Standard Duty Dry Piston Vacuum Pumps

Industry-Leading WOB-L® Piston Pump Technology Designed for a Broad Range of Laboratory and Industrial Applications


Piston pumps remain one of the most popular and most widely used vacuum technologies. Welch offers standard duty, oil-free vacuum pumps featuring the innovative WOB-L® piston technology that provides strong pumping dynamics and can support a wide spectrum of rough vacuum processes in which corrosion resistance is not required.
These versatile pumps stand out through their speed, ease of use and durability, ensuring extremely efficient and reliable performance. They combine superior vacuum and flow capabilities with the advantages of a lightweight, compact design, quiet operation and clean air flow, which makes them suitable for portable vacuum system applications.
The Welch portfolio comprises 17 WOB-L® piston dry vacuum pump models. They offer capacities of between 0.4 cfm and 7.1 cfm and pressure levels reaching 5 Torr. All of the pumps keep strong pumping speeds to near their ultimate vacuum pressure. Selected models can be used as pressure pumps.
Our offering includes single-head piston vacuum pumps, twin-head piston vacuum pumps and OEM and built-in pumps, as well as a broad selection of vacuum pump accessories.


How Does a WOB-L® Piston Vacuum Pump Work?

Piston vacuum pumps, whose primary elements include an electric motor, a crankshaft and a connecting rod with a piston located inside a cylinder, work on the principle of positive displacement. The power provided by the pump’s motor makes the crankshaft rotate. The connecting rod helps transform this rotary motion into the reciprocating motion of the piston.
As it moves up and down inside the cylinder, the piston creates vacuum on the downward stroke. The medium is then sucked in to the cylinder chamber through an open inlet valve. Depending on the design, one or multiple cylinders can be attached to the motor. In the latter case, the flow (parallel configuration) or vacuum (two-stage configuration) capability of the pump is increased.
The direct connection of the rod with the piston is the defining design feature of WOB-L® vacuum pumps. There is no wrist pin connecting the two elements which are a single item. The direct coupling results in a characteristic wobbling motion of the piston. The piston rides within a flanged polymer cup that guides it in the cylinder bore and seals it from the cylinder wall.
Air pressure expands the cup against the wall as the piston moves, which compensates for its wobble action. Such a design ensures high vacuum capabilities relative to the pump’s compact size and light weight, as well as moderate to high flows which tend to remain consistent over the product’s lifetime.

WOB-L® Piston Vacuum Pumps: Key Benefits and Applications

Welch’s WOB-L® piston dry vacuum pumps provide you with a number of benefits to help you improve and streamline your mission-critical vacuum processes. They include:

  • High performance – wobbling piston technology guarantees increased vacuum and flow capabilities within a smaller package.
  • Reliable operation – high-quality materials and unique design features ensure minimized maintenance requirements and translate into the product’s long life.

  • Vacuum regulation – the models are equipped with regulators and gauges for simple adjusting and monitoring the vacuum level.

  • Pump protection – an inlet water trap protects the pump from the incidental ingestion of water.

  • Motor security – all models feature 1PH motors with built-in thermal overload protection.

  • Noise reduction – a muffler ensures a very low sound level, which makes your daily work with our pumps more comfortable.


Each WOB-L® piston pump includes vacuum regulators, pressure regulators (single head models only) and gauges for simple adjusting and monitoring of vacuum level and delivery pressure. To protect the pump from the ingestion of water, an inlet water trap with a float ball rises to seal the pump if needed. A muffler ensures a very low sound level during pump operation, which makes the daily work with WOB-L more comfortable. Please note that only selected models can be used as pressure pumps.


Main Applications for WOB-L® Piston Vacuum Pumps

WOB-L® piston pumps are reliable dry vacuum/pressure pumps for physical and aqueous vapor applications, where corrosion resistance is not required (not recommended for pumping acidic, basic, or organic fumes).Our standard duty oil-free vacuum pumps are suitable for laboratory and industrial applications such as air sampling, aspiration, cell harvesting,drying, DNA/RNA extraction, filtration, package integrity testing, pick and place, vacuum bag parts forming, and vacuum ovens, among many others.