Explosion Proof Roots Blower
Explosion Proof Roots Blower
An explosion proof roots blower is designed for operation in potentially explosive atmospheres – where flammable gases, vapors, or dusts may be present. ATEX certification (Europe) or Class I/II (North America) is mandatory. Explosion proof blowers incorporate spark-resistant rotors, explosion-proof motors, gas-tight seals, and temperature monitoring.
Based on commissioning experience across chemical plants, oil refineries, biogas facilities, and grain handling operations, explosion proof roots blowers are essential for safety in hazardous areas. Non-explosion proof blowers in these environments create explosion risk – and legal liability.
This guide covers explosion proof requirements, ATEX certification, hazardous area classifications, and selection for explosive environments.
Table of Contents
What Is an Explosion Proof Roots Blower?
Hazardous Area Classifications
ATEX Directive Overview
Explosion Proof Requirements
Main Components – Explosion Proof Upgrades
Types Comparison Table
Industrial Applications
Engineering Advantages
Common Problems and Troubleshooting
Selection Guide
Cost Factors and Pricing
Procurement Considerations
Frequently Asked Questions
Final Thoughts
What Is an Explosion Proof Roots Blower?
An explosion proof roots blower is a positive displacement rotary lobe machine designed and certified for use in potentially explosive atmospheres. Explosion proof certification ensures the blower does not create ignition sources – sparks, hot surfaces, or static electricity – that could ignite explosive gas or dust mixtures.
Explosion proof features:
Explosion-proof motor (Ex d, Ex e, Ex n)
Spark-resistant rotors (aluminum, bronze, stainless steel)
Non-sparking materials
Gas-tight seals
Temperature monitoring (T-class)
Grounding and static dissipation
ATEX certification (Europe) or Class I/II (North America)
Based on hazardous area installation records, explosion proof roots blowers are mandatory for biogas, chemical, oil and gas, grain handling, and pharmaceutical applications with explosion risk. Non-explosion proof blowers in these applications are a serious safety hazard.
Hazardous Area Classifications
North America (Class/Division system):
| Classification | Description | Typical Applications |
|---|---|---|
| Class I, Division 1 | Flammable gases present during normal operation | Chemical plants, refineries |
| Class I, Division 2 | Flammable gases present only under abnormal conditions | Storage areas, wellheads |
| Class II, Division 1 | Combustible dust present during normal operation | Grain handling, coal |
| Class II, Division 2 | Combustible dust present only under abnormal conditions | Dust collection |
Europe/International (Zone system – ATEX):
| Classification | Description | Typical Applications |
|---|---|---|
| Zone 0 | Continuous explosive atmosphere | Inside tanks, vessels |
| Zone 1 | Likely explosive atmosphere | Chemical processing |
| Zone 2 | Unlikely explosive atmosphere | Storage, wellheads |
| Zone 20 | Continuous explosive dust | Inside dust collectors |
| Zone 21 | Likely explosive dust | Grain processing |
| Zone 22 | Unlikely explosive dust | Dust collection areas |
Gas groups (ATEX):
| Group | Representative Gas | Hazard Level |
|---|---|---|
| IIA | Propane | Least hazardous |
| IIB | Ethylene | Intermediate |
| IIC | Hydrogen, Acetylene | Most hazardous |
Temperature classes:
| Class | Maximum Surface Temperature |
|---|---|
| T1 | 450°C (842°F) |
| T2 | 300°C (572°F) |
| T3 | 200°C (392°F) |
| T4 | 135°C (275°F) |
| T5 | 100°C (212°F) |
| T6 | 85°C (185°F) |
ATEX Directive Overview
ATEX Directive 2014/34/EU:
Applies to equipment in potentially explosive atmospheres
Covers electrical and non-electrical equipment
Requires certification by notified body for Category 1 and 2
Requires documentation and marking
Mandatory for EU member states
Equipment categories:
| Category | Zone (Gas) | Zone (Dust) | Protection Level |
|---|---|---|---|
| 1G | Zone 0 | N/A | Very high |
| 1D | N/A | Zone 20 | Very high |
| 2G | Zone 1 | N/A | High |
| 2D | N/A | Zone 21 | High |
| 3G | Zone 2 | N/A | Normal |
| 3D | N/A | Zone 22 | Normal |
For roots blowers:
Category 2G is most common (Zone 1 gas applications)
Category 3G for Zone 2 (less hazardous)
Category 2D for Zone 21 dust applications
Explosion Proof Requirements
1. Explosion-proof motor.
Ex d (flameproof): most common for roots blowers
Ex e (increased safety): less common
Ex n (non-sparking): for Zone 2
Motor must be ATEX certified
2. Spark-resistant rotors.
Aluminum: lightweight, spark-resistant
Bronze: non-sparking, higher strength
Stainless steel: corrosion resistant, spark-resistant
Cast iron is not acceptable for ATEX
3. Non-sparking materials.
Casing: ductile iron with coating or stainless steel
Hardware: non-sparking materials
Gaskets: anti-static materials
4. Gas-tight seals.
Labyrinth seals with buffer gas
Double lip seals with purge
Magnetic seals (zero leakage)
Prevent gas leakage to atmosphere
5. Temperature monitoring.
Thermocouple at discharge
Automatic shutdown at set temperature
T-class compliance
6. Grounding.
All piping and equipment grounded
Static electricity dissipation
Grounding straps on flanges
7. ATEX marking.
CE marking with notified body number
ATEX classification (II 2G c T4, etc.)
Equipment identification
Main Components – Explosion Proof Upgrades
Rotor (impeller). Most critical for explosion proof compliance. Cast iron not acceptable – sparks on impact. Options: aluminum (lightweight, spark-resistant), bronze (non-sparking, higher strength), stainless steel (corrosion + spark-resistant). Expected lifespan: 25,000–40,000 hours.
Timing gears. Helical gears standard. Must be non-sparking materials. Inspection: measure backlash annually (0.05–0.10 mm).
Bearings. C3 or C4 clearance standard. Must be designed for temperature monitoring. Lifespan: 25,000–35,000 hours.
Casing. Ductile iron with epoxy coating or stainless steel. Must be conductive (grounding).
Shaft seals. Gas-tight seals mandatory – labyrinth with buffer gas, double lip with purge, or magnetic. Failure mode: gas leakage creates explosion hazard.
Motor. Ex d (flameproof) most common. Must be ATEX certified for gas group and temperature class.
Temperature monitoring. Thermocouple at discharge with shutdown at T-class limit.
Grounding. All components grounded.
Types Comparison Table
| Type | Pressure Range | Efficiency | Typical Lifespan | ATEX Suitability |
|---|---|---|---|---|
| Twin Lobe | 2–10 psig | 65–72% | 30,000+ hours | Limited – lower efficiency |
| Three Lobe | 2–15 psig | 72–78% | 35,000+ hours | Industry standard |
| High Pressure | 10–20 psig | 68–74% | 25,000–35,000 hours | Biogas, chemical |
| Vacuum Type | -5 to -12 psig | 60–68% | 25,000–30,000 hours | Vacuum conveying |
For explosion proof, three-lobe with spark-resistant rotors and Ex d motor is standard.
Industrial Applications
Biogas and landfill gas. Methane (50–70%), explosive. ATEX Zone 1 or 2. Category 2G, IIB, T3/T4. Stainless steel rotors. Explosion-proof motor. Gas-tight seals. Temperature monitoring.
Chemical plants. VOCs, hydrogen, solvents. ATEX Zone 1 or 2. Category 2G, IIB or IIC. Spark-resistant rotors. Gas-tight seals. Ex d motor.
Oil and gas refineries. Hydrocarbons, hydrogen. ATEX Zone 1 or 2. Category 2G, IIB or IIC. Bronze or stainless rotors. Ex d motor.
Grain handling. Grain dust explosions. ATEX Zone 21 or 22. Category 2D or 3D. Spark-resistant rotors. Dust-tight seals. Grounding.
Coal handling. Coal dust explosions. ATEX Zone 21 or 22. Category 2D or 3D. Hard-chrome or tungsten carbide rotors. Dust-tight seals.
Pharmaceutical. Flammable solvents, dust. ATEX Zone 1 or 2 (gas), Zone 21 (dust). Category 2G or 2D. Stainless steel. Ex d motor.
Wastewater treatment. Digester gas (methane). ATEX Zone 2. Category 3G, IIB, T3. Stainless steel. Ex n motor.
Engineering Advantages
Safety. Explosion proof roots blowers are designed to prevent ignition of explosive atmospheres. Non-explosion proof blowers are not safe for hazardous areas.
Compliance. Explosion proof certification is mandatory for hazardous areas. Non-certified equipment cannot be legally installed.
Reliability. Explosion proof components are designed for rigorous service. Explosion-proof motors, gas-tight seals, and temperature monitoring ensure reliable operation.
Debris tolerance. Roots blowers handle particulates and moisture better than other technologies.
Common Problems and Troubleshooting
| Problem | Cause | Diagnosis | Solution |
|---|---|---|---|
| ATEX certificate missing | Non-compliant equipment | Check documentation | Reject equipment |
| Gas leakage | Seal failure | Gas detection | Replace seals |
| Temperature >T-class limit | Over-pressure or wear | Check temperature | Reduce pressure. Replace rotors. |
| Motor trips | Explosion-proof motor overload | Check amps | Reduce pressure. Check cooling. |
| Rotor pitting | Corrosion | Inspect rotors | Replace with stainless steel. |
| Static discharge | Grounding failure | Check grounding | Repair grounding. |
| Bearing failure | Temperature or contamination | Oil analysis | Replace bearings. |
Selection Guide
Step 1 – Define ATEX classification.
Zone (0, 1, 2 for gas; 20, 21, 22 for dust). Gas group (IIA, IIB, IIC). Temperature class (T1–T6). Category (1, 2, 3).
Step 2 – Define gas/dust properties.
Gas composition, ignition temperature, explosion limits. Dust type, conductivity.
Step 3 – Select rotor material.
Aluminum: general ATEX. Bronze: higher strength. Stainless steel: corrosion + spark-resistant.
Step 4 – Select motor type.
Ex d (flameproof): most common. Ex e (increased safety): less common. Ex n (non-sparking): Zone 2.
Step 5 – Specify seals.
Labyrinth with buffer gas. Double lip with purge. Magnetic (zero leakage).
Step 6 – Specify temperature monitoring.
Thermocouple with shutdown at T-class limit.
Step 7 – Verify ATEX certification.
Notified body certificate. Current and valid. Matches equipment.
Common selection mistakes:
Specifying non-ATEX motor
Cast iron rotors – spark hazard
No temperature monitoring
Standard seals – gas leakage
No grounding
Wrong ATEX category for zone
Cost Factors and Pricing
Explosion proof roots blower cost components (100 HP class, 2026):
| Component | Standard Blower | Explosion Proof Blower | Premium |
|---|---|---|---|
| Base blower (three-lobe) | $8,500–11,000 | $10,000–14,000 | +15–25% |
| Spark-resistant rotors | Included (cast iron) | $3,000–6,000 | +30–50% |
| Ex d motor | Included (TEFC) | $3,000–6,000 | +20–40% |
| Gas-tight seals | Standard | $2,000–4,000 | +100–200% |
| Temperature monitoring | Optional | $1,000–2,000 | Included |
| ATEX documentation | N/A | $1,000–2,000 | N/A |
| ATEX certification | N/A | $2,000–5,000 | N/A |
| Total | $8,500–11,000 | $20,000–35,000 | +100–200% |
Complete explosion proof package (100 HP blower):
ATEX blower: $20,000–35,000
Ex d motor: included
Silencers: $1,500–2,500
VFD (Ex d enclosure): $6,000–10,000
Total FOB: $30,000–50,000
Annual operating cost:
Electricity: $52,000
Maintenance: $3,000–5,000
Total annual: $55,000–57,000
Procurement Considerations
When requesting quotes for explosion proof roots blower:
1. Specify ATEX classification.
Zone, gas group, temperature class. Category. Provide all application details.
2. Require ATEX certificate from notified body.
Check certificate is current. Verify notified body number. Match equipment.
3. Specify spark-resistant rotors.
Aluminum, bronze, or stainless steel. Cast iron not acceptable.
4. Specify explosion-proof motor.
Ex d, Ex e, or Ex n. Must match ATEX classification.
5. Specify gas-tight seals.
Labyrinth with buffer gas. Double lip with purge. Magnetic.
6. Specify temperature monitoring.
Thermocouple with shutdown. T-class limit minus 20°C margin.
7. Specify grounding.
All components grounded. Resistance < 1 ohm.
8. Request documentation.
ATEX certificate, Declaration of Conformity, technical file, test reports.
Red flags when sourcing explosion proof roots blower:
Cannot provide ATEX certificate from notified body
Cast iron rotors
Standard motor (not Ex d/e/n)
No temperature monitoring
Unfamiliar with ATEX requirements
Frequently Asked Questions
1. What is an explosion proof roots blower?
An explosion proof roots blower is a positive displacement rotary lobe machine designed and certified for use in potentially explosive atmospheres. It incorporates explosion-proof motors, spark-resistant rotors, gas-tight seals, temperature monitoring, and ATEX certification.
2. What ATEX classification do I need?
Zone 1 (gas): Category 2G. Zone 2 (gas): Category 3G. Zone 21 (dust): Category 2D. Zone 22 (dust): Category 3D. Gas group: IIA (propane), IIB (ethylene), or IIC (hydrogen). Temperature class: T1–T6 (must be below gas ignition temperature).
3. What motors are used for explosion proof roots blowers?
Ex d (flameproof) is most common – motor enclosure can contain internal explosion. Ex e (increased safety) – less common. Ex n (non-sparking) – for Zone 2 only. Motor must be ATEX certified for the gas group and temperature class.
4. What rotor materials are used for explosion proof roots blowers?
Aluminum: lightweight, spark-resistant. Bronze: non-sparking, higher strength. Stainless steel: corrosion resistant, spark-resistant. Cast iron is not acceptable – can create sparks on impact.
5. What seals are required for explosion proof roots blowers?
Gas-tight seals are mandatory – gas leakage creates explosion hazard. Labyrinth seals with buffer gas (nitrogen or air). Double lip seals with purge. Magnetic seals (zero leakage). Gas detection recommended.
6. Is temperature monitoring required?
Yes – temperature monitoring is mandatory. Discharge temperature must stay below T-class limit. Thermocouple with automatic shutdown at T-class limit minus 20°C margin.
7. What is the difference between ATEX and non-ATEX roots blowers?
ATEX blowers have explosion-proof motors, spark-resistant rotors, gas-tight seals, temperature monitoring, grounding, and ATEX certification. Non-ATEX blowers use standard motors, cast iron rotors, standard seals, and no ATEX certification.
8. How much does an explosion proof roots blower cost?
Explosion proof roots blowers cost 100–200% more than standard blowers. Example: 100 HP standard blower $8,500–11,000. 100 HP ATEX blower $20,000–35,000. Premium includes Ex d motor, spark-resistant rotors, gas-tight seals, temperature monitoring, and ATEX certification.
9. Can I convert a standard blower to explosion proof?
Not easily. ATEX requires certified components (motor, seals, rotors) and notified body certification. Converting a standard blower would require replacing motor, rotors, seals, adding temperature monitoring, and ATEX certification. Usually more cost-effective to purchase ATEX blower.
10. What documentation is required?
ATEX certificate from notified body, Declaration of Conformity, technical file (risk assessment, drawings, test reports), installation and maintenance instructions, and ATEX marking on equipment.
11. How long does ATEX certification take?
8–16 weeks depending on manufacturer and notified body. Plan ahead for hazardous area projects.
12. What is the notified body?
A notified body is an organization designated by an EU member state to assess conformity of ATEX equipment. The notified body issues the ATEX certificate.
13. Can explosion proof roots blowers handle dust?
Yes – explosion proof roots blowers are available for dust applications (Zone 21, 22). Dust ATEX requires Category 2D or 3D, dust-tight seals, spark-resistant rotors, grounding, and dust-tight construction.
14. What are the maintenance requirements for explosion proof roots blowers?
Regular maintenance is critical – ATEX components must remain in certified condition. Replace seals preventively. Check temperature monitoring. Verify grounding. Inspect rotors for wear. Document all maintenance.
15. What is the payback for explosion proof?
ATEX is not about payback – it is about safety and legal compliance. Non-ATEX equipment in hazardous areas creates explosion risk, legal liability, and insurance issues. The cost of ATEX equipment is justified by safety and compliance requirements.
Final Thoughts
After commissioning explosion proof roots blowers for hazardous area applications, here is my practical advice:
Selection logic. For any hazardous area application, specify an explosion proof roots blower with the correct category, gas group, and temperature class. Spark-resistant rotors (aluminum, bronze, stainless steel), Ex d motor, gas-tight seals, and temperature monitoring are mandatory. Zhanggu and other established manufacturers offer ATEX-certified blowers.
Explosion proof is about safety – not cost. The premium for ATEX equipment (100–200% over standard) is justified by explosion prevention and legal compliance. Non-ATEX equipment in hazardous areas creates explosion risk and legal liability.
Certification is non-negotiable. ATEX certification from a notified body is required. Request the ATEX certificate, Declaration of Conformity, and technical file before shipment. Verify the certificate is current.
Maintenance preserves certification. Explosion proof blowers must be maintained in certified condition. Replace seals on schedule. Verify temperature monitoring. Document maintenance.
The bottom line. Explosion proof roots blowers are mandatory for hazardous area applications. The safety and compliance requirements are not optional. Specify correctly. Verify certification. Maintain properly. The blower will operate safely in explosive environments.
