6.8 HP / 140 L / 8 bar Oil-Free Silent Air Compressor — Product, Sizing and Export Listing Guide

A 6.8 HP (≈5.07 kW) oil-free silent piston compressor with a 140 L receiver and 8 bar working pressure is a mid-size clean-air package for dental clinics, laboratories, aesthetic rooms, small workshops, painting, packaging, instrument air and light industrial stations. “Noiseless” should be treated as a marketing label; for quotations use a measured sound level, true FAD at 8 bar (not displacement), and an oil-free purity statement supported by filters/dryer and, where required, ISO 8573‑1 testing.

1. Indicative specification (export / factory-direct)

Rule for listings: never advertise “411/760 L/min high flow” without stating whether it is displacement at 0 bar or FAD at 8 bar. Buyers size clinics and factories on FAD at working pressure.

2. Why 6.8 HP + 140 L + 8 bar is a balanced package

• Flow headroom​ — 6–7 HP oil-free multi-head can serve several simultaneous tools. Reference 6 HP/140 L dental units deliver around 360 L/min at 8 bar ; 5 HP/140 L units quote 250 L/min FAD at 7 bar and up to 760 L/min displacement . A true 6.8 HP build should be specified against your peak demand, not the highest marketing number.

• 8 bar standard​ — dental handpieces, scalers, labs, small spray, packaging and instrument air normally run 5–8 bar; 8 bar gives regulator headroom.

• 140 L buffer​ — smoother than 60–100 L portables for multi-tool or multi-chair peaks; still movable on wheels, though heavier than 24–65 L cabinets.

• Oil-free​ — no cylinder lubrication, self-lubricating rings/valves; lower contamination risk for dental, lab, food, pharma and paint. Final purity still depends on drying and filtration.

3. “Noiseless / ultra-silent” — honest claims

For a 6.8 HP piston unit:

• Open piston plant room: often 70–84 dB(A) depending on speed/head count; one 3.3 kW/140 L “soundproof” model is listed at 84 dB(A) , showing that enclosure and head design matter more than tank size.

• Silent cabinet multi-head piston: commonly ≤70 dB(A) at 1 m; 6 HP/140 L dental examples list ≤70 dB , 5 HP/140 L piston ≤70 dB with cabinet claims down to ≤56 dB .

• Scroll oil-free 5–7.5 kW: much quieter in many cases, e.g. oil-free scroll ranges 4–15 kW at 8 bar and Anest Iwata scroll pumps 0.75–7.5 kW at 8–10 bar with “silent” positioning ; but scroll is a different product/price class.

Listing copy should say: “Low-noise oil-free compressor, XX dB(A) at 1 m loaded, per ISO 3744/ISO 2151” — not “noiseless.”

4. Oil-free does not automatically mean medical/food air

Specify the full clean-air train:

1. Oil-free pump​ — no lubricating oil in cylinder; self-lubricating piston rings or scroll with oil-free compression chamber.

2. Aftercooler​ — reduce discharge temperature before tank/filters.

3. Moisture separation + dryer​ — refrigerated ≈ +3 °C pressure dew point for general/lab/dental support; desiccant −40 °C or lower for strict medical/food/pharma.

4. Filtration​ — coalescing + particulate as minimum; activated carbon if odour/oil vapour matters; sterile 0.01–0.22 µm terminal for aseptic/medical breathing-support uses.

5. Purity certification​ — for compressed air, request ISO 8573‑1 class for oil/particles/water and the sampling point/method. “Class 0” is only valid with a total-oil test, not a marketing “oil-less” label.

6. Tank hygiene​ — epoxy/internal coating reduces corrosion and particulate shedding; automatic drain prevents moisture accumulation.

Use case guidance: dental/lab/light food packaging can use oil-free + dryer + graded filters; ICU/OR/anaesthesia/breathing air requires a validated medical-air system under local medical-gas codes, not a single portable 6.8 HP box.

5. Applications

• Dental clinic​ — 2–4 chairs with handpieces, scalers, micro-motors, drying. Size from true 8 bar FAD; a 6 HP/140 L model at 360 L/min may suit 2–3 busy chairs, marginal for 4 fully simultaneous operative chairs.

• Laboratory / analytical​ — sample prep, gloveboxes, small instruments, autoclave feed (not steam), particle/culture tools needing oil-free dry air.

• Aesthetic / dermatology​ — pneumatic platforms, laser handpiece cooling, minor surgical air.

• Workshop / MRO​ — nail/stapler, small grinders/sanders, tire inflation, occasional spray. 140 L handles intermittent peaks better than small pancake compressors.

• Painting / finishing​ — pair with aftercooler, dryer and coalescing/carbon filters; confirm CFM per spray gun at 8 bar.

• Food / pharma / packaging​ — use Class 0 evidence, coated tank, dryer and food-grade filtration.

• Oxygen concentrator / generator feed​ — oil-free is preferred; confirm flow, pressure and inlet filtration.

6. Duty cycle, cooling and staging

• Single-stage oil-free piston​ at 8 bar is common for 5–7 HP small packages; multi-head parallel cylinders improve heat removal and balance.

• Continuous running​ — standard oil-free piston is often intermittent/shift-rated. For 24/7 clinic/lab, derate, add forced cooling, or choose oil-free scroll/screw. A 5.5 kW oil-free piston reference runs two-stage with tank options and 75 dB(A) at 1.5 m ; scroll 5.5 kW lab units may list around 55 dB(A) but at different flow/price.

• Thermal protection​ — motor thermal cutout, head fans, cabinet temperature sensor; multi-head controllers can start/stop pumps in rotation to reduce heat .

• Tank fill/recovery​ — specify cut-in/cut-out pressure, motor restart delay and unloader to avoid short-cycling on a 140 L receiver.

7. Factory-direct quotation checklist

For OEM/private-label 6.8 HP / 140 L / 8 bar oil-free silent:

1. Performance​ — FAD at 5/7/8 bar in L/min; displacement vs FAD clearly separated; reference conditions.

2. Power​ — input watts, shaft HP, single/three-phase, voltage, starting current, motor insulation/class.

3. Pump build​ — number of cylinders/heads, rpm, single/multi-stage, ring/packing material, valve material.

4. Noise​ — dB(A) at 1 m loaded, test standard, cabinet type, fan speed control.

5. Tank​ — 140 L, steel grade, coating, PED/ASME/local code, auto drain, gauge/relief/regulator.

6. Oil-free proof​ — “no cylinder oil” statement; ISO 8573‑1 Class 0 oil report if claimed, with sampling point.

7. Dryer/filter options​ — refrigerated/desiccant PDP, micron grades, carbon, sterile terminal.

8. Controls​ — pressure switch vs PLC, digital display, alternation, IoT/alarms, remote start.

9. Certificates​ — CE, ISO 9001, optional ISO 13485/FDA-style dental, RoHS, pressure-equipment compliance.

10. Commercial​ — EXW/FOB/CIF, MOQ, lead time, OEM logo, manuals, warranty (piston commonly 1 year , some silent dental 2 years ), spare rings/valves/filters/drain.

8. Ready-to-post English listing copy

6.8 HP Oil-Free Silent Air Compressor, 140 L Tank, 8 bar​

Oil-free piston compressor for dental, laboratory, workshop and light industrial clean-air duty. 5.5 kW-class motor delivers stable 8 bar output through a low-noise cabinet and multi-head cooling system. The 140 L receiver buffers intermittent demand; self-lubricating piston rings and oil-free cylinders provide clean air without cylinder lubrication. Auto start-stop pressure control, aftercooler, intake filtration and optional refrigerated/desiccant dryer support dry, particle-controlled air for dental, medical-support, food and instrument applications.

Specifications: 6.8 HP / ≈5.07 kW • 140 L receiver • 8 bar working (10 bar max optional) • FAD XXX L/min at 8 bar (displacement up to XXX L/min depending on head config) • noise ≤XX dB(A) at 1 m loaded • 220 V 1-phase or 380 V 3-phase • auto drain • regulator • safety relief • aftercooler • optional ISO 8573‑1 Class 0 oil report. CE/ISO available; OEM logo, voltage and dryer/filter train customizable.

Replace XXX/XX with factory test data. If the factory can only give displacement at 0 bar, mark it clearly as “displacement, not FAD.”

9. FAQ

What is the real airflow of a 6.8 HP / 140 L / 8 bar oil-free compressor?​

It depends on head count, rpm, cooling and stage design. Comparable references include 6 HP/140 L dental at 360 L/min FAD, 8 bar ; 5 HP/140 L at 250 L/min FAD, 7 bar and 760 L/min displacement ; 6.72 HP/120 L at 420 L/min displacement, 8 bar . Ask for FAD at 8 bar, not displacement.

Is it really noiseless?​

No compressor is truly noiseless. A 6.8 HP piston in a silent cabinet is often ≤70 dB(A) at 1 m ; some acoustic cabinets claim ≤56–62 dB(A) , while open or smaller-enclosure units can be much louder. For library-quiet rooms, use oil-free scroll or install the piston in a remote plant room.

Can it be used for dental/medical breathing air?​

For dental instrumental air and lab air, oil-free + dryer + filters is usually sufficient. For ICU/OR/anaesthesia/breathing, design a certified medical-air system with redundancy, sterile filtration, alarms and local medical-gas compliance; do not rely on a single portable 6.8 HP unit.

What tank pressure and relief are safe?​

Set working 8 bar, relief above working but within tank MAWP, cut-out around 8.5–9 bar depending on design. Use PED/ASME/local-coded 140 L tank and automatic drain.

Single-phase or three-phase?​

If 6.8 HP is genuine shaft output on 220 V single-phase, current is high; 380/415 V three-phase is preferable for clinic/factory continuous duty. Verify site power before quoting.

How long do oil-free piston rings last?​

Depends on discharge temperature, humidity, duty cycle and gas cleanliness. Offer scheduled inspection of rings/valves/filters; multi-head cooling and aftercooling extend service intervals versus a single hot head.

What dryer should I pair with it?​

Refrigerated for general dental/lab/instrument (approx. +3 °C PDP); desiccant −40 °C or lower for medical/food/pharma/严格的 sterile use. Always add coalescing + particulate filters, and carbon only if odour/oil vapour is a concern.

A 6.8 HP / 140 L / 8 bar oil-free “noiseless” compressor is best sold on tested FAD, measured dB(A), tank code and a complete dryer/filter train—rather than on displacement numbers or the word “noiseless.” With multi-head cooling, auto drain, epoxy-coated receiver and ISO 8573‑1 documentation where needed, it serves dental, lab, workshop and clean-light-industrial air reliably.