37kW Roots Blower Vacuum Pump — Energy-Saving PMSM + VFD for Tissue Converting & Industry

The SLDS-3700LC is a 37kW energy-saving roots blower vacuum pump — a positive displacement blower and vacuum pump that powers the majority of large tissue paper converting lines across our customer base. In vacuum mode, it pulls −25 to −45 kPa with 31 m³/min suction flow through a DN200 outlet — the vacuum capacity that supports 4 to 6 high-speed folding machines on a common header. In pressure (blower) mode, the same machine delivers 25–45 kPa for pneumatic conveying, large-scale wastewater aeration, and centralized air supply. One host, two jobs, same spare parts.

For tissue paper manufacturers, the roots vacuum pump is production-critical. Every napkin, facial tissue, and paper towel transported through the folding section relies on steady vacuum. The 3700LC’s VFD constant-vacuum mode holds the target vacuum level as inlet filters load with paper dust — no operator adjustment, no line stops, no misfed sheets.

In pressure mode, the same PMSM motor’s 186 Nm torque holds rotor speed against rising back-pressure with less belt slip than a conventional induction motor. Whether pulling vacuum for tissue converting or pushing air for pneumatic conveying, the 3700LC consumes 30 to 65 percent less electricity than a conventional 37kW roots blower vacuum pump.

Product Positioning: Dual-Mode Versatility

At 37kW, the 3700LC occupies the power rating where most large tissue converting operations converge — making it our best-selling model to tissue paper customers in vacuum mode. But its capability set extends equally to pressure duty: pneumatic conveying, large-scale aeration, and centralized air supply. Every design decision, from the dual drive curves (vacuum and pressure) programmed into the VFD to the integrated inlet filtration that handles both paper dust (vacuum mode) and ambient industrial dust (pressure mode), reflects this dual-use DNA.

Choose the 37kW LC when:

• You operate 4–6 tissue folding machines (napkin, facial tissue, and/or paper towel lines) — this is the core application
• Your line speeds are in the 200–350 m/min range
• Vacuum stability across multiple machines on a common header is non-negotiable
• You need vacuum depth to −45 kPa — the range that keeps the VFD from running near its speed limit continuously
• You run 16–24 hours/day, 300–350 days/year, and electricity is a top-three operating cost
• You also need pneumatic conveying vacuum for bulk material transfer, and want one machine platform for both duties

Step down to 30kW when: you’re running 3–4 folding machines at moderate speeds, or your vacuum depth requirement stays within −40 kPa.

Step up to 45kW when: you have 7+ folding machines, line speeds above 350 m/min, or are running multiple high-speed lines from a single vacuum source.

Roots Vacuum Pump Working Principle — A Positive Displacement Machine

The 3700LC is a positive displacement blower and vacuum pump. Understanding that phrase explains how the machine behaves on your plant floor — and why it suits tissue sheet transport and bulk conveying better than a turbo or centrifugal unit.

What “positive displacement” means. Every revolution of the rotors moves a fixed volume of air from the inlet side to the outlet side. The machine displaces a known quantity of gas per turn, rather than accelerating it with an impeller (as a centrifugal or turbo blower does). That gives predictable, pulse-free flow: the vacuum or pressure you set stays steady, instead of surging with speed the way a dynamic machine does.

How the roots mechanism works. Inside the casing, two three-lobe rotors counter-rotate. They are synchronized by a pair of timing gears (the dual gearbox listed in our specifications) so the lobes mesh past each other without ever touching — the running clearance is measured in tenths of a millimeter. Because the rotors never contact the casing or each other, there is no gas-path wear and nothing in the air stream to lubricate.

• In vacuum mode, the rotating lobes continuously carry gas from the inlet toward the outlet, drawing a steady suction at the inlet. This is what holds each sheet on a tissue folding belt and pulls bulk material through a conveying line. The 3700LC moves large volumes at the moderate vacuum depths (down to −45 kPa) that sheet transport and conveying actually require.
• In blower mode, the action reverses: the lobes trap gas at the inlet and push it to the outlet, building pressure up to 45 kPa for aeration and centralized air supply.

Why a roots pump is a high-flow, moderate-vacuum device. That same non-contact clearance lets a small amount of gas slip back from the higher-pressure outlet side to the lower-pressure inlet side. This internal slip is the defining trait of a roots pump: very high pumping volume at shallow-to-moderate vacuum, rather than deep vacuum. For tissue sheet transport, napkin folding, and bulk conveying — applications defined by high flow at modest vacuum — that is exactly the right profile. It is also what sets a roots vacuum pump apart from an oil-sealed vane or liquid-ring pump, which trade flow for deeper vacuum.

For a full technical explanation — from rotor geometry to internal slip to ultimate vacuum limits — read our guide: [Roots Vacuum Pump Working Principle →]

Dual-Mode Specifications: Pressure Blower & Vacuum Pump

The 3700LC is one machine for two jobs. In tissue paper converting, it runs in vacuum mode — this is the configuration that drives the majority of our 37kW sales. In pneumatic conveying, wastewater aeration, and centralized air systems, it runs in pressure (blower) mode. Both modes share the same PMSM motor, dual-gearbox host, and VFD platform — only the process pipe connection differs.

💡 The 3700LC uses a larger cabinet than the 15–30kW models (1500×1350 vs 1400×1200 mm) to accommodate the larger gearbox and DN200 outlet that the 37kW power class requires. The additional cabinet volume also provides more internal acoustic volume for the silencer — contributing to noise control at the higher airflow rates.

Why the 37kW LC Is the Right Vacuum Pump for Tissue Paper Converting

This section is the core of this page. If you operate a tissue converting plant, here is why the 3700LC matters to your production.

Vacuum Stability = Line Uptime

Tissue converting is a continuous process. Paper unwinds from the parent reel, passes through embossing and folding stations, and is cut, stacked, and packaged — all in one synchronized line. At the folding section, individual sheets are transported by vacuum: a vacuum belt or suction roller grips each sheet and carries it through the fold geometry. If the vacuum level drops for half a second, the sheet isn’t gripped. It drifts. It jams. The line stops.

In a workshop with four folding machines running on a common vacuum header, vacuum stability is a system-level problem. When one machine cycles — a reel change, a jam clear, a speed adjustment — the change in vacuum draw propagates through the header and affects every other machine. A conventional fixed-speed vacuum pump has one response: run at full speed, bleed off excess, and hope the vacuum reservoir smooths out the transient. Sometimes it does. Sometimes it doesn’t.

The 3700LC’s VFD operates differently. It monitors vacuum level at the pump inlet hundreds of times per second and adjusts motor speed to hold the setpoint. When one machine’s vacuum demand changes — a reel change on line 2, a brief stop on line 4 — the VFD instantaneously adjusts pump speed to compensate. The vacuum level at lines 1, 2, and 3 doesn’t budge. No cascade. No jam cascade.

For the plant manager: fewer unscheduled stops. For the operator: no need to watch a vacuum gauge and manually throttle a bleed valve every time a machine cycles. For the business: more finished pallets per shift.

Oil-Free Vacuum — Non-Negotiable for Tissue Products

Vacuum pumps that use oil-injected screws or oil-lubricated vanes always carry a risk of oil mist carryover into the vacuum line. In metal fabrication or woodworking, a little oil in the vacuum line might not matter. In tissue converting, it matters acutely. Oil on a white napkin or facial tissue is a visible stain — a quality reject, a customer complaint, potentially a returned shipment.

The 3700LC’s gas path is completely isolated from the gearcase lubrication system by labyrinth seals. The rotors never touch the casing. No oil is injected for sealing or cooling. The result is 100% oil-free vacuum — every cycle, every shift, documented with material certificates and seal specifications supplied with every machine.

Handling Paper Dust

Tissue converting generates fine paper dust. Over hours of operation, that dust is drawn toward the vacuum pump inlet. Without adequate filtration, dust accumulates on rotors and inside the casing — reducing clearance, increasing internal leakage, and gradually degrading vacuum performance.

The 3700LC’s integrated inlet filtration system is front-accessible and replaceable without tools. In tissue mill duty, we recommend sizing the filter for the dust loading rate of your specific operation and establishing a filter change interval based on observed pressure drop — typically weekly to monthly depending on tissue grade and line count. The VFD’s real-time vacuum monitoring provides an early indicator: as the filter loads, the VFD increases motor speed to compensate. When speed reaches a preset threshold, it’s time to change the filter. No guesswork.

Energy Savings That Change the Budget

A 37kW vacuum pump running 16–20 hours a day, 300+ days a year, is a significant line item on the electricity bill. For a tissue mill with multiple lines, vacuum pump electricity is typically the single largest motor load in the plant after the paper machine itself.

Real-world worked example — tissue converting plant: A 37kW conventional roots vacuum pump powering 5 folding lines, running 18 hours/day, 320 days/year, consumes roughly 213,000 kWh per year. At $0.12/kWh: $25,600 annually. The SLDS-3700LC in vacuum mode cuts that by 35–55% — saving $9,000 to $14,100 per year.

For a plant running three 3700LC units — not unusual for a multi-line tissue mill — the annual savings total $27,000 to $42,300. That covers the salary of an additional operator. Or funds the next line upgrade. Or drops straight to the bottom line.

Payback on the upfront price premium: 18–30 months. For tissue mills in regions with electricity rates above $0.15/kWh (much of Europe, Southeast Asia, the Caribbean), payback is faster. For plants running 24/7, faster still.

Detailed Application: Tissue Paper Converting Line Configurations

Configuration A: 4–5 Napkin Folding Lines

A typical medium-to-large napkin converting plant runs 4–5 folding machines producing dispenser napkins, dinner napkins, or cocktail napkins. Line speeds: 200–300 m/min. Vacuum demand: steady during production with brief dips during reel changes.

The 3700LC serves this configuration with vacuum depth set to approximately −30 to −35 kPa, with the VFD operating in constant-vacuum mode. As individual lines cycle for reel changes, the VFD absorbs the transients without affecting the other machines. The pump typically runs at 70–85% of maximum speed in steady state — leaving headroom for the VFD to compensate during transients without hitting the speed limit.

Configuration B: Mixed Napkin + Facial Tissue Lines

Larger converting plants often run a mix of products on the same vacuum system — 2–3 napkin machines alongside 1–2 facial tissue lines. Facial tissue converting typically demands slightly deeper vacuum than napkin folding because of the lighter sheet weight and more complex fold geometry. The 3700LC’s −45 kPa vacuum depth provides the margin to serve the facial tissue vacuum requirement while maintaining headroom for transient response.

Configuration C: 5–6 Lines, Multi-Shift Operation

At 5–6 folding machines — the upper end of the 37kW range — the pump runs closer to its rated capacity. For plants in this configuration running 20–24 hours/day, the investment case for the LC over a conventional vacuum pump is strongest because the absolute dollars saved scale with operating hours. If your operation matches this configuration, also consider the 45kW model — particularly if you anticipate adding lines within the equipment’s service life.

Configuration D: Paper Towel Converting

Paper towel converting lines typically run heavier sheet weights and wider web widths than napkin or facial tissue, requiring higher vacuum flow to grip and transport the sheet. The 3700LC’s 31 m³/min suction flow and −45 kPa vacuum depth cover most paper towel converting applications up to 2–3 parallel lines. For 4+ towel lines, evaluate the 45kW model.

Other Applications

While tissue paper converting is the primary application for the 37kW LC, the machine’s capability set also serves two important secondary markets.

Pneumatic Vacuum Conveying

Bulk solids — cement powder, fly ash, flour, plastic pellets, grain — are routinely transported by vacuum conveying systems where leaks pull air in rather than blowing product out. A roots blower vacuum pump pulls vacuum on a receiver vessel; bulk material is drawn through a pickup wand and pipeline and drops out at the receiver.

Most conveying systems batch — load, pull vacuum, transfer, stop. The VFD’s variable-speed capability means the pump draws significant current only during the transfer phase. Between cycles, it idles at low speed or stops, then restarts with soft start — no current spike, no mechanical shock, no belt wear from repeated direct-on-line starts. For conveying systems with frequent batch cycling, the soft-start feature alone can extend belt life by a factor of two or more compared to conventional direct-on-line vacuum pumps.

Large Wastewater Treatment / Centralized Air Supply

In pressure mode, the 3700LC delivers 31 m³/min at 25–45 kPa for large aeration basins, centralized air supply networks, and multi-point aeration systems. The VFD’s constant-pressure mode is particularly valuable in centralized air systems where different branches of the distribution network open and close independently — the drive compensates for the resulting pressure fluctuations without operator intervention.

Noise Levels

At 74–84 dB, the 3700LC operates 8–13 dB quieter than a conventional 37kW roots blower. In a tissue converting hall — where multiple pumps may be running simultaneously in the same building as production equipment and operators — the cumulative noise reduction is significant. In industrial pressure applications (conveying, aeration), the same noise reduction applies. A 10 dB reduction is perceived as roughly half as loud.

The noise control system is shared across the LC series: proprietary 4-chamber resonant silencer with split-flow destructive interference geometry, dual acoustic materials (high-density compound for low frequencies, non-asbestos absorber for high frequencies), and six-sided acoustic insulation lining the entire cabinet interior. The 3700LC’s larger cabinet volume (1500×1350 mm footprint vs 1400×1200 for the 15–30kW models) provides additional internal acoustic volume for the silencer.

What’s Inside

Dual-gearbox roots host. Two synchronized gearboxes share the torque load. At 37kW, load-sharing is mechanically significant — the torque transmitted per gear tooth is lower, reducing contact stress and extending gear life. Rated for 18 years of continuous service. Three-lobe rotors, CNC-machined as matched pairs, dynamically balanced before assembly. The rotors never touch each other and never touch the casing wall — the clearance gap eliminates gas-path wear.

The 3700LC uses a larger gearbox than the 15–30kW models to handle the higher torque and accommodate the DN200 outlet. The belt drive from the PMSM motor to the gearbox input shaft follows the same proven layout as the entire LC series and our classic SL roots blowers.

PMSM motor, 186 Nm torque. Rare-earth permanent magnets, no rotor windings, no resistive rotor heating — holds above 93% efficiency at partial load. At 37 kW, the torque earns its keep in both roles: it holds rotor speed as vacuum deepens toward −45 kPa and pushes against rising back-pressure up to 45 kPa with less belt slip than a conventional induction motor. Belt-driven through the larger gearbox sized for this power class.

Tuned VFD with dual drive curves. One set mapped to vacuum duty, one to pressure duty — selected at the control panel as constant-vacuum or constant-pressure mode, with soft start and built-in protection.

The full engineering behind the PMSM + VFD drivetrain — how the two work together to cut energy 30–65% — is explained on the LC Series Overview page. Here we focus on what the 37 kW size delivers for tissue converting and industrial duty.

Proprietary 4-chamber resonant silencer. Split-flow geometry, dual acoustic materials, six-sided cabinet insulation. Effective in both pressure and vacuum configurations — the silencer geometry is symmetric. The larger cabinet of the 3700LC provides greater internal acoustic volume, and the silencer geometry is scaled accordingly.

Integrated inlet filtration. Front-accessible, tool-free replacement. In vacuum mode, captures paper dust from tissue converting. In pressure mode, protects the blower from ambient dust in conveying and industrial environments. The VFD provides filter-loading indication through speed trending in both modes: when the motor runs consistently faster to maintain the same setpoint, the filter is loading.

Vibration isolation. High-elasticity silicone damping pads. No anchor bolts. No grouted foundation. The 3700LC’s larger cabinet footprint (1500×1350 mm) provides a stable base without the need for additional mounting hardware.

Maintenance

The 3700LC is designed for production environments where maintenance staffing is lean and unplanned downtime is expensive — whether it’s running in vacuum mode on a tissue line or pressure mode in a conveying system.

Weekly: Check the oil sight glass. Visually inspect the inlet filter — in tissue mill duty, paper dust loading drives the inspection frequency; in industrial pressure duty, ambient dust determines the interval.

Monthly: Check belt tension. The VFD’s soft-start extends belt life by eliminating the current spike of direct-on-line starting, but belts are wear items and require periodic inspection, as with any belt-driven machine. Tissue mills and conveying operations typically see longer belt life on LC machines than on conventional pumps because the soft start dramatically reduces the peak tension that causes belt stretch.

As indicated: Replace the inlet filter element. The VFD’s speed trending provides an objective indicator in both modes: when the motor is running consistently faster than baseline to maintain the same setpoint (vacuum or pressure), the filter is loading and approaching replacement.

No motor bearings to grease — the PMSM is sealed. The wet-sump splash lubrication system has no external oil pump, oil filter, or cooling water connections. Every major subsystem — silencer cartridges, filter elements, VFD, control components — is modular and individually replaceable without disturbing the rest of the machine.

Also Available: Complete LC Series for Tissue Paper

• 15kW LC → — Single tissue folding line, entry-level converting
• 22kW LC → — 2–3 folding machines, small-medium workshops
• 30kW LC → — 3–4 folding machines, medium-high line speeds
• 45kW LC → — 6–8+ folding machines, large tissue mills, multi-line vacuum systems

All five LC models share the same PMSM motor platform, VFD architecture, and modular cabinet design. A plant running multiple LC machines at different power ratings — whether in vacuum mode for tissue lines or pressure mode for conveying and aeration — has one spare parts inventory, one maintenance procedure, and one supplier. See the LC Series Energy-saving Roots Blower Vacuum Pump → for side-by-side comparison and a tissue paper power selection guide.

Frequently Asked Questions

Q: Is the 37kW LC the right vacuum pump for my tissue converting plant?

If you operate 4–6 tissue folding machines (napkin, facial tissue, and/or paper towel lines) running at 200–350 m/min, the 37kW LC in vacuum mode is typically the correct sizing. This is our most commonly sold model to tissue paper customers. For 3–4 machines, consider the 30kW. For 7+ machines or line speeds above 350 m/min, evaluate the 45kW. Send us your machine count, models, line speeds, and current vacuum pump specs — we’ll confirm sizing and calculate your payback.

Q: How much can we save on electricity with the 37kW LC?

In vacuum mode: a 37kW pump running 18 hours/day, 320 days/year at $0.12/kWh — a typical tissue mill duty cycle — saves $9,000 to $14,100 annually versus a conventional fixed-speed vacuum pump. In pressure mode: a 37kW blower on a conveying system running 16 hours/day, 300 days/year at $0.10/kWh saves $5,300 to $9,900 annually. For plants with 3+ machines, multiply accordingly. Payback on the price premium: 18–30 months. We include a site-specific payback calculation with every quote.

Q: Will the 37kW handle paper dust from tissue converting?

Yes. The integrated inlet filtration system is designed for the paper dust loading rates typical of tissue converting operations. The front-accessible filter cartridge is replaceable without tools. The VFD provides a practical filter-loading indicator: as the filter gradually loads, the VFD increases motor speed to maintain target vacuum. When the speed trend shows consistently higher RPM for the same vacuum setpoint, it’s time to change the filter — objective, no guesswork.

Q: Is the vacuum truly oil-free for tissue products?

Yes. The gas path (rotors + casing) is completely isolated from the gearcase lubrication system by labyrinth seals. No oil is injected, no oil mist migrates. Zero oil carryover. This is documented with material certificates and seal specifications supplied with every pump. For tissue manufacturers, this means no risk of oil stains on white product — a quality reject that can cost a customer relationship.

Q: What happens to vacuum when one folding machine stops for a reel change?

The VFD’s constant-vacuum mode absorbs the transient. When one machine on the common vacuum header reduces its draw (reel change, brief stop), the VFD detects the resulting vacuum rise and reduces motor speed within milliseconds. The other machines on the header see no perceptible change in vacuum level. No cascade. No misfed sheets on the lines that are still running.

Q: Can the 3700LC replace our existing 37kW roots blower or vacuum pump?

Yes — in either mode. Whether you’re replacing a vacuum pump on a tissue converting line or a pressure blower in a conveying system, the 3700LC matches the same pressure/vacuum ranges and process connections. The integrated cabinet (1500×1350×1400 mm) replaces your existing machine, separate motor base, external silencers, and standalone control panel with a single packaged unit. Send us the nameplate data from your existing equipment — we’ll confirm the performance match in the correct mode and calculate your payback.

Q: We run both tissue converting (vacuum) and pneumatic conveying (pressure). Can we standardize on one machine?

Yes — the 3700LC is the same host in both modes, so a plant running vacuum for tissue lines and pressure for conveying can use identical 3700LC units for both applications. That means one spare parts inventory, one maintenance procedure, one supplier. See the LC Series Energy-Saving Roots Vacuum Pumps overview for how the dual-mode platform works across all five power ratings.

Q: How much does a 37kW energy-saving roots blower and vacuum pump cost?

The SLDS-3700LC carries a higher upfront price than a conventional 37kW roots blower or vacuum pump, reflecting the PMSM motor, VFD drive, and integrated cabinet. The payback on that price difference through electricity savings alone is 18–30 months — faster for high-duty-cycle tissue mills and conveying operations. We quote within one working day. Send your flow, pressure/vacuum requirements, operating hours, and electricity rate for an exact price with a payback calculation.

Q: How does a roots vacuum pump work, and what does “positive displacement” mean?

A roots vacuum pump is a positive displacement machine: two three-lobe rotors counter-rotate inside the casing, synchronized by timing gears so they never touch. Each revolution carries a fixed volume of gas from the inlet to the outlet, drawing steady suction at the inlet (vacuum mode) or pushing gas to build pressure at the outlet (blower mode). Because the rotors run with a small non-contact clearance, the 3700LC moves large volumes at moderate vacuum depths (down to −45 kPa) — ideal for tissue sheet transport and pneumatic conveying, where you need high flow at modest vacuum rather than deep vacuum. The non-contact design also means no gas-path wear and 100% oil-free operation.