SU1495204A1 - Method of creating explosion-proof gaseous atmosphere in ship cargo tank - Google Patents

Abstract

The invention relates to shipbuilding, in particular, to a method for creating an explosion-proof gas environment in a cargo tank of a vessel. The purpose of the invention is to increase the explosion safety and expand the scope. When receiving oil products, this method does not preliminarily inert the entire volume of the tank, but creates only a protective layer of inert gas separating the load from the air. The height of the protective layer H is determined by the ratio B≤H≥K ^. H _{^N. C} , where K is the safety factor of the layer height

H _{^N. C} - the height of the boundary layer over the oil product saturated with cargo pairs

B is the height of the piping systems above the tank bottom. The protective layer is created by introducing gas into the tank 1, which has been pre-cooled to a temperature that provides it with a density higher than the air density at the bottom of the tank. The moment of layer creation is recorded by sensors 3, which determine the content of oxygen and hydrocarbon vapors and are set at height H, i.e. at the top of the protective layer. When an inert protective layer is formed (between lines A - A - B - B), they proceed to receive the load. At the same time, the parameters of the content of oxygen and hydrocarbon vapors in the upper part of the protective layer rising with a load are constantly monitored. Over time, in the process of receiving cargo, the protective layer erodes due to the diffusion penetration of oxygen and hydrocarbon vapors into it. Sensors 3 record this change in parameters and give a signal in block 5 to lower them below the norm. Additional pumping of the cooled gas into the tank is made until the protective layer is restored. 1 il.

Description

The invention relates to shipbuilding, in particular, to a method for creating an explosive gas atmosphere in a cargo tank of a vessel.

The purpose of the invention is to increase the explosion and expansion of the scope.

The drawing schematically shows a scheme for implementing a method for creating an explosion-safe environment in a cargo tank of a vessel.

The cargo tank 1 is equipped with a float level gauge 2, sensors 3 for monitoring the oxygen content (Og) and hydrocarbon vapor PU (cargo), a gas outlet device 4, and also contains a unit 5 for controlling the preparation and supply of gas and the nitrogen inertization system (SIL), including blocks 6 and 7 for gas storage and cooling, gas supply control valve 8, processes 9 and 10 for gas supply to tank, valve 11. Cargo to tank 1 is supplied via pipeline 12 with valve 13 of the cargo system.

The implementation of the method is presented on the example of a tanker equipped with a nitrogen inertization system for kerosene tanks (T-1). The choice of example is characterized by the fact that the problem of reducing gas costs and inertization time is especially acute when inerting with expensive nitrogen. In addition, this system does not require the installation of additional expensive cooling equipment. The gas in the system is stored in cylinders under a pressure of about 20 MPa (200 kg / cm), and is fed into the tanks with a pressure of about 0.1 MPa. A decrease in gas pressure is accompanied by a natural physical process of cooling it. As a maximum of nitrogen, cooling can be obtained 25 ° C lower than its storage temperature in cylinders.

The method is carried out as follows.

The air temperature / is determined, and from the diagram, the corresponding air density p is at the bottom of the tank at the beginning of the inertization, / is determined by a portable thermometer lowered into the tank, or by stationary sensors (not shown).

Determine the required temperature of the cooled gas, tr, which gives it a density p, higher than p.

Start inerting tanks. The float of the level gauge 2 is installed on the bottom of the tank, i.e. in the lowest position. Sensors 3 connected to the level gauge 2 are installed at a height of 5 m from level gauge 2. The installation height of the sensors corresponds to the height of the protective layer for a given case (kerosene load (T-1) and tanker tank design) and is determined from the ratio

h k-hnc,.

where k is the safety factor of the height of the protective layer;

five

20

five

YU

five

0

0

five

0

five

/Zfl.c, - height of the boundary layer of the received cargo;

b is the distance from the bottom of the tank to the cargo pipelines located in it.

In this case, the received load is slightly evaporated, its /in.c. small (tends to 0.3 m), and the height b of the placement of cargo pipelines is 1.5 m, from where h is taken, 5 m. At m the protective layer provides a significant overlap of the height of the boundary layer and includes the height of the pipelines, ensuring the required nature of gas exchange and cargo protection (fire safety).

Start to create a protective layer at the bottom of the tank. To do this, gas from blocks 6 and 7 and valve 8 is piped through the open valve 11 and pipe 12 to the tank. When gas is supplied at a specified temperature f, the latter enters the lower part of the tank and, as the heaviest, stalet over its bottom, replacing the lower layers of air. At the same time, upper layers of air are displaced from the tank through the gas discharge device 4. The higher density of the gas compared to air prevents their displacement, ensuring that the air is expelled by the gas with only diffusion of oxygen from the air into the gas layers. As gas enters the tank, the protective layer with an oxygen content of 8% increases. At the moment when the concentration of O2 and PU taken from sensors 3 becomes explosion-proof, gas supply is stopped on the explosive line and the cargo is received. For this, the valve 11 is closed, and the valve 13 is opened and cargo (kerosene) is supplied through the cargo conduit 12.

As cargo arrives, its level rises (AA line). At the same time, the float of the level gauge 2 and the sensors 3 (line BB) are raised. A protective gas layer is also raised. Over time, the latter is saturated with hydrocarbon vapors and oxygen from the cargo and air. In addition, the gas is heated and in connection with all this, the boundary layer, which is limited by the lines SS-BB, erodes. Line CC shows conditionally a layer in which the content, i.e., in which burning is impossible. When the protective layer of the PU is saturated, it becomes much more difficult and even when the gas is heated to a temperature / does not tend to go up. As 02 and PU penetrate into the protective layer, the concentration of O2 and PU in the mixture on the explosive line approaches explosive values. When the values monitored by sensors 3 of O2 and PU parameters are outside the fireproof zone, the signal about this is transmitted to block 5, which includes gas pumping, which is terminated with the entry of these parameters into the set zone.

During the period of gas pumping, gas from blocks 6 and 7 through KvianaH 8 and pipeline 9 is fed to the upper part of the tank. However, due to its high density, it tends to occupy the lowest position, replacing the gas layers in the inert zone,

Claims (1)

Invention Formula A method of creating an explosion-proof gaseous medium in a cargo tank of a vessel, including cooling of inert gas and supplying it to a tank prior to receiving cargo, characterized in that, in order to increase the explosion where 6 is the distance from the bottom of the tank to the cargo pipelines located in it; k - margin of height of the protective layer; hn.e. height of the boundary layer of the received cargo, while in the process of receiving the cargo, when the concentration of the vapor of the cargo being transferred in the air reaches the maximum permissible safety and expansion of the area of application of the explosion-proof value of production is not, the inert gas is cooled to a temperature-additional supply of inert gas to the tanks at which its density exceeds the tank. density of air in the lower part of the tank, and supplying it to the tank is carried out before the formation of a protective layer in the tank with a height / determined by the ratio . .. where 6 is the distance from the bottom of the tank to the cargo pipelines located in it; k - margin of height of the protective layer; hn.e. height of the boundary layer of the received cargo, while in the process of receiving the cargo, when the concentration of the vapor of the cargo being transferred in the air reaches the maximum permissible intrinsic safety values produce an additional supply of inert gas to the tank.