Ulvac ULK and PBL Oil Diffusion Pumps

An oil diffusion pump gives high pumping speed at high vacuum with no moving parts. A heater boils pump fluid, and the vapor jets drive gas down toward a backing pump.

Ulvac, a Japanese vacuum equipment maker, builds the ULK series of oil diffusion ejector pumps for high vacuum and the PBL series for large gas loads in industrial processes. At Provac Sales, we supply Ulvac diffusion pumps and help you match the pump, fluid and backing pump to your system.

Ulvac Diffusion Pump Models We Carry

ULK Series Oil Diffusion Ejector Pumps

• ULK-04A, VG100 inlet, about 550 L/s with D-11 fluid and a 0.15 L fluid charge
• ULK-06A, VG150 inlet, about 1,200 L/s with D-11 fluid and a 0.35 L fluid charge
• ULK-10A, VG250 inlet, about 3,400 L/s for larger coating chambers
• ULK-14A, VG350 inlet, about 5,400 L/s for large batch systems

Pumping speeds are slightly lower with silicone fluid. Ultimate pressure is about 2.6×10^-5 Pa (2×10^-7 Torr) with D-11 and about 2.6×10^-6 Pa with silicone fluid.

PBL Series Booster Diffusion Pumps

• PBL-02, VG50 inlet, about 80 L/s
• PBL-04, VG100 inlet, about 200 L/s, with a stainless steel body and 1.8 kW heater
• PBL-06, PBL-10, PBL-14 and PBL-20, from about 500 to 7,000 L/s for large industrial systems

PBL pumps reach full speed around 10^-1 Pa, with an ultimate pressure of about 2.7×10^-2 Pa and a maximum forepressure of 40 Pa.

Some listings show a price and others are quote-based. Each product page lists inlet flange, pumping speed, heater power and fluid charge.

ULK vs PBL Pumps

• ULK pumps are high vacuum diffusion pumps with an ejector stage that gives a high critical backing pressure. They suit vacuum evaporators, coaters and high vacuum test systems.
• PBL pumps are booster pumps that work between a mechanical booster and a high vacuum diffusion pump. They move large gas loads at medium vacuum in processes such as metallurgy, plastic coating and chemical production.

How an Oil Diffusion Pump Works

A heater at the bottom of the pump boils the pump fluid. The vapor rises through a stack of jets and leaves the nozzles at high speed, pointed down and out toward the pump wall. Gas molecules from the chamber are knocked down by the vapor stream and carried toward the foreline.

The vapor condenses on the water-cooled pump wall and drains back to the boiler. An ejector stage near the outlet compresses the gas to the foreline, where a rotary vane or piston backing pump removes it.

Pump Fluid

• D-11 is a general-purpose hydrocarbon fluid
• Silicone fluids, such as D-31 and F-5, offer better heat stability and lower ultimate pressure
• PBL pumps use ULVOIL B-6

Use the fluid listed for your pump and do not mix fluid types. Check the product page or manual for the correct charge.

Key Features

• No moving parts, so long life and quiet running
• High pumping speed for the inlet size
• High critical backing pressure on ULK pumps
• A design that keeps pump fluid from flowing to the backing pump
• Stainless steel bodies on the PBL-02 and PBL-04
• Heaters immersed in the fluid on larger PBL pumps

Applications for Ulvac Diffusion Pumps

• Vacuum evaporators and thin film coaters
• High vacuum test and research systems
• Metallurgy and vacuum heat treatment
• Plastic and roll-to-roll coating
• Chemical and process gas handling

How to Choose the Right Ulvac Diffusion Pump

Before ordering, confirm:

• Inlet flange size, such as VG100 or VG150
• Pumping speed and the pressure range you operate in
• Gas load, to choose between ULK and PBL pumps
• Backing pump size and the forepressure it holds
• Cooling water supply, 19 to 25 °C
• Heater voltage and phase, and the pump fluid

Maintenance Tips

• Let the pump cool before venting to air to avoid oxidizing the fluid
• Keep cooling water flowing at the rated temperature and flow
• Check the fluid level and condition, and replace dark or cracked fluid
• Use a water-cooled baffle or cold trap to cut backstreaming
• Keep the foreline below the pump's maximum forepressure
• Clean the jet stack whenever you change the fluid

Signs Your Diffusion Pump Needs Service

• Base pressure rising over time
• Longer pumpdown than before
• Dark, thick or burnt pump fluid
• Long warm-up or a heater that does not reach temperature
• Fluid contamination in the chamber from backstreaming

Ulvac Diffusion Pumps Repair

Provac Sales services Ulvac diffusion pumps, including heater replacement, cleaning and fluid change. Submit an RMA request, complete the contamination data sheet and drain the pump fluid before shipping.

Note the fluid type on the RMA. See our pump repair page for more information.

Related Collections

• Ulvac scroll pumps, DIS dry scroll pumps
• Welch vane pumps, rotary vane backing pumps
• MD-Kinney piston pumps, backing pumps for large diffusion pumps
• All Ulvac products
• All diffusion pumps from every brand we carry

Find the Right Ulvac Diffusion Pump

Send us your pump model, inlet flange, required pumping speed, operating pressure, backing pump and heater voltage. We will recommend the right Ulvac ULK or PBL pump, confirm availability or quote a repair of your existing pump.

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

Ulvac Diffusion Pump FAQ

1. What is the difference between Ulvac ULK and PBL pumps?

ULK pumps are high vacuum diffusion ejector pumps for coaters and test systems. PBL pumps are booster pumps that move large gas loads at medium vacuum, reaching full speed around 10^-1 Pa.

2. What pumping speed does the Ulvac ULK-06A have?

The ULK-06A has a VG150 inlet and pumps about 1,200 L/s with D-11 fluid. The smaller ULK-04A pumps about 550 L/s through a VG100 inlet.

3. What fluid does an Ulvac ULK diffusion pump use?

ULK pumps run on D-11 hydrocarbon fluid or on silicone fluids such as D-31 and F-5. Silicone gives better heat stability and lower ultimate pressure. Do not mix fluid types.

4. What backing pump does an Ulvac diffusion pump need?

Use a rotary vane or piston pump sized for your gas load that holds the foreline below the pump's maximum forepressure, about 40 Pa for a ULK-04A or ULK-06A with D-11 fluid.

5. Can I vent an Ulvac diffusion pump while it is hot?

No. Turn off the heater and let the pump cool before venting. Air on hot fluid oxidizes it, which raises base pressure and leaves deposits on the jets.