Blower suppliers in Hyderabad: Roots, screw and side-channel blowers

Blower or compressor: where the line falls

A blower moves large volumes of air against a small pressure rise. A compressor makes high pressure for tools and plant air. The two overlap only in a narrow band, and using the wrong one is expensive: throttling 7 bar(g) plant air down to 0.5 bar(g) for aeration or agitation wastes most of the energy spent compressing it.

The band from about 1 to 3.5 bar(g) is a grey area served by low-pressure compressors or two-stage blowers. The full comparison is on blowers vs compressors.

Choosing the blower technology

Pick the technology from flow, differential pressure, running hours and how much the demand varies. Flow ranges below are typical; individual models vary.

Detail on each: Roots blowers, screw blowers, side-channel blowers and centrifugal and turbo blowers.

Worked example: aeration air for a 300 KLD STP

Apartment communities, hospitals, hotels and IT campuses in and around Hyderabad run their own sewage treatment plants, typically 100–1,000 KLD. Blowers are usually the largest electrical load on site. Here is a first-pass sizing using an oxygen-demand method. The figures are illustrative; the process designer’s oxygen demand, diffuser data and mixing requirement govern.

Inputs (illustrative): 300 m³/day sewage, BOD 250 mg/l, 95% removal; oxygen allowance 1.5 kg O₂ per kg BOD removed (covering carbonaceous demand and some nitrification); fine-bubble diffusers at 4.0 m depth with a field oxygen transfer efficiency of 8%; peak factor 1.5.

1. BOD load: 300 m³/d × 250 g/m³ = 75 kg/d. Removed: 75 × 0.95 = 71.25 kg/d.
2. Oxygen demand: 71.25 × 1.5 = 106.9 kg O₂/d = 4.45 kg O₂/h.
3. Oxygen in standard air (20 °C, 1.01325 bar(a)): air density 1.204 kg/m³ × 0.232 kg O₂/kg air = 0.279 kg O₂/m³.
4. Oxygen actually transferred: 0.279 × 0.08 = 0.0223 kg O₂ per m³ of air.
5. Average air: 4.45 ÷ 0.0223 = about 199 m³/h at standard conditions. Peak: 199 × 1.5 = about 299 m³/h (about 5.0 m³/min).
6. Convert to the blower inlet in a Hyderabad summer (0.950 bar(a), 45 °C): factor = (1.01325 ÷ 0.950) × (318.15 ÷ 293.15) = 1.158. Peak inlet flow = 299 × 1.158 = about 346 m³/h, 5.77 m³/min or 204 cfm.

That 15.8% uplift is why a blower sized from a standard-air figure on a sea-level datasheet runs short of air in May. Also check the diffuser maker’s minimum air per diffuser and the tank’s mixing requirement; in small tanks and MBBR reactors, mixing air sometimes exceeds the oxygen figure.

Worked example: discharge pressure and motor power

Continuing the same STP (illustrative):

1. Static head at 4.0 m: 1,000 kg/m³ × 9.80665 × 4.0 ÷ 100,000 = 0.392 bar.
2. Add diffuser loss 50 mbar, pipework and valves 30 mbar, margin 20 mbar: discharge = 0.392 + 0.100 = 0.492 bar(g) (7.1 psig).
3. Inlet pressure after a 10 mbar filter-silencer loss: 0.950 − 0.010 = 0.940 bar(a). Discharge absolute: 0.950 + 0.492 = 1.442 bar(a). Differential 0.502 bar; pressure ratio 1.442 ÷ 0.940 = 1.534. Inlet volume at 0.940 bar(a): 346 × 0.950 ÷ 0.940 = 350 m³/h = 0.0971 m³/s.
4. Adiabatic air power: P = 3.5 × p1 × Q1 × (r^0.2857 − 1) = 3.5 × 94,000 Pa × 0.0971 m³/s × (1.534^0.2857 − 1) = 3.5 × 94,000 × 0.0971 × 0.1300 = about 4.2 kW.
5. Shaft power at an overall efficiency of 55% (typical for a small Roots package): 4.15 ÷ 0.55 = about 7.6 kW.
6. Ideal discharge temperature from a 45 °C inlet: 318.15 × 1.534^0.2857 = 359.5 K, about 86 °C; the real figure is higher.

A 7.5 kW motor would already be overloaded, with nothing left for filter loading or diffuser fouling, so the motor goes up a size: 9.3 kW (12.5 hp) or 11 kW (15 hp), depending on the maker’s power figure at the chosen speed and the drive losses, with one duty and one standby blower. The water depth sets 80% of the pressure here; diffusers mounted 0.5 m deeper than drawn add 49 mbar, which raises both power and discharge temperature. Larger plants with variable load should read aeration blower turndown and low-pressure aeration blower integration.

Screw blower or Roots blower: when the energy saving is real

A screw blower compresses air inside its rotors; a Roots blower pushes air into the discharge, where back-flow does the compression. The penalty for external compression grows with differential pressure. The table compares an illustrative 20 m³/min duty at a Hyderabad inlet of 0.940 bar(a), assuming a Roots package efficiency of 78% against its ideal (isochoric) work and a screw package efficiency of 72% against isentropic work, both including drive and mechanical losses. On ideal work alone the Roots penalty is about 11% at 0.3 bar and 29% at 0.9 bar; the package savings below are smaller because the assumed package efficiencies differ (78% against 72%, the screw figure carrying gear and VSD losses). Real figures depend on the models compared.

Read it honestly: at 0.3 bar a screw blower barely pays; at 0.7 bar and above with long hours it usually does. Before replacing a Roots blower, log its actual differential, power and hours for a week. Lowering header pressure, cleaning diffusers and controlling air to dissolved oxygen often save more than a machine change. A larger worked comparison is on the screw blowers page.

Sizing for Hyderabad heat, altitude and power

• Air density. At 0.950 bar(a) and 45 °C, air density is 1.040 kg/m³ against 1.204 kg/m³ at 20 °C and sea level: 13.6% less mass for the same inlet volume. A positive-displacement blower still moves its rated m³/min, but delivers less oxygen and less conveying air per minute. Size on mass or standard flow converted to the worst inlet condition.
• Discharge temperature. Hot intake plus high differential pushes discharge temperature toward the relief and trip limits. Draw intake air from outside or a shaded, ventilated point, never from inside a hot blower room.
• Blower rooms and hoods. Acoustic hoods must ventilate the heat of the motor, casing and discharge pipe. Rooms that trap heat cause summer trips. See blower pulsation and silencing.
• Dust. Fine dust in industrial estates loads inlet filters quickly in dry months; every 10 mbar of filter loss adds differential and power. Fit a differential gauge.
• Monsoon peaks. STP inflow rises in the monsoon; standby blowers and diffuser grids must cope with the wet-season peak.
• Voltage and generators. Many STPs run on DG sets during outages. Check that the starter type and generator can take the blower’s starting current with an unloading valve open.

Pneumatic conveying blowers

Dilute-phase conveying of cement, flour, plastic granules, fly ash and food powders typically uses Roots or screw blowers at about 0.3–1.0 bar(g), or vacuum conveying at a few hundred mbar below atmosphere. The conveying designer sets the pick-up velocity and line pressure; the blower must then deliver that flow at the worst-case pressure and the hottest inlet, with a relief valve set above the normal line pressure. Hot discharge air can soften some plastics and sugars, so check discharge temperature against the product. Package and sizing detail is on pneumatic conveying blower packages.

Blower service checklist

The common faults behind breakdown calls: high discharge temperature (clogged filter, fouled diffusers, closed valve, hot intake), knocking (oil starvation, timing gear wear, rotor contact from overheating), low delivery (slipping belts, worn clearances, passing relief valve) and oil in the air (seal wear, overfilling, blocked vents). For a measured performance check, see vacuum and blower performance acceptance.

How Reddy Compressors helps

• Independent multi-brand supplier at Tarnaka, Secunderabad, operating since 2002; not an authorised dealer of any brand, with tie-ups with all major and reputed brands.
• Roots, screw, side-channel and centrifugal blowers: sales of new and used/refurbished units, rental, service and spare parts.
• Rental blowers for breakdowns, overhauls and temporary capacity, plus compressors and vacuum pumps for the same site.
• 20+ service engineers and technicians covering Telangana, Andhra Pradesh and districts within about 300 km of Hyderabad; supply across India and service elsewhere on a project basis.
• Open 7 days, 8:30–20:30. Call or WhatsApp 99590 60718 or 92468 88812, or email reddycompressors@gmail.com.

What to send us

• The application: STP or ETP aeration, conveying, process air, backwash, vacuum duty.
• Flow required (m³/min, m³/h or cfm, and whether standard or inlet), and discharge pressure or water depth.
• For aeration: plant capacity in KLD or MLD, diffuser type and depth, tank count.
• Running hours per day and how much demand varies.
• For an existing blower: nameplate photo, the symptom, belt and pulley sizes, and current readings.
• Site location, power supply or DG set, and room conditions.

Frequently asked questions

Who are the Roots blower suppliers in Hyderabad?

Reddy Compressors, Tarnaka, Secunderabad, is an independent multi-brand supplier of twin-lobe and tri-lobe Roots blowers, new and used/refurbished, and also rents, services and supplies spares for them. We are independent and not tied to one brand, so we start from your flow, pressure and running hours and then shortlist machines. For STPs we size from the plant capacity and diffuser depth. Send the duty or a nameplate photo on WhatsApp at 99590 60718.

What is a rotary screw blower?

It is a low-pressure, oil-free screw machine for blower duties, typically about 0.5–1.2 bar(g), which compresses the air inside its rotors instead of relying on back-flow at the discharge as a Roots blower does. That is why it uses less power at higher differentials and is usually sold with a VSD. In Hyderabad it makes most sense on STPs, ETPs and conveying lines that run long hours at 0.5 bar(g) or more. How it works and how to select one is on our screw blowers page.

Is a low pressure screw blower better than a Roots blower?

It depends on your site’s differential and running hours. In the illustrative comparison above, a screw blower saves about 8% of shaft power at 0.5 bar, 12% at 0.7 bar and 16% at 0.9 bar. At 0.3–0.4 bar, or for a few hours a day, the saving is small and a Roots blower is often the better value: lower cost, simpler to rebuild. Log your existing blower’s differential, power and hours before deciding, and fix diffuser and header pressure problems first.

Do you offer blower service in Hyderabad?

Yes. We service Roots, screw, side-channel and centrifugal blowers across Telangana, Andhra Pradesh and districts within about 300 km of Hyderabad: belt and oil service, filter and silencer work, relief and non-return valve checks, bearing and seal replacement, and diagnosis of overheating, knocking or low delivery. Spares are identified from the nameplate and the old part before quoting. Service elsewhere in India is offered on a project basis.

Can I rent a blower for an STP in Hyderabad?

Yes. Blower rental is commonly used while an STP blower is overhauled, during commissioning, or for temporary extra capacity. To match a hire blower, send the flow, discharge pressure or diffuser depth, the pipe connection size, supply voltage or DG set details, and how long you need it. A hire blower must be set up with its relief valve, non-return valve and silencers like a permanent unit.

Why does my Roots blower overheat in summer?

Hot intake air raises discharge temperature for the same pressure ratio, and summer often coincides with loaded filters, fouled diffusers and blower rooms with poor ventilation. In the worked example above, a 45 °C intake gives an ideal discharge of about 86 °C at only 0.49 bar(g), before losses. Check filter differential, discharge pressure against the commissioning value, oil level, belt tension and where the intake air comes from.

Can I use my air compressor instead of a blower?

For small or occasional jobs, yes, but it is costly for continuous duty. A compressor spends its energy reaching 7 bar(g); regulating that down to 0.5 bar(g) for aeration or agitation throws most of it away. For continuous low-pressure air, a blower typically uses a fraction of the power. Measure the compressed air used, convert it to power and compare with a correctly sized blower.

Related pages

• Centrifugal and turbo blowers
• Roots blowers
• Screw blowers
• Side-channel blowers
• Blowers vs compressors
• Wastewater aeration blower turndown
• Blower pulsation and silencing
• Pneumatic conveying blower packages
• Reddy Compressors in Hyderabad