RU2618199C2 - Method for determining delayed action of subsurface fire-extinguishing system of the reservoir for storage of flammable or combustible liquids - Google Patents

Abstract

FIELD: measurement technology.

SUBSTANCE: invention relates to determination of delayed action of automatic tanks for highly flammable fluids. Method involves determining for one linear input of a subsurface fire-fighting system the total length and inner diameters of foamer solution lines, extending from the room with electric drive valves to high-pressure foam generator assembly (HFG), foam lines passing from HFG to rupture membrane and inside the tank. Then the consumption of foamer solution and the foam expansion ratio are determined, after which the time interval needed to fill the foamer solution lines with foamer solution and foam lines – with foam is determined, foam line passing from HFG to the rupture membrane. Value of pressure at which the membrane breaks is determined. It is followed by calculating the time interval needed for pressure in the foam line to reach the value at which the membrane breaks, and calculating the time interval between the membrane rupture and foam filling the foam line inside the tank. Speed of foam floating to the surface of the liquid is calculated and time interval needed for foam to float to the surface of the liquid is calculated. Delayed action of subsurface fire-extinguishing system is defined as the sum of the time intervals needed to fill foam line and foamer solution line, time of increase of pressure in the foamer solution line to the value at which the membrane breaks, time from the rupture of the membrane until foam line filling inside the tank and time of foam floating to the surface of oil.

EFFECT: result of the disclosed method includes higher accuracy of determining the delayed action of a subsurface fire-extinguishing system.

1 cl, 1 dwg

Description

The invention relates to the field of fire fighting equipment, and in particular to the determination of the inertia of automatic foam fire extinguishing installations (UPP) of tanks for flammable or combustible liquids (LVF and GF), in particular oil and oil products, by supplying fire-extinguishing foam to the LVF and GF layer (sublayer extinguishing) in the control and modernization of existing and designing new SCP.

The prior art systems and systems for sublayer fire fighting in tanks with flammable or combustible liquids [patent for invention RU 2411053 C1, publ. 02/10/2011, IPC: А62С 3/06, А62С 5/02], [patent for utility model RU 117298 U1, publ. June 27, IPC: А62С 35/00], [patent for utility model RU 21145 U1, publ. 12/27/2001, IPC: А62С 3/06, А62С 35/00], which include mortar pipelines with electric valves, foam pipelines equipped with high-pressure foam generators, non-return valves, bursting membranes, internal piping with foam nozzles.

In a number of regulatory documents [SP 5.13130.2009. Fire protection systems. Automatic fire alarm and fire extinguishing installations. Norms and design rules. Approved and enforced by Order of the Ministry of Emergencies of Russia dated March 25, 2009 No. 175. SECTION 5.2.6, 6.3.1.4], [SP 155.13130.2014. Warehouses for oil and oil products. Fire safety requirements. Approved and enforced by order of the Russian Ministry of Emergency Situations dated December 26, 2013 No. 837. Appendix A, paragraph A4], [SNiP 2.11.03-93. Warehouses for oil and oil products. Fire regulations. Approved by the decision of the State Committee for Architecture and Construction dated April 26, 1993 No. 18-10. Appendix 3, paragraph 4] contains regulatory requirements, according to which the inertia of stationary fire extinguishing systems should not exceed 3 minutes. At the same time, the inertia of the fire extinguishing installation is understood to mean the time from the moment the controlled factor of the fire reaches the threshold of the sensing element of the fire detector until the fire extinguishing agent begins to flow into the protected zone.

In the prior art, no methods have been found for determining the inertia of sub-layer fire extinguishing systems that take into account the time of “ascent” of the foam after exiting the foam nozzle, as well as the time of pressure rise in the foam pipe to a value sufficient to rupture the membrane, namely, to a value exceeding the hydrostatic pressure of the liquid stored in the tank, which depends on the level of liquid spill in the tank and on the multiplicity of the foam.

The problem to which the invention is directed, is to create a method for determining the inertia of sub-layer fire extinguishing installations, taking into account the inertia parameters indicated above.

The technical result of the invention is to increase the accuracy of determining the inertia of a sub-layer fire extinguishing installation.

This problem is solved, and the technical result is achieved by the fact that in the method of determining the inertia of a sub-layer fire extinguishing installation (SCP) for a tank for storing flammable or combustible liquids, the total lengths of the pipelines passing from the room with electric actuated valves (PEZ) to the node are determined for one linear input of the SCP high-pressure foam generators (HSV), the length of the foam pipe passing from the HSV unit to the bursting membrane, and the foam pipe passing inside the tank; determine the inner diameter of the mortar pipes, the inner diameter of the foam pipe passing from the HSV assembly to the bursting membrane, and the foam pipe passing inside the tank; determine the flow rate of the foaming agent by one linear input of the soft starter taking into account the total flow rate of the solution of the foaming agent with a minimum working pressure of HSV and the number of linear inputs of the soft starter into the tank; measure the foam multiplicity of the foam fire extinguishing installation; calculate the time interval for filling the solution with the blowing agent foaming agent and the time interval for filling the foam of the foam pipe passing from the HSV unit to the bursting membrane; determine the pressure value at which the membrane ruptures; calculate the time interval of the rise in pressure in the foam pipe passing from the HSV assembly to the bursting membrane to the value at which the membrane breaks, taking into account the maximum level of oil spill in the tank and the level of foam pipe installation inside the tank; calculate the time interval from rupture of the membrane to the foam filling the foam inside the tank; measure the rate of foam rise to the surface of the liquid at various levels of oil spill in the tank, determine the average speed of the rise of foam, and taking into account the data obtained, calculate the time interval for the rise of foam to the surface of the liquid; the inertia of the foam fire extinguishing installation is defined as the sum of the time intervals for filling the mortar pipelines and the foam pipe passing from the HSV unit to the bursting membrane, the rise time of the pressure in the foam pipe passing from the HSV unit to the bursting membrane, to the value at which the membrane breaks, the time from the membrane rupture until the foam is filled with foam in the tank and the time the foam emerges onto the surface of the oil.

The invention is illustrated in the drawing, which shows the technological scheme of the installation of a sublayer fire fighting tank for storing flammable or combustible liquids, and the positions indicated:

1 - a tank for storing flammable or combustible liquids;

2 - linear input soft starter;

3 - mortar line passing from the SEZ to the HSV assembly;

4 - a foam pipe passing from the HSV assembly to the bursting disc;

5 - foam pipe passing inside the tank;

6 - high-pressure foam generator;

7 - bursting disc;

8 - foam nozzles for sub-layer fire fighting;

9 - pipe for installing the unit of periodic tests;

10 - overhead flow meter;

11 - pressure gauge;

12 - a room with electric gate valves.

The method is further explained with reference to the drawing.

A method for determining the inertia of a sublayer fire extinguishing installation (SCP) for a tank for storing flammable or combustible liquids 1 was developed to enable verification of the calculation of the inertia of the response of the SCP performed during the design to the actual values and to determine the need to change the design of the SCP to match its inertia with standard indicators.

The inertia of the fire extinguishing installation is determined by the time from the moment the controlled factor of the fire reaches the threshold of the sensing element of the fire detector, sprinkler sprinkler or inducement device until the fire extinguishing agent begins to flow into the protected area.

When using a sublayer foam supply system, the protected area of the tank is considered to be a mirror of a combustible or flammable liquid. Therefore, the method of determining the inertia of the sublayer foam supply systems should include the time of “ascent” of the foam after exiting the foam nozzle 8, which will depend on the size of the reservoir 1 for storing the flammable liquids and liquids, the viscosity of the oil and the level of loading of the flammable liquids and liquids.

Foam under the liquid layer is supplied from foam nozzles 8 mounted on a looped pipe filled with liquid and under hydrostatic pressure, while the overpressure of the liquid in the looped pipe can be up to 0.2 MPa, which can have a significant effect on the pressure rise time in the pipe up to the burst pressure of the membrane.

The inertia of the foam fire extinguishing installation consists of the following time intervals:

- the time of filling the pipelines from the SEZ to the site of HSV 3;

- the time for filling the foam of the foam from the HSV assembly to the bursting disc 4;

- the time the foam pressure rises to the membrane rupture pressure in the foam pipe from the HSV assembly to the bursting membrane 4;

- the time of filling the foam inside the tank 5 and the receipt of foam to the foam nozzles 8;

- the time the foam rises to the surface of a flammable or combustible liquid.

The claimed method of determining the inertia of the soft starter for the storage tank for flammable liquids and flammable liquids is as follows.

Initially, for one linear input 2 of the soft starter, the total lengths of the solution pipelines 3, passing from the room with electric gate valves (PEZ) 12 to the node of high-pressure foam generators (HSVs) 6, the length of the foam pipe 4 passing from the block HSV 6 to the bursting membrane 7, and the foam pipe 5, are determined passing inside the tank 1. Determine the internal diameters of the pipelines 3, foam 4, passing from the node HSV 6 to the bursting membrane 7, and foam 5, passing inside the tank. These parameters are determined depending on the type of tank 1 for storing flammable liquids and flammable liquids, the type of soft starter installed on tank 1, and the design dimensions of the mortars and foam pipelines.

Then, the flow rate of the foaming agent solution is determined by one linear input of the softener Q _lin taking into account the total flow rate of the foaming solution Q _total at the minimum working pressure of HSV and the number of linear inputs of 2 softener into the tank n. To determine the total flow rate of the blowing agent solution at the minimum working pressure of HSV, the flow rate of the blowing agent is measured using an overhead flow meter-counter 10 installed between the PEZ 12 and the HSV assembly 6 on each of the linear inputs 2 of the soft starter, and the total flow rate of the blowing agent solution is obtained as the sum measured costs for each linear input of soft starter. The value of the average flow rate of the foaming agent solution for one linear input of the soft starter is defined as Q _lin = Q _total / n.

After that, measure the foam multiplicity of the foam fire extinguishing system using the method consisting in measuring the mass before and after filling the foam with a foam collecting tank, followed by the calculation of the foam multiplicity. A periodic testing unit is connected to the pipe 9, the soft starter is started, the beginning of a steady supply of foam from the high-pressure foam generator 6 is recorded, and then the foam is sampled into a measured container. Measure the volume of the selected foam. After the complete destruction of the foam in the measuring tank, measure the volume of the foaming agent solution and determine the ratio of the foam as the ratio of the volume of the foam to the volume of the solution of the foaming agent.

The calculation of the time interval for filling the solution with the foaming agent of the solution pipelines 3 and the time interval for filling the foam with the foam 4 passing from the HSV unit 6 to the bursting membrane 7 is carried out according to the following formula:

where D _{1 (2)} is the inner diameter of the solution pipe from the SEZ to the HSV unit or the foam pipe from the HSV unit to the bursting membrane;

L _{1 (2)} - the total length of the pipelines from the SEZ to the HSV node or the length of the foam pipe from the HSV node to the bursting membrane;

Q _lin - the average flow rate of the foaming agent solution over a single linear input;

K is the multiplicity of the foam.

The total filling time of the solution piping 3 and the foam piping 4 located from the SEZ to the bursting membrane is determined as follows:

The rupture of the membrane 7 occurs at the moment when the foam pressure in the foam pipe passing from the HSV 6 to the bursting membrane 7 exceeds the hydrostatic pressure of the liquid stored in the tank 1 by the amount necessary to rupture the membrane 7 installed in the soft starter. The value of the pressure of the rupture of the membrane is determined by the pressure gauge 11 installed between the node HSV 6 and the bursting disc 7.

The calculation of the time interval of the rise in pressure in the foam 4 passing from the HSV 6 to the bursting membrane 7 to the value at which the membrane ruptures, taking into account the maximum level of oil spill in the tank 1 and the level of the foam 5 inside the tank, is carried out in accordance with the following ratio:

where P _burst is the burst pressure of the membrane;

P _atm is atmospheric pressure.

Since when the membrane ruptures, the foam is under pressure in excess of the hydrostatic pressure of the oil, then additional compression of the foam is not required to displace the oil from the foam pipe 5 inside the tank. The experimentally determined time for filling the T-shaped foam nozzles 8 does not exceed 10% of the time for filling the foam pipe inside the tank. With this in mind, the time interval from rupture of the membrane 7 to the filling of the foam 5 inside the tank and the beginning of the exit of the foam from the foam nozzles 8 is:

where D ₃ - the inner diameter of the foam inside the tank;

L ₃ - the total length of the foam inside the tank.

The average rate of foam ascent to the surface of the liquid is determined taking into account measurements by means of a stopwatch of time intervals after the start of foam exit from the foam nozzles 8 from the occurrence of waves to the appearance of foam on the surface of the flammable liquids and liquids in the tank 1, obtained for different heights of flammable liquids and liquids in the tank. Next, calculate the time interval for the rise of the foam on the surface of the liquid:

where H _inflow - the height of the inflow of flammable flammable liquids and GF in the tank;

h _{int. foam} - the height of the foam inside the tank;

- скорость всплытия пены.

- foam ascent rate.

As a result, the inertia of the foam fire extinguishing installation is defined as the sum of the time intervals for filling the solution pipelines 1 and the foam 4 passing from the HSV assembly to the bursting membrane, the time of the pressure rise in the foam 4 passing from the HSV assembly to the bursting membrane, to the value at which the membrane ruptures , the time from the rupture of the membrane to the foam filling the foam 5 inside the tank and the time the foam ascends to the surface of the oil:

Then, the obtained inertia value of the foam fire extinguishing installation is compared with the standard value of inertia and the conclusion is made about the need to make changes to the design of the foam fire extinguishing installation to match the inertia of the soft starter to the standard value. In particular, it can be concluded that it is necessary to change the lengths or internal diameters of the solution pipelines or foam pipelines while ensuring the necessary pressure is maintained at the exit of the foam nozzles.

As a result of the implementation of the inventive method, an increase in the accuracy of determining the inertia of a sub-layer fire extinguishing installation is achieved.

Claims (11)

A method for determining the inertia of a sub-layer fire extinguishing (SCP) installation of a tank for storing flammable or combustible liquids, which consists in the fact that: - determine for one linear input of the SCP the total lengths of the solution pipelines passing from the room with electric drive valves (PES) to the site of high-pressure foam generators (HSV), the length of the foam pipe passing from the HSV unit to the bursting membrane, and the foam pipe passing inside the tank; - determine the inner diameter of the mortar pipes, the inner diameter of the foam pipe passing from the HSV assembly to the bursting membrane, and the foam pipe passing inside the tank; - determine the flow rate of the foaming solution by one linear input of the soft starter taking into account the total flow rate of the solution of the foaming agent with a minimum working pressure of HSV and the number of linear inputs of the soft starter into the tank; - measure the foam multiplicity of the foam fire extinguishing installation; - calculate the time interval for filling the solution with the foaming agent of the solution pipelines and the time interval for filling the foam of the foam pipe passing from the HSV unit to the bursting membrane; - determine the pressure value at which the membrane ruptures; - calculate the time interval of the rise in the pressure in the foam pipe passing from the HSV assembly to the bursting membrane to the value at which the membrane ruptures, taking into account the maximum level of oil spill in the tank and the level of foam pipe installation inside the tank; - calculate the time interval from rupture of the membrane to the foam filling the foam inside the tank; - measure the speed of the rise of the foam on the surface of the liquid at various levels of oil spill in the tank, determine the average speed of the rise of the foam and calculate the time interval of the rise of the foam on the surface of the liquid; - the inertia of the foam fire extinguishing installation is defined as the sum of the time intervals for filling the mortar pipelines and the foam pipe passing from the HSV unit to the bursting membrane, the rise time of the pressure in the foam pipe passing from the HSV unit to the bursting membrane, to the value at which the membrane ruptures, the time from rupture membranes until foam is filled with foam in the tank and the time the foam emerges onto the surface of the oil.

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