What the heck is a PD (Positive Displacement) Combination Unit?

Vac2Go Operation

When renting a combination unit vacuum truck and before beginning any municipality or other work which would require a combination unit vacuum truck, it’s important to understand the work you will be doing so you know which type of combo unit is right for you. Below are the features of a “PD” combination unit vacuum truck.

On the front of the vacuum truck, there is a hose reel with the operating controls located at the front and back of the reel. On top of the vacuum truck you will find the boom assembly as well as storage racks with additional aluminum tube sections to give you better access to debris in the manhole or catch basin. The boom enters the forward bulkhead of the debris body where debris is knocked out of the airstream and onto the floor. The airstream is further filtered by optional cyclone filters mounted to the rear of the debris body.  A PD unit uses a Positive Displacement blower to create the air stream. Located between the frame rails is a transfer case. The transfer case, when used, will disconnect the rear wheels in blower mode and drive the blower. Above and in front of the transfer case is the PD blower, which creates the air stream. A micron strainer is located behind the blower to catch any carryover that could potentially enter the blower. Above the blower is a silencer that dampens the exhaust noise generated by the blower while working. The silencer is critical as without it the noise would prevent workers from safely operate the truck.

PD Unit Diagram

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