High Pressure Compressors

Piston compressors are the preferred technology for high and very high pressure applications, where other compressor types cannot reach the required pressures.

Pressure Ranges

Category	Pressure	Typical Applications
Standard	100-175 PSI (7-12 bar)	General industrial
Medium-High	175-500 PSI (12-35 bar)	Testing, molding
High	500-3,000 PSI (35-200 bar)	PET, blow molding
Very High	3,000-6,000 PSI (200-400 bar)	Diving, industrial
Ultra High	>6,000 PSI (>400 bar)	Special, hydrogen

Multi-Stage Design

To achieve high pressures, multiple stages of compression are required:

    1st Stage      2nd Stage      3rd Stage      4th Stage
    ┌───────┐      ┌─────┐        ┌───┐          ┌─┐
    │       │      │     │        │   │          │ │
    │       │  →   │     │   →    │   │    →     │ │  → 5,000 PSI
    │       │      │     │        │   │          │ │
    └───────┘      └─────┘        └───┘          └─┘
    Large          Medium         Small          Minimal

    1 bar          10 bar         50 bar         200 bar → 350 bar

Compression Ratio Per Stage

For maximum efficiency, each stage has a similar compression ratio:

Final Pressure	Stages	Ratio Per Stage
175 PSI	2	~4:1
500 PSI	3	~4:1
3,000 PSI	4	~4:1
6,000 PSI	4-5	~4:1

High Pressure Applications

PET Bottle Blowing

    ┌─────────────────────────────┐
    │         Preform             │
    │            │                │
    │            ↓                │
    │    ┌───────────────┐        │
    │    │ 500 PSI air   │───→    │
    │    │ "blows" the   │        │
    │    │ preform       │        │
    │    └───────────────┘        │
    │            │                │
    │            ↓                │
    │       PET Bottle            │
    └─────────────────────────────┘

Parameter	Typical Value
Pressure	500-600 PSI (35-40 bar)
Flow	High, intermittent
Air quality	Dry, oil-free
Stages	3

Breathing Air (Diving/Firefighting)

    High Pressure     Special          Diving
    Compressor       Filtration       Cylinders

    ┌──────┐          ┌──────┐          ┌──┐
    │      │    →     │ Carb │    →     │  │
    │ 4-5  │          │ Act  │          │  │
    │Stages│          │Molec │          │  │
    │      │          │ Siev │          │  │
    └──────┘          └──────┘          └──┘
     5000 PSI         Grade D            Fill

Parameter	Typical Value
Pressure	3,000-5,000 PSI (200-350 bar)
Quality	Grade D (OSHA) or higher
Purity	< 25 ppm CO, < 1,000 ppm CO₂
Moisture	Dew point < -50°F

Hydrostatic Testing

For testing pressure vessels, piping, valves:

Parameter	Typical Value
Pressure	Variable, up to 10,000+ PSI
Medium	Generally water (safer)
Use	Intermittent

Special Gas Compression

• Nitrogen for laser cutting
• Hydrogen for fuel cells
• CNG (Compressed Natural Gas) for vehicles

Design Considerations

Special Materials

At high pressures, materials must withstand extreme stresses:

Component	Material
Cylinders	Forged steel, special alloys
Pistons	Hardened steel
Valves	Stainless steel, Inconel
Packings	PTFE, graphite, metallic
Piping	Seamless steel, high pressure

Cooling

Cooling is critical in high-pressure compressors:

    Stage 1    Intercooler    Stage 2    Intercooler    Stage 3
       │           │             │           │             │
       ▼           ▼             ▼           ▼             ▼
    ┌─────┐    ┌───────┐     ┌─────┐    ┌───────┐     ┌─────┐
    │     │───→│ ≋≋≋≋≋ │────→│     │───→│ ≋≋≋≋≋ │────→│     │
    └─────┘    └───────┘     └─────┘    └───────┘     └─────┘
                  ↑                         ↑
             Cold water                Cold water

• Intercoolers between each stage
• Aftercooler after the last stage
• Water cooling preferred for high pressure
• Discharge temperature control at each stage

Safety

Element	Function
Relief valves	At each stage
Rupture discs	Valve backup
Pressure sensors	Continuous monitoring
Auto shutdown	For overpressure or overtemperature
Ventilation	Well-ventilated area
Barriers	Protection against failures

High Pressure = High Risk

High-pressure compressors store enormous amounts of energy. A failure can be catastrophic. Only trained personnel should operate and maintain this equipment.

Specialized Maintenance

Shorter Intervals

Higher pressure means more stress on components:

Component	Interval (High Pressure)
Valves	Every 500-1,000 hours
Rings	Every 1,000-2,000 hours
Packings	Every 500-1,500 hours
Oil	Every 250-500 hours
Overhaul	Every 4,000-8,000 hours

Critical Inspections

Inspection	Frequency
High pressure leaks	Daily
Safety valves	Monthly
Piping and connections	Monthly
Vibration analysis	Quarterly
Hydrostatic test	Annual or per code

Specialized Manufacturers

High-pressure compressors are manufactured by specialized companies:

• General industrial applications
• Diving and rescue systems
• PET blowing
• Special gases

Supplier Selection

For high pressure, work with specialized manufacturers who offer:

• Proven design for the specific application
• Expert technical support
• Available spare parts
• Required certifications (ASME, CE, etc.)