Parker 391PSS-4-4 Compression Pipe Coupler 1/4-18 Ss

Product Description

The PARKER 391PSS-4-4 is a compression tube pipe coupler body designed to connect compression tubing to a male NPT threaded port. Constructed from 316 stainless steel, it delivers reliable corrosion resistance in demanding fluid and gas handling applications. The fitting transitions from a compression end to a 1/4-18 MNPT thread, providing a secure, leak-resistant joint without the need for soldering or brazing. Rated to 150 psi maximum working pressure, it is suited for systems where pressure integrity and material compatibility are critical. Licensed plumbers, pipefitters, and HVAC technicians commonly install this type of fitting in refrigeration, instrumentation, and process piping lines.

This coupler body is used in applications requiring a reliable transition between compression tubing and NPT-threaded components. Typical installations include instrumentation tubing runs, low-pressure pneumatic lines, refrigerant sensing lines, and similar light-duty process connections. The 316 stainless steel construction makes it appropriate for mildly corrosive environments and applications where standard brass fittings are not suitable. It is sold individually and is a direct drop-in style fitting for standard compression-to-MNPT configurations.

Key Features

• 316 stainless steel body for corrosion resistance in demanding service environments
• Compression x MNPT end connections for tool-accessible, braze-free installation
• 1/4-18 NPT thread size for compatibility with standard pipe ports
• 150 psi maximum working pressure rating
• Operating temperature range of 0 degrees F to 65 degrees C (approximately 149 degrees F)
• Sold as a single unit with no minimum order beyond one piece

Compatibility

Designed as an OEM-style replacement or new-installation fitting for compression tube to male NPT threaded connections in instrumentation, refrigeration sensing, and light-duty process piping systems.

Installation Notes

This fitting is typically installed by licensed plumbers or pipefitters working on instrumentation or process piping systems. Shut off system pressure and depressurize the line completely before disassembly or installation. Hand-tighten the compression nut first, then advance with a wrench per standard compression fitting practice — do not overtighten, as this can damage the ferrule and compromise the seal. Follow applicable IPC and local piping codes for pressure testing after installation.