Autonomous Gas Supply

2023 Author: Douglas Hoggarth | [email protected]. Last modified: 2023-05-24 11:23

• Autonomous gas supply at home
• Operational characteristics of autonomous gas supply
• How the autonomous gas supply system works
• What gas is used in the autonomous gas supply system
• How to choose a gas tank
• Installation of autonomous gas supply
• System maintenance

The main and very serious disadvantage of placing a house away from the benefits of civilization is the complete absence of the usual communications. There is no trace of electricity, gas supply, water supply and sewerage in the ecologically clean wilderness. And if the last two types of communications can somehow still be organized at the expense of a well and a toilet with a septic tank, then a quality life and rest without electricity / gas is simply impossible - we are too used to them. There may be two options for solving the problem - a wind generator (although it will not be able to provide a level of comfort by 100% or will cost too much) or an autonomous gas supply complex. Let's consider the components and possibilities of autonomous gas supply in more detail …

Autonomous gas supply at home

There is no sensation in this - many settlements are not equipped with a gas pipeline to this day. The only option to save money when cooking on electricity was and is cylinders with liquefied propane-butane - a service contract was concluded, 50 or 80-liter gas cylinders were purchased and, as they became empty, a specially equipped truck brought a full cylinder to the gas filling station. taking away empty instead.

If the need for gas arises only for cooking, if the gas cylinder delivery service serves the area without problems, then such a "balloon" method of gas supply is quite suitable. For cooking in a small family (2-3 people), the contents of a 50-liter bottle will last for a couple of months. In this version of gas supply, you need to have two cylinders filled with gas in the house - one attached to the gas stove, the second - a spare one (useful between changing the first empty cylinder to a full one).

But what if the house is so far from settlements that the delivery of a full cylinder of gas will cost more than the cost of the cylinder itself and the gas in it? If gas is needed for space heating and electricity generation? The solution here will be a more serious system of autonomous gas supply - its capacity for gas is not transported, liquefied gas is transported into it!

A cylindrical tank for storing a propane-butane mixture (gas holder) is made of 10 mm cold-rolled steel, it is designed for a pressure of 1.6 MPa, looks like a railway tank and has a unique serial number. The propane-butane mixture pumped into this tank is in a liquid state, gradually evaporating and going to household appliances that make up the comfort of our life. The gasholder manufacturing plants produce containers with a volume of 2,700 m3 to 20,000 m3, the smallest is intended for a house with an area of not more than 200 m ², the largest - for buildings with an area of more than 1000 m ². It is required to replenish gas reserves in such a container 2-3 times a year by ordering an autogas carrier.

Operational characteristics of autonomous gas supply

First of all, due to its autonomy, it is up to the owner of the equipment to decide when, how and in what volumes to use gas entirely. There will be no lowering of the pressure in the system, so frequent on the main gas supply lines, there will be no outages at the most crucial moment.

From the point of view of economy, the liquefied gas system is inferior only to a gas boiler connected to the main line, but outperforms liquid fuel (diesel) and electric boilers. The average full payback period, according to the manufacturers of gas tanks, is three years.

In terms of practicality and service life, the minimum life of the autonomous gas supply system is 20-30 years (provided that the installation is done professionally). Spontaneous gas leaks and ignition are completely excluded.

This equipment is highly environmentally friendly - no combustion waste, no smell, no threat of soil contamination during spills.

The autonomous gas supply system allows you to fully cover the needs for heating, heating water for hygienic needs, cooking, supplying electricity (this requires the installation of a gas generator - the cost is from 43,000 rubles).

How the autonomous gas supply system works

Its main elements are: a gas tank (underground or aboveground, the first option is better); gas pipeline that can withstand high pressure; evaporator (brings the gas pressure in the gas pipeline to atmospheric); low pressure gas pipeline (through it, vaporous gas enters the devices that consume it).

In addition to the properties already described, gasholders are vertical and horizontal (the second type is cheaper than the first). In terms of the area of the "evaporation mirror", horizontal gas tanks are more efficient, but the vertical gas tank can be submerged to a greater depth (due to its design) and therefore is less affected by the low temperatures of the cold season. The gas tank for vertical installation does not need an evaporator - its outer surface extracts heat well from the ground.

Domestic manufacturers of liquid gas storage tanks produce only horizontal gas tanks, the range of imported manufacturers is wider and includes vertical gas tanks. However, there are few imported vertical gas tanks on the Russian market - European horizontal tanks for liquefied gas are presented much more widely.

A prerequisite is that each gas tank must be protected against corrosion! Manufacturing companies choose their anti-corrosion coating - it can be bituminous or glass-bitumen (up to 4 mm thick), epoxy (0.8 mm) or polyurethane (1.5 mm), and consist of an 8 mm isoplastic layer. Such a method of protection against corrosion is effective - galvanic protection (cost - from 15,000 rubles), consisting of a reference electrode (Cu / CuSO4) connected to 2-3 magnesium alloy anodes placed in the ground near the gas tank. The principle of such protection: magnesium anodes are oxidized, restoring the iron of the container and extending its service life for decades. The anodes are gradually destroyed during this reaction - one set of them will last about 5 years.

Each gasholder is equipped with a reduction head or a neck (cost - from 55,000 rubles), which is included in the mandatory set of imported containers, which are often sold separately in domestic ones. The reduction head protects the equipment for monitoring and controlling the gas tank - relief and safety shut-off valves, a level meter and pressure regulator, a filling level sensor (signaling device) and a gas carrier grounding device, a reducer and a pressure gauge - from moisture and dust.

Elements of the gasholder equipment:

• a relief (safety) valve equipped with a pressure gauge, which independently lowers the pressure in the tank when its critical increase. Discharges gas;
• a safety shut-off valve that stops the flow of gas in the vapor state (vapor phase) at a dangerously high pressure, its breakdown, or a drop in pressure in the system caused by damage to the gas pipeline;
• a level meter showing the gas carrier operator the critical filling level of the tank (more than 85% of the internal volume of the gas holder);
• a sensor (indicator) of the filling level, which informs about the critical filling of the tank and automatically stops the supply of LPG to the tank from the autogas carrier;
• an autogas carrier grounding device that grounding the LPG delivery vehicle to avoid sparks;
• reducer that reduces gas pressure.

Filling the gas tank over 85% of the internal volume threatens to depressurize it. Cause: The rise in temperature causes severe expansion of the liquid propane contained in the LPG. And it is impossible to compress liquefied propane inside the gas tank …

Through the high-pressure gas pipeline, the propane-butane mixture is directed to the evaporator - a device that increases the amount of evaporated gas mixture in case of insufficient natural evaporation. An evaporation plant (cost - from 145,000 rubles) needs a heat carrier - hot water or steam, an electric heater. If the capacity of a heating boiler or the total capacity of several boilers consuming gas from one gas tank does not exceed 100 kW, then there is no need for an evaporating unit and natural evaporation will be sufficient.

The vaporous mixture of propane-butane is supplied to the consuming devices via steel or polyethylene pipes with a diameter of 23 to 63 mm. Pipes made of HDPE (low pressure polyethylene) are quite suitable - they easily withstand low gas pressure, do not rot and do not damage when the soil in which they are laid moves.

Attention: When installing gas pipes, only a welded connection is allowed! Near the point of entry of the gas pipeline into the building, a basement unit is created, equipped with a flange connection - from it the entry into the house is made (only a steel pipe is used!)

What gas is used in the autonomous gas supply system

The most profitable for consumers is the use of natural gas (methane). However, it is delivered only by mainline - through gas pipelines, and their laying is quite expensive. Autonomous gas supply uses hydrocarbon gas compressed to a liquid state (abbreviation - LPG) - it is obtained from oil. It consists of a mixture of two gases - propane and butane. Propane has excellent volatility even at low temperatures, but in the warm season, the pressure of the gas phase of its vapor quickly rises to a high value of 1.6 MPa. In addition, propane is not cheap - the gas mixture is made cheaper by combining propane with butane, which is less susceptible to evaporation at high summer temperatures and is cheaper than propane. The percentage of propane to butane in the gas mixture depends on the current season:in summer, the percentage of propane to butane is lower (50:50 or 60:40), in winter it is higher (about 70:30).

Attention: LPG is not toxic, but heavier than air - if it leaks, this gas will accumulate at the lowest point in the area. For this reason, it is strictly forbidden to build boilers that consume hydrocarbon gas in basements or basements, the total area of window openings in which does not exceed 1 m ².

How to choose a gas tank

In terms of volume, it is impractical to choose a capacity less than 2.7 m3 (cost: ground-based from 142,000 rubles, underground - from 225,000 rubles), even if the area of the building is small and you visit it only periodically. The reason is simple: it is not profitable for fuel companies to deliver small volumes of liquefied gas over long distances, because time, fuel and man-hours (operator-driver time) are consumed. Most of them will either refuse or break the price.

According to the power of the consuming equipment: a 10 kW heating boiler consumes 1.44 liters of liquid propane-butane mixture per hour, i.e. with 10-hour daily work, the gas supply in the tank will last for 5.5 months. Accordingly, with a boiler power of 15 kW, it is advisable to choose a 4.5 m3 gas tank, with 20 kW - 6.4 m3, a 30 kW boiler will require a 10 cubic gas tank. Considering that it is forbidden to fill the tank for LPG by more than 85% of the internal volume, filling the gas tanks according to the described ratio of the boiler power / tank capacity will need about 1.5-2 times per year.

Installation of autonomous gas supply

Before opting for one installation organization, monitor the proposals, make sure of the professionalism of potential performers. Try to purchase only certified equipment and only from well-known suppliers working for a long time in the market - more guarantees that the system will work without emergency situations.

Not a single company performing the installation work of such systems will agree to carry out installation work without a gasification project developed specifically for this facility. The project consists of: general plan, characteristics of the gas tank (tank installation); lightning protection, grounding and chemical protection solutions; outdoor gas pipeline plan; characteristics of the condensate collector and the evaporator unit (if required).

When planning the placement of an autonomous gas supply system, the following fire safety conditions are taken into account:

• distance from any residential building - from 10 m;
• from the reservoir (well, well) - 15 m;
• from a septic tank, garage, spreading tree - 5 m;
• from the fence - 2 m;
• from the power line - at least half the length of its support.

The driveways for the LPG carrier must be carefully planned - this tank-equipped truck is not particularly agile.

Upon completion of design work and approval of all issues, the installation process begins:

1. The pit is torn off to a depth below the freezing point of the soil - the distance from the upper part of the gas holder to the surface of the earth must be at least 1,500 mm. Trenches are torn off for gas pipes - below the freezing point, with a depth of 1,900 mm near the gas tank and with a decrease in the trench depth to 1,500 mm at the base of the building (the point of entry of the gas pipeline into the house). Earthwork can be performed both by the customer and by the installation organization;
2. A concrete slab is placed in the prepared foundation pit - it will serve as the basis for the gas tank capacity and prevent its displacement during ground movements. The container is installed on a concrete slab, between it and the slab a layer of reinforced acid-alkali-resistant rubber is laid, fixed on a concrete base with stainless steel anchors through the fasteners of the legs or through steel hoop strips. Upon completion of the installation of the gas tank, it is certified for technical suitability - before this test, it is impossible to pump liquefied gas;
3. The lightning rod of the ground loop is mounted, its resistance is measured. If necessary, an evaporation unit is installed;
4. A condensate collector is installed at the lower point of the gas pipeline - it will receive non-evaporated propane-butane fractions, warm up due to the natural heat of the soil and re-enter the gas pipeline. The gas pipeline is being laid to the point of entry into the house - a flexible polyethylene pipe of the design diameter, 10-15 m long. Sand is poured into the bottom of the trench before laying;
5. The gas pipeline is being put into operation - from the basement to the points of gas consumption in the building, gas controllers are installed, which are triggered automatically. The queue of testing the autonomous gas pipeline system for the quality of installation work - the compressor is pumping air under a pressure of 5 kg / cm ²;
6. A day later and according to the results of test work, the gas tank and the gas pipeline are covered with sand (sand is an excellent conductor of heat), and soil is filled up with a layer of 100 mm to the ground level. The injected air is removed by flushing the system with nitrogen;
7. Installation is complete. At the first LPG injection, the presence of a representative of the installation organization is mandatory!

System maintenance

It does not need user control - the system's sensors will cope with emergency situations on their own. Every 10 years, the equipment and the integrity of the LPG tank are checked by a representative of the installation organization or the manufacturer of the gas tank.

The rules for using autonomous gas supply are explained to the user by a representative of the installation organization.