Quick Reference Guide

SILENCING THEORY

In simple terms, silencing is the act of reducing noise to an acceptable level for the location or working conditions surrounding the noise producing equipment. MAXIM’s money saving line of stock silencers readily solves noise problems of many applications. Comparison of the typical attenuation curves for individual silencer models will show the relative capabilities of different designs.

CHAMBER TYPE SILENCERS
MODELS M21, M31, M41, M51 AND MUL

Chamber type silencers provide the best noise control across the entire audible range. The basic design incorporates non-resonant side tube arrangements to permit passage of the exhaust gases from one chamber to another. This creates a reversal of flow and develops a predictable amount of back pressure. Another important feature of chamber type silencers is the availability of side inlet exhaust connections. Units of this type, except for spark arrestor designs, can also be supplied with side outlet exhaust connections. These side connections, while having little effect on the pressure drop, will in many instances, greatly facilitate installation of the silencer by eliminating the need for elbows in the piping.

SILENCER MODEL

M21Good chamber type silencer. Use in areas where background noise is relatively high and constant and the need for higher degree of silencing is minimal. Expected attenuation is 17 to 20 dBA.M31Better chamber type silencer for residential areas where background noise is present but not objectionable. With expected attenuation of 20 to 24 dBA, the M31 is intended to bring most exhaust noise levels down to match the ambient noise levels.M41Excellent chamber type silencer. Use an M41 in quiet residential area where background noise is relatively low and critical grade silencing is desired. Expected attenuation is 24 to 28 dBA.M51Best chamber type silencer for “Hospital Grade” silencing. Use an M51 for the highest degree of silencing for areas requiring the maximum noise reduction available from standard chambered silencer design. Expected attenuation is 28 to 32 dBA.MULThe MUL is comparable to the M31 for pipe thread sizes 1″ to 31/2″. COMPACT CHAMBER TYPE SILENCERS
MODELS MD26, MD36

Compact design is engineered to provide a “critical” grade of attenuation while minimizing space usage. Excellent application for packaged power and process skids where space is a
premium. Dual inlets and other custom designs can be easily incorporated.  Low Temperature design not only reduces skin temperature, but radiated noise as well.  Heavy duty, welded construction with temperature resistant insulation within a double wall construction. The inlet and outlets are standard with ANSI drilled 125/150 lb flanges. Standard finish is high temperature resistant silicone black. Alternate finishes may be available upon request. Standard material is carbon steel. Stainless steel is optional.

SILENCER MODEL

MD26Expected attenuation is 28-32 dBAMD36Expected attenuation is 33-37 dBA

CHAMBER TYPE SPARK ARRESTOR SILENCERS
MODELS MSA1, MSA2, MSA3 AND MSA4

Spark arrestor silencers have application in marine service, refineries and other hazardous environments. These are chamber type designs. Theretention of hot carbon and soot particles minimizes danger and helps to provide a cleaner area and atmosphere.

SILENCER MODEL

MSA1Highly efficient spark arrestor silencer with M21 attenuation characteristics. Expected attenuation is 17 to 20 dBA.MSA2Highly efficient spark arrestor silencer with M31 attenuation characteristics. Expected attenuation is 20 to 24 dBA.MSA3Highly efficient spark arrestor silencer with M41 attenuation characteristics. Expected attenuation is 24 to 28 dBA.MSA4Highly efficient spark arrestor silencer with M51 attenuation characteristics. Expected attenuation is 28 to 32 dBA. 

LOW PRESSURE DROP, STRAIGHT THROUGH SILENCERS
MODELS MT21, MT31 AND MT41

Straight through silencers have an unobstructed passage through the silencer with no reversal of flow. The result is a pressure drop across the silencer only slightly above that caused by an equivalent length of pipe. Side connections are not practical in this design due to increase in pressure drop and price. Since noise attenuation provided by straight through design is less than that provided by chamber design silencers incorporating a reversal of flow, the MT series is best used in applications where low pressure drop is the primary consideration.

SILENCER MODEL

MT21For noise control applications requiring low pressure drop. Expected attenuation is 13 to 16 dBA.MT31For average attenuation of objectionable noise where effective though not complete silencing is required with low pressure drop. Expected attenuation is 16 to 19 dBA.MT41For better than average noise attenuation with low pressure drop requirements. Expected attenuation is 19 to 22 dBA. 

MARINE ENGINE WET EXHAUST SILENCERS
MODELS MP-11, MP-31 AND MP-41

Constructed of stainless steel, the MAXIM MP series silencers are available for wet marine engine exhaust applications. Water is injected upstream of the silencer in sufficient quantity to reduce the exhaust temperature to a maximum of 200o F. The MP-11 may be installed in series with an MP-31 or MP-41 to provide additional attenuation.

SILENCER MODEL

MP-11Low pressure drop with good performance. Expected attenuation is 15 to 18 dBA.MP-31Medium pressure drop with better performance. Expected attenuation is 20 to 25 dBA.MP-41Highest performance for a wet exhaust application. Expected attenuation is 30 to 35 dBA. 

VENT SILENCERS FOR COMPRESSED AIR, GAS AND STEAM
MODELS VT-S, VT-1, VT-2 AND VT-3

The MAXIM VT series silencers are designed to attenuate high frequency noise associated with venting of high pressure air, gas or steam to atmosphere. These ruggedly designed silencers feature all welded construction with concentric acoustically packed panels.

SILENCER MODEL

VT-1Good vent silencer for controlling noise generated by pressurized gases released to atmospheric pressure. Expected attenuation is 35 to 40 dBA.VT-2Better vent silencer for controlling noise generated by pressurized gases released to atmospheric pressure. Expected attenuation is 42 to 45 dBA.VT-3Best vent silencer for controlling noise generated by pressurized
gases released to atmospheric pressure. Expected attenuation is 50 to 55 dBA. 

ABSORPTIVE DESIGN
INTAKE MODELS: FP, FPC, FPS
DISCHARGE MODELS: FPE, FPCE, FPSE

Intake models are built “cleaned for intake service.” The FPE model in stock sizes 4″ through 12″ is also built clean for intake use and may be substituted for the FP. The “E” designation on any FP design indicates that the silencer is built to withstand hot engine exhaust service.

Absorptive silencer designs are compact and have low pressure drops. They are ideal for many applications for fan intakes and discharges, engine air intakes, small steam vents and centrifugal compressor inlets where absorption of high frequency noise is important. An FPE, FPCE, FPSE installed in series with an M-line chamber type silencer, can provide 10-20 enhancement of the overall dBA silenced exhaust noise of a reciprocating engine. Addition of an absorptive design silencer may improve the overall attenuation of the system by 10 to 20 dBA.

SILENCER MODELFP / FPEStraight through, absorptive silencer design with no center panel for low pressure drop service. Expected attenuation is 20 dBA.FPC / FPCESimilar to the FPE but with an internal center panel which displaces part of the nominal flow area. Pressure drop is higher but the FPC is more compact in diameter, length and weight. Available in sizes 14″ and up, the FPC is excellent for engine and compressor intakes and fan intakes and discharges. Expected attenuation is 20 to 25 dBA.FPS / FPSEDesigned with a center panel, the FPS / FPSE body diameter is enlarged to enable an annular flow passage equal to the full nominal flow area. Pressure drop is intermediate between the FP and FPC models. Expected attenuation is 15 to 30 dBA. 

PRESSURIZED SERVICE, ASME CODE DESIGN
MODELS ILL AND ILM

Designed to ASME Code, MAXIM offers the models ILL and ILM to reduce the noise generated by valves and compressors. Typical noise reductions associated with high pressure applications is within the range of 15 dBA to 30 dBA.

BLOWER SILENCERS
MAXIM MODEL MB11, MB21 AND MB31

Highly efficient in acoustic design, the MB series is used to reduce the noise radiating from blower piping or blower opening. Typical applications are for rotary positive blower intake and discharge, vacuum pump intake and discharge, and centrifugal blower intake and discharge.

SILENCER MODELMB11With its straight through acoustically packed design the MB11 offers good silencing for many blower applications. Typical attenuation is 15 to 30 dBA.MB21An efficient economical design, the MB21 is useful for blower noise reduction in applications where some background noise is always present and high degree silencing is not required. Typical attenuation is about 24 dBA.MB31A superior design, the MB31 incorporates an acoustically packed connection with a chamber type design to offer a high degree of attenuation of blower intake or discharge noise. Typical attenuation is about 30 dBA.

 

Please e-mail Mark Coulson or call 1-251-928-1234.

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