Since 1983, Girovac has been at the forefront of the UK vacuum industry. With over 40 years of hands-on expertise, we have seen vacuum technology evolve from simple mechanical tools to the highly sophisticated systems found in modern manufacturing, laboratories, and freeze-drying facilities today.
For an industrial engineer, understanding the "how" behind the hardware is essential for system design, troubleshooting, and effective maintenance. At its simplest, a vacuum pump does not "suck" in the traditional sense; instead, it creates a pressure differential that allows gas molecules to be pushed out of a sealed volume.
In this guide, we break down the fundamental principles of vacuum generation and the specific mechanics of the most common industrial pump types.
The Fundamental Principle: Positive Displacement
The vast majority of industrial vacuum pumps: including rotary vane, claw, and diaphragm types: operate on the principle of positive displacement. The process follows a consistent, cyclic mechanical rhythm:
- Expansion: An internal cavity increases in volume, causing the internal pressure to drop below that of the vacuum chamber.
- Induction: Gas molecules from the chamber are drawn (or rather, pushed by the higher pressure) into this new, larger cavity.
- Sealing: The cavity is mechanically sealed off from the inlet.
- Compression: The volume of the cavity is reduced, increasing the pressure of the trapped gas.
- Exhaust: Once the internal pressure exceeds atmospheric pressure, a valve opens and the gas is discharged.
By repeating this cycle thousands of times per minute, the pump effectively "pumps" gas molecules out of the system, creating a vacuum.
1. Rotary Vane Vacuum Pumps: The Industry Workhorse
The rotary vane pump is perhaps the most ubiquitous piece of equipment in the medium vacuum range. It is prized for its reliability, compact footprint, and ability to achieve deep vacuum levels.
How it Works
Inside a cylindrical housing (stator), a rotor is mounted eccentrically. This rotor contains longitudinal slots that house several sliding vanes. As the rotor turns, centrifugal force (often assisted by springs) pushes these vanes outward against the stator wall, creating a series of individual chambers.
As these chambers move past the inlet, they expand and capture gas. As they continue their rotation toward the exhaust, the eccentric mounting causes the chambers to shrink, compressing the gas until it is forced out through the exhaust valve.
Oil-Sealed vs. Dry
- Oil-Sealed: Most industrial models, like the Edwards E2M8 shown above, use vacuum oil to seal the tiny gaps between the vanes and the stator. This oil also provides essential lubrication and cooling.
- Dry: In applications where oil contamination is a risk, dry rotary vane pumps use self-lubricating carbon vanes. While cleaner, they generally cannot achieve the same ultimate vacuum levels as their oil-sealed counterparts.
At Girovac, we maintain a significant stock of reconditioned rotary vane pumps: specifically the Edwards E2M5 and E2M18 models: which are fully serviced in our workshop and supplied with a 6-month warranty.
2. Claw Vacuum Pumps: The Modern Choice for Efficiency
Claw pumps represent a significant step forward in dry vacuum technology. They are widely used in industrial processes where continuous, low-maintenance operation is required, such as in wood processing or packaging.
How it Works
A claw pump features two intermeshing, non-contacting rotors shaped like "claws." These rotors rotate in opposite directions within a housing. Unlike the rotary vane pump, there is no contact between the rotors themselves or the housing wall.
As the claws rotate, they create a void that opens to the inlet, trapping a specific volume of gas. As the rotation continues, this gas is compressed within the claw geometry and eventually released through the discharge port.
As the UK distributor for MIL'S, we offer their French-engineered SIRELLA and EVISA ranges. These units are specifically designed for demanding industrial environments, offering high volumetric efficiency and significantly reduced maintenance requirements compared to contact-based pumps.
3. Diaphragm Vacuum Pumps: Precision and Purity
When a process requires a completely oil-free environment: such as in laboratory analytical equipment or delicate chemical processes: the diaphragm pump is the preferred solution.
How it Works
The diaphragm pump uses a flexible membrane (the diaphragm) that moves back and forth, driven by a rod and crankshaft.
- On the downstroke, the diaphragm pulls away from the head, increasing the volume of the chamber and drawing gas in through a one-way check valve.
- On the upstroke, the diaphragm compresses the gas, forcing it out through an exhaust check valve.
Because the gas path is completely isolated from the drive mechanism, there is zero risk of oil contamination. These pumps are robust, can handle corrosive gases (when fitted with PTFE components), and are surprisingly quiet.
4. Liquid Ring Vacuum Pumps: Handling the Heavy Lifting
For applications involving high levels of moisture, vapours, or even "dirty" gas streams, the liquid ring pump is exceptionally resilient.
How it Works
The impeller is mounted eccentrically inside a cylindrical casing partially filled with a sealant liquid (usually water). As the impeller spins, centrifugal force forms a "liquid ring" against the casing wall.
Because the impeller is offset, the blades dip deeper into the liquid ring at the top and less so at the bottom. This creates expanding and contracting gas pockets between the blades, acting like a "liquid piston" to draw in and compress gas. This design is effectively "self-cooling" as the liquid absorbs the heat of compression.
Why Expert Servicing is Non-Negotiable
A vacuum pump is a precision instrument. Even a microscopic scratch on a vane or a slight degradation in oil quality can lead to a significant loss in performance or total system failure.
At Girovac, we operate a dedicated workshop in North Walsham, where our engineers apply over four decades of experience to the repair and servicing of all major European brands, including Leybold, Edwards, VacuuBrand, KNF, GAST, Busch, Rietschle, and Pfeiffer.
Our service includes:
- Full Strip-Down and Cleaning: Removing contaminants that can cause internal wear.
- Component Inspection: Measuring tolerances against manufacturer specifications.
- Vacuum Testing: Every pump, whether a new MIL'S unit or a reconditioned generic, is rigorously tested to ensure it reaches its ultimate vacuum pressure before leaving our site.
- 6-Month Warranty: We stand by our workmanship (on all reconditioned oil-lubricated models like the E2M5 and E2M18).
Selecting the Right Pump for Your Facility
Choosing a vacuum pump involves more than just looking at the "ultimate vacuum" figure. Industrial engineers must consider:
- Flow Rate (Pumping Speed): How quickly do you need to evacuate the chamber?
- Chemical Compatibility: Are you pumping corrosive vapours or simple air?
- Maintenance Intervals: Can your process afford the downtime for frequent oil changes?
- Total Cost of Ownership: Sometimes a higher initial investment in a dry claw pump saves thousands in oil and filter costs over its lifetime.
All Things Vacuum
Whether you need a single O-ring, a bespoke vacuum system design, or a specialized freeze-dryer service, Girovac provides a total solution. We pride ourselves on offering expert advice that is grounded in 40 years of practical engineering experience.
Looking ahead, we remain committed to providing the UK's most reliable and cost-effective vacuum solutions. If you have a technical question or require a quote for a new or reconditioned pump, our team is ready to assist.
Contact us today: [email protected]