Welch SCSpro Dry Scroll Vacuum Pumps Background

Welch SCSpro Dry Scroll Vacuum Pumps

Shop Welch SCSpro dry scroll vacuum pumps, including the SCSpro 15 with about 280 L/min pumping speed and 0.012 Torr ultimate vacuum. Oil-free, quiet and built with a self-cleaning air flush, in 115 V and 230 V versions.

Welch SCSpro15 Dry Scroll Pump, New

Welch

Welch SCSpro15 Dry Scroll Pump, New

$ 5,624.00
Welch 2546 Dry Piston Pump

Welch

Welch 2546 Dry Piston Pump

$ 978.00

Welch SCSpro Dry Scroll Vacuum Pumps

Welch WOB-L pumps are oil-free piston pumps that give rough vacuum, pressure or both from one compact unit. With no oil in the pump, there is nothing to change, nothing to contaminate your sample and no oil mist at the exhaust.

WOB-L pumps are found on lab benches, in medical and analytical instruments and in field sampling equipment because they are small, simple and run for years with little care. At Provac Sales, we supply Welch WOB-L pumps new and rebuilt, and we service them in our own shop.

Welch Dry Pump Models We Carry

Small WOB-L Pumps

  • Welch 2511, the smallest WOB-L, sold as a bare pump and as the 2511-75 aspiration system
  • Welch 2515, offered as a complete aspiration station
  • Welch 2522, a compact dry piston pump for vacuum and pressure

Mid-Size WOB-L Pumps

  • Welch 2534, about 1.2 CFM with vacuum to about 70 Torr
  • Welch 2546, a vacuum and pressure pump for filtration and sampling
  • Welch 2562, a higher-flow single-head pump

High-Flow WOB-L Pumps

  • Welch 2561 and 2567, twin-head pumps for faster pumpdown
  • Welch 2581, about 3.5 CFM, the largest-flow WOB-L
  • Welch 2585, a twin-head pump for deeper vacuum

Portable Pumps

  • Welch 2050 and 2060 compact pumps, including DC versions for portable use

Many listings are rebuilt units. Some show a price and others are quote-based. Each product page lists free air flow, vacuum, pressure rating and voltage.

Vacuum, Pressure and Twin-Head Models

  • Single-head WOB-L pumps are the simplest choice for light vacuum or pressure. They suit aspiration, sampling and small filtration setups.
  • Twin-head pumps, such as the 2561, 2567 and 2581, add flow or depth. Heads can run in parallel for more flow, or in series for deeper vacuum, depending on the model.
  • Many WOB-L pumps can supply pressure from the exhaust side as well as vacuum at the inlet. Check the pressure rating on the product page before using a pump as a compressor.

How a WOB-L Piston Pump Works

WOB-L stands for wobble piston. The piston is fixed rigidly to a connecting rod that rides on an eccentric on the motor shaft. As the shaft turns, the piston moves up and down and rocks slightly in the cylinder.

A flexible cup seal on the piston keeps the cylinder sealed through that rocking motion. On the down stroke, gas enters through the inlet valve. On the up stroke, it is compressed and pushed out through the exhaust valve.

The bearings are sealed, so no oil is needed anywhere in the pump.

Key Features

  • Completely oil-free, with no oil changes and no oil mist
  • Vacuum and pressure from one pump on many models
  • Compact, light and easy to build into instruments
  • Long-life piston cup seals and valves
  • Single- and twin-head designs for more flow or deeper vacuum
  • Aspiration and filtration stations available ready to use

Applications for Welch WOB-L Dry Pumps

  • Vacuum filtration and aspiration
  • Air and gas sampling, including environmental monitoring
  • Medical and analytical instruments
  • Gel dryers, desiccators and degassing
  • Lab air supply for pressure filtration and agitation
  • Vacuum pick-and-place and holding fixtures

How to Choose the Right Welch Dry Pump

Before ordering, confirm:

  • Whether you need vacuum, pressure or both
  • The vacuum level or pressure your process needs
  • Free air flow for your flask, filter or instrument
  • Whether liquid or vapor could reach the pump, so you can add a trap
  • Supply voltage and frequency, or DC for portable use
  • Duty cycle, continuous or intermittent

Maintenance Tips

  • Replace piston cup seals and valves at the interval in the manual or when performance drops
  • Use a vacuum trap or filter flask so liquids never reach the pump
  • Keep the inlet filter clean on dusty processes
  • Keep the cooling fan and air paths clear
  • Do not run a pressure model above its rated outlet pressure

We stock service kits for common Welch WOB-L models.

Signs Your WOB-L Pump Needs Service

  • The pump no longer reaches its rated vacuum or pressure
  • Longer pumpdown on your filter flask or sample line
  • Squealing or knocking, which can mean worn bearings
  • The motor runs hot or trips its thermal protection
  • Liquid or debris has entered the pump

New vs Rebuilt Welch WOB-L Pumps

WOB-L pumps are simple, so a rebuild restores most of their original performance. A rebuild usually includes new piston cups, valves and gaskets, a bearing check and a performance test for vacuum and pressure.

A rebuilt pump is a cost-effective way to replace a pump built into an instrument without changing the mounting or connections.

Welch Dry Pumps Repair

Provac Sales repairs and rebuilds Welch WOB-L dry piston pumps, including seal and valve replacement. Submit an RMA request and complete the contamination data sheet before shipping. See our pump repair page for more information.

Related Welch Collections

Find the Right Welch WOB-L Dry Pump

Send us your application, required vacuum or pressure, flow, supply voltage and duty cycle. We will recommend the right Welch WOB-L pump, confirm new or rebuilt availability, or quote a rebuild of your existing pump.

Browse our inventory above or contact our vacuum specialists at 831-462-8900.

Welch WOB-L Dry Pump FAQ

1. What does WOB-L mean on a Welch pump?

WOB-L refers to the wobble piston design. The piston is fixed to its connecting rod and rocks slightly as it moves, with a flexible cup seal keeping the cylinder sealed. This removes the need for a wrist pin and oil.

2. Can a Welch WOB-L pump supply pressure as well as vacuum?

Many models can. The inlet gives vacuum and the exhaust gives pressure. Check the pressure rating on the product page and do not exceed it.

3. How deep a vacuum does a WOB-L pump reach?

WOB-L pumps give rough vacuum. A Welch 2534, for example, reaches about 70 Torr. Twin-head models go deeper. For lower pressures, choose a scroll or rotary vane pump.

4. Do Welch WOB-L pumps need oil?

No. WOB-L pumps are oil-free. The bearings are sealed and the piston uses a dry cup seal.

5. Which Welch WOB-L pump is best for vacuum filtration?

A single-head pump such as the 2522 or 2546 handles most filtration setups. For several filter stations or faster flow, step up to a twin-head pump like the 2561 or 2581, and always use a trap to keep liquid out of the pump.