Degassing Vacuum Pump Selection Guide: Matching the Right Pump to Your Process

How Vacuum Degassing Works

The physics is captured by Henry's Law: the amount of gas dissolved in a liquid is proportional to the partial pressure of that gas above the liquid. Drop the pressure over a resin, an oil, or a molten metal, and dissolved gases come out of solution, form bubbles, rise, and escape. Falling pressure also expands mechanically trapped bubbles, helping them break free and reach the surface. The vacuum pump's role is to create that low-pressure environment and carry the released gas away continuously, for as long as the material keeps outgassing.

A note on terminology: degassing is often confused with deaeration. Deaeration refers specifically to stripping air and oxygen from process liquids. Degassing is the broader job — removing hydrogen from molten steel, moisture and air from transformer oil, CO2 and volatiles from resins, or solvent vapor from a coating mix. How efficiently any of this happens depends on five factors: the depth of vacuum applied, the temperature of the material, the surface area exposed, the residence time under vacuum, and how well the material is mixed or circulated through the vacuum zone.

Where Degassing Vacuum Pumps Earn Their Keep

• Resins, epoxies, and casting compounds. Mixing and pouring trap air inside the compound. Left in place, that gas cures into nodules, cavities, and hollows — weak points in structural castings and cosmetic rejects in potting and encapsulation work. Vacuum degassing before the pour is the standard fix.
• Transformer, hydraulic, and lubricating oils. Removing dissolved air and moisture prevents foaming, oxidation, and cavitation downstream, and restores the dielectric strength that transformer oil needs in electrical service.
• Steel and metal melts. Vacuum treatment pulls hydrogen out of molten steel before it can form flakes that cut yield strength and invite structural failure. Reducing dissolved carbon at the same time produces more ductile grades. Modern mechanical systems built around Roots blowers and dry screw backing pumps increasingly handle this duty in place of steam ejectors.
• Plastics, rubber, and composites. Degassing melts and mixes protects mold integrity and surface finish, and prevents internal voids that only appear after demolding.
• Battery, pharmaceutical, and specialty chemical processes. Lithium-ion electrode slurries are degassed so coatings lay down uniform and pinhole-free; solvent-bearing mixes in pharma and fine chemicals need pumps that tolerate aggressive vapors without contaminating the product.

Choosing the Pump Technology

Dry Screw Vacuum Pumps: For Solvents, Corrosives, and Clean Processes

A dry screw degassing vacuum pump keeps oil out of the pumping chamber entirely, so there is nothing to emulsify with condensed solvent or water vapor, no oil changes between batches, and no hydrocarbon back-migration into the process. That makes dry screw the default choice for resin and coating mixes that release solvent vapor, for battery slurry degassing, and for pharmaceutical duty where purity is audited. InPowerVac builds air-cooled and water-cooled dry screw models, and for volatile or corrosive off-gas the range includes a chemical resistant vacuum pump line with TA10 titanium-alloy wetted parts.

Oil-Sealed Rotary Vane Pumps: Deep Vacuum at the Lowest Cost

For clean degassing duty — transformer and lube oils, filled resins without aggressive solvents, laboratory and pilot work — an oil sealed rotary vane vacuum pump is hard to beat on economics. InPowerVac single-stage oil sealed models reach an ultimate vacuum of 20 Pa or better and cover pumping speeds from 4 to 1200 m³/h, so one frame size serves everything from a bench degassing chamber to a large oil treatment skid. Imported bearings and shaft seals, an anti-backflow oil design, and British oil mist filter technology keep the exhaust clean and the oil where it belongs during long unattended runs. Used correctly, the gas ballast valve lets these pumps handle respectable water vapor loads without milking the oil.

Roots-Boosted Systems: For Large Vessels and Fast Cycles

Degassing a large tank, an autoclave, or a high-throughput oil purification line asks for more pumping speed than a single backing pump delivers economically. Pairing a roots vacuum pump as a booster with a rotary vane or dry screw backing pump multiplies effective speed in the pressure range where outgassing actually peaks, cutting pump-down time and holding chamber pressure steady as gas load surges. InPowerVac supplies this as an engineered vacuum pump system — air-cooled or gas-circulation cooled Roots stages matched to the backing pump and the duty cycle — rather than a loose combination of parts the buyer has to integrate alone.

Technology Comparison at a Glance

Six Selection Factors That Actually Matter

• Working pressure, not ultimate vacuum. Define the pressure your process must hold during degassing, then compare pumps on their speed at that point on the curve — not on the headline ultimate figure.
• Pumping speed versus gas load. Chamber volume sets the pump-down time, but the material's outgassing rate sets the steady-state load. Resins and slurries outgas far longer than an empty vessel leak test would suggest.
• Vapor and carryover behavior. Moisture, solvent vapor, and fine resin mist all travel toward the pump. Plan gas ballast, inlet filtration, or a condenser before blaming the pump.
• Chemical compatibility. Acidic or solvent-laden off-gas calls for coated or titanium-alloy wetted parts; standard cast iron will not survive long in that service.
• Duty cycle and heat management. Batch degassing a few times per shift is a different duty from a continuous oil purification line. Match air- or water-cooling to how the pump will actually run.
• Total cost of ownership. Oil, filters, energy, and downtime outweigh the purchase price over a pump's life. Dry pumps cost more up front and less per year; oil-sealed pumps invert that equation.

Keeping a Degassing Pump Healthy

Degassing duty concentrates wear in predictable places. On oil-sealed pumps, run the gas ballast during high-vapor phases so moisture leaves with the exhaust instead of dissolving into the sump, and check oil color between batches — milky oil means water contamination and an immediate change with fresh, correctly graded vacuum pump oil, since degraded oil is the fastest way to lose ultimate vacuum mid-cycle. An exhaust oil mist filter recovers oil vapor, keeps the machine room clean, and stretches the interval between top-ups. On dry screw pumps, attention shifts to cooling water flow or fan condition and to purge settings on corrosive duty. In both cases, stocking genuine vanes, seals, and filters turns a potential multi-day stoppage into a short planned intervention.

Frequently Asked Questions

Is vacuum degassing the same as vacuum deaeration?

No. Deaeration is the specific removal of air and oxygen from process liquids. Degassing is broader — it covers hydrogen from molten metals, moisture from oils, and CO2 or solvent vapor from resins and mixes, alongside ordinary air removal.

Which pump should I choose for resin degassing?

If the resin system releases solvent vapor or is even mildly corrosive, choose a dry screw pump; there is no oil for the vapor to attack. For filled, solvent-free resin systems on a tight budget, a two-stage oil-sealed rotary vane pump with gas ballast does the job well.

How deep a vacuum does degassing need?

Most resin, oil, and slurry degassing works in the rough-to-medium vacuum range, well within reach of single-stage pumps. What matters more than the ultimate figure is holding a stable working pressure while the material outgasses — which is why speed at the working point, vapor tolerance, and, on large vessels, a Roots booster matter more than the brochure's best-case number.

Why Process Plants Work with InPowerVac

InPowerVac, the international brand of Zhejiang Yingpa Electromechanical Co., Ltd, has manufactured vacuum equipment since 2000 and supports degassing applications from laboratory chambers to industrial oil treatment and battery production lines. The company operates two production bases in Zhejiang and Hebei — including a 70,000-square-meter plant added in Taizhou in 2023 — with 92 sets of processing equipment, 30 of them imported. Dry screw rotors are machined in-house on 32 Mazak processing centers, and every pump passes through material testing, dynamic balancing, three-coordinate measurement, and a dedicated vacuum test room before shipment.

That manufacturing depth backs a catalog covering every technology discussed above: single-stage and two-stage rotary vane pumps, air- and water-cooled dry screw pumps in standard, chemical-resistant, and titanium-alloy builds, Roots boosters, and complete engineered vacuum systems, plus the oils, vanes, and filters that keep them running. The same equipment serves customers such as Foxconn, Huawei, Samsung, and the Tata Group across lithium battery, semiconductor, pharmaceutical, and metallurgical processes, and the engineering team routinely configures customized systems for special degassing duties.