Roots Blower Inquiry

A roots blower inquiry is the first step in purchasing a positive displacement blower. The quality of your inquiry determines the quality of the quote you receive. Incomplete or incorrect inquiries lead to inaccurate quotes, wrong equipment, and unexpected costs. Based on reviewing thousands of inquiries over two decades, the most common mistakes are missing specifications, incorrect units, and incomplete application data.

This guide covers what to include in a roots blower inquiry, how to specify requirements, and how to compare quotes. Use it to get accurate pricing and avoid costly mistakes.

Table of Contents

• What Is a Roots Blower Inquiry?

• What to Include in Your Inquiry

• How to Specify Requirements

• Common Inquiry Mistakes

• How to Compare Quotes

• Red Flags in Quotes

• Frequently Asked Questions

• Final Thoughts

What Is a Roots Blower Inquiry?

A roots blower inquiry is a formal request for quotation (RFQ) sent to manufacturers or suppliers. It should include all technical and commercial specifications required for the supplier to provide an accurate quote.

A complete inquiry includes:

• Operating conditions (flow, pressure, temperature, altitude)

• Application details (what the blower is doing)

• Component specifications (motor, bearings, seals, coatings)

• Accessories required (silencers, VFD, filters, base frame)

• Commercial terms (delivery, payment, warranty)

• Documentation requirements (test reports, drawings)

Based on inquiry reviews, the most common mistake is incomplete information. An incomplete inquiry produces an incomplete quote – leading to unexpected costs and wrong equipment.

What to Include in Your Inquiry

1. Operating conditions.

• Flow required (ACFM or SCFM – specify which)

• Pressure required (psig or inches Hg)

• Inlet temperature range

• Ambient temperature range

• Site altitude

• Duty cycle (continuous or intermittent)

2. Application details.

• What is the blower doing? (aeration, conveying, vacuum, biogas)

• What is the gas? (air, biogas, corrosive, dusty)

• Any special requirements? (oil-free, explosion-proof, food-grade)

3. Component specifications.

• Motor efficiency: IE3 minimum for continuous duty

• Motor voltage and enclosure (TEFC, XP, TEBC)

• Bearing brand: SKF, FAG, NSK, or Timken

• Rotor material: cast iron, stainless steel, or coated

• Seal type: lip seals, labyrinth, or carbon-graphite

• Coating: hard chrome, epoxy, or PTFE

4. Accessories.

• Inlet silencer (with filter element)

• Discharge silencer

• Base frame and coupling

• VFD (if required)

• Inlet filter (specify micron rating)

• Acoustic enclosure (if required)

• Pressure gauge, temperature gauge

• Relief valve, check valve

5. Documentation.

• ISO 1217 test report

• Dimensional drawings

• Installation manual

• Spare parts list with pricing

• Warranty terms

• Certifications (CE, ATEX, UL)

6. Commercial terms.

• FOB point (factory or port)

• Delivery lead time

• Payment terms

• Warranty period (12 months from commissioning or 18 months from shipment)

• Incoterms (FOB, CIF, DDP)

How to Specify Requirements

Flow specification:

• Specify ACFM at operating conditions, not SCFM

• Include altitude and temperature for correction

• Example: "500 ACFM at 8 psig, 3,000 ft elevation, 90°F ambient"

Pressure specification:

• Specify pressure at blower discharge flange

• Include margin for fouling (1–2 psig)

• Example: "10 psig at discharge flange, with 2 psig fouling margin"

Motor specification:

• Specify efficiency class (IE3 minimum)

• Specify voltage and phase

• Specify enclosure (TEFC standard)

• Example: "IE3, 460V, 3-phase, 60Hz, TEFC"

Materials specification:

• Specify rotor material (cast iron, 316L, hard chrome)

• Specify casing material (ductile iron, stainless, epoxy coated)

• Specify seal type (lip, labyrinth, carbon)

• Example: "316L stainless rotors, labyrinth seals with buffer air"

Accessories specification:

• List all required accessories

• Specify pressure drop limits for silencers

• Specify VFD requirements (if applicable)

• Example: "Inlet silencer with 5-micron filter, discharge silencer"

Common Inquiry Mistakes

1. Using SCFM instead of ACFM.
Suppliers need ACFM at operating conditions. SCFM undersizes the blower. Always specify ACFM and provide altitude/temperature.

2. No pressure margin.
Systems clog – filters load, diffusers foul. Specify pressure with margin (1–2 psig). Sizing exactly at clean conditions guarantees overload.

3. No motor efficiency specified.
Supplier may quote IE2 to lower price. Specify IE3 minimum for continuous duty.

4. No bearing brand specified.
Supplier may use unbranded bearings. Specify SKF, FAG, NSK, or Timken.

5. No material specification.
Supplier may quote cast iron for corrosive/abrasive service. Specify required materials.

6. No accessories listed.
Supplier may quote blower only – silencers, VFD, base frame extra. List all required accessories.

7. Incomplete commercial terms.
Specify FOB point, delivery lead time, payment terms, warranty. Avoid surprises.

How to Compare Quotes

Step 1 – Verify specifications match.
Ensure all quotes are for the same specifications. If one quote uses IE2 and another uses IE3, compare apples to apples.

Step 2 – Check flow and pressure.
Verify flow is ACFM at operating conditions. Verify pressure includes margin.

Step 3 – Compare efficiency.
Request ISO 1217 test reports. Calculate overall efficiency. A 2% efficiency difference on 100 HP costs $2,400–3,000/year.

Step 4 – Check component quality.

• Bearing brand: SKF/FAG/NSK – or unbranded?

• Motor: IE3 – or IE2?

• Rotor: stainless/hard chrome – or cast iron?

• Seals: labyrinth – or lip?

Step 5 – Compare total cost of ownership.
Calculate 10-year total: purchase + energy + maintenance. Lowest quote may not be lowest total cost.

Step 6 – Check lead time and warranty.

• Lead time: 4–8 weeks standard

• Warranty: 12 months from commissioning – or from shipment?

Step 7 – Get everything in writing.
All specifications, pricing, and terms in writing. Verbal promises not binding.

Red Flags in Quotes

1. "Equivalent" bearings. Ask for actual brand. Low-cost bearings fail early.

2. SCFM instead of ACFM. Clarify units. SCFM quotes undersize blower.

3. No test report. Supplier may not test blowers. Require ISO 1217 test report.

4. "Standard" motor without efficiency class. IE3 is standard for continuous duty. IE2 is obsolete.

5. Cast iron rotors for corrosive/abrasive. Specify stainless or coated.

6. No silencer pressure drop specified. Silencer adds pressure drop – affects performance.

7. Warranty from shipment, not commissioning. Blower may sit in warehouse – warranty expires.

8. 100% upfront payment. Reputable suppliers accept 30% deposit, 70% before shipment.

9. No spare parts pricing. Ask before purchase – some suppliers raise prices after.

10. Unclear FOB terms. Clarify shipping costs – unexpected costs can add 10–20%.

Frequently Asked Questions

1. What should I include in a roots blower inquiry?
Operating conditions (flow ACFM, pressure psig, temperature, altitude), application details, component specifications (motor, bearings, seals, coatings), accessories (silencers, VFD, filters), commercial terms (lead time, payment, warranty), and documentation requirements (test reports, drawings).

2. What is the most common mistake in a roots blower inquiry?
Using SCFM instead of ACFM. SCFM is at standard conditions (14.7 psia, 60°F). At altitude or high temperature, ACFM is higher. Sizing with SCFM undersizes the blower. Always specify ACFM and provide altitude and temperature.

3. How do I specify flow correctly?
Specify ACFM at operating conditions. Include altitude and temperature. Example: "500 ACFM at 8 psig, 3,000 ft elevation, 90°F ambient." If you have SCFM, provide it with the correction: "500 SCFM corrected to ACFM at site conditions."

4. What motor efficiency should I specify?
IE3 minimum for continuous duty. IE2 saves upfront cost but loses energy for 15+ years. IE3 pays back in 18–24 months. IE4 for high energy cost or very long duty. Specify "IE3 motor" in the inquiry.

5. What bearing brand should I specify?
SKF, FAG, NSK, or Timken. These are the industry standards. Specify the brand in the inquiry. "Equivalent" bearings are not equivalent – they fail earlier.

6. What accessories should I include?
Inlet silencer (filtration + noise reduction), discharge silencer (pulsation damping), VFD (variable speed), base frame and coupling, pressure and temperature gauges, relief valve, check valve. List all required accessories – don't assume they are included.

7. What is the difference between FOB and delivered price?
FOB is the price at the factory or port. Delivered price includes shipping, insurance, and import duties. FOB China to US: add $800–2,500 for shipping. Always ask for delivered price to compare total cost.

8. How do I compare quotes from different suppliers?
Verify specifications match. Check flow and pressure units. Compare efficiency (request ISO 1217 test reports). Check component quality (bearings, motor, rotors). Calculate total cost of ownership (purchase + energy + maintenance over 10 years). Compare lead time and warranty.

9. What is the typical lead time for a roots blower?
4–8 weeks for standard units (cast iron, three-lobe, IE3 motor). 10–14 weeks for stainless steel rotors, helical profiles, or special coatings. Expedited delivery (2–3 weeks) adds 15–25% premium. Always confirm lead time in writing.

10. What warranty should I expect?
12 months from commissioning or 18 months from shipment – whichever comes first. Extended warranty available for 24–36 months at 3–5% of blower cost. Warranty excludes damage from debris, blocked filters, misalignment, or improper lubrication.

11. How do I verify efficiency claims?
Request ISO 1217 test report for the actual blower model. The report must show flow, pressure, shaft power, and temperature at three operating points. Calculate overall efficiency = (flow × pressure) / (power × 229). Compare to manufacturer claims. Reject suppliers who cannot provide test reports.

12. What spare parts should I include in the inquiry?
Request pricing for one set of bearings, one complete seal kit, two inlet filter elements, and one belt set if belt drive. For remote sites, add one timing gear set. Ask for spare parts pricing before placing the order.

13. What is the payback for IE3 vs IE2 motor?
IE3 motor adds 15–20% to motor cost. On 100 HP continuous duty (8,000 hours/year, $0.10/kWh), IE3 saves approximately $1,500–2,000 annually compared to IE2. Payback: 18–24 months. For continuous duty, IE3 pays.

14. How do I handle payment terms?
Standard: 30% deposit with purchase order, 70% before shipment. Letter of credit for larger orders. Avoid suppliers demanding 100% prepayment. For large orders ($100,000+), negotiate 30% deposit, 40% prior to assembly, 30% before shipment.

15. What documentation should I request?
ISO 1217 test report, dimensional drawings, installation manual, spare parts list with pricing, warranty terms, material certificates (for stainless steel), and applicable certifications (CE, ATEX, UL). Request all documentation before payment.

Final Thoughts

After reviewing thousands of roots blower inquiries, here is my practical advice:

The quality of your inquiry determines the quality of your quote. Incomplete inquiries produce inaccurate quotes. Be specific. Provide all operating conditions, component specifications, and accessories. The more information you provide, the better the quote.

Specify ACFM, not SCFM. This is the most common mistake. SCFM at standard conditions is not the same as ACFM at your site. Correct for altitude and temperature. Provide altitude and temperature in the inquiry.

Specify IE3 motor and bearing brand. Suppliers may cut costs with lower-grade components. Specify IE3 motor and SKF/FAG/NSK bearings. This ensures quality.

Get everything in writing. All specifications, pricing, and terms in writing. Verbal promises are not binding. If it's not on the quote, it's not included.

The bottom line. A well-written roots blower inquiry gets you accurate quotes, the right equipment, and no surprises. Zhanggu and other manufacturers respond to complete inquiries with complete quotes. Take the time to specify correctly. It saves time and money in the long run.