Pump Type Follows:

Wednesday, April 29, 2009

The Application of Vertical Wet-Pit Pump

Like all pumps, the vertical wet-pit pump has advantages and disadvantages. One disadvantage is that installation does not require a separate dry pit to collect the pumped liquid. If the impeller (first-stage impeller in multistage pumps) is submerged, no priming problem exists and the pump can be automatically controlled without fear of its ever running dry. Moreover, the available NSPH is greater (except in closed tanks) and often permit in higher rotative speed for the same service conditions. A second advantage is that the motor or driver can be located at any desired height above fixed level.

 

It has the following mechanical disadvantages:

  1. the possibility of freezing whom idle
  2. similar installation
  3. the inconvenient of lifting out and dismantling of inspection and repair, no matter how small
  4. the pump bearing have a relative short life unless the water and bearing design are ideal.

 

In the summary the vertical wet-pit pump is the best pump available for some applications. Its not ideal be the most economical for certain installations, a poor for some, and the least desirable for still others,

 

Monday, April 27, 2009

Volute Pump

A variety of wet pit pumps are available. The liquid pumped, be it clean water, sewage, abrasive liquids or slurries, dictates whether a semi open or an enclosed impeller will be used, whether the shafting will be open or closed to the liquid pumped, and whether the bearings will be submerged or located above the liquid.

A single volute pump with a single suction enclosed nonclog impeller, no pump-out vanes or wearing ring joints on the back side of the impeller, and enclosed shafting. The pump is design to be suspended from an upper floor by means of a drop pipe and for pumping sewage or other solid laden liquids. To seal against leakage along the shaft at the point where it passes through the casing, a seal chamber or a stuffing box is provided.

In most application these volute pumps have been replaced with vertical wet-pit pump with the stuffing box/seal chamber in the discharge head. This pump is suitable for pumping heavy concentration of solid material (such as sludge or slurries) or in certain food processing application, but other type of impeller can be substituted. Pumped liquid leakage from casing is relieved back to the suction through holes in the support pipe. The seal chamber or stuffing box at the driver floor elevation is used only when gas tight construction is desired. The lower and any intermediate sleeve bearing are grease-lubricated as shown, but gravity feel oil lubrication is also available in other design. The upper anti friction thrust bearing is grease-lubricated. A solid shafts motor and flexible shaft are used.

An interesting design of the wet-pit pump uses a single stage, double suction impeller in a twin volute casing. Because the axial thrust is billings are externally lubricated, either with oil or with water. The lower bearing its lubricated from an external pipe connection.

Friday, April 24, 2009

Propeller Pump

Originally, the term of vertical propeller pump was applied to vertical wet pit diffuser or turbine pumps with a propeller or axial flow impellers, usually for installation in an open sump with a relatively short setting. Operating head exceeding the capacity of a single stage axial flow impeller might call for a pump of two or more stages or single stage pump with a lower specific speed and a mixed flow impeller. High enough operating heads might demand a pump with mixed flow impellers and two or more stages. For lack of a more suitable name, such high head design have usually been classified as propeller pump also.

Although vertical turbine pump and vertical modified propeller pump are basically the same mechanically and could even be of the same specific speed hydraulically, a basic turbine pump design is suitable for a large number of stage. A modified propeller pump, design, however, is basically intended for a maximum of two or three stages.

Most wet pit drainage, low head irrigation, and storm water installation employ conventional propeller or modified propeller pumps. These pumps have also been used for condenser circulating services, but a specialized design dominates this field. As large power plants are usually located in heavily populated areas, they frequently have to use badly contaminated water (both fresh and salt) as a cooling medium. Such water quickly shortens the life of fabricated steel. Cast iron, bronze, or an even more corrosion resistant cast metal must therefore be used for the column pipe assembly. This requirement means a very heavy pump if large capacities are involved. To avoid the necessity of lifting this large mass for maintenance of the rotating parts, some design are built so that the impeller, diffuser and shaft assembly can be removed from the top without disturbing the column pipe assembly. These design are commonly designated as pullout design.

Like vertical turbine pumps, propeller and modified propeller pumps have been made with both open, and enclosed line shafting except for condenser circulating services, enclosed shafting, using oil as a lubricant but with a grease lubricated tail bearing below the impeller, seems to be favored. Some pumps handling condenser circulating water use enclosed shafting but with water (often from another source) as the lubricant, thus eliminating any possibility of oil getting into circulating water and coating the condenser tubes.

Wednesday, April 22, 2009

Couplings Jaw

The Wrap N Snap (WNS) coupling eliminates the need for dismantling connected equipment while replacing or inspecting the elements because of it’s wrap around rubber connecting element. This eliminates excessive downtime on machinery which dramatically improves productivity.

With modular hub design and a spacer option, and a range of prebored hubs, the wrap N Snap (WNS) coupling is perfect for quick installation, maintenance, and is unsurpassed for quality, and flexibility.

WNS Coupling Features:

The WNS coupling allows inspection and replacing within minutes. Modular hub design allow the same hubs to be used for different models. Hubs are fully machined which guarantees a smooth contact surface, ease of alignment and excellent balance. Hubs come prebored and keyed to standard IEC motor shaft sizes. Spacer couplings are available for pump applications. Water, dust, oil and greases do not affect performance.

Selection

  • Service Factor
    Determine appropriate Service Factor from the table.
  • Design Power
    Multiply running power of driven machinery by the service factor. This gives Design Power which is used as a basis for coupling selection.
  • Coupling Size
    Refer to respective table for your required coupling type and read from the appropriate speed column until a power equal to a greater than the Design Power is found.
  • Bore Size
    Refer respective coupling dimensional table to check that the required bores can be accommodated.

Monday, April 20, 2009

Vertical Turbine Pumps

Vertical turbine pumps were originally developed for pumping water from wells and have been called deep-well-pumps, turbine well pumps, and bore hole pumps. As their application to other fields has increased, the name vertical turbine pumps has been generally adopted by manufacturers. This is not too specific is designation because the term turbine pump has been applied in the past to any pump employing a diffuser. There is now a tendency to designate pumps using diffusion vanes as diffuser pumps to distinguish them from volute pumps. As that designation becomes more universal, applying the term vertical turbine pumps to the construction formerly called turbine well pumps will become more specific.

The larger fields of application for the vertical turbine pump are pumping from well for irrigation and other agricultural purposes, for municipal water supply, and for industrial water supplies, as well as for processing, circulating, refrigerating, and air conditioning. This type of pump has also utilized for brine pumping, mine dewatering, oil field repressuring and other purposes.

Vertical turbine pumps should be designed with a shaft that can be readily raised or lowered from the top to permit proper positioning of the impeller in the bowl. An adequate thrust bearing is also necessary to support the vertical shafting, the impeller, and the hydraulic thrust developed when the pump is in service. As the driving mechanism must also have a thrust bearing to support its vertical shaft, it is usually provided with one large enough to carry the pump parts as well. For this two reasons, the hollow-shaft motor are sometimes made with their own thrust bearings to allow for a belt drive or for drive through a flexible coupling by a solid shaft motor, gear, or turbine. Dual driven pumps usually employ and angle gear with a vertical motor mounted on its top.

Sunday, April 12, 2009

Bases and Support for Vertical Pump

Vertical shaft pumps like horizontal shaft units, must be firmly supported. Depending upon the installation, the unit can be supported at one or several elevations. Vertical unit are seldom supported from walls, but even that type of support to sometimes encountered.

Occasionally, a nominal horizontal shaft pump design is arranged with a vertical shaft and a wall used as the supporting foundation. Regular horizontal shaft units can be used for this purpose without modification, except that the blade-plate is attached to a wall. Careful attention must be given to the arrangement to the pump bearings to prevent the escape of the lubricant. Installation of double suction, single-stage pumps with the shaft in the vertical position are relatively rare, except in some marine or navy applications. Hence, manufacturers have few standard pumps of the kind arrangement so that a portion of the casing forms the support (to be mounted pumps on soleplantes).

Wednesday, April 8, 2009

Vertical Single Suction Pump

Vertical single suction pumps with bottom suction are commonly used for larger sewage, water supply or condenser circulating applications. Such pumps are provided with wing feet that are bolted to soleplates grouted in concrete pedestal or piers. Sometimes the wing feet may be grouted right in the pedestal. This must be suitably arranged to provide proper access to any handholes in the pump and to allow clearance for the elbow suction nozzle if these are used.

If a vertical pump is applied to a condensate service or some other service for which the eye of the impeller must be vented to prevent vapor binding, a pump with a bottom single inlet impeller is not desirable because it does not permit effective venting. Neither does vertical pump employing a double suction impeller. The most suitable design for such applications incorporate a top single inlet impeller.

If the driver of a vertical pump can be located immediately above the pump, it is often supported on the pump itself. The shaft of the pump and driver may be connected by flexible coupling, which required that each have its own thrust bearing. If the pump shaft is rigidly coupled to the driver shaft or an extension of the driver shaft, a common thrust bearing is used, normally in the driver.

Although the driving motors are frequently mounted on top of the pump casing, one important reason for the use of the vertical shaft design is the possibility of locating the motors at an elevation sufficiently above the pump to prevent the accidental flooding of the motors. The pump and its driver may be separated by an appreciable length of shafting, which may required already bearing between the two units.

Bearings for vertical dry-pit pumps and for intermediate guide bearings are usually antifriction grease lubricated types to simply the problem of retaining a lubricant in a housing with a shaft projecting vertically through it. Larger units, for which antifriction bearing are not available or desirable, use self-oiling Babbitt steady bearings with spiral oil grooves. The pump is connected by rigid coupling to its motor which is provided with a line and a thrust bearing.

Tuesday, April 7, 2009

Vertical Pump

Vertical shaft pump fall into two classifications: dry-pit and wet-pit. Dry pit pumps are surrounded by air, the wet-pit types are either fully or partially submerged in the liquid handled.

Vertical Dry-pit Pumps

Dry pit pumps with external bearings include most small, medium, and large vertical pumps, most medium and drainage and irrigation pumps for medium and high heads, many large condenser circulating and water supply pumps, and many marine pumps. Sometimes the vertical pumps is preferred (especially for marine pumps) because it saves floor space. At other time it is desirable to mount a pump at a low elevation because of suction conditions, and it is also preferable or necessary to have the pump driver at a high elevation. The vertical pump is normally used for large capacity applications because it is more economical than the horizontal type, all factor considered.

Many vertical dry-pit pumps are basically designs with minor modifications (usually in the bearings) to adapt them for vertical shaft drive. This is not true of small and medium sized sewage pumps, however. In this units, purely vertical design in the most popular. Most of these sewage pumps have elbow suction nozzle because of their suction supply is usually taken from a wet well adjacent to the pit in which the pump is installed. The suction elbow usually contains a handhole with a removable cover to provide easy access to the impeller.

The dismantle one of these pumps, the stuffing box head must be unbolted from the casing after the intermediate shaft or the motor and motor stand have been removed. The motor assembly is drawn out upward, complete with the stuffing box head, the bearing housing and the like. This rotor assembly then be completely dismantled at a convention location.

Thursday, April 2, 2009

Motor For Hazardous Areas

Motor used within a hazardous location require a higher level of protection against the risk of harmful occurrences. PPA motors are available in the three most common high protection configurations. Exe, ExnA (formally Exn) and ExtD (formally DIP), all supplied with a protection rating of IP66. Most PPA hazardous area motor versions are available in frame sized 80 to 400. Combination of protection such as Exe and ExtD, or ExnA and ExtD, are also available.

International and Australian Standards

AS/NZS2381.1 specifies general requirement for the selection of electrical equipment and its installation and maintenance, to ensure safe use in areas where handled, stored or otherwise used, and which are therefore potentially hazardous.

The term flammable material includes gases, vapors, liquids, mist, solids and dusts, but does not include those materials which are specifically manufactured as explosives or materials which are inherently explosive.

The requirements of the listed standards apply only to the use of electrical equipment under normal or near normal atmospheric conditions. The requirements specified for hazardous location electrical equipment are supplementary to and not alternative to any requirements which would apply to equipment and installations in non hazardous areas.