installation, m ³ ; d _cp.H , d _cp.M - average diameter (size) of the hole of nature and model, respectively.

For the given conditions - the volume of the room W _H , the permissible pressure R _D , the nature and concentration of the explosive mixture, it is necessary to determine the required area of the hole and the mass of the easy-to-discharge element so that condition (2) is satisfied.

When designing easily resettable devices, the main task is to establish such values of the area of the hole (openings) and characteristics of easily resettable structures - weight and strength, so that the condition

where ΔP _P = P _P -P ₀ ; ΔP _L = P _L -P ₀ ; ΔР _D - permissible pressure from the condition of strength or bearing capacity of the main structures of buildings, MPa; P ₀ - atmospheric pressure, MPa; R _D - the maximum pressure on the walls during the explosion of the gas and vapor-air mixture in the vessel with an opening enclosed by an easy-to-discharge element, MPa; P _P - the maximum pressure on the walls during the explosion of the mixture in a semi-closed volume, i.e. the hole is open from the moment of ignition, MPa.

To do this, first from relation (1) find R _D.M for the model installation:

Then, empirically, in a laboratory setup, the required value of K _sb and the mass of the discharged element should be determined from the condition:

To _sat = Sotv / W,

where Sotv - hole area, m ² ; W is the volume of the explosive chamber, m ³ .

Set the spring compression to approximately (10 ÷ 15) gm. Choose the current of the electromagnet so that equality (5) holds. Switch contacts 5 to working position. Carry out the first test at the maximum discharge opening, which is closed with the lightest element, such as plastic wrap. If the valve 19 did not work during the explosion of the mixture, then the pressure did not exceed ΔPdm

In the next test, the hole is reduced (a ring with a smaller hole is screwed in), etc. If the valve 19 works (opens), then the value of the area of the hole that was before the valve worked will be the smallest sufficient to satisfy condition (1), i.e.:

ΔF = Fe.m-Fpr = ΔRd.m Scl, (1)

where Fe.m - the force of the electromagnet, pressing the valve to the hole, N / m ² ; Fpr - spring compression force opening the valve, N: Fpr = (10 ÷ 15) gm, where g = 9.81 m / s ² ; m is the mass of the core of the electromagnet with the valve, kg; Scl - the area of the valve opening, m ² .

For the found area of the hole, determine the ratio To _sb = Sotv / W.

The setup of the installation during pilot explosions should be performed in the following sequence: with open holes - the discharge and blocked by valve 19 and open cranes 16 and 24, the chamber is blown. In the discharge hole put (screw) a ring with the desired area of the hole. The switch 5 includes an auxiliary device on which the compression of the spring and the current of the electromagnet are set so that condition (1) is satisfied.

The position of the movable contact 9 of the rheostat 8 is fixed, and the switch 5 is placed in the working position. The toggle switch 10 turns on the current of the electromagnet, while closing the valve and valve 16. The required amount of flammable liquid is introduced into the evaporator, which for a given concentration and volume of the blast chamber can be determined by the formula (6). After 3 ÷ 5-minute exposure, the valve 24 is closed and the ignition is turned on by turning on the toggle switch 13. The effectiveness of this size of the hole area is fixed by the actuation or failure of the valve 19.

2. Determining the allowable weight (mass) of the discharged element per unit area of the hole

The hole area is set equal to or greater than the value specified in paragraph 1. The first test is carried out with the lightest discharge element. If the valve 19 does not work, then the next test is carried out with a heavier discharge element. Thus, several explosions are carried out, at each of which the weight of the discharged element is increased by a certain amount until the valve 19 is activated. The previous value of the weight of the discharged element is the largest that can be allowed for condition (1) to be fulfilled. The found value of the weight of the discharged element must be divided by the area of the hole in order to obtain the desired value - the permissible weight of the easily discharged enclosing structures per unit area of the hole (opening). The setup sequence for conducting experimental explosions is the same as in paragraph 1.

Claims (1)

A device for selecting a hole size for an easily ejected structural element and its mass, designed to protect buildings and structures from explosions, containing an explosive chamber, in the upper base of which there is an opening overlapped by an easily ejected element, the opening area can be changed by screwing interchangeable rings, and the discharge element overlaps the opening in a ring over which a protective shield is fixed, the second hole being blocked by a valve that is pressed against the hole by an electromagnet and a spring that opens when opening the contacts, and the force pressing the valve and a compression spring is installed so that the total force equal allowed by the pressure multiplied by the valve opening area, i.e .:
ΔF = Fe.m-Fpr = ΔRd.m Scl,
where Fe.m - the force of the electromagnet, pressing the valve to the hole, N / m ² ; Fpr - spring compression force opening the valve, N: Fpr = (10 ÷ 15) gm, where g = 9.81 m / s ² ; m is the mass of the core of the electromagnet with the valve, kg; _{ΔР D.M} - differential pressure for a model installation; Skl - valve opening area, m ² , the easy-to-eject element contains a metal armored frame with metal armored casing and lead filler having four fixed support pipes at the ends, and four support rods that are telescopically inserted into the fixed pipes in the coating of the explosive object - supports of the panel, and the filler is made in the form of a dispersed air-lead system, moreover, the lead is made in the form of crumbs, and the support rods are made elastic, while it additional It additionally contains elastic, damping, collapsing, single-acting elements that are attached to the support rods to the abutment sheets by means of a damping base with screws, and a single-use sleeve made of brittle, collapsing material, such as porcelain, is attached to the base, coaxially with the screw, by means of a flange. that the cavity between the disposable sleeve made of a brittle, collapsing material, such as porcelain, and the elastic part of the collapsing element, filled with construction foam, which connects the leaf springs with a single-use sleeve, forming a spatial damper, which contributes to the reliable fastening of the leaf springs and receives the first shock impulse.

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