Page 35 - 2010-2022 hose manufactureing ability and guide

Occasionally this type of wire is also used as an The hose should be able to conform to the
external helix embedded in and flush with the smallest anticipated bend radius without
rubber cover to provide protection against overstress. The minimum bend radius is
cutting and abrasion and to increase crush generally specified by the manufacturer and is
resistance. Rectangular wire is generally steel, the radius to which the hose can be bent in
although aluminum may also be used. service without damage or appreciably
shortening its life. The radius is measured to the
Half-Round Wire inside of the curvature.
Half-round steel wire is used mainly as a
protective spiral armor on the exterior of a hose. Textile reinforced hoses have a tendency to
It is wound with the flat side against the hose kink as the bend radius is reduced. Generally, a
cover to provide maximum surface contact. It is helix of wire is used when a hose must with
stand severe bends without flattening or
available in stainless steel or steel with tin-
coated or galvanized finishes. kinking.
Some indication of relative hose flexibility
Wire Finishes
can be determined from the manufacturers
Wire finishes for steel wire can be either one minimum bend radius recommendations. The
of two types, (1) brass drawn finish, or (2) bend radius does not necessarily reflect the
coated finish. The most commonly used finish force required to bend the hose to this radius,
in the hose industry is brass (drawn finish), or which is a major factor in flexibility. Different
galvanized (coated finish). Other finishes hose constructions may require significantly
include bronze, liquor, and tin. Helical round different forces to attain the same minimum
wires used as helical wound in the body of a bend radius.
hose may have a drawn copper finish, or may be
Generally, the preferred hose is the more
unfinished (bright). Rectangular steel wires used flexible hose, provided all other properties are
in the bore of a hose usually have a galvanized
finish. essentially equivalent. There are exceptions to
this as in sand blast hose where minimizing the
Alloy and Non-Ferrous Wires bending in service increases hose life.
Under certain service conditions, carbon steel Suction and Vacuum
wire is not suitable. An alloy wire is used
Most hose is used for pressure service;
instead. One of the most commonly used is however, some applications require the hose to
stainless steel which offers exceptional
resistance to corrosion and heat. Where light resist collapse in suction and vacuum service.
weight is essential, alloys of aluminum are used. Such hose is subjected to crushing forces
because the atmospheric pressure outside the
Static Wires hose is greater than the internal pressure. The
Static wires and other conductive materials hose can collapse and restrict the flow unless
are used in hose to prevent static electricity the hose is constructed to resist these pressure
buildup. Wires can be made from many metals differentials.
including copper, steel, monel, aluminum and The most common method of preventing
tin-coated copper. Static wires may be solid, hose collapse is to build a helical wire
stranded, or braided. reinforcement into the hose body. The size and
PHYSICAL CHARACTERISTICS spacing of the wire reinforcement depends on
the size of the hose and the expected pressure
OF HOSE
differential for the application. In suction
Flexibility and Bend Radius applications approaching a perfect vacuum,
Flexibility and minimum bend radius are most of the carcass plies are applied over the
important factors in hose design and selection if wire reinforcement. The hose is constructed
it is known that the hose will be subjected to with high adhesion between the tube and the
sharp curvatures in normal use. When bent at carcass to prevent tube separation. Suction hose
too sharp an angle, hose may kink or flatten in must be specifically designed for the service for
the cross-section. The reinforcement may also which it is used. Each element — tube, textile
be unduly stressed or distorted and the hose life reinforcement, size, spacing, and location of the
wire reinforcement — must be carefully

RMA/IP-2/2003 14