What is Cast Union?
The cast union is a special pipe fitting consisting of three parts,
designed specifically for pipeline points that require frequent
disassembly or maintenance. It includes two threaded ports and a
central nut for locking. Tightening the nut can tighten the two
ends, forming a reliable seal. The ingenious structure of the union
allows it to provide a secure connection while allowing easy
disconnection without rotating the pipeline, greatly facilitating
equipment replacement and pipeline maintenance work.
Introduction to Thread Types
Threaded fittings primarily adhere to two major international
thread systems: NPT and BSP. The thread angle of NPT (American
Standard Pipe Taper Thread) is 60°, relying on the thread's own
taper (1:16) for sealing. The thread angle of BSP (British Standard
Pipe Thread) is 55°, which is divided into taper threads (BSPT) for
sealing and parallel threads (BSPP). This union adopts NPT threads,
which are the most common connection form in North America and the
general industrial field.
CF8M/316 Material Properties
The selection of CF8M/316 stainless steel material is crucial for
ensuring the long-term reliable operation of the union. Due to the
presence of molybdenum, the 316 grade exhibits superior corrosion
resistance, particularly against chloride corrosion, compared to
the 304 grade. For the union, this means that its precise threads
and sealing surfaces are less prone to getting stuck or damaged due
to rust, ensuring both the sealing performance during daily
operation and the ease of disassembly for maintenance after many
years.
SMLSCO Production Process
Our cast pipe fittings are produced using precision casting (sol
silica) technology to achieve excellent dimensional accuracy and
surface finish. The process begins with the creation of a wax mold,
which is then coated with multiple layers of refractory material to
form a ceramic shell. The shell is then heated, causing the wax to
melt and flow out. Next, molten stainless steel is poured into the
hollow shell. After the steel cools and solidifies, the shell is
broken off to obtain a high-precision pipe fitting blank. The blank
is then machined, tapped, and other processes to produce the final
product.
Application of Casting Fitting Union
Class 150-pound cast union fittings are core components that
enhance maintenance convenience for low-pressure piping systems.
They are typically installed at both ends of equipment such as
pumps, valves, filters, and storage tanks, or at locations in the
pipeline where maintenance disconnection points need to be
reserved. In commercial water supply and drainage, HVAC, and
general industrial fluid piping, the use of union fittings can
greatly simplify the installation, maintenance, and replacement
processes of equipment, saving long-term maintenance costs.
