In Short
A silencer must be supported independently of the engine, allowed to expand when hot, and installed with drains placed where water collects and where they can be reached. Most silencer problems on site come from poor installation rather than the silencer itself, so these points should be planned before the exhaust steel goes up.
The silencer is usually the last item on the exhaust drawing to get any attention, and on site it is often hung wherever the pipe happens to reach. Most of the trouble we hear about later comes from that moment rather than from the silencer itself: a cracked manifold, a flange that will not stay tight, water standing in the shell, a drain plug nobody can reach. None of it is difficult to avoid, but it has to be thought about before the steel goes up.
The Engine Should Not Carry the Exhaust
A silencer is heavy, and the pipe that joins it to the engine is long. If that weight hangs from the turbocharger outlet, the engine ends up holding part of its own exhaust system, and the vibration of a running engine works on every joint between the two. The rule on site is simple: the engine carries nothing but its flexible connection. Everything after it is carried by the building, the container frame or a stand of its own.
Supports come in two kinds. Fixed points hold the pipe in place and take its weight; sliding or hanging supports carry the weight but let the pipe move along its length. Where each one goes decides which way the pipe grows when it heats up, and that is planned together with the route rather than added afterwards.
Hot Steel Grows
An exhaust runs from cold to very hot every time the engine starts, and the steel lengthens as it warms. A pipe fixed rigidly at both ends has nowhere to go, so it pushes on whatever holds it: the engine, a wall, a roof frame or the silencer flanges. Over many starts that shows up as cracked welds, leaking gaskets and bent brackets.
Flexible bellows take this movement, as well as the engine's own vibration on its mounts. They are placed where the movement collects, at the engine and on long straight runs, and they are installed at their working length, neither stretched nor squeezed to make up for a pipe that was cut wrong. A bellows used to absorb a misalignment has already spent part of its life before the engine runs.
Which Way Up, and Where the Water Goes
Silencers are built to be mounted horizontally, vertically or either way, and the drawing says which. The orientation matters for the drains, for the way the internals were designed, and for absorptive sections whose fibre should not settle to one end. A unit turned through ninety degrees on site to fit a gap may no longer drain or perform as intended.
Water reaches the exhaust from two sides: rain through the outlet and condensate from the gas itself. A rain cap or a flap at the outlet keeps the first out. The second is led away by drains at every low point of the line and of the silencer shell, with a slight fall on horizontal runs so that nothing stands inside. A drain that is plugged, painted over or pointed at a cable tray does more harm than none, so where the drain water goes is part of the installation too.
Leave Room to Reach It
Exhaust parts need looking at during their life: flange bolts, gaskets, drains, test points for back pressure and emissions, and on some units an inspection opening. Lagging, a container roof or a tight plant room can make all of them impossible to reach without taking something apart. Clear space around the flanges and the drains, and a way to lift the silencer out if it ever has to be replaced, cost little at the planning stage and a great deal later.
Send us the layout and the mounting position with the engine data, and AXON plans the supports, flexible connections and drains with the silencer as one exhaust path.
What the installation covers
- Supports that keep the weight of the exhaust off the engine
- Fixed and sliding points planned with the pipe route
- Flexible bellows at the engine and on long runs, at their working length
- Silencer orientation as designed for its type
- Rain protection at the outlet and drains at every low point
- Access to flanges, drains and test points, and a route to lift the unit out
What to send with an enquiry
- Engine model and the engine data sheet
- Planned exhaust route with the mounting position of the silencer
- Indoor, container or outdoor installation
- What the supports can be fixed to: building, roof, container frame or a stand
- Where drain water may be led on site
- Any limits on space for maintenance and replacement
Questions we are often asked
Can the silencer be supported from the engine?
No. The engine should carry only its flexible connection. The silencer and the pipe are carried by the building, the container frame or their own stand.
Why does an exhaust need flexible bellows?
Because the pipe lengthens when it is hot and the engine moves on its mounts. The bellows take both movements so that they do not load the engine, the welds and the flanges.
Can a silencer be mounted in any position?
Only if it is built for it. Many units are designed for horizontal or vertical mounting only, and turning one on site can stop it draining and change how it works.
Where should exhaust drains be fitted?
At every low point of the pipe and the silencer shell, with a slight fall on horizontal runs, and led to a place where the water does no harm.
What is most often forgotten when installing a silencer?
Access. Flanges, drains and test points end up behind lagging or structure, and nobody planned how the unit could be lifted out if it ever had to be replaced.