When the heat carrier is heated in closed heating systems, an increased pressure is created. The liquid at a temperature of 90 ° C increases in volume by 3.55%. So that the excess amount of coolant does not spoil the radiators or pipes, a membrane tank is installed for heating. The safety structure of a metal container and a flexible membrane absorbs excess water, returning the pressure to normal.
- The device and principle of operation of the membrane tank
- Principle of operation
- Types of membrane tanks
- Fixed
- Flanged with replaceable diaphragm
- Advantages and disadvantages
- Volume calculation
- Requirements and recommendations for installing a diaphragm tank
- Equipment selection rules
- Possible breakdowns
- Popular models
- Wester WRV 50
- Wester WRV 200 top
The device and principle of operation of the membrane tank
The expansion tank is a sealed metal container, the inner part of which is divided into two parts by an elastic membrane. One compartment is filled with air, the second will receive water during expansion. The tank body is made of steel. Powder coating protects the metal from corrosion. By the type of heating networks, devices are divided into two groups:
- open;
- closed.
The open-type expansion tank must be at the highest point in the circuit. It is made of steel, the most common is the rectangular shape. The tank serves to remove excess liquid and air dissolved in it. Its design is very simple - two nozzles are cut into a metal container with a lid - for the intake and discharge of water. The cistern is often installed in the attic. In a cold room, it must be insulated with foam. The advantages of the open design are simple operation and low cost.
Diaphragm expansion vessels for closed-type heating systems must be tight. The steel tank is designed for long-term operation. Its working part is an elastic membrane. It is made of special heat-resistant rubber. Depending on the type of tank, a balloon or diaphragm-type membrane is used.
Principle of operation
In water heating systems, a heat transfer fluid circulates. It expands when heated. The surplus goes through the connecting pipe to the membrane tank. Elastic rubber stretches, one compartment is filled with liquid, and air is compressed in the second. After cooling the water in the circuit, the pressure decreases. Compressed air straightens the diaphragm and pushes the fluid back into the system.
During movement, the liquid does not come into contact with air. This reduces the likelihood of corrosion development.
Types of membrane tanks
For the heating system to operate at maximum efficiency, it is important to choose the right membrane tank.
Fixed
The fixed membrane design is recommended for small heating systems. In such circuits, the pressure is relatively stable and there are no sudden jumps. The flexible element is rigidly fixed and cannot be removed for replacement in the event of a malfunction. The advantage of this option is the low price.
Flanged with replaceable diaphragm
A feature of the tank design is the fixation of the balloon-type membrane on the neck with a flange. The bolt fastening allows you to securely hold the rubber part during operation. If it breaks, you can remove the part and replace it with a new one. Repairability extends the life of an expensive tank.
Advantages and disadvantages
The main advantage of the equipment is the prevention of leaks and other emergencies arising from pressure surges. Cisterns are required on long circuits. They contain a significant volume of water, which, when expanded, creates an increased load on the joints, radiators and pipes.
Equipment advantages:
- air ingress into the line is excluded;
- the equipment is designed for water of any quality;
- there is no evaporation of liquid;
- an emergency increase in pressure is prevented;
- installation is possible anywhere;
- system maintenance is simplified, regular topping up of the coolant is not required.
The disadvantages include heat loss and the rather high cost of membrane tanks compared to open-type tanks.
Volume calculation
The parameters of the tank should prevent the increase in pressure when the heat carrier is heated. For an approximate calculation of a system with a capacity of up to 150 liters, you can use the formula: tank volume - 10% of the system volume. In the case of using antifreeze, the parameter increases to 15%. For calculations, the capacity of the loop is required. You can find out the parameter by the water meter during the filling of the system. It is also calculated by adding up the volume of all nodes, pipes, radiators and a boiler. There are online calculators for the calculation.
A more accurate value will be given by a calculation using the formula: V = V1 x Bt / (1- (Pmin / Pmax))where:
- V - tank volume;
- V1 - the volume of fluid in the circuit;
- Bt - coefficient of thermal expansion of the coolant, is found in the table;
- Pmin - factory pressure in the tank;
- Pmax - the maximum pressure in the system, is determined at the moment the safety valve is activated.
Correctly selected expansion tank volume helps to extend the life of the heating system.
Requirements and recommendations for installing a diaphragm tank
You can install the equipment yourself by following the instructions. When working, they adhere to the installation requirements:
- The first step is choosing a location. Ensure free access to the reservoir for maintenance. A good place is the section of the return line between the pump and the boiler.
- For the safety of a closed circuit, the installation of a safety valve, an air vent, a pressure gauge and a thermometer will be required.
- A drain valve is installed in front of the inlet pipe to drain water from the tank.
- Filters must not be installed in the area between the tank and the heating system.
- Before connecting the equipment, check the pressure of the gas space. If necessary, pump air.
- The tank should not be located in a room with subzero temperatures.
The tank is securely fastened to the wall, and there should be no additional load on it. Large models are floor mounted. We recommend a connection diagram with the inlet located at the bottom. Experts advise making a detachable connection between the pipe and the drain valve in front of it. If necessary, the expansion tank can be easily dismantled.
The manufacturer indicates the requirements for the amount of antifreeze in the composition of the coolant. The stated proportions must not be exceeded.
Equipment selection rules
The main characteristics of the membrane tank, which are guided when buying:
- volume;
- maximum pressure;
- membrane and body material;
- working temperature.
These criteria will ensure the reliability of the heating operation. Insufficient or excessive reservoir volume will not allow the normal pressure in the circuit to be established. The type and material of the diaphragm and body affects the life of the equipment. High-quality rubber can withstand a large number of expansion and contraction cycles. To prevent corrosion of the housing, it must have a protective coating.It is worth considering the dimensions of the product and considering the installation location. Experts advise buying products from well-known manufacturers. Low product costs are often indicative of the use of inferior materials.
Possible breakdowns
During the operation of the equipment, owners are advised to inspect the case for leaks and damage every six months. It is also necessary to measure the pressure in the gas chamber. The condition of the membrane is checked once every 2 years. In the absence of operation, water is drained from the tank.
Common malfunctions:
- Pressure drop in the gas compartment - it is necessary to pump air through the nipple using a pump.
- Damage to the case - mechanical stress or corrosion can cause cracks. You can restore the tightness of the container at the service center.
- Leaking air valve - due to high loads and hot water, rubber can crack. It is better to replace the damaged part on time.
You can repair the equipment on your own. To replace the membrane, you will need to drain the water, dismantle the container and relieve the pressure. Then unscrew the flange bolts holding the rubber piece. The old membrane is removed and replaced with a new one. All procedures are carried out in reverse order.
Popular models
The Russian trade mark Wester produces membrane tanks for cold and hot water supply, as well as heating. The WRV series is designed to compensate for the expansion of the heating medium. It includes models of various capacities - from 8 to 10,000 liters. The body of the products is painted red.
Wester WRV 50
The device is used in closed-type heating systems. Its volume is 50 liters. the arrangement of the case is vertical, floor mounting. The model is manufactured from durable carbon steel. The membrane is made of food grade synthetic rubber. It is replaceable, the flange on the neck of the tank allows to put and fix a new elastic part. The design is designed for pressures up to 5 bar.
Wester WRV 200 top
Membrane tanks for heating Wester wrv200 top are made of complex drawing steel. Heat-resistant elastic EPDM rubber is used to separate the inner chamber. The part is replaceable. Operating temperature range from -10 to + 100 ° C. The design can withstand pressures up to 10 bar, its volume is 200 liters. Floor placement.
The expansion tank is a simple but functional part of the heating system. Prevents breakdowns caused by a sudden increase in pressure. Its installation will ensure the safe and stable operation of all working units.
