Quiet vibration-free performance from today’s high-revving diesels SILENCING AND EXHAUST SYSTEMS Components to build exceptionally quiet exhaust systems One of a series of brochures on products from Halyard 3

HMI SILENCING AND EXHAUST SYSTEMS Every HMI product in this brochure is designed and manufactured in Britain Noise is tiring. Noise user it turns pleasure into hard work. Our objective noise reduction of around specialist dual chamber water separation units. EXHAUST ACHIEVING? A marine engine exhaust system ejects the cooling water as well as silencing The system must create flow of exhaust gasses, known as back pressure, There are four main objectives: 1 To reduce noise by between 2 To cool the exhaust, and eject the engine cooling water through the exhaust without excessive back pressure. 3...

INDEPENDENT TESTS These tests studied the reduction in exhaust noise using our exhaust silencers. Halyard also offers products to reduce airborne noise, and vibration or structure borne noise. In-line silencers Mike Wake, a technical journalist and former editor of the Royal Institute of Naval Architects Smallcraft Journal, tested a smaller non turbo engine with no silencer, then with a rubber silencer, and finally with an HMI silencer. Noise doubles every three decibels, Dual chamber silencers Motor Boat and Yachting's test power boats with twin diesels dual chamber silencers. Noise doubles...

That's the vital question. The engine's cooling water is usually added to the exhaust right behind the engine. Will water run naturally out of the exhaust? Will it drain when you stop the engine? Might it collect in the exhaust and run back into the engine if the boat pitches? Is the exhaust system diameter large enough to allow free flow without creating high back pressure? Let's looks at the basics of good exhaust design. Engine well above waterline? This engine is sited well above the waterline, with a gradient steeper than 1 in 8 to the back of the boat. The water will run naturally down...

EXHAUST DIAMETER? crucial to avoiding back pressure problems. Longer systems create more back pressure. Sharp bends create more back pressure. Large cooling water flows cause more back exhaust system, the less tips given below assume hull is above waterline above water under way. On a small diesel without a turbo the hose diameter can often be the same as the engine manufacturer's outlet, as long as the system is below 3m in length with no more bends than the Lift Silencer system illustrated above. We can give informal help on the phone, but it is wise to check with the engine Give us a ring...

Halyard produces CRP silencers using specialist resins, allowing remarkably high temperatures if the cooling water supply blocks for short periods. Silencers are usually made from filament wound CRP plant, which is hand-laminated with flat sheet bases. Every single silencer produced is pressure tested individually to guard against leaks. Every silencer is gel-coated after number on the label links into a Quality Assurance system which allows us to trace each operator CRP is used as the base material to avoid the corrosion and acoustic problems of welded stainless units, and to avoid the low melting...

HMI Lift silencers are designed for use with engines positioned Thousands are sold each year and major users include most quality British production boatyards where excellent acoustics and good temperature resistance are paramount. HMI Lift Silencers are as popular with generators as they are with propulsion engines. Details of the full range of sizes price list. lift silencers The side in, top out lift silencer is the best selling small lift Smaller silencers have smart, resin transfer moulded lids. Every unit is pressure tested and gel- coated for a durable and smart In many applications a...

HMI In-Line silencers are used where the engine is well above the water-line, or where a high-riser has been fitted to achieve a 1 in 8 gradient from the engine to the transom outlet. They are simple to specify and fit, and ideally need to The internal design requires the exhaust gasses and water to bubble through a layer of water on the bottom of the silencer to reduce noise. They offer excellent noise reduction and are widely used on both pleasure and commercial Oval In-Line Silencers Our oval silencers are hand-moulded for use where the round body unit cannot be accommodated. They give the...

HMI High Risers combine two features: They raise the engine exhaust outlet to exhaust system, and they have a carefully calibrated range of water spray holes sized to make water jet into the exhaust gasses at full power to maximise the cooling effect. Each each is equipped with heat protecting jackets tailored HMI HIGH RISE SPRAY HEADS Spray heads Many engine manufacturers make a standard spray head for use when a high riser is not needed. If not Halyard can help. We can also produce spray heads with particular spray patterns for installations where Modular spray head This modular spray head...

HMI EXHAUST WATER SEPARATORS This larger separator is designed for use where the generators cooling water flow rate exceeds 40 litres diameter. Individual applications must be checked for correct sizing. It may also be used with propulsion The mid-engine separator is an easy solution for most engines with exhausts from 60mm (2.5") upwards. Units are produced in batches using the same proven technology as HMI silencers. The internal pipe work and body are both from Halyard's tough filament wound tube, and every unit is pressure tested. The unit comes with differing body sizes to match the varying...

Halyard developed the concept designs and produces systems for engines ranging from small diesel generators through to mighty power providers on craft. Fitting a water separator into the exhaust to replace the gooseneck removes water once it has done its cooling job, draining this quietly away below waterline. Back pressure separator removes the principal cause of back pressure and stops the sploshing noise which accompanies every marine engine ticking over in a harbour away in a quiet haven nearby boats. separators reach a point where more economic production had separators represented a huge...