Glaunach Silencer Handbook

GLAUNACH Silencer Handbook

I NOISE II PRODUCTS III ACCESSORIES FOR SILENCERS IV CALCULATION V MATERIAL CODES & STANDARDS VI SURFACE TREATMENT VII INSTALLATION VIII INSULATION IX AVOIDANCE OF FAULTS

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NOISE - Handbook I page 2 of 67

© GLAUNACH GMBH Edition 02.2007

1. NOISE LEVEL “Sound Power Level" and "Sound Pressure Level" are two commonly confused characteristics of sound. Both have the same unit of measure (the Decibel) and the term "Sound Level". However, to understand how to measure and specify sound, we must first understand the difference between these properties: Sound Power Level (abbr.: Lw or SWL or PWL) is the acoustical energy emitted by the sound source, and is an absolute value. It is not affected by the environment. Think of it like a light bulb, which radiates light in every direction. If you could measure all the energy radiated by the bulb, then this would be the equivalent of sound power.

Sound Power Level dB

rustle of leaves 15 mosquito buzzing 45 normal conversation 55 bird singing 60 vacuum cleaner 70 street traffic 80 air compressor 90 jack hammer 100 hard rock music 110 propeller plane taking off 120 walkman (full volume) 130 jet plane taking off 140 shotgun 160 rocket during lift off 170 cannon shot 180 love song of blue whales 190 navy Sonar (at 3kHz) 200

100 m 50 m

100 dB Sound Power

Level !

100 dB Sound Power

Level !

100 dB Sound Power Level



Sound Pressure Level (abbr.: Lp or SPL) is a pressure disturbance in the atmosphere whose intensity is influenced not only by the strength of the source, but also by the surroundings and the distance from the source to the receiver. Sound pressure is what our ears hear and what sound meters measure. Let’s have a look to the light bulb again: Brightness is more than a matter of wattage. How far is the bulb from the observer? What colour is the room and how reflective is the wall surface? Is the bulb covered with a shade? If you take all of these factors affect of how much light reaches the receiver, this would be the equivalent of sound pressure.

Sound Pressure Levels dB @ feet @ m

normal conversation 60 3 1 highway Traffic 70 50 15 diesel truck 90 33 10 freight train 100 200 60 jet plane taking off 110 1000 300 Auto horn 120 3 1 pneumatic riveter 130 3 1 jet take off 140 100 30 artillery fire 150 500 150 firework 160 3 1 jet take off 180 1 0.3

100 m 50 m

52 dB Sound Pressure

Level !

58 dB Sound Pressure

Level !

100 dB

Sound Power Level

rule of thumb

each doubling of the distance = 6dB noise reduction



2. FREQUENCIES

The frequency is a measure of how frequently a vibration repeats itself (oscillates) or the number of waves passing by in a second. A hertz is the unit of frequency – 1 oscillation per second; a kilohertz (kHz) is 1000 hertz – 1000 oscillations per second. Decibels with the sound pressure scale adjusted to conform with the frequency response of the human ear. A sound level meter that measures A-weighted decibels has an electrical circuit that allows the meter to have the same sensitivity to sound at different frequencies as the average human ear. There are also B-weighted and C-weighted scales, but the A-weighted scale is the one most commonly used for measuring loud noise. Calculation of an A weighted octave band

Frequency (Hz)

Measured Lp

(dB) A-Scale Correction

(dB) Corrected LpA

(dB)

31.5 94 -39 55

63 95 -26 69

125 92 -16 76

250 95 -9 86

500 97 -3 94

1,000 97 0 97

2,000 102 +1 103

4,000 97 +1 98

8,000 92 -1 91

Note: The A-scale correction factors are fixed values. The A-weighted sound level can now be calculated by combining the corrected band levels:

here: LPA = 105,5 dB(A)

The frequency range of human hearing is about 20 hertz to 20,000 hertz

LPA = 10 log10 (Σ 10LpA/10)



Peak Frequency For the reduction of the noise intensity, knowledge of the peak frequency is important. Strouhal's calculation method provides a simple way to find this frequency:

s = Strouhal's number w = speed in m/s d = diameter in m

However, the peak frequency is not exactly in the range of Strouhal's calculation. Other components are also important. Strouhal's formula shows only, that the peak frequency increases when the diameter decreases. Shifting the Peak Frequency Since it is easier to attenuate high frequencies than deep frequencies, we use a diffuser pipe to change peak frequencies. This shifts low frequencies to high frequencies and as a positive side effect, the noise level is reduced too.

d

wsf ×=

Blow Off Pipe Diffuser Pipe

63 125 250 500 1K 2K 4K 8K 63 125 250 500 1K 2K 4K 8K



3. VALVE NOISE

There is no international standard for the calculation of valve noise. Glaunach uses several methods to estimate the unknown noise level of a valve. In most cases however, we can use values from our database, which we have developed from many tests on site. For a rough estimation of the unsilenced noise level, we recommend two formulas: VDI 2713* "Noise reduction in thermal power stations" specifies the following formula for the determination of the sound power level: According to this formula, only the quantity and the temperature are determining factors. More recent studies of exhaust valves have shown that the difference in pressure is the decisive factor for the sound's intensity. Both methods of calculation are indirectly related, since increases of quantity and temperature cause the pressure difference to rise. However, a comparison of different calculation methods shows that figures resulting from the "VDI*-Formula" are rather too high. API RP521**

* VDI = Verein Deutscher Ingenieure (German Association of Engineers)

** API = American Petroleum Institute

noise from valves can be expected to be in the region of 130 to 170 dB(A) Lw

Lp30m = L + 10 log (0.5 MC²)

LW0 = 17 log M + 50 log To - 15



4. NOISE REDUCTION

In order to meet environmental demands, noise reduction requirements continue to increase. Design and construction of valves, silencers, and piping systems are therefore constantly improved. Traditional vent silencer designs require an absorption component to attenuate high frequency noise generated at the venting valve outlet. The expanded gas travels between baffles of straight or ring shape, where noise energy is reduced through viscous friction. Such a construction is cumbersome, as it requires very large silencers. This design necessitates the addition of an expansion chamber, installed upstream of the baffles, in which the turbulent flow can be calmed.

How can we reduce valve noise efficiently? a. By transferring pressure drop from the valve to a silencer. Spring-loaded safety valves functioning automatically can be subjected to a back pressure amounting to 10 - 40 % of the set pressure. This means that part of the pressure difference can be absorbed in a controlled process within the silencer. b. By using diffuser pipes with small holes (< ∅ 8mm), so that the peak frequency is increased. Because high frequencies are easier to attenuate than lower ones. A very high noise reduction can be achieved through several concentrically arranged pressure stages. c. By combining diffuser technology with traditional absorbing technology. Through the arrangement of absorption material immediately after the pressure stages, developing whirls and the resulting noise are reduced and partially absorbed. What are the typical noise limits ?

USA: API Medical Research Report EA 7301. (Ref 2) This document dates from 1973. It set a limit of 115 dB(A) to steady sound, and 140 dB (peak) to impulsive noise. These were based on the data in the US. OSHA 1970 Act. EU: 86/188/ECC. (Ref 4) … if a maximum value of the unweighted instantaneous sound pressure level is greater than 200 Pa (140 dB) "suitable and adequate" ear protectors must be used…

noise limits, for the avoidance of hearing damage should be in the range from 100 to 125 dB(A) Lw

PRODUCTS - Handbook II page 8 of 67

GLAUNACH GMBH Edition 02.2007

ABSORBING SILENCER type A

application - any vent or blow-down application

- boiler start-up and purge - turbine bypass

media gas, air, steam,

pressure drop 0 dB

noise reduction 25+ dB

design circular baffles reduce the noise and allow thermal expansion of the construction. The absorber cover is totally made from stainless steel. The inlet nozzle is connected to a diffuser pipe that redirects the gas flow. The silencer can be extended with additional absorbers to achieve a higher noise reduction.



DIFFUSER SILENCER type D




pressure drop > 0,2 bar / > 3 psi

noise reduction up to 50 dB

design several diffuser stages and a fine stainless steel wire mesh are the basic principle of diffuser silencers. This technology supports a substantial smaller and lighter construction compared to absorbing silencers.



DIFFUSER SILENCER

type DA






design the type DA diffuser silencer is similar to type D, except that the silencer shell is equipped with an additional insulation. The insulation is needed for temperature and noise control.



COMBINED SILENCER (DIFFUSER + ABSORBER)

type DAA





noise reduction 50+ dB

design the type DAA diffuser silencer is a combination of type A and type DA silencer. With additional absorbers almost any noise reduction can be achieved.



INLINE DIFFUSER SILENCER

type INLINE

application in particular for closed systems

- any vent or blow-down application - condenser injection - turbine bypass

media steam, gas, air,



design for noise control at pipes, we manufacture the Inline Silencer. This type is similar to the Diffuser Silencer D. Many small diffuser holes disengage the fluid into a fine stainless steel wire mesh.



DUMP TUBE

application - low pressure

- condenser injection - turbine bypass - redirection of the gas flow - pressure control - temperature control




design carbon or stainless steel dump tubes are furnished with a customized number and size of diffuser holes.



DIFFUSER

type DIFFUSER


- condenser injection - turbine bypass - redirection of the gas flow - pressure control - temperature control


pressure drop 0 bar / 0 psi


design diffusers are used for same applications as dump tubes, but with a higher noise reduction. The fluid passes through several diffuser stages and through a fine stainless steel wire mesh.



COLLECTING PIPE

type COLLECTING PIPE

application to connect more than two blow-off pipes into one

silencer, we recommend to use a collecting tube. Valves with different set pressures can be combined. Therefore the down stream pressure of all valves needs to be equated.



noise reduction up to 15 dB (without silencer)

design silencers equipped with collecting pipes are designed for the maximum possible flow level

40 psi

80 psi

145 psi

80 psi



RENTAL SILENCER

type DA & DAA

application - any vent or blow-down application - boiler start-up and purge - turbine bypass

with the construction of new boilers, equipment change, or repair work, debris may be introduced into the piping system. This must be removed before the process gas or steam is used. These contaminants are removed by “blowing free“ the piping. Often silencers are used that do not withstand the continuous stress or which become ineffective as a result of obstructions in the diffuser. Glaunach has developed a special Silencer which can be used repeatedly. This silencer allows the replacement of a diffuser cartridge in the event its performance is impeded by debris and back pressure becomes too high.




design DA or DAA Diffuser Silencers, but with exchangeable diffuser cartridge

ACCESSORIES - Handbook III page 17 of 67


LIFTING LUGS

application all products are equipped with lifting lugs

purpose lifting lugs are furnished on all units for ease of handling

design carbon or stainless steel typically from the same material as silencer shell

IDENTIFICATION PLATE

application all products are equipped with an identification plate

purpose identification and design information

design anodized aluminium or stainless steel (extra charge)

PRESSURE GAUGE

application on customers request

purpose connection for instruments for pressure or temperature measuring at the silencer inlet nozzle.

design carbon or stainless steel closed with a plug

(½ inch whitworth thread)



DEWATERING PIPE

application all products are equipped with a dewatering device

purpose drainage for condensation and rainwater

design carbon or stainless steel typically from the same material as the silencer shell

EAVE RING

application all kinds of vent silencers

purpose drip mould for rain water and connecting point for external insulation

design carbon or stainless steel typically from the same material as welded on

COLLAR SHEET application all kinds of vent silencers

purpose In-roof installations, drip

mould for rain water and connecting point of external insulation

design carbon or stainless steel typically from the same material as welded on



BRACKETS

application all kinds of products

purpose support

design carbon or stainless steel

typically from the same material as welded on

LEGS

application all kinds of products

purpose support

design customized from carbon or stainless steel typically from the same material as welded on

RAIN CAP (WEATHER HOOD)


purpose protection for heavy rain or

snow fall

design typically from the same material as silencer shell according to the required noise level, the rain hood is equipped with an absorbing face



GOOSE NECK


purpose redirection of the gas flow

design customized from carbon or stainless steel typically from the same material as silencer shell

FLANGE application inlet nozzles, outlet pipe,

dewatering

design plain flange or flange kit including nuts, bolts, gasket and 2nd flange - according requested standard

OUTLET EXTENSION application all kinds of vent silencers

purpose Extension of the silencer

outlet

design customized from carbon or stainless steel typically from the same material as silencer shell



MULTIPLE INLETS


purpose combination of different

inlet pipes into one silencer

design for simultaneous flow

EXCHANGEABLE DIFFUSER CARTRIDGE

application diffuser silencers

purpose for mediums with

impurities which may plug the diffuser an affect the back pressure

design wrapped with a stainless steel wire mesh.

ABSORBER

application all kind of vent silencers

purpose noise reduction by

absorbing materials

design circular baffle elements made by a perforated plate from stainless steel. The internals are heat resistant glass fabrics and noise absorbing materials.



HEATING application all kinds of silencers and diffusers

purpose - for zones with extremely low ambient temperatures

- if no temperature is transferred to the silencer

design a heating system of 200 W will be used for silencers with outside diameter of up to 2 m. the heating capacity should be increased to 400 watts for silencers of larger diameters. the heating cartridge consists of a stainless steel pipe and a connecting shell. The pipe penetrates into a block of steel, which is welded to the silencer bottom. The connecting shell, made of aluminum is affixed at the outer end of the heating cartridge's pipe. Inside there are connection clamps and a thermostat which switches the heating cartridge on and off. No additional control device is necessary, however, a control light in the control room is recommended. The complete heating unit is fixed on the silencer with one bolt and can easily be exchanged if necessary.



EXPANSION JOINTS

application all kind of silencers and diffusers

purpose for vertical and/or horizontal movement of the entrance pipe

caused by thermal expansion.

design - pressurized expansion joints (stainless steel) - non pressurized expansion joints (stainless steel) - sliding brackets - sliding diffuser

BIRD SCREEN


purpose prevent birds from nesting

inside the silencer

design stainless steel grating at the silencer outlet



INSULATION CLIPS*


purpose thermal and acoustical

wool insulation

design spikes or clamps

* See also “Handbook VIII Insulation”

CALCULATION - Handbook IV page 25 of 67


1. REDUCED NOISE LEVEL (Lr) The required noise level Lr must be specified by the customer. This level must be conforming to the local requirements, in conjunction with the requirements of the end user. If you are unsure about these requirements we recommend to limit the Sound Power Level according to US OSHA: Personnel protection-OSHA 1910.95

When employees are subjected to sound exceeding those listed in the table below, feasible administrative or engineering controls shall be utilized. If such controls fail to reduce sound levels within the levels, personal protective equipment shall be provided and used to reduce sound levels within the levels of the table.

If the variations in noise level involve maxima at intervals of 1 second or less, it is to be considered continuous.

____________ PERMISSIBLE NOISE EXPOSURES ____________ | Duration per day, hours | Sound level dB(A) slow response _____________________________ __________________________ | 8 | 90 6 | 92 4 | 95 3 | 97 2 | 100 1 1/2 | 102 1 | 105 1/2 | 110 1/4 or less | 115 ________________________________________________________

When the daily noise exposure is composed of two or more periods of noise exposure of different levels, their combined effect should be considered, rather than the individual effect of each. If the sum of the following fractions: C(1)/T(1) + C(2)/T(2) C(n)/T(n) exceeds unity, then, the mixed exposure should be considered to exceed the limit value. Cn indicates the total time of exposure at a specified noise level, and Tn indicates the total time of exposure permitted at that level. Exposure to impulsive or impact noise should not exceed 140 dB peak sound pressure level. More details at: http://www.osha.gov It is important to know that if several valves open at the same time, there is an additive effect to the overall noise level.



NOTE the distance from the

silencer axis to the silencer shell must be considered in

noise calculations

2. ADJUSTMENTS DETERMINED BY DISTANCE Usually the sound level is evaluated from the silencer shell at a specific distance. To calculate adjustments determined by distance, following methods can be used: Hemispherical Radiation

The noise level from silencers (installed on a roof) radiates out hemispherical into the environment. The sound pressure level decreases according to the following formula: Example: 5m beside the silencer exit you have measured Lp5m = 90 dB a) Calculate the Sound Power Level Lw b) Calculate the Sound Pressure Level in a distance of 20m from the outlet Lp20m

a)

∆Lr = 10 log (2 π (0.5+5)²)

∆Lr = 22,7

Lw = Lp5m + ∆Lr = 90 + 22,7 Lw = 112,7 dB

b) Lp20m = Lw – 10 log (2 π r²)

= 113,5 – 10 log (2 π (0.5+20²) Lp20m = 79,3 dB

or Lp20m = Lp5m – 20 log (r2/r1) = 90 – 20 log (0.5+20)/(0.5+5)

Lp20m = 78,6 dB

∆Lr = 10 log (2 π r²)

0.5m 5m

r



3. TRANSMISSION FACTORS (∆∆∆∆L) The sound level adjustments determined by distance are only valid within 25 m from the noise source. If the evaluation level is at a distance greater than 25 meters, the following parameters should be considered:

∆La = air reflecting measure in dB

∆LΦ = direction correction in dB ∆Ls = screen measure in dB ∆Lv = vegetation attenuation measure in dB ∆Lrx = area reflecting measure in dB ∆Lb = bottom attenuation measure in dB

Most of these can only be identified by an acoustic engineer at site. For that reason we only have a look at ∆La and ∆LΦ:

∆∆∆∆La Air reflection measure Sound absorption in the air depends on the frequency, temperature, and humidity. The following chart represents approximate frequency adjustments for dB/m at 10°C and an air humidity of 70%.

f(Hz) 125 250 500 1K 2K 4K 8K

dB / m 0,001 0,001 0,002 0,004 0,008 0,021 0,052



∆∆∆∆LΦΦΦΦ Direction Correction

110°

90°

80°

45°

Silencer

Roof

0°

Vertical silencers direct the sound energy up. For vertical applications, depending upon the angle of reflection, the following increases apply:

Angle of reflection Φ 110° - 90 ° 90 ° - 80 ° 80 ° - 45 ° 0 °

Correction in dB 0 1 3 20

Φ= angle of reflection between silencer axis and evaluation point.

Because of the higher noise level at the silencer outlet, the silencer should always blow upward. Rain caps reflect the sound, even when they have an absorbing surface. Therefore, we recommend that rain caps should only be used if absolutely necessary. Under normal circumstances, the point of noise reduction is below the horizontal axis of the silencer outlet. For such points, no correction is necessary.



4. UNSILENCED SOUND POWER LEVEL OF VALVES The following two calculations can be used for a rough estimation of the unsilenced sound level of a valve. VDI 2713

Lw0: Sound Power Level of the valve in dB M: capacity in t/h (if M < 10 t/h then M = 10 t/h) T0: gas temperature at the valve in K

This formula identifies the total Sound Power emitted by a source. The Sound Power is the acoustical energy emitted by the sound source, and is an absolute value. It is not affected by the environment or distance.

ANSI/API RP 521

Lp30m: Sound Pressure Level 30 meters (100 feet) from stack tip in dB L: noise intensity at 30 meters (100 feet) from stack tip dB M: capacity in in kg/s C: Speed of sound in the gas at he valve in m/s This formula identifies the total Sound Pressure emitted by a source. Sound Pressure is a pressure in the atmosphere whose intensity is influenced not only by the strength of the source, but also by the surroundings and the distance from the source to the receiver. Sound Pressure is what our ears hear and what sound meters measure.

Lw0 = 17 log M + 50 log To - 15

Lp30m = L + 10 log (0.5 MC²)



Example:

Calculate the Sound Power Level of a Safety Valve: Medium: H2O Steam Capacity: 100 t/h Upstream Temperature: 500 °C Upstream Pressure: 50 bar Downstream Pressure: 8 bar VDI 2713

M = 100 t/h

T0 = 500°C + 273,15 = 773.15 K

Lw0 = 17 log (100) + 50 log (773.15) – 15 ≈ 163 dB

ANSI/API RP 521 PR = 50/8 ≈ 6

You have to refer to ANSI/API RP 521 (Guide for Pressure-Relieving and Depressuring Systems) to get the noise intensity from the L/PR diagram. L = 60 dB

M = 100 t/h = 27.8 kg/s

C = 664 m/s (from “properties of water and steam”)

Lp30m = 60 + 10 log (0.5 * 27.8 * 664²) = 128 dB

∆Lr = 10 log (2 π 30²) = 38

Lw0 = Lp30m + ∆Lr = 128 + 38 ≈ 166 dB



5. DETERMINATION OF DYNAMIC INSERTION LOSS (DIL) in order to obtain a correct result for the calculation of the sound power level of silencers (LW), the required evaluation level (Lr) of the silencer needs several adjustments (∆lr ) and transmission factors ∆La, ∆Lrx, ∆Ls, ∆Lv, ∆Lb The transmission factors . ∆Lrx, ∆Lrs, ∆Lrv, ∆Lrb.are not considered here as their calculations are very difficult.

Example 1:

Valve capacity M = 100 t/h Temp. in front of the valve t0 = 500°C Pressure in front of the valve p0 = 100 bar The required evaluation level Lr is 85 dB(A) at a distance of 7 meters Calculate the necessary dynamic insertion loss (DIL) for a silencer: The noise source is rather close (<25m), a distance depending noise reduction can be made without corrections.

Lw0 = 17 log 100 + 50 log (273 + 500) - 15 = 163,4 dB(A)

∆Lr = 10 log (2 π 7²) = 24,9 dB Lw = 85+24,9 = 110 dB(A)

DIL = Lw0 - Lw = 163,4 - 110 = 53,4 dB

Lw = Lr + ∆Lr - ∆LΦ + ∆La

DIL = Lw0 - Lw

7m



Example 2:

Valve capacity M = 100 t/h Temp. in front of the valve t0 = 500°C Pressure in front of the valve p0 = 100 bar The required evaluation level Lr is 50 dB(A) at a distance of 300 meters on a hill, 50 meters above the steam outlet. The maximum noise level was measured at a frequency of 2000 Hz

Calculate the necessary dynamic insertion loss (DIL) for a silencer:

Lw0 = 17 log 100 + 50 log (273 + 500) - 15 = 163,4 dB(A)

∆Lr = 10 log (2 π 300²) = 57,5 dB

direction correction (see page 5)

Φ = 80°

∆LΦ = 3 dB air reflection (see page 4)

∆La = 0,008 × 300 = 2,4 dB

Lw = 50 + 57,5 - 3 + 2,4 = 106,9 dB(A)

DIL = Lw0 - Lw = 163,4 - 106,9 = 56,5 dB

300m 50m

Φ



6. THERMAL EXPANSION

Thermal expansion α in 10-6 m /m°C between 20° and ... 100 °C 200 °C 300 °C 400 °C 500 °C 600 °C

α 11.1 12.1 12.9 13.5 13.9 14.1

Example: A pipe-line made of carbon steel has a length of 12 m and is loaded with a max. operating temperature of 490 °C. A sliding diffuser shall be provided to allow thermal expansion. For the temperature range 20°C to 500°C α is 13.9

∆l = 12 × 13.9 × 490 × 10-6 = 0.0817 m An expansion joint for vertical movement of 81.7 mm is required

7. REACTION FORCES Reaction force from the vertical blow-off are calculated as follows:

R = Reaction force in N Sa = Outlet surface in m² wa = Blow off velocity of the expanded gas in m/s va = Specific volume of the expanded gas in m³/kg

R = wa² x Sa / va

∆l = l × α × t × 10-6



Example: The outlet of a steam silencer has an open area of 0,7854 m² The capacity of the silencer is 20 kg/s, the temperature of the steam at the silencer outlet is 300°C at atmospheric pressure.

You will need a Steam Table to read out the specific volume (va) of steam at 300°C and atmospheric pressure Sa = 0,7854m²

M = 20 kg/s refer to steam table: va(300°C) = 2,63887 m³/kg

Qa = M * va(300°C) = 52,8 m³/s

Wa = Qa / Sa = 67,2 m/s

R = wa² * Sa / va = 1344 N

R

NOTE due to the restricted velocity inside of vent silencers, the reaction forces are

rather low and can be neglected



8. WIND AND EARTHQUAKES GLAUNACH silencers are built so compact that the wind forces can be led off over the shell without any problems. The support of GLAUNACH silencers, e.g. brackets or legs are designed to withstand any possible loads from wind or earthquakes. Nevertheless, the supporting structure, which is not scope of supply, should be examined by a stress analyst.

9. BACKGROUND NOISES ISO/DIS 11820.2 - Acoustic-Measurements This standard specifies how silencers are to be measured in specific applications. This standard cannot be used as the sole guideline for noise measurements, as it only provides for the measurement of ducted silencers. In chapter 1.2-b) Blow-down silencers are expressly mentioned. Table „Corrections for background noise“ shows that the background sound pressure level alone must be more than 3 dB lower than the measured operating sound source during the test. During the control measurement at a silencer all ambient noise, noise reflection of the valve and piping, must be accordingly lower. Under ideal conditions, it is often required that silencers meet extremely low silenced levels, e.g. 85 dB(A) at 1 meter from the silencer opening. Actual site visits reveal that the blow-off pipe between silencer and roof or valve is not damped, or the valve is outside and radiated noise levels from these sources are often overlooked. According ISO/DIS 11820.2 the control measurement is invalid! In the standard for different installation conditions, recommendations for the arrangement of the measuring points are given. The standard requires that measuring points be arranged on the silencer axis in front of the blow-off outlet. With blow-off silencers, however, the medium flows out of the silencer outlet at high velocities and high temperatures. As a result, it is not recommended that microphones be arranged in the gas path at the silencer outlet. ∆LΦ Direction Correction. Generally one point of reference is arranged laterally, beside or under the silencer opening. If the customer requires a point of reference over the silencer opening, a direction correction is to be made.



SYMBOLS SYMBOL UNIT DESCRIPTION

Φ ° angle of reflection

α 10-6 m /m°C expansion factor

C m/s speed of sound

DIL dB dynamic insertion loss

f Hz frequency

L dB noise intensity – API RP 521

∆l m thermal expansion

∆LΦ dB direction correction

∆La dB air reflecting measure

∆Lb dB bottom attenuation measure

Lp dB sound pressure level

Lr dB required evaluation level of the silencer

∆Lr dB noise level reduction by distance

∆Lrx dB area reflecting measure

∆Ls dB screen measure

∆Lv dB vegetation attenuation measure

Lw dB sound power level

M kg/s capacity (mass-flow of moving fluid)

p0 bar(g) pressure upstream of valve

PR - pressure ratio

Qa m³/s quantity (volume-flow of moving fluid)

r m distance

R N reaction force

Sa m² free area at silencer outlet

t0 °C temperature upstream of valve

T0 K temperature upstream of valve

va m³/kg specific volume

wa m/s velocity (speed of moving fluid)

MATERIALS, CODES & STANDARDS - Handbook V page 37 of 67

© GLAUNACH GMBH 2005 Edition 06.2005

NOTE

Materials used in the construction of silencers follow European standards and are stated on the following pages. In some cases, we will substitute higher grade materials in place of lower grade materials. Upon request, ASTM-materials and others can be used. Since blow-off silencers are normally loaded for short durations of time, maximum actual working time is based on 10,000 hrs.

1. SILENCER MATERIALS

Item Part Material No. up to 400°C up to 510°C up to 540 °C

1 Jacket sheet FE360B P265GH 16Mo3

2 Perforated plate 1.4301 1.4301 1.4541

3 Absorption material Mineral wool and long strand glass lining

4 Diffuser plate P265GH 16Mo3 16Mo3

5 Perforated plate P265GH, 16Mo3 16Mo3 16Mo3

6 Diffuser tube St35.8 I 16Mo3 16Mo3

7 Diffuser material 1.4301 1.4301 1.4541

8 Dewatering pipe St35.8 I St35.8 I St35.8 I

9 Entrance pipe St35.8 I 16Mo3 13CrMo4-5

10 Flange C 22 16Mo3 13CrMo4-5

1

2

3

4

5

6

7

8

9

10



2. MATERIAL ANALYSIS

DIN Chemical composition

No.

Mat. No. Symbol %C %Si %Mn %P %S %Mo %Cr %Ni %Ti

DIN EN 10025 1.0037 FE360B ≤0,17 - - ≤ 0,045 ≤ 0,045 - - - -

DIN EN 10028 T2

1.0425 P265GH ≤ 0,20 ≤ 0,40 0,50 - 1,40 ≤ 0,030 ≤0,025 ≤0,08 ≤0,30 - -

DIN EN 10028 T2

1.5415 16Mo3 0,12 - 0,20

≤0,35 0,40 - 0,90 ≤0,030 ≤0,025 0,25 - 0,35 ≤0,30 - -

DIN EN 10028 T2

1.7335 13CrMo4-5

0,08 - 0,18

≤0,35 0,40 - 1,00 ≤0,030 ≤0,025 0,40 - 0,60 0,70 -1,15 - -

DIN 17175 1.0305 St35.8 I ≤0,17 ≤0,35 0,40 ≤0,05 ≤0,05 - - - -

DIN 17441 1.4301 X5CrNi 1810

≤0,07 ≤1,0 ≤2,0 ≤0,045 ≤0,03 - 17,0-19,0 8,5-10,5 -

DIN 17441 1.4541 X6CrNiTi 1810

≤0,08 ≤1,0 ≤2,0 ≤0,045 ≤0,03 - 17,0-19,0 9,0-12,0 ≥5x%C≤

0,8

3. TENSILE TEST

Material

Yield stress

Proof stress

Tensile strength

Elongation

Symbol N/mm2 0,2 % 1 % N/mm2 %

P265GH ≥255 130 (400°C) - 410-530 ≥23

16Mo3 ≥275 140 (500°C) - 440-590 ≥24

13CrMo4-5 ≥300 165(500°C) - 440-590 ≥19

St35.8 I ≥240 - - 350-450 ≥25

1.4301 - 195 230 500-700 ≥40

1.4541 - 200 235 500-730 ≥35

4. LOWER LIMITING VALUE - CREEP RUPTURE STRENGTH

DEPENDENT ON THE TEMPERATURE ACCORDING TO DIN EN 10028 T2 (DIN 17175)

Material 380 390 400 410 420 430 440 450 460 470 480 490 500 510 520 530 540 550 560 570

P265GH, (St35.8 I)

10000 h N/mm² 183 169 153 139 126 114 102 90,4 80 68,8 60

100000 h N/mm² 132 118 106 94,4 82,4 72,8 63,2 55,2 47,2 40 33,6

16Mo3

10000 h N/mm² 238 218 198 178 157 137 118 100 81,,6

100000 h N/mm² 196 167 139 114 93,6 74,4 59,2 47,2 37,6

13CrMo4-5

10000 h N/mm² 296 278 262 243 218 191 167 143 123 103 87 73 61

100000 h N/mm² 228 201 176 152 130 110 92,8 75,2 62,4 48,4 39 32 26

tension applied to the original cross section which leads to rupture after 10000 or 100000 hrs.



5. COMPARISON OF INTERNATIONAL STANDARDS

Germany W-Nr. DIN

France AFNOR

Great Britain B.S.

Italy UNI

Sweden SS

USA AISI/SAE/ASTM

1.0425 P265GH

A 42 CP; AP

1501 Gr. 161-400; 151-400 1501 Gr. 164-360; 161-400 1501 Gr. 164-400; 154-400

Fe 410 1 KW; KG; KT Fe 410 2 KW; KG

1430 1432 A 516 Gr. 60 1)

1.5415 16 Mo 3

15 D 3

---

16 Mo 3 (KG; KW)

2912 A 204 Gr. A

4017

1.7335 13 CrMo 4-5 15 CD 3.5 15 CD 4.5

620-440 620-470 620-540

1501-620; 621

14 CrMo 3 16 CrMo 3

2216

A 182-F11; F12

A 387 Gr. 12 Cl.2

1.0305 1) St 35.8 I --- --- C14 --- A106Gr.A

1.0402 C 22

AF 42 C 20 XC 25 1 C 22

055 M 15 070 M 20

1449 22 HS, CS

C 20 C 21 C 25

1450 (M) 1020 M 1023

1.4301 X 5 CrNi 18 10

Z 4 CN 19-10 FF Z 5 CN 17-08 Z 6 CN 18-09 Z 7 CN 18-09

304 S 15 304 S 16 304 S 17 304 S 18 304 S 25 304 S 31

X 5 CrNi 18 10

2332 2333

304 304 H

1.4541 X 6 CrNiTi 18 10

Z 6 CNT 18-10

321 S 18 321 S 22 321 S 31

321 S 51 (490; 510) 321 S 59 LWCF 24

X 6 CrNiTi 18 11

2337

321

Source: Key to Steel, 16th Edition (1992) / P265GH included as H II; 16Mo3 as 15Mo3; 13CrMo4-5 as 13CrMo44

1) not included in the international comparison of norms of the Key to Steel.

6. QUALIFICATIONS We are qualified to manufacture silencers according to PED or ASME



7. APPLICABLE CODES FOR VENT SILENCERS

EU US

Certified Quality Assurance

Code / Guidline

Harmonized Standards

Welder Performance Qualific.

Welding Procedure Specification

Approval of welding procedures

Marking

Inlet Pipe Matetrials

Non Destructive Testing

Sandblasting

ISO 9001 : 2000, EN 729-2 PED 97/23/EC AD-2000, TRD, EN 13480 EN 287-1/ A1 EN 288-3 / A1 ÖNORM 7812, AD2000-HP0, TRD 201 PED 97/23/EC Kat I,II,III EN, DIN ISO-EN 473 VT, PT, RT, MT, UT ISO 12944/4- SA 2½

ISO 9001 : 2000 ASME Section VIII Div.1; B31.1 NBEP NA ASME Section IX ASME Section IX NA NA ASTM, ASME ASNT SNT-TC-1A-VT, PT, RT, MT, UT SSPC-SP 10



8. QUALITY CONTROL

Quality Assurance covering construction and production of ventsilencers follows standards and rules of (ISO, TRD, TRB, AD-instructional pamphlets) or purchaser's own specified quality assurance procedures and quality assurance system.

Quality of Materials:

The quality of the materials for pressure leading parts is determined by

Inspection Certificates according. to DIN 50049 (DIN EN 10204):

• 3.1A for pre material 16Mo3, 13CrMo4-5

• 3.1B for pre material P265GH, St35.8 I or ASTM materials

• 2.2 for all other materials

Quality check of the welded joints:

Our company furnishes proof that conditions according to AD-brochure HP 0 are fulfilled. Conditions related to appropriate production according to the general principles for materials are given. We have appropriate:

• production and welding equipment, • welding personnel and welding supervision personnel, • testing facilities, • test personnel and test supervision personnel.

If necessary, welding qualification can be supplied in accordance with ASME

SEC.IX.

If a “Code“ stamp according to ASME is prescribed, the inspection is made by

the “Authorized Inspection Agency“

Quality Management:

GLAUNACH’s Quality Management System is in accordance with ISO 9001.

Our Quality System was first certified in 1993 by Lloyd’s Register and continues

to be constantly supervised and recertified annually.



SURFACE TREATMENT - Handbook VI page 43 of 67


GENERAL INFORMATION

Attention to details while applying corrosion protection extends the service life of silencers substantially. For parts, that are particularly corrosion endangered, (e.g. thin perforated plates and flowed through absorbing materials), stainless steel is used. All carbon steels are sand-blasted and get a heat resistant protective coating. The flow-loaded internals are covered with a single and the exterior surface with a double primer. During transport and assembling the coating might be damaged. Therefore a repairing kit is supplied with Glaunach silencers. The repair kit includes a can of original painting and a roll-brush. You’ll find the repair kit at the silencer inlet. The internals of the inlet pipe and the diffuser don’t get a coating, since it would not survive the first blow-out. For transport the silencer inlets are closed with a plastic cap.



1. SURFACE TREATMENT FOR CARBON STEEL

According to standard for the silencers the following surface treatment is provided: Silencer Inlet Pipe and Diffuser

- Hand tool cleaning - slightly coated with oil

Silencer Shell Internals

- Blast clean by compressed air with cast iron grit - Surface preparation grade SA2 1/2 according to DIN 55928T4 - Single coating with ethyl silicate zinc rich primer

Silencer Shell Exterior < 400°C (750°F) temperature load

- Blast clean by compressed air with cast iron grit - Surface preparation grade SA 2½ according to DIN 55928T4 - Double coating with ethyl silicate zinc rich primer

At a temperature load of approximately 450°C (840°F), this coating loses its corrosion resistance since the zinc particles melt. Nevertheless, pure aluminium silicon coatings with a temperature resistance of more than 500°C (932°F) offer less corrosion protection, since the mechanical resistance is very poor. Even without temperature load, pure aluminium silicon coatings may not prevent corrosion. Silencer Shell Exterior > 400°C (750°F) temperature load

- Blast clean by compressed air with cast iron grit - Surface preparation grade SA3 according to DIN 55928T4 - Coating with aluminium in an electric arc spraying process - Sealer with aluminium silicon paint.



2. SURFACE TREATMENT FOR STAINLESS STEEL

Degreasing Grease, oil, cutting fluids, drawing compounds and other lubricants must be removed from the surface of stainless steel components before heat treatment (to prevent carbon pick-up) or final passivating treatments (to enable full access by the treatment). Parts must also be degreased prior to further assembly by welding, again to prevent pick-up of carbon at high temperature. Problems associated with chemical cleaning processes can be avoided by using mechanical cleaning. With all mechanical cleaning processes great care must be taken to prevent the stainless steel surface from becoming contaminated by iron, steel or iron oxide particles. Wire Brushing Wire brushing is useful to remove light heat tint, but again brushes must be of stainless steel, and these must never be used on materials other than stainless steels. Pickling and Passivation Pickling is an acid treatment to remove high temperature scale produced in welding, heat treatment or hot working. It also removes red rust from corrosion of the steel or from corrosion of contaminant iron or steel particles. Note that passivation is not sufficiently aggressive to remove this corrosion product after the free iron has begun to rust. High temperature dark scale is not only undesirable for aesthetic reasons - it also results in a reduced corrosion resistance of the underlying steel surface layer.



3. SAMPLES

Sandblasting

Iron Grit Blasting: SA 2 ½ Iron Grit

Blasting: SA 3

Colours

Ethyl Silicate Zinc Carboline 11 Aluminium Coat Thermaline 4700

INSTALLATION - Handbook VII page 47 of 67


1. INSTALLATION OF VENT SILENCERS

- Vent Silencers should be installed as high as possible.

- The inlet pipe downstream of the silencer, should be sized sufficiently to keep gas velocities low. - Bends should be avoided since they generate turbulences and flow noise. - Some back pressure at the silencer inlet should be allowed. Glaunach Vent Silencers are of such a light and compact construction, that in some cases the silencer is carried by the blow-off pipe without any other support.

RULE OF THUMB

higher inlet pressure = smaller and cheaper construction



2. SUPPORTING STRUCTURE UNDER THE ROOF

The silencer is mounted at the blow-off pipe which is supported under the roof. In case of elongations due to temperature, the silencer moves upwards. The only precaution to be taken is the fitting of a suitable seal at the roof's passage. Wall thickness of the blow-off pipe must be thick enough to withstand wind forces.

3. SUPPORTING STRUCTURE IN THE ROOF

Fixation of the silencer by brackets which are bolted to girders.



4. SUPPORTING STRUCTURE ON THE ROOF

The silencer is mounted on brackets which are fixed on the roof. The blow-off pipe must be allowed to move sufficiently downwards or upwards, otherwise a compensator should be provided. If requested the diffuser of the silencer can be arranged “sliding” in the silencer shell. With this construction, the addition of an impact sound separation between diffuser and silencer is supplied.

5. FLEXIBLE INSTALLATION OF THE SILENCER

The silencer can be mounted on balancing bearings to aide in the expansion process. In this case residual powers are permanently exerted on the pipe nozzles.



6. DEWATERING

In each diffuser silencer, rain water and must be drained by an unpressurized dewatering pipe at the bottom of the silencer. During starting up of the silencer, condensation of steam in the silencer is possible and hot water can come out. In such cases, especially in cold climatic zones, we recommend that the dewatering pipe is arranged close to the insulation. This will prevent the drain from freezing.

Please note that hot water may flow to the roof. For this reason, we recommend to arrange a plate beneath the dewatering pipe to avoid damages of the roof. Dewatering of rain-water through the diffuser inlet into the blow-off pipe or by a by-pass has to be avoided for the following reasons:

• Pollution caused by sand, dust, birds, etc., may penetrate into the

pressurized pipe system and could plug the system. • Due to the back pressure in front the diffuser, steam will escape through the

drain and considerably impair the effectiveness of the silencer.



7. STORAGE

If the silencers are stored outdoors, the inlet pipe and dewatering pipe must be directed upwards, to prevent rainwater from entering the silencer. Plastic covers are used to close the entrance and dewatering pipe. For long-term storage, the silencers must be placed under a roof.

8. FIRST BLOW OFF Before the first blowing off process, please remove all covers and shipping brackets. Before start-up, the blow off pipes should be cleaned without a silencer. Impurities such as ferric-oxide and organic materials may block the silencer. Silencers should not be installed close to facades, as the jet of steam could cause damage. Furthermore, sound reflection off walls can intensify the level of sound by about 10 dB

9. SLIDING DIFFUSER On delivery of the silencer with sliding diffuser, the sliding diffuser is fixed with 3 bolts in the required position. After installation, the bolts must be removed. After the first blow off process we recommend to adjust the tension of the stuffing box, so tightness is guaranteed. If insulation above the stuffing box is provided, tension should be made and lock washers should installed.

10. SPARE PARTS Spare parts are not needed for a two-year operation or longer unless the silencer is provided with a heating element.

NOTE Please also refer to the installation manual which is part of

any project documentation.

INSULATION - Handbook VIII page 52 of 67


1. NOISE REFLECTION OF BLOW-OFF PIPES

The blow-off silencer reduces the sound power level of a valve. Each valve and associated discharge piping radiates noise, which is not attenuated by the silencer. In VDMA* 24.422, regulations for the calculation of the noise reflection of relieving valves are mentioned. In VDI** 3733, calculation methods for the calculation of noise reflection of blow-off pipes is discussed. By means of these regulations we provide in the following a simplified table, where the noise reflection of a blow-off pipe can be determined.

DN “ 4bar 9bar 14bar 19bar 24bar 29bar

40 1 1/2“ 56 53 52 50 49 48

50 2“ 54 51 50 48 47 47

65 2 1/2“ 52 49 48 46 45 45

80 3“ 51 48 46 45 44 43

100 4“ 49 46 45 43 42 42

150 6“ 46 43 41 40 39 38

200 8“ 45 42 40 39 38 37

250 10“ 45 42 40 39 38 37

300 12“ 45 42 40 38 36 37

350 14“ 44 41 40 38 37 37

400 16“ 44 41 39 37 36 36

450 18“ 44 41 39 38 37 36

500 20“ 44 41 39 38 37 36

600 24“ 43 40 38 37 36 35

700 28“ 42 39 37 36 35 34

800 32“ 41 38 36 35 34 33

With formula 1a and 1b (see Handbook I) the inside sound power level of a valve can be calculated. According to this formula, only the steam quantity and the steam temperature is decisive for the intensity of the inside sound power level LW0. For the calculation of the attenuation of the blow-off pipe behind the valve, the following parameters are important.

• inside diameter of the pipe • wall thickness of the pipe • length of the transmission area • pressure inside the pipe • density

There are two methods of insulation: Acoustic Insulation & Thermic Insulation *VDMA = Verein Deutscher Maschinenbau-Anstalten **VDI = Verein Deutscher Ingenieure



With the parameters from Tab.1 the noise reduction can be determined. Practically an approximate value with an exactness of ± 2dB is enough. With the following table, the noise pressure level of an 11 meter long blow-off pipe, in 1 meter distance from the uninsulated blow-off pipe, can be determined (Fig.1). The precondition of this example is that the valve and the total blow-off pipe is situated inside of a boiler house. If the valve and the blow-off pipe are located outside the noise reduction Di reduces for 10 dB (Fig.2).

closed boiler house open boiler house

100°

1m

1m

Lr

LP 1

1m

Lwv

10m

100°

Lr1m

11m

Lwv

Fig. 1

Fig.2



Example:

• valve capacity 50 t/h • temperature in front of the valve 500°C • pressure in front of the valve100 bar • admissible sound pressure level of the silencer in 1m distance is 96 dB(A)

according to formula from Handbook “Noise” :

• pressure in the blow-off pipe 9 bar • blow-off pipe DN 300 / 12”

Sound pressure level 1m beside the blowoff pipe: Beside the uninsulated blow-off pipe, the sound pressure level is about 20.3 dB higher than at the silencer outlet.

LP1 = LW0 - Di = 158.3 - 42 = 116.3 dB(A)

LW0 = 17 log 50 + 50 log (273 + 500) - 15 = 158.3 dB(A)

noise reduction according Tab. 1 Di ≈ 42 dB

The uninsulated blow-off pipe beneath the silencer requires acoustic insulation, to meet the noise

requirement !



2. INSULATION OF BLOWOFF PIPES

Figure 3 shows, a recommendation, as to how noise reduction of 20 to 30 dB can be obtained. In most of the cases, both the silencers and blow-off pipe are influenced by temperatures. The insulation must be selected and installed such that it can withstand thermal growth and environmental changes. The strength of the insulation should depend on the pipe diameter. A total thickness of 100-120 mm is sufficient, thicker layers may not improve the noise reduction. Our quotes will indicate whether the silencer must be insulated or not. Our silencer design will determine if the insulation must extend from the eave ring or the collar sheet (see Handbook III) down to the roof or blow off pipe penetration. The plate thickness of the silencer body is usually 5 mm. If the silencer must be installed in a climatic zone where danger of freezing exists, the dewatering pipe should be made to protrude only a few centimetres out of the insulation, or it should be connected to the boiler house. The blow-off pipe represents a temperature bridge. The temperature of the boiler house will be transmitted to the diffuser over the blow-off pipe.

Insulation between eave ring and the roof Design for the insulation of a silencer with support under roof.

Fig.3

A long and non-insulated dewatering pipe is especially endangered to freeze !



Insulation between the collar sheet and the roof Design for the insulation of a silencer with very high noise reduction and support over roof.

Fig.4

Design for the insulation of a silencer with very high noise reduction and support in the roof.

Fig.5



3. RECOMMENDATIONS FOR ACOUSTIC INSULATION

The area of the blow-off pipe between the passage through the roof and the bottom of the silencer - eave ring or collar sheet - should get absorbing sound insulation. This will prevent radiated noise emissions from the blow-off pipe and will prevent rainwater from entering the building through the roof opening Description of the construction A combined steel aluminium covering is used for the construction. This cover is to be constructed such that it does not come in contact with the steel aluminum connections. At these points suitable contact protective agents are to be used. Materials and materials quality Spacer, resp. supporting structure These must be made of material St37.2 or equivalent. The sub-construction consists of spacer rings made of hoop steel 30 x 3 mm, with springy spacers which can take up all the thermal expansion of the ducts.The spacer rings must be fixed at a maximum distance of 940mm or 37”in an axial direction. Insulating materials The only material allowed are mineral wool mats with a minimum specific weight of 100 kgs/m³, with one side quilted on galvanized wire mesh. The area between pipe and outside insulation should not be filled-in except in case a mat insulation is not feasible. Mineral wool mats which have suffered a change of thickness because of moisture or of mechanical influences must be excluded. These mineral wool mats must be able to withstand long storage periods without change of their quality. The mineral wool mats must be cut to size and be fixed firmly around the pipe. The fixation of the mats is made with wire pins (at least 4 pieces /m²) and clips. The wire pins are welded on the blowoff pipe. Minimum thickness of the mineral wool 2 x 60 mm. External lining Seawater resistant aluminium sheet accord. to DIN1745 must be used for the external lining of thermal insulation and the combined thermal-sound insulation.

Al Mg 3 F 23, half hard DIN1725Bl.1,W.Nr.3.3535 Al Mg Mn F 23, half hard DIN1725/Bl.1,W.Nr.3.3527 Al Mg Mn F 23, half hard DIN1725/Bl.1,W.Nr.3.3528

For the acoustic insulation galvanized steel plate is to be used as an intermediate layer. The steel plate must be deadened. The sound absorbing material may not consist of bitumen mass, since a temperature load is present. At the piping, each second seam is to be made as a stretch seam in order to ensure the stretch ability. The aluminium sheet of the external lining must be overlapped as shown in The external lining must be absolutely secured against slipping.



Sheet metal screws thread-forming screws DIN 7513, material no. 1.4300 (V2A) and cylindrical sheet metal screws B oder BZ DIN 7971, material no. 1.4300 (V2A). Contact protection As contact protection strips from KlingeritTM or a glass fabrics are to be used.

Flat steel welded on here

Screw connection M8x40

In distances from max. 940mm rigid spacer ring

hoop-steel 30x3

rigid spacer ring made of

Klingerit-intermediate layer*)

rivet 5

40 x 4 40 x 4



Eaves ring, (firmly welden to the bottom of the s ilencer)

Silencer

Intermediate layer for separation of Impact sound and thermal insulation min. Thickness 5 mm of material Klingerit or Fixingclamps required for more than OD 200 mmmmmmmmmmmmmmmmm In case of temperatures over 200°C -shaped S-Clamps are to be used in order to compensate stop the extension. Distance from clamp to clamp 300 - 400 mm

Mineral wool mats with specific weight Of min. 100 kg/m³, qui lted on a galvanized wire mesh

space ring

Expansion seam with permanent-elastic seal

Wire nail with clips for fix ing the mineral wool min. 4 pcs. per m²

Aluminium plate Rock wool mat Sound absorbing material* *) Galvanized steel plate* *) Rock wool mat

min. 2 x 60 mm

Entrace pipe

glass fabric*)

AVOIDANCE OF FAULTS - Handbook IX page 60 of 67


In order to reach a satisfactory function and attenuation of the silencer, attention should be paid to some aspects which, if neglected, could cause malfunctions.

1. INSTALLATION OF VENT SILENCERS

It does not make sense to determine the dimension of the blow-off pipe according to that of the valve outlet and then increase it shortly in front of the silencer. The high blow-off speed leads to pressure losses in the blow-off pipe and to an increase in sound emission from the pipe.

� �

proper insulation of the blow-off pipe

the blow-off pipe is not insulated and too small

If the flow rate in the blow-off pipe is kept low and the permissible pressure loss in the silencer is diminished, then it comes to a more economical and acoustical efficient solution.



Unfortunately it happens quite often that very high noise reductions are required, but uninsulated pipes or valves are arranged nearby the silencer. In such a case, the noise level will be determined by the blow-off pipe or the valve, and not by the silencer.

�

the noise level emitted by the blow-off pipes is higher then the reduced noise level of the silencer

the blow-off pipe is insulated, but the valve is not

130 dB

90 dB

80 dB

90 dB



Vent Silencers should not be installed in front or nearby a building. This causes noise reflections which increases the sound level.

� �

silencers installed on the roof with optimum noise and safety performance

lethal installation inside a building

WARNING

- steam at the silencer outlet is extremely hot - vent silencers must be installed in such a way, that no person can

be exposed to the steam flow during blow off at any time



2. DEWATERING OF VENT SILENCERS

� �

to avoid damage of the roof use a plate or a cup beneath

the silencer drainage

don’t by-pass the drain the silencer may be damaged and

the noise level will increase

the uninsulated dewatering pipe should be as short as possible

don’t elongate the drain pipe ice plugs may prevent dewatering



4. DIFFUSER DESIGN

GLAUNACH

OTHER

seamless diffuser pipes are used stainless-steel wire mesh reduce

swirls

perforated plates are used as diffuser the absence of wire mesh

cause flow noise

small borings achieve a higher noise reduction

perforated holes have a larger diameter with less noise reduction

for safety reasons all pressurized welds are tested

other manufacturer don’t care



5. ABSORBER DESIGN

GLAUNACH

OTHER

strong and heat resistant glass fabrics cover absorbing materials

cheaper fleece materials are blown out shortly

absorbers are totally made from stainless steel

absorbers made from carbon steel will rust out shortly

continuous welding on all parts guarantees long service life

cheaper spot welding results in vibrations and early fatigue



6. CATASTROPHIC FAILURES BY POOR DESIGN In the last years, we’ve repaired and replaced many silencers from other manufacturers. At the following example, the steam jet hits the head of the diffuser with sonic speed and high temperature. This destroyed the diffuser immediately and furthermore destroyed the core of the absorber and blew it away.

poor design

destroyed diffuser

absorber blew out

The diffuser cage and absorber was removed and replaced by a Glaunach Diffuser. Now the silencer works without any problems.

silencer repaired by Glaunach

replacement of diffuser

installation of the repaired silencer



Another example of a catastrophic failure caused by a cost saving design. The absorber blew out of the silencer and hit the ground.

Documents

Glaunach Silencer Handbook