Steam Exhaust Heads / Silencers

Droplet separators for roof vents

Exhaust heads, also commonly referred to as exhaust silencers, are a special type of centrifugal separator designed to be installed at the end of a vent pipe. The most common application for exhaust heads are for venting steam from a boiler blowdown tank, although there are some industrial processes that exhaust air containing entrained droplets which are also applicable to this type of centrifugal separator.

The four most common reasons for using an exhaust head for steam venting are:

1. Aesthetics – reducing the opacity of discharged steam
2. Environmental – reduce carry-over of water vapor and any contaminants it might contain to the surrounding area (such as oil and water treatment chemicals)
3. Economics – reclaim and recycle boiler treatment water/chemicals
4. Reduction of condensation on rooftops

Exhaust heads for non-steam applications might include venting of reactors and mixing vessels to reduce carryout of product and additives.

The primary difference between an exhaust head and centrifugal separator is that exhaust heads are NOT a pressure vessel. Since an exhaust head is attached to the end of a pipe with one side always open to atmospheric pressure, its “design pressure” is “atmospheric”. This is frequently misunderstood because although it is still a fully welded product with a connection corresponding to the pressure class of the pipe it is installed, the exhaust head itself (when properly sized) will not experience more than atmospheric pressure.

It is commonplace for exhaust heads to be referred to as “silencers” and although there is a muffling effect with regards to the exhaust sound, this noise reduction is a byproduct of the indirect exit path and not a design factor; exhaust heads are not designed to reduce the vent sound, rather they are designed to reduce droplet carry-out by removing 99% of entrained droplets larger than 10 microns.

We offer exhaust heads made of cast iron, carbon steel and stainless steel (304 or 316). Refer to the sizing chart below which is an indication of the internal element size required. The element size and inlet connection size is usually the same, although we can reduce the connection size to match your existing vent pipe size as needed.