Castair CNS12 — 1/2" Compression Nut and Sleeve
The CNS12 is a 1/2-inch compression nut and sleeve set from Castair, used in the discharge tube connections on air compressor installations. This is the hardware that makes a compression fitting seal — the nut threads onto the fitting body and the sleeve (ferrule) compresses against the tubing OD to create a leak-free connection without soldering or flaring.
Castair sells the CNS12 as a replacement or additional set for installations using Castair discharge tubes (DT12 — 1/2-inch discharge tube with fittings) or anywhere a 1/2-inch compression fitting is needed on the discharge side of a piston compressor. If you are building a new installation or replacing damaged compression hardware, this is the correct part for 1/2-inch copper or suitable tubing at the compressor discharge connection.
What This Part Does
- Compression Nut: Threads onto the male fitting body and, when tightened, forces the sleeve to compress against the tubing OD, creating a seal.
- Compression Sleeve (Ferrule): Deforms slightly as the nut is tightened, conforming to the tubing OD and the fitting seat for a leak-free joint. Replace any damaged, cracked, or over-compressed ferrule — a compromised ferrule will leak.
- 1/2" Tube OD: Fits 1/2-inch OD tubing — verify your tubing outside diameter before ordering. Compression fittings size to tubing OD, not to pipe thread nominal size.
- Replacement Hardware: Order CNS12 when the original nut and sleeve are damaged, cross-threaded, or missing. Do not reuse a ferrule that has already been compressed onto tubing in a previous installation — the deformed ferrule will not seal properly on new tubing.
Where This Part Is Used
- Discharge tube connections between the compressor pump head and the check valve or receiver inlet on Castair and compatible piston compressors.
- Any compression fitting installation on the discharge side of the air system using 1/2-inch OD tubing.
- Pairs with the Castair DT12 (1/2-inch discharge tube with fittings) for complete discharge tube assemblies.
Related Castair Parts
- CNS34: 3/4" compression nut and sleeve — same design for larger 3/4-inch tubing
- DT12: 1/2" discharge tube with fittings — complete assembly that uses CNS12 hardware
- DT34: 3/4" discharge tube with fittings — uses CNS34 hardware
- CA1212: Compression adaptor 1/2" x 1/2"
- CE1212: Compression elbow 1/2" x 1/2"
Technical Specifications
- Part Number: CNS12
- Tubing Size: 1/2" OD
- Contents: Compression nut and compression sleeve (ferrule)
- Application: Compressor discharge tube and compression fitting connections
- Manufacturer: Castair, Spicer, Minnesota
Why Buy From Air Compressor Factory Direct?
We have sold Castair parts and components since 2016 and carry their full accessories and replacement parts lineup. If you are unsure whether the CNS12 is the right part for your installation, call 866-217-0063 and we will confirm it. Free shipping on qualifying orders, full manufacturer warranty, free technical support.
Call 866-217-0063 for quick answers and help!
