How loud is an unsilenced steam vent?

A safety valve or start-up vent discharging steam or gas at high velocity easily reaches 130 to 150 dB(A) close to the outlet. Legal limits at the site boundary are typically 45 to 60 dB(A) at night, so 40 dB or more of attenuation is common.

What is the difference between an absorbing and a diffuser silencer?

An absorbing silencer discharges to atmosphere with no pressure drop and absorbs the noise in baffle stages lined with mineral wool. A diffuser silencer uses the available pressure: the gas expands through many small bores into wire mesh, which breaks the jet noise at the source in a smaller and lighter unit, at the cost of a pressure drop of 0.2 bar or more.

Does the silencer affect the safety valve?

It can. A diffuser silencer builds up back pressure at the valve outlet, which must stay within the limit for the valve type: around 10 percent of set pressure for conventional spring-loaded valves, more for bellows or pilot-operated valves. We check this when sizing.

What do you need to size a silencer?

The medium, mass flow, inlet pressure and temperature, allowable back pressure, inlet size, the required sound pressure level and the distance at which it applies, and the installation situation. From that we select the type, the number of stages and the accessories.

Vent Silencers

Vent, blow-off and inline silencers for safety valve outlets, boiler start-up, turbine bypass and hydrogen venting: absorbing, diffuser and combined types, dump tubes and micro silencers, sized per flow, pressure and required attenuation.

Also known as: vent silencer, blow-off silencer, blowdown silencer, steam vent silencer, safety valve silencer, diffuser, dump tube, hydrogen silencer.

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Brands

Vent Silencers

GLAUNACH (Austria) engineers vent, blow-off and inline silencers for steam, air, natural gas, technical gases and hydrogen: absorbing, diffuser and combined types, dump tubes and diffusers, micro silencers, plus weather hoods, bird screens, heaters and other silencer accessories. Every silencer is sized for the flow, pressure and required attenuation.

Models

Medium

20 of 20 models

Vent silencers4

GLAUNACH type A absorbing silencer

Circular baffle absorbing silencer in stainless steel with mineral wool and glass fabric lining and a radial diffuser inlet. No pressure drop, 25 dB or more depending on the number of absorber stages.

GLAUNACH type D diffuser silencer

Single- or multi-stage small-bore radial diffuser wrapped in finely woven stainless steel wire mesh. Up to 50 dB in a substantially smaller and lighter unit than an absorbing silencer.

GLAUNACH type DA diffuser silencer with insulated shell

Type D diffuser silencer with an additional glass fabric and mineral wool insulation of the inner shell for better thermal and acoustic insulation of the outer shell.

GLAUNACH type DAA combined diffuser / absorber silencer

Integrated combination of a type DA diffuser silencer with one or more type A absorber stages, for 50 dB and more. Covers almost any noise reduction requirement.

Inline silencers2

GLAUNACH inline diffuser silencer

Diffuser silencer for closed systems: muffled in-line expansion of pressurised gases without releasing them to atmosphere. Up to 50 dB.

GLAUNACH inline micro absorber silencer

Absorber section of sound-absorbing stainless steel mesh for pressure-free gases in closed systems, for example electrolysis plants. No pressure drop, 15 dB or more.

Diffusers and dump tubes4

GLAUNACH dump tube / diffuser pipe

Multi-stage dump tube expander with application-specific number, size and arrangement of diffuser stages and holes, in carbon or stainless steel. Up to 35 dB.

GLAUNACH diffuser

Multi-stage small-bore radial diffuser surrounded by a pack of finely woven stainless steel wire mesh, for dump tube duties that need better attenuation. Up to 50 dB.

GLAUNACH fish mouth diffuser

One- or two-stage small-bore axial diffuser for dump tube duties in confined space. Up to 15 dB.

GLAUNACH micro silencer

Compact one- or multi-stage axial diffuser in wire mesh for small inlets from 1.25" to 6" and vent capacities below 10 t/h: anti-icing, cryo-gas, vapour lines. Up to 15 dB.

Hydrogen silencers4

GLAUNACH H₂ micro silencer

Compact hydrogen vent silencer that reduces the pressure inside the silencer, for lines where some back pressure is acceptable. Designed to ASME BPVC and PED.

GLAUNACH H₂ purge silencer

Absorptive hydrogen silencer for purging and venting with very low pressure loss, for fuel cell systems and electrolysis plants where back pressure is not acceptable.

GLAUNACH LH₂ silencer for liquid hydrogen

Silencer developed for liquid hydrogen: designed for material behaviour at cryogenic temperatures and the large volume expansion of LH₂, to PED, ASME or NASA recommendations as required.

GLAUNACH H₂ inline silencer

Inline hydrogen silencer as diffuser, absorptive or combined design depending on the allowable back pressure, for integration into existing piping. Designed to PED and ASME.

Accessories6

GLAUNACH hydrogen vent accessories: lambda vent, rain cap, deflector

Lambda vent for upward discharge and dilution to DVGW G 442, H₂ rain cap with rain-resistant vent, vertical discharge deflector and drainage for hydrogen silencers.

GLAUNACH weather hoods

Weather hood "rain & snow" with sound-absorbing inner surface, and weather hood "rain, snow, sand & dust" with integrated dust trap and rinsing drain, for vent silencer outlets.

GLAUNACH bird screen and outlet extension

Stainless steel grating over the silencer outlet, peripheral or axial, against nesting birds, dropped tools and for operator protection; outlet extensions customised to the installation.

GLAUNACH silencer heater

Heater preventing precipitation or condensate from freezing in the silencer, for very low ambient temperatures and lines that transfer no heat to the silencer.

GLAUNACH exchangeable diffuser cartridge and absorber

Replaceable diffuser cartridge of multi-layer wire mesh in a pipe cage for media with particulate or aggressive matter, and replacement absorber baffle elements for vent silencers.

GLAUNACH silencer accessories overview

Standard and optional fittings for GLAUNACH silencers: lifting lugs, ID plate, gauge port, dewatering pipe, eaves ring, collar sheet, brackets, stands, goose neck, flanges and multiple inlets.

Not seeing the size, connection or rating you need? Most of these models are built to order and our suppliers' engineers adapt them. Send us what you have and we work it out. Send us your requirement →

Silencers are needed wherever a gas or steam is released to atmosphere or expanded inside a system at high velocity: safety valve outlets, boiler start-up and purge vents, turbine bypass and condenser dump lines, compressor blow-off, and increasingly hydrogen vents on electrolysers and refuelling stations. Ritec supplies GLAUNACH silencers for these duties and sizes them per application.

Three ways to silence a vent

Absorbing silencers (type A) discharge straight to atmosphere with no pressure drop. The gas is spread by a radial diffuser inlet and the noise is absorbed in circular baffle stages lined with mineral wool and glass fabric. Attenuation starts at 25 dB and rises with each added stage.

Diffuser silencers (types D and DA) use the pressure that is available anyway. The gas expands through a multitude of small bores into a pack of finely woven stainless steel wire mesh, which breaks the jet noise where it is generated. They reach up to 50 dB in a much smaller and lighter unit, with a pressure drop of at least 0.2 bar.

Combined silencers (type DAA) put both principles in one shell for the strictest limits, 50 dB and more.

Inside the system

Where the gas must stay in the piping, inline silencers and dump tubes do the same job under pressure: multi-stage diffusers for condenser injection and turbine bypass, fish mouth diffusers for confined spaces and micro silencers for small lines below 10 t/h.

Hydrogen

Hydrogen venting is exceptionally loud and carries an ignition risk. GLAUNACH builds dedicated H₂ micro, purge, inline and liquid hydrogen silencers to PED and ASME, with lambda vents and rain caps that direct the discharge upward and keep the hazardous zone within DVGW G 442.

Sizing

Every silencer is engineered for its duty. Send us the medium, flow, pressures, temperature, allowable back pressure and the noise target, and we return a selection with dimensions, weight and the accessories the site needs: weather hood, bird screen, heater, supports and flanges.

Frequently asked questions

How loud is an unsilenced steam vent?: A safety valve or start-up vent discharging steam or gas at high velocity easily reaches 130 to 150 dB(A) close to the outlet. Legal limits at the site boundary are typically 45 to 60 dB(A) at night, so 40 dB or more of attenuation is common.
What is the difference between an absorbing and a diffuser silencer?: An absorbing silencer discharges to atmosphere with no pressure drop and absorbs the noise in baffle stages lined with mineral wool. A diffuser silencer uses the available pressure: the gas expands through many small bores into wire mesh, which breaks the jet noise at the source in a smaller and lighter unit, at the cost of a pressure drop of 0.2 bar or more.
Does the silencer affect the safety valve?: It can. A diffuser silencer builds up back pressure at the valve outlet, which must stay within the limit for the valve type: around 10 percent of set pressure for conventional spring-loaded valves, more for bellows or pilot-operated valves. We check this when sizing.
What do you need to size a silencer?: The medium, mass flow, inlet pressure and temperature, allowable back pressure, inlet size, the required sound pressure level and the distance at which it applies, and the installation situation. From that we select the type, the number of stages and the accessories.