Air reduces heat transfer
Air trapped in a radiator or an exchanger plate effectively shrinks the heating surface. Since capacity drops, the system runs longer; nobody looks for the real cause.
Product group 05
Separator & Filtration Group
There are two invisible enemies in a closed circuit: air and sludge. Both reduce heat transfer, wear out the pump, and bill you for the failure years later.
Size rangeDN25 – DN300
Pressure classPN10 / PN16
Operating temperature0 °C … +110 °C
TypeAir · dirt · combined · magnetic
Combined air and dirt separator · internal element and drain cross-section
Why it's needed
What does air and sludge in the circuit cost you?
A significant share of system complaints don't come from the boiler or the pump — they come from air and sludge circulating in the loop. Both progress quietly.
It drives the pump toward cavitation and wear
Air bubbles reaching the suction collapse at the impeller inlet. Noise, vibration and, over time, material loss begin. Seal life shortens noticeably.
Sludge accelerates corrosion
Magnetite and corrosion particles settle in the low-velocity zones of the line. Localized corrosion begins beneath the buildup; the pipe eventually gets pitted through from the inside.
A strainer can't catch micro-bubbles
A conventional strainer catches visible particles; it can't catch dissolved air or micro-bubbles. An air separator slows the flow velocity, brings bubbles to the surface, and vents them.
A magnetic separator attracts iron sludge
In a closed circuit, most of the sludge is magnetite. A magnetic rod collects these particles, removing even ones fine enough to pass through a strainer.
The first months after commissioning are critical
In a new installation, weld slag, installation debris and dissolved air are at their most concentrated. Regularly draining the separator in the first months directly reduces the number of failures in the years that follow.
Types
Which type, for which job?
Separators are distinguished by what they capture; most installations need both.
Air separator
Slows flow velocity to carry micro-bubbles to the surface, then vents them to atmosphere via an automatic air vent. Placed at the boiler outlet, the hottest point.
- Micro-bubble separation
- Automatic air vent
- Positioned at the boiler outlet
Dirt separator
Slows flow to let particles settle, collecting them at the bottom. Drained via a valve. Placed at the pump suction or the boiler return.
- Positioned close to the pump suction
- Drained via a bottom valve
- Requires periodic draining
Combined and magnetic type
Captures air and sludge in a single body; types with a magnetic rod also attract magnetite. Preferred where space is tight.
- Two functions in one body
- Magnetic rod captures magnetite
- An advantage in tight boiler rooms
Selection criteria
What data determines the right separator?
Size and type selection depend on flow velocity just as much as line diameter.
ParameterWhy it mattersWhat we need from you
Line diameter and flow rate
If the separator's diameter matches the line, flow velocity can stay too high for effective separation. One size up is usually the right choice.
DN size + m³/h
Substance to be separated
Air only, sludge only, or both? The presence of magnetite calls for the magnetic type.
Air / sludge / combined
Mounting location
An air separator goes at the hottest point, a dirt separator ahead of the pump. If the location is wrong, the equipment won't do its job even if it's the right unit.
Boiler outlet / pump suction
Operating pressure and temperature
Determines the body's pressure class and the internal element's material. Plastic internals can't be used at high temperature.
PN class + °C
Fluid type
Water, a glycol mix, or treated circuit water. Glycol viscosity affects separation efficiency.
Fluid + % glycol
Connection type
Flanged, threaded or welded. Should be planned together with isolation valves so it can be removed and cleaned.
Flanged / threaded
Drain and service access
Clearance is needed below the bottom drain valve for a bucket to fit. If the magnetic rod needs to be pulled out, allow clearance above too.
Service clearance dimensions
Insulation requirement
Condensation and heat loss on a hot line, sweating on a cold one. The insulation jacket needs to be planned from the start.
Yes / no
This much is enough for a quote
You don't need all of it. We'll work out anything missing together with you.
Create a quote request- Line diameter and flow rate
- System type (heating, cooling, process)
- Operating temperature and pressure
- Fluid type and glycol ratio
- New installation or addition to an existing system
- Available clearance at the mounting location
FAQ
Questions from the field
The four questions we hear most often at the quote stage.
I have an air vent — do I still need an air separator?
An air vent releases free air that collects at high points. It can't catch the micro-bubbles circulating dissolved in the water, which stay trapped at the system's hottest point. An air separator does exactly that job — it doesn't replace the vent, the two work together.
I already have a strainer — do I need a separator too?
A Y-type strainer catches particles larger than its mesh and eventually clogs, producing pressure loss. A dirt separator, on the other hand, slows the flow to settle much finer sludge and doesn't clog. Both are used together ahead of critical equipment.
How often should I drain it?
A few times in the first week and once a week for the first month is a reasonable start for a newly commissioned system. Once the system settles, every three to six months is enough. The color of the drained water tells you the real interval — once it runs clear, you can space it out further.
Does the magnetic type really make a difference?
In closed heating circuits, most of the sludge is magnetite — iron oxide — and it's very fine-grained. It passes through a strainer easily but wears down pump seals and exchanger plates. A magnetic rod captures these particles; you'll see the difference at the very first drain, especially in older installations with steel piping.
Next step
Let's keep your circuit clean
Share the line diameter and system type, and let's determine the right separator and mounting location together.