Pouring - PROPERTIES

Despite the diversified applications, there are only two techniques of polyurethane foam production: SPRAYING and POURING.

POURING 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.

Semicylinder 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.

PUF 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 area.

The benefits of polyurethane foam sectional insulation include:

• 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.

PUF 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.



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