CPVC has become an important engineering thermoplastic due to its
relatively low cost, high heat deflection temperature, chemical inertness and
outstanding mechanical, dielectric, and flame and smoke properties.
At basic level, CPVC is a PVC
homopolymer that has been subjected to a chlorination reaction.
One of the most attractive
features of CPVC piping is its
resistance to corrosive chemicals – the same chemicals that can degrade and
reduce the service life of many metals, potentially causing expensive
maintenance, disruption of operations and property damaging leaks in these
systems.
Whenever CPVC piping is used, the protection against external damage shall
be provided with protective metallic covering with galvanized carbon steel pipe
(1 size bigger than CPVC pipe).
Chemical resistance issues can
show up in a number of ways, with the most common problems being softening,
degradation and cracking. If CPVC pipe
has been incorrectly specified for a particular chemical application, or if
it’s unintentionally coming into contact with an incompatible material, several
modes of failure can result, as per the followings.
- Softening - a type of pipe failure characterized by a swollen and/or distorted appearance which eventually causes a failure by ballooning and ductile fracture, or by distortion of the system.
- Degradation - can manifest itself in many ways, including blackening and blistering, can be caused by prolonged exposure to conditions in excess of recommended temperature, pressure and chemical concentration.
- Environmental stress cracking - generally presents itself as a crack with glossy fracture surface that occur in regions of high mechanical stresses. It depends on both the presence of the chemical and a significant level of mechanical stress.
CPVC Standard
PIPES : ASTM F 441
FLANGES
: ASTM F 439 up to 3”/ ASTM F 437 for Threaded fittings.
FITTINGS :
ASTM F 439 S.W up to 3”, ASTM F437 Union up to 3”
ASTM F 437 for Threaded fittings.
VALVES :
Body ASTM- D-1784
Trim –As per
manufacturer standards.
Notes:
a) Complete piping system shall be
enclosed in Galvanized carbon steel pipe for protection against mechanical
damage. The size of cover shall be one size higher than the line size.
b) All CPVC material shall be type
IV Gr. 1 complying to ASTM-D-1784 (Class-23447-B)
c) Union shall be provided on one
side of SCRD valves to facilitate its removal.
d) Maximum test pressure for valve
and fabrication assembly shall be 225 psi.