Technical Resource
Chemical Injection Quill Selection Guide
A practical guide to selecting and sizing chemical injection quills for pipeline and process applications.
Fixed vs Retractable vs Spray — Which Type?
Fixed quills are the simplest and most economical option for permanent installations where the system can be shut down for maintenance. Retractable quills are essential for live systems where shutdowns are impractical — offshore platforms, remote locations, and critical production systems. Spray quills are used in large-diameter pipes (typically 12 inches and above) where single-point injection would not achieve adequate mixing.
Material Selection
The quill material must resist both the process fluid and the injected chemical. SS316L handles most aqueous chemicals. Hastelloy C276 is required for strong acids, high chloride, or H2S service. Alloy 20 is a cost-effective alternative for sulfuric acid applications. PVC or CPVC quills are suitable for low-pressure, low-temperature water treatment applications.
Sizing: Tube OD and Length
Tube OD is selected based on the required chemical injection flow rate and the available injection pressure. Typical sizes range from 6 mm to 12 mm OD. Length is determined by the pipe diameter — the quill tip should typically reach the center third of the pipe for optimal mixing. For retractable quills, the maximum stroke length must accommodate the full insertion depth plus clearance.
Tip Configuration
Open-end tips are the simplest but may cause localized high concentration. Multi-port tips distribute chemical across a wider area. Spray nozzle tips atomize the chemical for rapid mixing but require higher injection pressure. The choice depends on the pipe diameter, chemical viscosity, and the required mixing performance.
Connection and Integration
Quills are typically connected via NPT threaded fittings for sizes up to 2 inches, or flanged connections for larger or higher-pressure applications. An integrated check valve is recommended to prevent process fluid backflow into the chemical injection line during pump shutdown or pressure surges.
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