Instrument Air Purpose

Pneumatic instruments, control valves, and actuators require steady air supply at consistent pressure. Air compressors cycle on-off creating pressure variations. Storage vessel buffers these fluctuations maintaining stable pressure for sensitive instruments.

Vessel Design

Horizontal or vertical pressure vessel with compressed air inlet from dryer, outlet to distribution headers, drain for condensate removal, pressure gauge, safety relief valve. Simple storage volume without complex internals. Sizing provides adequate capacity reducing compressor cycling.

Operating Pressure

Typical 100-125 psig matches standard instrument air systems. Design pressure higher per code requirements typically 150-175 psig. Pressure regulators downstream reduce to instrument requirements usually 20-40 psig.

Storage Capacity

Volume sized for minutes of air consumption at operating pressure. Larger vessels reduce compressor starts extending equipment life. Typical sizing 10-50 gallons per scfm compressor capacity. Application-specific calculation balances cost versus performance.

Material Selection

Carbon steel construction per ASME Section VIII suitable for compressed air. Internal surface quality important preventing contamination of clean air system. External coating protects against atmospheric corrosion.

Air Quality

Instrument air requires drying to -40F dewpoint and filtration to 1 micron preventing moisture and contamination in instruments. Vessel receives treated air from dryer. Drain removes any condensate accumulation though properly dried air contains minimal moisture.

Pressure Control

Compressor starts when vessel pressure drops to low setpoint. Stops at high setpoint. Differential typically 10-20 psi. Proper control minimizes cycling while maintaining adequate pressure. Pressure switch or transmitter triggers compressor operation.

Applications

Refineries, chemical plants, power stations, manufacturing facilities, and any industrial operation using pneumatic instruments and control valves. Critical utility ensuring process control reliability.

Drain System

Manual or automatic drain at bottom removes condensate accumulation from compression process or atmospheric moisture ingress. Regular drainage prevents water carryover to instruments causing control problems or corrosion.

System Integration

Vessel connects between air compressor, dryer, and distribution headers. Backup nitrogen supply often provided for critical instruments during air system failures. Proper piping design ensures uninterrupted supply.

Performance Benefits

Stabilizes pressure for consistent instrument operation. Reduces compressor cycling extending equipment life. Provides surge capacity during high demand periods. Simple proven compressed air storage technology.

Construction Standards

Design per ASME Section VIII Division 1 with U-stamp. Relief valve sized for compressor capacity. Foundation for vessel weight. Complete documentation with capacity calculations and material certifications.

ERGIL instrument air vessels provide reliable compressed air storage ensuring stable pneumatic control systems in industrial facilities.