Removing air from the heating system – simple and convenient solutions

The presence of air in heating systems leads to the formation of corrosive processes and other physicochemical phenomena that threaten the efficiency and performance of central heating elements. Gases in the installation disturb circulation, reduce the culture of the installation, and contribute to a significant increase in the costs of operating and maintaining the heating system. For this reason, it is necessary to take appropriate steps to remove air from the system.

In this article you will read about:

• what effect does the air (gases) present in central heating installations have?
• how to bleed heating systems,
• what air separators to use and how to install them correctly.

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What problems do gases cause in the system?

The presence of air in the central heating system (or more precisely: any gases in free, dissolved or micro-bubble form) can lead to numerous problems and malfunctions of the system and, consequently, to failures and defects of the central heating system.

The condition and amount of air in the system is determined by Henry's Law. This law states that: the solubility of gases in liquids increases in proportion to the decrease in temperature and the increase in liquid pressure. Similarly, the solubility of gases in liquids decreases in proportion to the increase in temperature and pressure.

Air present in the central heating system can lead to a decrease in its operating culture, disruptions in water circulation, a decrease in pump efficiency and the risk of their damage, as well as corrosion of the system. The presence of air in the system also affects the water pressure in the system. All this affects the increase in expenses for home heating and the costs of operating and maintaining the system. The low operating culture of the air-filled part of the system is primarily due to the noisy flow of liquid. Then we can hear crackling, knocking, and humming sounds. The symptoms of air-filled pumps are noises coming from the inside of the housing and a decrease in its efficiency. In the case of disruptions in water circulation in the system, the cause may be air cushions. Flow disruptions inside the system often also occur as a result of incorrect operation of diaphragm expansion vessels. In such a situation, the pressure should be checked and then the system should be vented.

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The phenomenon of cavitation and its impact on heating installations

Air and unfavorable operating conditions of the installation can lead to damage or destruction of the pump. Gases mixed with water can accelerate the wear of pump bearings and seals due to its incorrect lubrication and cooling. The phenomenon of cavitation also occurs. It consists in the formation and disappearance of steam-gas bubbles in pipelines, pump flow channels, fittings. A conscious installer knows that in such situations the pressure in the installation should be checked.

Vapor-gas bubbles appear in areas of reduced pressure and rapidly implode in the zone of higher pressure, increasing the pressure increase of the liquid flowing into these areas to even 350 MPa. This leads to the formation of pitting and damage to the materials from which the pipelines and fittings are made. Additionally, the cavitation phenomenon is accompanied by electrochemical corrosion. These problems are caused by air in the installations, which leads to a drastic increase in the costs of use and maintenance. In order to protect the heating installation from these problems, automatic air vents and properly selected air separators should be used.

Overview of separators that allow air to be removed from the central heating system

Air occurs in the system in three forms: free air, microbubbles and air dissolved in water. Automatic air vents are able to remove free air and work mainly when filling or emptying the system. According to Henry's law, changes in the pressure and temperature of the water in the system will determine whether microbubbles of air appear or disappear in a given place. A drop in pressure and/or an increase in temperature will cause the microbubbles to precipitate, which will be removed by a flow air separator. Therefore, these devices are installed in systems where the temperature is the highest, e.g. at the supply, right after the boiler.

In order to precipitate microbubbles from the water stream, it is necessary to cause a disruption of the flow. This is achieved by placing an obstacle in the stream or forcing this phenomenon using a special design of the device. Such an obstacle - an element that will cause a disruption of the flow in Spirovent separators is the spirotube (spiral pipe). Thanks to the special design of the spirotube, very high efficiency has been achieved with very small pressure drops. The precipitated microbubbles rise to the top, where there is an automatic air vent that removes the accumulated air from the installation. In order to remove almost all gases from the installation water, regardless of pressure and temperature, vacuum separators (vacuum deaerators) should be used.

A wide range of functional, reliable and comfortable air separators are products from Spirotech ( Spirovent separators ) and Flamco. Currently, on the market you will find 7 devices separating air from water, which you can easily adapt to the type and specificity of the hydraulic installation and your own needs and preferences.

Brass separator Spirovent Air

The basic separator is the brass separator SPIROVENT Air. This device allows for continuous separation of air from water in the installation. It is mounted on horizontal pipelines. It has threaded connections (3/4", 1", 1 1/4", 1 1/2" and 2") and clamp connections (22 mm). Working pressure up to 10 bar, temperature up to 110°C. Separators for installations with pressure up to 25 bar and temperature up to 200°C are also available for sale. For larger, industrial installations, devices made of steel are available. Designed for horizontal pipelines of sizes DN50-DN300 (larger on request) with weld-in and flanged connections.

Spirovent RV2 separator

A modern and effective separator that effectively removes air from water is the Spirovent RV2 Microbubble Separator . This device is made with a rotating flange, allowing installation on horizontal, diagonal and vertical pipelines. It is available with 22 mm and 28 mm clamp connections and with internal threads 3/4", 1", 1 1/4", 1 1/2" and 2" . Working pressure up to 6 bar, temperature up to 110°C.

Spirovent Solar Separator

If you are looking for a valve for solar installations, be sure to check out the SPIROVENT Solar microbubble separator model. These types of separators are equipped with a thermostatic AutoClose closing mechanism, which prevents the heating medium from evaporating from the solar installation (protection against dry running). Basic versions are designed for horizontal pipelines (versions for vertical pipelines are also available). Working pressure up to 10 bar, temperature up to 180°C.

Installation of separators for central heating

Separators are easy and quick to install. The air separator should be installed as close as possible to the place where gases precipitate. Usually, the device is installed directly behind the heating boiler on the supply pipeline.

We cordially invite you to familiarize yourself with our wide range of separators. Removing air from the heating system has never been so easy!