There are two tanks on the market that are very similar to each other. This is an expansion tank and a hydraulic accumulator. The question of what is the difference between a hydraulic accumulator and an expansion tank worries many, because their appearance confuses consumers. The purpose of both tanks, as well as design features are very different.
The purpose of the equipment
An expansion tank is used in the heating system of private houses. Its functional duties are compensation for the expansion of water or other coolant. The liquid pumped into the heating of the house, when heated, begins to expand in volume, creating increased pressure. In order not to break the elements of the network, an expansion tank is installed, where excess volume of heated water is collected.
The hydraulic accumulator is an element of the plumbing system of a private house. Its functional purpose is to create pressure inside the network when the pump unit is not working.
The tanks are painted in different colors: the expansion tank in red, the accumulator in blue.
Design Features
Outwardly, both tanks differ from each other only in color. In the market they are presented horizontal and vertical execution. As for the internal filling, the devices are a steel tank, into which an inserted membrane is inserted.
Since the expansion tank is used in a system with hot water, the membrane in it is made of polymers that do not change their technical characteristics in contact with hot liquids. Manufacturers use EPDM, SBR, butyl rubber and nitrile rubber for this.
In hydraulic accumulators, membranes are also used. But they differ in the form of their performance. In these containers, the demarcation material is presented in the form of a pear. In expansion tanks, this is simply a partition dividing the container into two parts.
Water in the accumulators gets into the pear without touching the walls of the steel tank. Here, the starting material for the membrane is food rubber.
Principle of operation
The expansion tank works simply. The coolant, expanding, enters the lower part of the tank, filling it. If the volume of water increases, it presses on the membrane by itself, pushing the latter to the walls of the second upper part of the tank. Therefore, it is very important to accurately select the tank in the ratio of its volume to the volume of the coolant located inside the heating system of a private house.
Everything happens exactly the same with a water hammer, only several times faster. It is the expansion tank that makes it possible not to fail other elements of the heating system when fast heating of the coolant occurs.
The hydraulic accumulator works almost as well, but air is pumped into the space between the rubber bulb and the walls of the tank under a certain pressure. It creates pressure inside the water supply network. Everything happens like this:
- Water pumped by the pump enters the pear.
- The latter expands, squeezing the air pumped in the factory.
- The latter presses on the pear, pushing out the water.
The accumulator has two main functions:
- Having a certain volume, it allows the pump to not turn on when opening a consumer. While the water in the pear is under pressure from the side of the injected air, the pressure inside the water supply will always be. As soon as the pressure of water and air is equalized, the pump unit will immediately turn on.
- The accumulator creates a constant and stable pressure inside the pipes of the water supply system. Accordingly, all household appliances, especially washing machines and dishwashers, work without failures.
Hydraulic accumulators of large volumes, in the range of 50-100 liters, are an additional volume of water that is constantly under pressure. This is convenient in cases where the power supply is turned off and the pump simply cannot pump water. In suburban villages, this phenomenon is not rare.
The hydraulic accumulator, like the expansion tank, well restrains the hydraulic shocks of the water system, protecting it from breakdowns.
Other distinctive features
The differences between the two devices must be approached from the standpoint of the possibility of replacing each other. Here it is necessary to take into account the fact that the accumulator is used in the drinking water system. Therefore, its pear-shaped membrane is made of food rubber, which does not spoil the characteristics of the water itself, does not change its color and smell. It is not worth putting an expansion tank in the water supply, because its membrane will first of all give the pungent smell of rubber to the water.
The main function of the accumulator is to create pressure inside the water supply. It is not possible to do this with an expansion tank.
The use of a hydraulic accumulator as an expansion tank is possible. But there is one point that concerns the pressure of the injected air. In the heating system, the coolant moves at a low speed created by the circulation pump. This pressure is not enough to overcome the pressure of the injected air. This may cause a problem. It is not difficult to solve it: the air must be vented (bleed). In the upper part of the tank there is a nipple through which air can be pumped into the chamber with a conventional air pump. Through it, air can be bleed.
The volume of the expansion tank is selected based on the volume of the coolant in the heating system of a private house. The ratio is 10% of the water inside the heating.
As for the accumulator, there are no such strict parameters when choosing it. More often, its functionality is taken into account, because, in fact, it is a capacity for a supply of water. Therefore, the larger this device is, the better.
Installation Rules
This is the only position that has no differences between the two tanks. Typically, both tanks are connected to the pipe wiring with the help of American women, making the connections detachable. This makes it easy to disconnect the device if it is necessary to repair or replace it with a new one.
As for the installation site, there is no difference either, if the heating system in its design has a circulation pump. If heating is a gravity-fed network, the coolant in it moves under the action of physical laws (heated up, cold down), so the installation location of the expansion tank is the highest point of the heating circuit.
The first thing you need to pay attention to when choosing a hydraulic accumulator and an expansion tank is the color of the tank. This is a factor that will not make a mistake. The remaining characteristics are selected for each network individually, taking into account their complexity and performance.
