Pouring - PROPERTIES
Despite the diversified applications, there
are only two techniques of polyurethane foam production: SPRAYING
is chiefly used for molded products and is based on the unique property
of polyurethane foam to form a rigid foamed plastic from a mixture
of two liquid substances. If components A and B are mixed and poured
into a molding tool, the expanding plastic will fill its entire
volume, replicating all the minutest details of the geometry and
contours of the mold cavity.
The most widely used applications of the
pouring method are related to the manufacture of:
• sectional insulation for pipelines, insulated
panel and sandwich constructions;
• decorative fittings (skirting, rosettes, etc.);
• wood imitation furniture parts;
• car bumpers, yacht hulls, instrument panels and housings;
• foamed polyurethane office chairs and car seats;
• baths and washbasins;
• tank armor anti-radiation liners and hollow charge-proof plating;
• running shoe and boot soles;
• cork jackets and safety buoys.
Apart from the pouring equipment, these
applications require high-quality molds and other production tooling.
The feed selection depends on the particular product. The choice
of the composite determines such end product properties as density,
durability, flexibility, heat-resistance, etc.
|Polyurethane Foam Semicylinders for
Thermal Insulation of Pipelines
The most typical application of the pouring
process is the production of sectional insulation, because PUF is
highly efficient for pipelines that contain recycling cooling media
with temperatures as low as minus 200°Ń and heating media with temperatures
up to plus 180°Ń.
In order to produce a polyurethane foam
semicylinder, the mixture of components A and B is poured into a
molding tool, which is previously lubricated with mold release.
and cylinder Molds for PUF Sectional Insulation Manufacture
When poured, the mixture foams, expands,
and then sets solid, filling the entire cavity of the mold. The
sectional insulation molding time is 10 to 15 minutes.
The main requirements for the mold are
an exact matching of its geometry with the desired dimensions of
the part and a high strength capacity, since the expanding polyurethane
foam pressurizes the mold from inside to 3 or 5 atmospheres.
Semicylinders, furniture parts and molds for it
One should note that the manufacture of sectional
insulation requires substantial investment in job engineering, due
to the necessity of keeping a large inventory of molds. The minimum
recommended stock is 7 or 8 different standard sizes, at least six
pieces of each.
Thermal insulation products (sectional insulation
and bends) may be implemented with additional facing of glass-fiber
fabric, foil, or other material. The process of shop-floor polyurethane
foam molding is designed for manufacture of any required number
of thermal insulation semicylinders to be further mounted on a pipeline
using wire or band clamps or adhesive compounds.
When making semicylinder insulation for pipes,
one should pay special attention to a pipeline’s anticorrosive protection,
because the condensate that accumulates between the pipe and the
sectional insulation cannot escape or evaporate and thus speeds
up pipe corrosion.
The functional performance of sectional insulation
is identical to that of sprayed polyurethane foams. With neglect
of the time spent for in-plant manufacture of semicylinders, the
efficiency of this pipeline winterization technique is many times
higher than the sprayed PUF insulating efficiency for the same surface
The benefits of polyurethane foam sectional insulation
• a three to fourfold decrease in a pipeline’s
heat energy loss as compared to the normal loss values;
• a low labor content, a five to six times reduction of the thermal
insulation mounting time, and a substantial decrease in the overall
pipeline installation time;
• a substantially higher durability of the insulation as compared
to traditional materials;
• weather-independent assembly and disassembly;
• multiple usability;
• a quick access to damaged areas;
• a high productivity rate – up to 150 running meters of insulation
per shift for two workmen.
Semicylinders, mold and PUF panel
The density of sectional insulation may be varied
from 50 to 120 kg/m3, and the thermal conductivity factor may range
from 0.025 to 0.027 W/(m·K).
For steam conduits and other pipes of similar
application used at temperatures above +120°Ń, insulation should
be made in two phases: a felt or basalt wool cooling layer and a
subsequent polyurethane foam insulation layer.
It can be said for sure that in terms of labor consumption, durability,
reusability, and a notable heat loss reduction, polyurethane foam
thermal insulation products are more economical than the traditional
mineral wool blankets for pipelines.
|Polyurethane Foam Preinsulated Pipes
This is the most advanced
pipeline insulation technique. The principle of this method is that
polyurethane foam is poured into the gap between the pipe to be
insulated and a larger-bore polyethylene or galvanized steel tube,
thus forming a monolithic heat and water proof three-layer structure.