Chemical Pump Design Considerations

Casting Integrity Practically all the major components of chemical pumps are castings. There is probably more concern in chemical pump applications than in any other type of service because leakage, loss of product, and downtime can be extremely costly, as well as very dangerous.

Mechanical Properties There are several factors that determine whether a certain material can be utilized for a particular design. Materials may possess outstanding corrosion resistance but may be completely impossible to produce in the form of a chemical pump because of their limited mechanical properties. Accordingly, it is advisable to be aware of the mechanical properties of any material being considered in a corrosion evaluation program. Most materials are covered by ASTM or other specifications; such sources can be used for reference.

Weldments Welded construction should impose no limitation, provided the weldment is as good as or better than the base material. Materials requiring heat treatment to achieve maximum corrosion resistance must be treated after welding, or other adjustments must be made to make certain corrosion resistance is not sacrificed.

Section Thickness Pressure-containing parts are generally made thicker than required for handling a noncorrosive liquid so that full pumping capability will be maintained even after the loss of some material to the corrosive medium. Parts that are subject to corrosion from two or three sides, such as impellers, must be made considerably heavier than their counterparts in water or oil pumps. Pressure-containing parts are also made thicker so they will remain serviceable after a specified amount of corrosive deterioration. Areas subject to high velocities, such as the cutwater of a centrifugal pump casing, are reinforced to allow for the accelerated corrosion caused by the high velocities.

Threads Threaded construction of any type in the wetted parts must be avoided whenever possible. The thread form is subject to attack from two sides, and a small amount of corrosive deterioration can reduce the holding power of the threaded joint.

Gaskets Gasket materials must resist being corroded by the chemical being handled. Compressed synthetic fibers and elastomers have been used extensively for corrosion services. Fluorocarbon resins are used because of their almost complete corrosion resistance.

Power End This assembly, consisting of the bearing housing, bearings, oil or grease seals, and bearing lubrication system, is normally made of iron or steel components; thus it must be designed to withstand a severe chemical plant environment. For example, where venting of the bearing housing is required, special means of preventing the entrance of water, chemical fumes, or dirt must be incorporated into the vent design.

The bearing that controls axial shaft movement is usually selected to limit shaft movement to 0.002 in (0.051 mm) or less. Endplay values above this limit have been found detrimental to impeller and mechanical seal operation.

Water jacketing or fan cooling of the bearing housing may be necessary under certain conditions to maintain bearing temperatures below 180°F (82°C), the limit used in most applications.

Maintenance Maintenance of a chemical pump in a corrosive environment can be a very costly and time-consuming item. When evaluating materials and design factors, maintenance aspects should be high on the priority list. The ease and frequency of maintenance are critical items and should be considered part of a preventive maintenance program. Such a program can be the most effective way of eliminating emergency shutdowns caused by pump failure. Furthermore, the knowledge gained in a routine preventive maintenance program can be of unlimited value when a breakdown does occur because repair personnel will have acquired a thorough knowledge of the construction details of the pump.

Renewable Energy Eco Friendly

Renewable Energy Eco Friendly

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.

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