RU2515013C1 - Bench to test explosion-proof structures of buildings and facilities - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: in a bench for testing of explosion-proof structures of buildings and facilities, a blast chamber is equipped with an easily dropped element installed in the end part of the vessel, closed with a safety screen, in parallel to a mechanical pressure indicator with a tumbler of indicator motor start. The blast chamber with a spark plug and a button to star ignition are arranged oppositely to the end part of the vessel, closed with a safety screen. The vessel is equipped with nozzles for blowing of the blast vessel, a nozzle for pouring of the flammable liquid is fixed in the vessel wall above contacts of the spark plug, elements that participate in testing: a pressure indicator, a spark plug, a nozzle for pouring of flammable liquid, a nozzle for blowing of the blast vessel is chosen by tensile strength exceeding the strength of the investigated easily discharged element. Blast pressure is recorded with a mechanical pressure indicator.

EFFECT: increased efficiency of protection of buildings, structures and process equipment against explosions.

2 cl, 4 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 industries 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. 2458213 (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 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 test bench for explosion-proof structures of buildings and structures, the blast chamber is equipped with an easy-to-reset element, which is installed in the end of the vessel, closed by a safety screen, in parallel with a mechanical pressure indicator with a toggle switch for turning on the indicator engine, and an explosion chamber with an ignition plug having the ignition switch, positioned opposite the end of the vessel, closed by a safety screen, while the vessel is equipped with fittings for blowing the explosion of the vessel after the experiment, and the nozzle for pouring combustible liquid with the plug installed on it is fixed in the vessel wall above the contacts of the spark plug, with the elements involved in the test: pressure indicator, spark plug, nozzle for pouring combustible liquid, nozzle for blowing the explosive the vessels are selected according to 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 internal volume of the vessel is purged with air, and the required concentration of the vapor-air mixture is provided by pipetting the liquid through the nozzle, which is closed with a stopper after pouring the liquid.

Figure 1 presents a diagram of the test bench for explosion-proof structures of buildings and structures, figure 2 is a graph of pressure over time on the walls of the vessel during the explosion of gas-vapor mixtures; figure 3 is a diagram of an explosion-proof panel coating (or roof) of an explosive or radioactive object, figure 4 is a diagram of an elastic damping element.

The test bench for explosion-proof structures of buildings and structures (figure 1) 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 an opening overlapped by the easy-to-remove element 2. The area of the opening can be changed by screwing in the replaceable rings 21. The discharge element 2 overlaps the opening in the ring 21, over which the protective shield 3 is fixed. The second opening is blocked by a valve 19, which is pressed against the hole by the electromagnet 12 and opens with a spring 11 when the contacts 4 open. The force of pressing the valve and compressing the spring is set so that the total force is equal to the permissible pressure Multiplied by the valve opening area, i.e.

$$\Delta F=F\mathrm{uh}.m-FPR=\Delta Pd.mS\mathrm{to}l,\left(\mathrm{one}\right)$$

where Fe.m - the force of the electromagnet, pressing the valve to the hole, N / m ² ; Fpr - spring compression force opening the valve, H: 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 vapor es windows in the walls of the evaporation tube fall into the chamber and mixed with air to 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 is blocked by a valve 16. In another, opposite, the end (side) wall of the explosive chamber 1 has an opening for a fitting 23 for the tube 22, which is blocked by a valve 24, which serves to maintain atmospheric pressure in the chamber 1 during liquid evaporation.

The explosion-proof panel (Fig. 3) consists of an armored metal frame 25 with an armored metal sheathing 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 the fixed support tubes 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.

The filler can be made in the form of spherical crumbs 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 test bench for explosion-proof structures of buildings and structures works as follows.

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).

If the explosion occurs in a semi-closed volume, i.e. in the vessel there is a hole open from the moment of ignition of the mixture, then the change in pressure occurs along curve 2 (figure 2). In this case, the maximum value of pressure P _p will depend on the ratio of the area of the hole to the volume of the vessel and may be significantly less than the total explosion pressure P _in , which would be an explosion in a closed vessel.

The influence of the weight of easily ejected structures on the pressure value during an explosion is explained by their inertia. In order not to interfere with the free flow of gases, the easy-to-erase structure after destruction should be discarded a certain distance from the opening. This requires some time, during which the pressure has time to increase by a certain amount. The figure graphically shows the variation in time of the pressure P t in a building during the explosion, and drop walling (P ₀ - atmospheric pressure, t ₀ - start the explosion or ignition point). If the explosion occurs in a closed volume, for example in a sealed steel vessel, then the pressure on the vessel walls changes along curve 1. Point P _B corresponds to the maximum pressure during the explosion of gas and vapor-air mixtures in a closed vessel. Usually this value is 5 ÷ 7 kg / cm ² (500 ÷ 700 kN / m ² ).

In an explosion in a vessel with an opening closed by an easily ejected device, the pressure changes first along curve 1, i.e. as in a closed vessel, up to the point P _p (t _p ) corresponding to the moment of destruction of the easily ejected element.

The protective device for explosive objects (figure 1) consists of an armored metal frame 25 with an armored metal casing 26 and a filler - lead 27. The filler can be made in the form of spherical crumbs 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.

In the coating of the object 31 at the opening 32 symmetrically with respect to the axis 33, at least three support rods 28 are embedded, telescopically inserted into the fixed nozzle supports 30, embedded in a metal frame 25. To fix the limit position of the panel, the sheets are welded to the ends of the support rods 28 stops 29. 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, moreover, the lead is made in the form of crumbs. Elasto-damping elements 34 are fixed in the upper part of the support rods 28, one end of which is rigidly connected by its base 35 to the abutment sheets 29, and the other is freely positioned.

Each of the elastic-damping elements 34 (Fig. 4) is fixed by means of screws 36 with its base 35, made in the form of a circular disk of a hard vibration-damping material of the Agat type, on stop sheets 29, rigidly connected to the rods 28. The base 35 of the elastic-damping element is connected to a sleeve 37 of an elastomer having a central hole through which the shaft 28 passes. The sleeve has at least three holes 38 coaxial with the shaft 28 in which elastic elements 39, for example coil springs, are arranged, The upper end of which, by means of fasteners 40, is connected to the base 35, and the lower end is in a free (unpressed) state and protrudes beyond the lower plane of the sleeve 37 at a distance determined by the force developed by the shock wave.

In an explosion inside an industrial building (not shown in the drawing), the frame 25 rises with the armored metal casing 26 and the filler from the action of the shock wave and overpressure is released through the open opening 32.

In this case, the elastic damping elements 34 are compressed, extinguishing the energy of the explosion, and then return the panel to its original state.

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, abutment sheets 29 are used. In order to damp (soften) shock loads when the panel is returned, 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 crumbs, and the support rods 28 can be 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.

Figure 2 presents a graph of the pressure over time on the walls of the vessel during the explosion of gas-vapor mixtures: 1 - in the explosion in a closed vessel; 2 - in case of explosion in a vessel with an opening open from the moment of ignition; 3 - in the event of an explosion in a vessel with a hole closed by an inertia-less easily resettable device; 4 - in case of explosion in a vessel with an opening closed by an easily ejected device having inertia.

Then, if it were opened instantly, then the pressure change from the point P _P (t _P ) would occur along curve 3. The maximum pressure would be P _P (with a sufficient hole area). But since the movement of the easily ejected structure from the hole due to its inertia occurs in a certain time, the pressure will change along curve 4 with a maximum pressure value of P _l

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

$$\Delta P_P\le \Delta P_L\le \Delta P_D,\left(2\right)$$

где ΔP_П=P_П-P₀; ΔP_Л=P_Л-P₀; ΔP_Д - допускаемое давление из условия прочности или несущей способности основных конструкций зданий, МПа; P₀ - атмосферное давление, МПа; P_Л - максимальное давление на стенки при взрыве газо- и паровоздушной смеси в сосуде с отверстием, огражденным легкосбрасываемым элементом, МПа; P_П - максимальное давление на стенки при взрыве смеси в полузамкнутом объеме, т.е. отверстие открыто с момента воспламенения, МПа. $$$$

where ΔP _P = P _P -P ₀ ; ΔP _L = P _L -P ₀ ; ΔP _D - allowable 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 gas and vapor-air mixtures in a vessel with an opening enclosed by an easily ejected 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

$$\Delta P_N=\Delta P_M\sqrt[5]{{\left(\frac{W_M}{W_N}\right)}^2{\left(\frac{d_{\mathrm{from}R.N}}{d_{\mathrm{from}R.M}}\right)}^3}\left(3\right)$$

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

For given conditions - the volume of the room W _N , the permissible pressure P _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 fulfilled. To do this, first from relation (2) find P _D.M for the model setup:

$$\Delta P_{D.M}=\Delta P_{D.N}\sqrt[5]{{\left(\frac{W_N}{W_M}\right)}^2{\left(\frac{d_{\mathrm{from}R.M}}{d_{\mathrm{from}R.N}}\right)}^3}\left(\mathrm{four}\right)$$

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

$$K_{\mathrm{from}b}=S\mathrm{about}t\mathrm{at}/W,\left(5\right)$$

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 enclosed by 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 strength or bearing capacity of the main structures.

The explosion-proof panel operates as follows.

In an explosion inside an industrial building (not shown in the drawing), the panel 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. In order to damp (soften) shock loads when the panel is returned, 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 crumbs, and the support rods 29 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 norms established that the area of easily-vented structures should be at least 0.05 m ² per 1 m ^{3 of the} volume of an explosive room for industries of categories A and E and at least 0.03 m ² per 1 m ³ for industries of category B. The weight of easily-vented structures should be no more than 120 kg / m ² .

The device 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 an opening overlapped by the easy-to-remove element 2. The area of the opening can be changed by screwing in the replaceable rings 21. The second opening is closed by the valve 19, which is pressed against the hole by the electromagnet 12 and opens by the spring 11 when the contacts 4 are opened. The pressure of 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.

, $$\Delta F=F\mathrm{uh}.m-FPR=\Delta Pd.mS\mathrm{to}l$$

,

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 ÷ 5) 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 the 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

$$W_{g.\mathrm{well}}=\sqrt{\frac{2W_{\mathrm{to}}{\mu }_{\mathrm{well}}C{P}_0}{(200-C)RT{\rho }_{\mathrm{well}}}}\left(7\right)$$

where W _to - the volume of the explosive 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-grad); 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 krapus 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 the evaporation of the liquid.

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

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.

The area of the hole is set equal to or greater than the value that is established 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).

Claims (2)

1. A test bench for explosion-proof structures of buildings and structures, containing an explosive chamber, in the upper base of which there is an opening overlapped by an easily erasable element, characterized in that the area of the opening can be changed by screwing interchangeable rings, and the discharged element overlaps the hole in the ring above which is fixed a protective screen, the second hole being blocked by a valve, which is pressed against the hole by an electromagnet and opened by a spring when the contacts open, and the force the compression of the valve and compression of the spring is set so that the total force is equal to the allowable pressure multiplied by the area of the valve opening, i.e.
ΔF = Fe.m-Fpr = ΔPd.m Scl,
where Fe.m - the force of the electromagnet, pressing the valve to the hole, N / m²;
Fpr - spring compression force, opening valve, H;
Fpr = (10 ÷ 5) gm ,
where g = 9.81 m / s²;
m is the mass of the core of the electromagnet with the valve, kg;
Scl - valve opening area, m². 2. A test bench for explosion-proof structures of buildings and structures according to claim 1, characterized in that the easily-emitted element contains a metal armored frame with metal armor plating and lead filler, having four fixed support pipes at the ends, and in the coating of an explosive object is rigidly sealed at least three support rods with stop sheets in the upper part, which are telescopically inserted into the fixed support pipes in a metal armored frame, while in the upper part of the supports of elastic rods, elastic-damping elements are fixed, one end of which is rigidly connected by its base to the abutment sheets, and the other is loosely located, each of the elastic-damping elements being fixed by screws with its base, made in the form of a round disk made of a hard vibration-damping material of the Agat type, on abutment sheets rigidly connected to the rods, and the base of the elastic damping element is connected to an elastomer sleeve having a central hole through which the rod passes, and The tray has at least three openings, coaxial with the rod, in which elastic elements are located, for example, coil springs, the upper end of which is connected to the base by means of fasteners, and the lower end is in an unpressed state and protrudes beyond the lower plane of the sleeve determined by the force developed by the shock wave.

Images