22KW Roots Type Vacuum Pump | SLV Series Classic Longtech Roots Vacuum Pump

The SLV series is a roots blower vacuum pump — a roots type vacuum pump built on the same three-lobe rotor platform as our pressure blowers. And here’s something that surprises most first-time buyers: the machine that blows air into your aeration tank is mechanically identical to the machine that pulls a vacuum on your pneumatic conveyor. The only difference is which port you connect to your process.

Hook up the discharge side, and it’s a roots blower. Hook up the inlet side, and it’s a roots vacuum pump. Same rotors. Same gears. Same bearings. Just plumbed differently.

Our SLV series is the vacuum-configured version of the same three-lobe roots-type blower we’ve been building for over a decade. This is a roots-type vacuum pump in the classic sense — positive displacement, oil-free gas path, rated down to −5000 mmAq. If you already use our SL pressure blowers, the SLV will feel familiar — same castings, same oil system, same maintenance routine. If you’re new to Slovdson, this page covers what you need to know to spec one.

How a Roots Blower Becomes a Roots Vacuum Pump

A roots blower vacuum pump works on the same principle as its pressure counterpart — it doesn’t compress air internally. It traps a pocket of gas between the rotors and the casing wall, then carries that pocket from the inlet port to the outlet port. The “compression” happens at the outlet — the trapped gas meets the higher-pressure gas already in the discharge line, and the pressure equalizes almost instantly.

When you run the machine as a blower, atmospheric air enters the inlet, gets moved through, and exits against whatever back-pressure your process creates.

When you run it as a roots vacuum pump, you flip the logic. Your process vessel or pipeline connects to the inlet port instead. The blower pulls gas out of that system, creating a partial vacuum. The outlet side just vents to atmosphere — through a silencer, or into a downstream treatment system. This is the roots vacuum working principle in its simplest form: constant-volume displacement generating suction.

The important thing: the rotors never touch each other, and they never touch the casing wall. The clearance gap is small — fractions of a millimeter — but it’s always there. So the gas you’re pulling through the pump doesn’t get contaminated with oil from the gearcase, and it doesn’t pick up metal particles from rotor contact. For food packaging, chemical processing, pharmaceutical manufacturing, and any application where gas purity matters, this matters. The lubrication system is sealed on the gear side, isolated from the gas path by labyrinth seals.

Roots Type Vacuum Pump Structure Diagram

SLV Series Roots Type Vacuum Pump Specifications

Same twelve frame sizes as our pressure blowers. Different performance curves because the thermodynamics shift when you’re pulling vacuum instead of pushing pressure. The table covers the full range from our compact SLV-040 up to the SLV-400 for large-volume industrial vacuum service.

Larger frames (SLV-350, SLV-400) handle suction flows up to 362 m³/min. If you’re pulling vacuum on a large volume — a bulk material unloading system, a central vacuum network, a process that needs fast pump-down — those are the ones to look at.

A note on vacuum sizing: the flow rate you see on our spec table is measured at the inlet, under vacuum conditions. Don’t confuse it with the displaced volume inside the blower — the actual suction flow drops as vacuum level increases, which is normal for any positive-displacement vacuum pump. If you send us your required suction flow and target vacuum level, we’ll select the right frame and speed for you.

Noise Levels (Vacuum Service)

Noise characteristics in vacuum operation are similar to pressure duty — the same mechanical components, the same gas pulsation pattern. Below are the typical noise ranges measured at 1 meter with standard silencers installed:

A note specific to vacuum applications: intake noise increases as vacuum level deepens, because the pressure differential across the inlet port grows. If your process runs at the high end of the vacuum range (−4000 mmAq and above), pay extra attention to inlet silencer sizing. We spec our vacuum silencers to match each model’s full operating envelope, but an acoustic enclosure is worth considering for installations near occupied work areas.

How to Size Your Vacuum Pump (STP Conversion)

Our performance tables are based on STP standard conditions (20°C, 10332 mmAq atmospheric pressure, 65% RH). For vacuum sizing, the conversion works the same way but in the suction direction:

Flow rate conversion: Q₂ = Q₁ × (P₁/P₂) × (T₂/T₁)

Pressure conversion: Ps = [(10332 + P₂) / (10332 + P₁) − 1] × 10332

The key thing to remember with vacuum: as the suction pressure drops (deeper vacuum), the actual mass flow through the pump decreases. That’s inherent to the roots vacuum pump working principle — the blower displaces a fixed volume per revolution, but the gas density at the inlet keeps dropping as vacuum increases. Always size for your worst-case operating point. If you share your process data with us, our engineers will build the performance map at your specific conditions.

Where SLV Roots Type Vacuum Pumps Do the Work

Pneumatic Conveying

This is the single largest application for the SLV series. Bulk solids — cement powder, flour, plastic pellets, fly ash, grain — move through pipelines on a stream of air. You can push them (pressure conveying) or pull them (vacuum conveying).

Vacuum conveying has a few advantages that matter in practice: leaks pull air in rather than blowing product out. Loading points can be open hoppers rather than sealed pressure vessels. And the system naturally lends itself to multiple pick-up points feeding one destination.

A typical setup: the SLV pulls vacuum on a receiver vessel. Bulk material is drawn in through a wand or hopper at the pick-up point, travels through the pipeline, and drops out in the receiver as the air velocity drops. The blower exhausts to atmosphere through a silencer and, in dusty applications, a bag filter. For abrasive materials (fly ash, sand, mineral powders), the vacuum filter tank on the inlet side is mandatory — it catches any carryover before it reaches the rotors.

Vacuum Packaging

Food processors and pharmaceutical manufacturers use vacuum to pull air out of packaging before sealing. It extends shelf life, prevents oxidation, and compresses the product for storage and shipping.

The SLV works here because it delivers oil-free vacuum. Even trace oil mist in the vacuum line would contaminate food-contact surfaces and degrade product quality. Our roots vacuum pumps don’t inject oil into the air stream — the lubrication system is sealed on the gear side, isolated from the gas path by labyrinth seals. This is the same oil-free architecture that makes roots-type vacuum pumps the standard in food and pharma applications worldwide.

Tissue Paper Processing

This is a market we know particularly well. Tissue converting lines — the machines that fold, cut, and package facial tissue, napkins, and paper towels — use vacuum to pick up and transport individual sheets through the folding section. The vacuum needs to be steady and reliable because a fluctuation mid-cycle means a misfed sheet, which means a line stop and lost production.

Our smaller SLV frames (SLV-040 through SLV-100) are the standard choice here. The SLV-065 and SLV-080 are particularly popular in tissue mills — compact enough to mount near the converting line, powerful enough to hold consistent vacuum across the full folding drum width. We’ve supplied these to tissue mills across China and Southeast Asia, and our service team knows the application.

Other Industrial Vacuum Applications

• Soil vapor extraction — pulling volatile organic compounds out of contaminated soil for environmental remediation
• Central vacuum cleaning systems — factories, textile mills, grain elevators with multiple cleaning stations
• Vacuum holding and lifting — glass handling, sheet metal transfer, printed circuit board pick-and-place
• Laboratory and hospital central vacuum — for applications where oil-free vacuum is a non-negotiable safety requirement

Vacuum-Specific Accessories

The accessories for vacuum service overlap with the pressure side, but there are a few worth calling out in detail:

• Vacuum filter tank (Model B-050 ~ B-400) — Mounted on the inlet side, upstream of the blower. Catches debris, carryover, and any solids before they reach the rotors. If you’re conveying anything abrasive, fibrous, or sticky, this is not optional. We stock filter tanks sized to match each SLV model, with accessible drain ports for cleaning.
• Vacuum relief valve — Works the opposite way from a pressure relief valve. If the vacuum level gets too deep (system blockage, closed valve, filter blinding), this opens to admit atmospheric air and protect the blower from pulling beyond its rated vacuum. Without one, the blower can pull itself into a range where discharge temperatures spike and clearances close up.
• Inlet silencer (Model I-050 ~ I-400 indoor / O-050 ~ O-400 outdoor) — Same function as the pressure side, but sized for vacuum service. Intake noise increases with vacuum level, so silencer selection matters more here than on a pressure blower.
• Check valve (Model C-050 ~ C-400) — On the discharge side. Prevents backflow if the blower stops while connected to a shared exhaust manifold or pressurized downstream system.

For the full accessory ecosystem — flexible joints, vibration absorbers, T-joints, common baseplates — these are identical to the pressure side. See our SL Series blower accessories for the complete list.

Construction & Materials

The SLV shares the same platform as the SL pressure blower. Here’s what’s inside:

The wet-sump splash lubrication system needs no external oil pump and no cooling water. The gear dip and splash disc fling oil into the bearings on every revolution. Maintenance is straightforward: drain and refill oil on schedule, check oil level weekly, clean the inlet filter. Detailed maintenance intervals are in the operating manual we ship with every unit.

Installation Notes for Vacuum Service

The layout mirrors the pressure setup, but the filter tank goes on the inlet:

Process → Vacuum Filter Tank → Inlet Silencer → Flexible Joint → SLV Blower → Flexible Joint → Check Valve → Discharge Silencer → Atmosphere

Key points to get right:

• Discharge temperature: In vacuum service, the discharge air is warm — sometimes hot. Compressing gas from sub-atmospheric to atmospheric pressure generates more heat than you’d see in the equivalent pressure application. The discharge silencer and piping will run warm. We spec our discharge silencers for continuous service at these temperatures, but if your installation has people working near the exhaust, route the discharge pipe away from walkways or insulate it.
• Filter tank placement: The vacuum filter tank must be installed as close to the blower inlet as practical, with the drain valve accessible. If the application generates heavy condensate (humid intake air, wet product), install a condensate trap upstream of the filter.
• Room ventilation: A roots vacuum pump in a closed room will heat the space over time. The motor and the discharge piping both reject heat. If the blower room doesn’t have forced ventilation, size a ventilation fan — especially for SLV-150 and larger.

Same Machine, Two Configurations

If you’re already running SL pressure blowers, the SLV is mechanically the same platform. Same gears. Same bearings. Same oil seals. Your maintenance team doesn’t need to learn a different machine. Spare parts inventory covers both sides — bearings, oil seals, gaskets, and filter elements are interchangeable across SL and SLV models of the same frame size.

And if your process changes — you need to switch from blowing to vacuum, or run both on site — the same machine platform handles both jobs. That’s not a marketing claim. That’s just how positive-displacement blowers work: the rotors don’t care which port is inlet and which is outlet.

See our pressure blower range: SL Series Three-Lobe Roots Blower →

Frequently Asked Questions

Q: What is a roots vacuum pump and how does it work?

A roots vacuum pump is a positive-displacement pump that uses two or three interlocking lobed rotors to trap and move gas from the inlet (vacuum side) to the outlet (atmosphere side). The roots vacuum pump working principle is constant-volume displacement: each revolution moves a fixed pocket of gas. As the pump runs, gas is continuously removed from the sealed process volume, creating and maintaining a partial vacuum. Unlike liquid ring or rotary vane pumps, there’s no internal compression and no oil in the gas path — the rotors don’t touch each other or the casing wall.

Q: What’s the difference between a roots vacuum pump and a roots blower?

Mechanically, none. The same three-lobe rotor assembly, gear train, and bearing system serve both functions. The difference is which port you connect to your process. Connect the discharge port → it’s a blower. Connect the inlet port → it’s a roots vacuum pump. Slovdson’s SL (pressure) and SLV (vacuum) models share the same platform, which means spare parts, maintenance procedures, and operating knowledge carry over between the two.

Q: How much does a roots vacuum pump cost?

Roots vacuum pump price depends on frame size, vacuum level, motor specification, and accessories (filter tank, silencers, valves). A compact SLV-040 unit for tissue converting is at the entry level; a fully-accessorized SLV-200 package with vacuum filter tank and silencers for pneumatic conveying is a capital equipment investment. We quote within one working day with a detailed line-item breakdown. For reference: our most popular vacuum models (SLV-050 through SLV-100 for packaging and tissue applications) represent the best value in terms of flow-per-dollar.

Q: Can a roots vacuum pump run continuously?

Yes. The SLV series is designed for continuous duty — same as the SL pressure blowers. The oil-lubricated splash system has no external pump to fail, and bearings are sized for L10 life exceeding 40,000 hours at rated vacuum conditions. Many of our SLV units run 24/7 in tissue converting lines and pneumatic conveying systems where any unplanned stop is costly.

Q: Does the SLV produce oil-free vacuum?

Yes. The gas path (rotors + casing) is completely isolated from the gearcase lubrication system by labyrinth seals. No oil is injected into the gas stream, and there is no metal-to-metal contact in the pumping chamber. This is essential for food packaging (oil contaminates product), pharmaceutical manufacturing (oil violates GMP), and laboratory vacuum (oil vapors skew results).

Q: What’s the maximum vacuum the SLV series can pull?

All SLV models are rated to −5000 mmAq maximum vacuum in a single-stage configuration. (For deeper vacuum requirements, a roots booster pump paired with a backing pump can achieve significantly lower absolute pressures — contact our engineering team to discuss your target vacuum level.)