XII Международная студенческая научная конференция Студенческий научный форум - 2020

If in the recent past, ordinary gas cylinders were mainly used to provide gas to a country house, modern autonomous gas supply has a slightly different principle. It is based on the gas holder system, which has an incomparably large volume, which makes it possible to continuously supply gas for a whole year. Autonomous gas supply of a country house gives the owner tangible benefits with minimal costs and hassle. That is why autonomous gasification of the house is the modern choice of most owners of country houses.

Gas-holder device

Gaz-holder - a tank for storing gaseous substances, such as, for example, natural gas, biogas, liquefied petroleum gas, air, etc.

Structurally, the gas holder system is a one-piece tank consisting of durable steel sheets that are painted with several layers of paint with epoxy resin, which gives the structure additional strength and corrosion protection. On top is the neck used to refuel the tank. The higher the neck, the better the protection of the tank from heavy rainfall and meltwater, which is especially important for areas with severe climatic conditions.

The shut-off and control valves of this system include the following elements:

- safety valve;

- indicator of filling the tank with liquefied gas;

- condensate drain valve;

- filling valve;

- pressure gauge;

- a reducer for adjustment of working pressure.

Due to the fact that this equipment undergoes a large number of rigorous checks before commissioning, it is absolutely safe and raises few questions during operation.

Types of gas holders

Gas holders - facilities for storing gases under excessive pressure. According to its size, gas holders of low (up to 4-5 kPa) and high (up to 3 MPa) pressure are distinguished.

Structurally, all domestic gas holders can be divided into models of horizontal or vertical location of the tank. Horizontal ones are easier to install (from the point of view of earthworks), but they take up more space, which can be critical for small areas. Vertical in this regard is more convenient. In addition, they are more buried, so liquefied gas is less cooled, which is necessary for its normal supply (temperature should be above zero). Otherwise, the rate of evaporation of liquid gas inside the tank decreases sharply, and the fuel begins to enter the heating system in insufficient quantities.

Distinguish gas tanks of variable and constant volume. Variable volume gas storage tanks store gas at a pressure close to atmospheric and ambient temperature. Variable-volume gas holders were used not so much for long-term storage of gas as to maintain gas pressure within safe limits when it was consumed. Modern constant-volume gas holders are cylindrical or spherical steel tanks and are capable of storing gas at pressures up to 1.8 MPa.

The most popular volume of domestic gas tank is five-cubic (4.85 m³). This volume allows for year-round heating (as well as hot water and cooking) of a house of approximately 150 m². For small houses (less than 100 m²), gas tanks with a volume of 2-3 m³ are used, and for large mansions, models of a larger volume, up to 20 m³, respectively, several gas holders or vapor installations of LPG (liquefied petroleum gas) are used.

The container volume changes with the amount of stored gas, for large gas holders it can reach 50,000 m³ with a cylinder storage diameter of 60 m.

Gas holders can be made of reinforced concrete, steel or rubber.

Reinforced concrete or steel wet-type gas holders consist of a vertical cylindrical basin filled with water and a bell open from the bottom that rises as the amount of gas increases. In piston (dry) gas holders, the pool is absent, and the volume is regulated by moving the piston tightly fitted to the lower reservoir.

According to the method of sealing gas space, wet and dry gas holders are distinguished. In the first, sealing is carried out using a hydraulic (usually water) shutter, and in the second, by any other means (for example, using stuffing box seals).

A wet gas tank consists of a steel water tank with external and internal guides, one (bell) or two (bell and telescope), movable links for gas storage, the so-called gas inlet (outlet) chamber, an automatic gas volume indication system and bell position signaling as well as safety devices for heating, chamber ventilation and water heating in the gas tank in winter. The bell and telescope are vertical cylindrical tanks (the first, mounted inside the second, with a roof, but without a bottom, the second without a roof and a bottom), installed in another vertical cylindrical tank (with a bottom but without a roof) of a larger diameter, filled with water, which provides sealing of the gas space inside the moving links during the operation of the gas tank.

Gas is supplied under the bell and telescope through a pipeline through a hydraulic shutter located in the chamber and a gas riser; gas intake from the gas tank is carried out in the reverse order. The hydraulic shutter also serves to drain condensate from the gas and disconnect the gas tank from the gas networks for the period of repairs and stops. When gas fills the space under the bell, the latter pops up, moving vertically up the guides, engages with the telescope, picks it up and continues to move under the pressure of the incoming gas. The bell and telescope are supported on rails using the upper and lower rollers. When the gas pressure under the bell is balanced by its weight, or at the same time by the weight of the bell and telescope, the bell stops rising. The weight of the bell with the telescope balances the gas pressure of 1.5-2.0 kPa. To increase the gas pressure, the bell is loaded with special weights. The maximum weight of the goods is chosen so as to ensure the gas pressure under the bell 4-5 kPa.

The gas holder is mounted with a pipe to discharge excess gas into the atmosphere or without it. In the first case, the discharge is done automatically by a valve connected by a lifting device to the bell, in the second - by shutting off the supply of excess gas. The discharge pipe also serves to protect the gas tank from lightning strikes; in the absence of a pipe, lightning receivers are installed on the guides of the gas holder.

Advantages of such gas holders: high operational reliability, ease of maintenance. And there are also disadvantages: the need for heating in the winter, relatively high metal consumption and, accordingly, the limited amount of stored gas (up to 100 thousand m3). Wet gas holders are used, as a rule, as buffer tanks on the suction lines of compressors.

Dry gas tanks are used to store gases at low or high pressure. Sealing of low pressure gas holders is carried out mainly with the help of elastic glands. Advantages of such gas tanks: low metal consumption, then. volumes of stored gas (up to 500 thousand m3), the disadvantage is the relatively low reliability of the sealing element. Spherical gas holders are used to create emergency gas reserves: air for instrumentation and automation systems, nitrogen for fire extinguishing systems, air and nitrogen for purging process devices, etc.

Installation of a gas-holder system

There are many reasons why consumers start using a gas tank:

- lack of natural gas near highways;

- the high cost of connecting to the main gas pipeline;

- low pressure of natural gas in the gas pipeline.

The gas holder is a container for storing liquefied petroleum gas (LPG for short), which, as a result of evaporation, is supplied through the gas pipeline to the house. Modern gas tank systems have special distribution equipment that regulates the gas supply and controls its amount in the tank. The control takes place in automatic mode, however, if necessary, the gas supply can be shut off manually.

Such gas storages can have ground or underground placement. For country houses, the second option is most optimal, since it allows you to save free space in the adjacent territory. In addition, the location of the tank below the level of freezing of the earth helps to create the right operating conditions, which will not depend on the ambient temperature.

Underground location involves the use of a special concrete slab, which is placed at the bottom of the pit and serves as the base for the gas tank. In the process of laying the pipeline from the gas storage to the house, it is recommended to use a condensate collector that collects moisture, which may be contained in the vapor phase during intensive operation of the gas boiler.

The size of the pit depends on the capacity of the tank used.

The gas tank installation workflow consists of several stages:

1. A specialist’s visit to the site (the company’s engineer will take measurements, determine the best place to place the gas tank in compliance with all safety standards, calculate the volume of the gas tank needed for the required needs, taking into account the size of the house);

2. Earthwork and installation of a gas tank (experts dig a pit where a tank with propane-butane mixture is placed; a reinforced slab is placed on its bottom to avoid soil shrinkage; a gas tank is mounted on it (a gas tank is being installed); work is being done to dig trenches for laying pipes and gas supply to the structure itself);

3. Gas holder piping (pipelines of the required diameter are selected, laid in trenches, they are welded and connected to the tank, pipelines are brought into the house; equipment is installed to control the entire system and control its functioning);

4. Refueling a gas tank with a propane-butane mixture (all necessary work on transporting fuel and refueling a gas tank is carried out by highly qualified gas stations with extensive experience and the necessary specialized equipment (a set of control and measuring instruments, as well as designs for draining fuel and to refuel hard-to-reach gas tanks (more 25 meters from the gas carrier); liquefied gas is a mixture of propane and butane, the percentage of which varies in summer and winter, therefore ost services refilling the gas tank is different depending on the season, the use of a summer gas in the winter can lead to zabutanivaniyu containers, due to higher interest ratio of butane fuel);

5. Commissioning (a trial run is carried out, parameters are adjusted in the house network).

The average term for the entire range of works on installation and installation of an autonomous gasification system is 3-5 days.

Advantages and disadvantages of a gas-holder

The gas holder is a quality replacement for household gas cylinders. Equipped with control and safety systems, the gas tank is protected from the possibility of exceeding the safe gas pressure by a relief valve (if the pressure in the tank rises above 15.6 atm. The valve discharges excess gas into the atmosphere).

A sufficient amount of liquefied gas in the gas tank allows you to install a gas water heater, which can fully provide one bathroom, including a shower or bath, and a kitchen. Minimum costs will allow you to get a high level of amenities, and one refueling may be enough for the entire warm period.

The gas holder will be an excellent solution for autonomous heating. Favorably different in price from their underground counterparts, the ground gas tank still does not require excavation, so that all landings and buildings on the plot will remain intact.

The gas holder can be used for heating and hot water supply year-round, while in winter only a minimal heating system is required to ensure sufficient evaporation of liquefied gas.

A gas holder is the best option for gasification if it is planned to bring main gas to the house soon. At the same time, equipment for the boiler room is purchased based on future needs, and is temporarily tuned to liquefied gas.

The undoubted advantage of using volumetric gas storages is the ability to ensure complete autonomy for a country house in terms of gas supply, it is not inferior in its efficiency to the main gas supply. The presence of regulatory equipment allows you to achieve a high level of safety and efficiency during operation. In addition, this type of fuel is the most environmentally friendly, due to the absence of harmful waste and air emissions.

The main disadvantage of this type of autonomous gas supply is the large cash costs for the acquisition, installation (but this is a one-time expense) and gas refueling. However, if it is not possible to connect to the central gas main, and the house is actively used for a whole year, then this system, at all initial costs, pays for itself quickly enough in comparison with electricity.

System maintenance

Vessels that are constantly located and operating under pressure, in accordance with federal standards and requirements in the field of industrial safety, must undergo a technical examination with the following frequency:

- External and internal examinations - once every 4 years;

- Acoustic emission monitoring of the vessel - once every 8 years.

The safety relief valve should be checked as follows: briefly need to be forced to open. This action should be carried out at least once a month, or as written in the manufacturer's instructions, if valve detonation is not provided.

Maintenance and repair of valves must be carried out by specialists with a frequency of once a year.

For maximum efficiency of the gas holding system, the main criterion is the use of high-quality LPG. Therefore, when refueling, it is advisable to use the services of specialized organizations that will not only provide good raw materials, but can also check all devices for operability.

Precautionary measures

The tank should be located at least 5 meters from the residential property. Filling occurs at 85% of the total volume. Mandatory periodic equipment prevention.

Delivery, refueling and maintenance should be carried out by a company licensed by the Federal Service for Ecological, Technological and Nuclear Supervision.

Thus, gas holders are safe gas supply systems. Gas is stored in the tank without access of air at a pressure of 5–6 atm, and air cannot get there in any way. And if depressurization occurs, the explosion will still not happen, since the gas will be discharged into the atmosphere, where it will disperse to a safe concentration. That is why it is impossible to place the gas holder in the premises - so that the gas does not accumulate during leakage. In addition, a safety valve is installed in the gas tank, which relieves excess pressure if, for one reason or another, the tank is hot.

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