DL, PVT and HELIX silencers are designed to be installed in correspondence with the discharge (standard silencers) or injection line (both standard and compact silencers) of lobe vacuum pumps without lubrication, used to create a vacuum inside tanks. The compact injection muffler replace the standard injection muffler. It is installed on the PVT side. The suction group is developed to make the installation easier on stationary or mobile vacuum-pressure plants, conveying air.

The silencers carry out two main functions:

- attenuate the noise produced by decompressor operation;

- filter the suctioned air (at injection) in order to prevent powdery particles over a determined size from entering the pump, thus compromising its operation.

Each category has the following two types: Filtered (for injection installation); Non-filtered (for discharge installations).