Factors To Consider

Factors to consider in using composite materials for pump parts are mechanical properties, abrasion and corrosion resistance, temperature, costs, weight and insulating properties, exposure to sun, fire resistance, and chemical resistance.

Mechanical Properties The composite pump or parts must be designed to withstand the loads/stresses of the operating conditions. If the existing metal part design were simply replicated in a composite, the composite part could fail. Excessive stresses for a composite pump at the nozzle area or at the bearing housing can cause the pump housing to creep. The result is part distortion or bending and shaft misalignment.

A solution to this problem is to calculate the stress levels in the composite part and design within the composite's elastic limit. These complex stress calculations are now done on a routine basis with the aid of a computer and non-linear FEA (finite element analysis) programs.

Abrasion and Corrosion Resistance The abrasive wear on 316 stainless steel is caused by the continuing removal of the metal's protective oxidation layer on the metal's surface. Composites do not need a protective layer and therefore have better resistance to mild abrasives. However, some composites are subject to corrosion by caustic liquids.

As background, metallic materials deteriorate from any one or combination of the following electrochemical reactions: galvanic action, pitting, corrosive attack, crevice corrosion, intergranular corrosion, and stress corrosion. The temperature, pH, formation, removal of an oxide corrosion barrier, or the velocity of the solution affects the rate of corrosion in a metal's surface.

Temperature Most composite pump materials are limited to operating temperatures below 300°F (150°C) for non-corrosive liquids and under 250°F (120°C) for corrosive liquids. Like metals, there is a reduction of mechanical properties for composites with increasing temperature.

Costs There are three areas of cost to consider when evaluating a composite part: development costs, initial capital costs, and cost savings. Developing costs would include the following:

• Designing the part for composites

• Evaluating and testing alternative composite materials

• Prototype molding the parts

Initial capital costs are in the cost of the molds to produce the parts. Cost savings in manufacture and use include the following:

• Little or no corrosion increases the time between maintenance and extends the useful life of the pump.

• Reduced secondary machining cost at manufacture (the parts are near "net shape")

• Integrating several parts into one assembly results in a less expensive part, lower inventories, and less assembly time.

• Quality control cost is reduced as part tolerance is primarily determined by the mold.

The initial cost of a composite pump versus a metallic pump is typically as follows:

• equal or slightly more expensive than an all 316 stainless steel pump

Weight and Insulation Properties With a significant reduction in weight compared to metal, the composite pump is easier to handle during installation and maintenance removal. As an example, an immersion sump pump that is usually 3-10 ft long weighs only 10-30% of a comparable metal pump.

Added insulation on the pump to conserve high temperature process heat is usually not needed on a composite pump, as the composite is a natural insulator when compared to metal. This saves the cost to fabricate an insulation cover over the pump and provides easier access for maintenance.

Exposure to the Sun Some composites are susceptible to the UV (ultraviolet) rays of the sun. 2% carbon black in the resin is an effective UV blocker. HALS (hindered amine light stabilizers) can also be added to the composite to effectively prevent damage by the UV rays of the sun.

Fire Resistance In a severe fire, thermoplastic composites will melt and burn and ther-moset composites will char and ash. If the composite reaches 400-500°F (204-260°C), there will be distortion of the pump and the pump will be lost. Because of the insulating properties of a composite pump housing, however, the liquids inside the pump will be cooler than if the pump were metal.

Fire retardant additives can be used with composite materials, but they may affect optimum mechanical properties. Most thermoset composites are self-extinguishing in a fire, but the pump manufacturer should be consulted to determine if there is a potential for toxic fumes if the composite is burned.

Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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