Standard grade industrial silencers are commercially fabricated vessels.   The steel used in the construction is commercial grade.  The welding is per AWS D1.1, Sections 8.15 and 9.25 “Quality of Welds” static and dynamically loaded structures.  These sections allow a certain amount of porosity.  The seams of the silencer are lap or butt joint welds.  The F & D head to shell are lap joint welds.  The nozzles to shell joints are fillet welds.  The nozzle to flange is a double fillet weld, the inside and outside edge of each flange is welded together.

When the silencer is welded together, minor pinhole leaks may appear.  These pinhole leaks are considered negligible and they are allowed per AWS D1.1.

To quantify as leak tight a test must be conducted on all of the external welds.  Bubble tests are visual indication of leaks (Stoddard Specification S-167.)  All tests must be performed before painting since painting can produce false positive readings.

Intake Silencers draw air into a system and typically, unless the intake system is pressurized, is not a leakage concern. Discharge Silencers in a pressure system are a leakage concern and given the application will require testing. All testing is performed at an additional charge.

ASME Code vessels are pressure tested as part of their certification and do not require leak testing. The typical industrial silencer is not an ASME Code vessel since it is not to be operated above 15 psi.

Any further questions regarding leak tight construction should be directed to Stoddard Silencers’ at the number shown above or by email at