The JZJW type Roots-vertical oil-free reciprocating pump unit is composed of a ZJ type Roots pump as the main pump and a WLW type vertical oil-free reciprocating pump as the fore pump connected in series. It overcomes the shortcomings of the WLW type vacuum pump, which has a high ultimate pressure and low pumping speed at a certain pressure, while retaining the advantages of the ZJ type Roots pump, such as rapid operation and high pumping speed. Therefore, this unit is widely used in vacuum distillation, vacuum evaporation, dehydration crystallization in the chemical industry; freeze-drying in the food industry; vacuum drying in the pharmaceutical industry, and other processes.
    Since the WLW type vacuum pump uses oil-free self-lubricating materials to achieve clean vacuum, after installing a tail gas collection device at the exhaust port, this unit can collect gases that cannot be condensed or compressed in high vacuum systems, such as pentadiene, benzene, toluene, etc., avoiding environmental pollution caused by their low boiling points and difficulty in collection.