T 8084 EN
Series 3381 · Type 3381 Silencer
DIN and ANSI versions

Application
Noise attenuation for liquids, gases and vapors · Velocity reduction at the valve outlet for gases and vapors
Valve size

DN 40 to 800·NPS 1½ to 32

Pressure rating

PN 10 to 400·

Class 150 to 2500

Type 3381 Silencer acting as a fixed restriction to reduce thesound pressure level.
• Single attenuation plates in Type 3381‑1 (see Fig. 3 andFig. 4) or reduced version with single attenuation plates as
Type 3381‑1R (see Fig. 5)• System with two to five attenuation plates in a housing(Type 3381-3, Fig. 8) or as a wafer-type version (Type3381-4, Fig. 9)• Flow velocity reduction of compressible media at the valve
outlet• Used in conjunction with SAMSON Series 240 and Se‑
ries 250 Valves
Versions–

Type 3381‑1 · Single attenuation plates mounted between
the valve or a pipe expander and the pipe flange (Fig. 3,Fig. 4).

–

Type 3381‑1R · Reduced construction using less material:
single attenuation plates with reduced diameter and possi‑
bly reduced thickness, clamped between the valve or apipe expander and the pipe flange (Fig. 5). Available instandard materials in DN 200/NPS 8 and larger basedon the pressure rating as specified in Table 2.

–

Type 3381‑3‑X · Silencer with two to five attenuation
plates located in one housing. An additional pipe expand‑er is not required (Fig. 8).

–

Type 3381‑4‑X · System with two to five attenuation plates
installed as a wafer-type version. Usually downstream of apipe expander (Fig. 9).

Fig. 1: Type 3241-7 Control Valve with Type 3381-3 Silencer

Further versions
Fig. 2: Type 3381‑3‑3 Silencer–

Combination of Type 3381‑1 and Type 3381‑1R with twoattenuation plates in varying valve sizes (Fig. 6, Fig. 7)–

Special materials (e.g. Monel, Hastelloy) · On request–

Welding ends · On request–

Special materials for Type 3381‑1R for valve sizes< DN 200/NPS 8 · On request–

Larger valve sizes · On request–

JIS version · On request

SAMSON AKTIENGESELLSCHAFT · Weismüllerstraße 3 · 60314 Frankfurt am Main, Germany
Phone: +49 69 4009-0 · Fax: +49 69 4009-1507 · samson@samsongroup.com · www.samsongroup.com

Edition April 2021

Principle of operation
The Type 3381 Silencer provides noise attenuation by acting
as a fixed restriction. The silencer raises the pressure of themedium flow at the valve outlet and reduces the pressure
downstream of the silencer to the required downstreampressure p2. As a result, the sound pressure level is reduced. In
applications using compressible media, it additionally lowers
the flow velocity at the valve outlet.
The pressure reduction per attenuation plate (Δp) depends onthe flow rate and the prevailing operating temperature.
Generally, the pressure reduction is between 5 and 7 bar.
A five-stage silencer (Type 3381-3-5 and Type 3381-4-5)
normally provides a maximum pressure drop of 35 bar.
Type 3381‑1 Silencer
In Type 3381‑1 the attenuation plate can be installed up‑
stream and/or downstream of the pipe expander (Fig. 3,Fig. 4, Fig. 6). The nominal size of the attenuation plate de‑pends on the nominal size of the valve or pipe expander.

Fig. 5: Type 3381‑1R: Reduced construction with attenuation platedownstream of the pipe expander

Combination from Type 3381‑1 and Type 3381‑1R
The Type 3381‑1 and Type 3381‑1R can be combined with
one another (Fig. 6, Fig. 7). Two attenuation plates of different
valve sizes are installed: one at the valve outlet and one
downstream of the pipe expander.

Fig. 3: Type 3381‑1: Attenuation plate on the valve upstream of a
possible pipe expander
Fig. 6: Attenuation plates at the valve and downstream of the pipeexpander

Fig. 4: Type 3381‑1: Attenuation plate downstream of pipe
expanderType 3381‑1R Silencer
In Type 3381‑1R, the diameter and possibly the thickness of
the attenuation plates are reduced compared to Type 3381‑1(Fig. 5).

Fig. 7: Attenuation plates at the valve and downstream of the pipe
expanderOnly the valve sizes and nominal pressures listed in Table 2
can be combined with one another for this version (in stan‑dard materials).

2T 8084 EN

Type 3381‑3‑X Silencer

Dimensions

In Type 3381‑3‑X, two to five attenuation plates can be in‑stalled one after the other in one housing (Fig. 8). The valvesizes of the inlet and outlet can vary: the nominal inlet size ofthe housing corresponds to the nominal valve size. The nomi‑
nal outlet size corresponds to the downstream nominal pipe
size. A pipe expander is already integrated into the housing.

The dimensions of Type 3381‑3‑X and Type 3381‑4‑X dependon the number of attenuation plates and the nominal pressure.
Further details are available on request.
Note concerning all versions
The pipe expander is not included in the scope of delivery.

The “x” in the type designation indicates the number of atten‑
uation plates installed. The silencer is delivered as a ready-toinstall unit with nuts and bolts (but without gaskets).
Type 3381‑4‑X Silencer
In Type 3381‑4‑X, two to five attenuation plates are clamped
between the valve outlet or pipe expander and the pipeline(wafer-type version). A pipe expander must be installed if thenominal size of the attenuation plates is larger than that of thevalve (Fig. 9).
The “x” in the type designation indicates the number of atten‑
uation plates.

12

Legend3

1Valve outlet

2Silencer

3

Pipeline

4Pipe expander

Fig. 8: Type 3381‑3‑5: Five attenuation plates in a housing

142

3

Fig. 9: Type 3381‑4‑5: Five attenuation plates clamped between the pipe expander and pipeline (wafer-type version)

T 8084 EN3

Table 1: Technical data
Type 3381‑1, Type 3381‑1R, Type 3381‑3‑X or Type 3381‑4‑X Silencer
Version according toMaterial

DIN
Forged steel
P250GH · 1.0460

1)

Valve size
Pressure rating2) 3)

Type of connection
Temperature range
1)
2)
3)
4)

4)

ANSI
Forged stainless steel
1.4401Forged stainless steel
A182 F316

Forged steel A105

DN 40 to 800

NPS 1½ to 32

PN 10 to 400

Class 150 to 2500

All DIN EN versions

All ANSI versions–50 to +400 °C–58 to +750 °F

Other materials on request
Only valve sizes possible according to the standard
Varying pressure ratings for the inlet and outlet cannot be implemented
Other temperature ranges on request

Table 2: Possible wafer-type versions for Type 3381‑1R as well as for combinations of Type 3381‑1 and Type 3381R
Note:–Wafer-type version only for standard materials according to Table 1–

Only valve sizes possible according to the standard and depending on the nominal pressure
DIN EN versions

ANSI versions

Valve size

Pressure rating (min.)

Valve size

Pressure rating (min.)

DN 200

PN 400 and higher

NPS 8Class 2500 and higher

DN 250

PN 250 and higher

NPS 10Class 1500 and higher

DN 300

PN 100 and higher

NPS 12Class 600 and higher

DN 350

PN 63 and higher––

DN 450

PN 40 and higher

NPS 16 and larger

All pressure ratings

DN 600 and larger

All pressure ratings––Selecting and sizing the silencer and the upstream control
valve
Always size the silencer together with the upstream control
valve to achieve the best results.
1. Calculate the suitable KVS coefficient according toIEC 60534.
2. Select nominal size from Table 2.
3. Select materials, pressure and temperature from Table 1
and from the pressure-temperature diagram (seeu T 8000‑2)
The number of attenuation plates and the nominal size is de‑termined from the operating data.

Order specifications:
Valve size/pipe di‑ DN … or NPS …
ameter
Upstream and downstream of the vena
contracta
Pressure rating

PN … or Class …
According to DIN, ANSI or JIS

Material

According to Table 1

Process medium

Density in kg/m³ and temperature in °Cor °F

Flow ratekg/h or m³/h
In standard or operating state with min‑imum, normal and maximum flow rate

Associated Information Sheetu T 8000-X

Specifications subject to change without notice

T 8084 EN

2021-04-28 · English

Operating pressure bar or psi
with minimum, normal and maximum
flow rate