Vacuum pump systems have high energy consumption due to incorrect sizing

Vacuum trucks designed for wet applications like sewer and industrial cleaning tend to operate with overcapacity. And often these trucks are also built with bigger vacuum systems than necessary.

Vacuum truck users rarely complain over too much performance. Lack of performance, however, is a different story.

Hence, many truck builders rather over-dimension the vacuum pump systems. Simply just as a precaution to keep their customers satisfied.

With overcapacity we create problems in other areas of the truck design. The extra need for energy must be found in more power and handled in bigger transmission and hydraulics.

Furthermore, the extra energy will create heating problems in the system and unnecessary clogging of filters etc.

The correct capacity for a conventional vacuum truck designed for wet applications is basically calculated by two parameters: Suction-hose dimension and topic.

For solid topics as stone, sand and bricks, the air speed must be around 35 m/s or 115 ft/s. Capacity above this point will rarely benefit the performance of a vacuum truck, unless the truck is specifically designed for excavation.

For fluid topics with specific gravity like water, the air speed can be lowered to around 25 m/s or 83 ft/s. The length of the suction hose will also affect the air speed due to pressure loss. But only with very little impact and insignificant for a suction hose length below 50 meters.

For excavation jobs the air flow is essential and therefore the “bigger is better” principal is often used. However, an air flow above 35 m/s will not enable the truck to do more difficult jobs, only to do them faster.

The length of the suction hose will also affect the air speed due to pressure loss. But only with very little impact and insignificant for a suction hose length below 50 meters.

For fluid handling applications, there will be no benefits from a high air-flow in the system. For these applications, the parameters are: the area in the suction hose and level of vacuum. Basically, this means that the size of the vacuum pump, is not as important as the pump’s ability to create vacuum. The most important factor in this application is the size of the suction hose.

The length of the suction hose has a significant impact for this application and should always be as short as possible.

Download our filling time diagram example to learn more about the crucial effect from a bigger suction hose.

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