When sizing screw air compressors, engineers typically focus on motor power, rotor geometry, and operating pressure. However, one often overlooked factor is atmospheric pressure, which is closely tied to altitude. Since higher altitudes mean lower inlet pressure, understanding this relationship is crucial for accurate performance predictions.
At a fixed rotational speed and internal design, a screw compressor’s only variable is the intake pressure. When intake pressure drops at high altitude, so does the aimed air delivery.
🧠 1. The Science Behind Volume Change
By Boyle’s law (PV = constant at constant temperature), the volume of gas compresses inversely with pressure. In simpler terms:
- Higher intake pressure → more mass of air per cycle → higher delivery
- Lower intake pressure (higher altitude) → less air per cycle → reduced output
Since the rotor cavity volume is fixed, altitude becomes the defining variable.
📊 2. How Altitude Impacts Delivery
Empirical data shows:
| Altitude Range | Delivery Reduction per 100 m Gain |
|---|---|
| 0–2,000 m | 1.24% |
| 2,000–3,000 m | 1.59% |
| 3,000–4,000 m | 1.81% |
For example:
- A 1,000 m, delivery drops ~11.75%
- A 2,000 m, ~22.11% decrease
- A 3,000 m, ~33.62%
- A 4,000 m, ~44.68%
🎯 3. What This Means for Your Application
- Sizing: If your plant is at 2,500 m altitude, compensate for the ~30–35% capacity loss by upsizing the compressor or adding backup units.
- Specification: Always specify location altitude when ordering compressors to ensure accurate performance curves.
- On-Site Testing: Factory-rated performance (at sea level) will not match site conditions—plan for field validation.
🛡️ 4. Baldor’s Approach to Altitude Compensation
A Baldor, our compressor selection process includes:
- Intake pressure correction based on project altitude
- Customized rotor selection to optimize performance under local conditions
- On-site performance testing and adjustment
📸 5. Suggested Graphics to Enhance the Article
- Diagram: Compressor Rotor + Inlet Pressure Apportionment
- Graph: Delivery vs Altitude Plot (0–4,000 m)
- Infographic: Altitude Correction Table
- Image: Field setup of a compressor at high altitude
Let me know which visuals you’d like me to create for your site!
✅ Conclusione
Altitude significantly affects screw compressor air delivery due to lower intake pressure. Our data show a nearly linear decline in capacity—up to 45% loss at 4,000 m. For reliable supply, it’s essential to adjust specifications and perform performance corrections.
At Baldor, we help you engineer accurate, altitude-adjusted systems that maintain efficiency and uptime, regardless of elevation.
📩 Need help specifying compressors for high-altitude operations? Contact us
