Welch Diaphragm Vacuum Pumps

Diaphragm pumps give clean, oil-free vacuum for everyday lab work. With no oil in the pump, there are no oil changes, no oil mist at the exhaust and no oil that can be contaminated by solvent vapors.

Welch, now part of Ingersoll Rand along with the Ilmvac line, has built laboratory vacuum pumps for more than a century, and its diaphragm range covers everything from simple filtration pumps to chemistry-duty PTFE pumps for rotary evaporators. At Provac Sales, we supply Welch diaphragm pumps and service them in our own shop.

Welch Diaphragm Pump Models We Carry

Standard Duty Lab Pumps

• Welch Model 2019, a compact pump with about 37 L/min free air flow and vacuum to about 24 in Hg, for filtration, desiccation and degassing
• Welch Model 2025, a self-cleaning dry vacuum pump for general lab use

Chemistry-Duty PTFE Pumps (Ilmvac)

• Welch Ilmvac 2052, a dry chemical-duty pump for solvent work
• Welch Ilmvac 2062, a higher-flow PTFE pump for larger evaporators and multiple users
• Welch Ilmvac 2163, a high-capacity diaphragm pump for large rotary evaporators, ovens and botanical extraction

MPC Series

• Welch MPC series multi-stage diaphragm pumps for deeper vacuum and chemistry systems

Some listings show a price and others are quote-based. Each product page lists free air flow, ultimate vacuum, voltage and connections.

Standard Duty vs Chemistry Duty

Choose by what the pump will see:

• Standard duty pumps suit air and water vapor. Vacuum filtration, aspiration, desiccators and degassing are their main jobs. They cost less and are easy to maintain.
• Chemistry-duty pumps use PTFE heads, diaphragms and valves, so they resist solvents, acids and corrosive vapors. Use them on rotary evaporators, vacuum ovens and concentrators where solvent vapor passes through the pump.

How a Diaphragm Pump Works

A motor turns an eccentric that drives a connecting rod up and down. The rod flexes a diaphragm clamped between the head and the pump body.

As the diaphragm moves down, the chamber expands and gas enters through the inlet valve. As it moves up, the gas is compressed and pushed out through the outlet valve.

Multi-stage pumps link two or more heads in series, so each stage lowers the pressure further. The diaphragm seals the chamber from the crankcase, so no oil ever touches the pumped gas.

Key Features

• Completely oil-free, with no oil changes and no oil mist
• Quiet, compact and light enough for benchtop use
• PTFE wetted parts on chemistry-duty Ilmvac models
• Low maintenance, with diaphragms and valves the main wear parts
• Multi-head designs for deeper vacuum and higher flow

Applications for Welch Diaphragm Pumps

• Rotary evaporation and solvent recovery
• Vacuum filtration and aspiration
• Vacuum ovens, desiccators and gel dryers
• Centrifugal concentrators and sample preparation
• Botanical and essential oil extraction
• Degassing and general laboratory vacuum

How to Choose the Right Welch Diaphragm Pump

Before ordering, confirm:

• The vacuum level your process needs, in Torr, mbar or in Hg
• Free air flow for your flask, oven or manifold size
• Whether solvents, acids or corrosive vapors pass through the pump
• How many users or instruments share the pump
• Supply voltage and frequency
• Whether you need a vacuum controller, condenser or catch pot

Maintenance Tips

• Replace diaphragms and valves at the interval in the manual, or sooner on solvent service
• Run the pump with the inlet open for a few minutes after pumping condensable vapors so moisture clears the heads
• Use a cold trap or exhaust condenser on heavy solvent loads
• Empty catch pots and collection vessels before they fill
• Keep the cooling fan and air inlets clear

We stock diaphragm and valve kits for common Welch models.

Signs Your Diaphragm Pump Needs Service

• The pump no longer reaches its rated vacuum
• Pumpdown on your evaporator or filter flask takes longer than before
• Clicking, flapping or new noise from the heads
• Cracked, swollen or stiff diaphragms
• The motor runs hot or the pump stalls on start

New Pumps and Replacement Kits

Most diaphragm pump wear happens in the diaphragms and valves. These can be replaced on the bench with a kit and basic tools, and a new kit restores rated vacuum in most cases.

A pump that has lost vacuum is usually worth servicing rather than replacing. Replace the whole pump when the motor or bearings are worn, or when the heads are cracked or badly corroded by chemicals.

Diaphragm Pumps on a Rotary Evaporator

For rotary evaporation, a chemistry-duty pump with PTFE wetted parts is the safe choice. Add a vacuum controller to hold the boiling point of the solvent, and an exhaust condenser to recover solvent before it leaves the pump.

This protects the diaphragms, cuts bumping and foaming, and keeps solvent vapor out of the lab.

Welch Diaphragm Pumps Repair

Provac Sales services Welch diaphragm pumps, including diaphragm 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

• Welch dry pumps, WOB-L oil-free piston pumps for vacuum and pressure
• Welch scroll pumps, SCSpro scroll pumps for deeper dry vacuum
• Welch vane pumps, DuoSeal and CRVpro pumps for high vacuum
• All Welch vacuum pumps
• All diaphragm pumps from every brand we carry

Find the Right Welch Diaphragm Pump

Send us your application, required vacuum level, flow, the vapors you pump and your supply voltage. We will recommend the right Welch diaphragm pump, confirm availability or quote diaphragm and valve kits.

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

Welch Diaphragm Pump FAQ

1. What is the difference between a standard and a chemistry-duty Welch diaphragm pump?

Standard pumps are built for air and water vapor in jobs like filtration and desiccation. Chemistry-duty pumps, such as the Ilmvac 2052, 2062 and 2163, use PTFE wetted parts that resist solvents and corrosive vapors on rotary evaporators and vacuum ovens.

2. Do Welch diaphragm pumps need oil?

No. Welch diaphragm pumps are dry pumps. There is no oil to change, and no oil mist at the exhaust.

3. Which Welch diaphragm pump is best for a rotary evaporator?

Use a chemistry-duty PTFE pump such as the Ilmvac 2052 or 2062 for a single evaporator, or the 2163 for large flasks and higher solvent loads. Add a vacuum controller and condenser for best results.

4. How deep a vacuum can a diaphragm pump reach?

Single-stage lab pumps reach rough vacuum suitable for filtration, around 24 in Hg on a Model 2019. Multi-stage chemistry pumps go deeper, into the low Torr range. For deeper vacuum, look at a scroll or rotary vane pump.

5. How often should Welch diaphragms be replaced?

It depends on hours and process vapors. Replace diaphragms and valves when the pump no longer reaches its rated vacuum, or at the interval in the manual. Solvent work and condensing vapors shorten diaphragm life.