Application To Pumps

Gas turbines are available to drive centrifugal pumps in a wide range of speeds and sizes, from 40 bp (30 kW) to over 20,000 hp (15,000 kW). It is not practical to list here all the avail able units because they are too numerous and are continually being upgraded and added to. A listing can be found in Sawyer's Gas Turbine Catalog, which is published annually.

Pipeline Service Crude oil pipeline service has seen a tremendous growth in the use of gas turbine drivers since the mid-l950s, and this trend will continue as crude oil production becomes more and more remote from its markets. The advantages of the gas turbine for this application are as follows:

1. Installed cost is usually lower than that of a corresponding reciprocating engine.

2. Variable-speed operation allows maintenance of a specific discharge pressure under a wide range of operating conditions, thus achieving maximum flexibility.

3. Normal gas turbine control system is easily adapted to unattended operation and remote control.

4. Operating experience has proved the gas turbine to have a high degree of reliability.

5. Gas turbines can be packaged into modules for ease of transportation and erection.

Water Flooding An important aspect of oil production is the use of secondary recovery methods to increase the output of crude oil reservoirs whose pressure does not allow the crude to flow freely to the surface. Flooding the reservoir with high-pressure water has been a primary technique for years. The development of high-pressure centrifugal pumps has allowed increased water flow into oil fields.

As most oil production is located in remote areas, the packaged gas turbine driver has become increasingly popular. Figure 9 shows a typical 3300-bhp (2460-brake kW) split-shaft gas-turbine-driven centrifugal water flood pump package. A cutaway view of a typical 1100-hhp (820-brake kW) gas turbine is shown in Figure 10; note the reduction gearing at the exhaust end for direct driving of a pump. Supporting systems, such as starter, lubrication oil pumps, governor, and fuel oil pumps, are driven off the accessory pods located at the air inlet end. Offshore platform installations require drivers with a minimum vibration as well as small, unbalanced inertial forces. The gas turbine fits both of these descriptions very well.

Cargo Loading Another interesting application of this prime mover is in the field of cargo loading, where units are currently in operation charging tankers with crude oil. Selection of a gas turbine pumping unit with critical speeds above the normal operating range allows great flexibility of operation, particularly during final topping operations.

FIGURE 9 A 3300-bhp (2460-bkW) gas turbine-driven waterflood package (Solar Division of International Harvester)
FIGURE 10 Cutaway view of 1100-bbp (820-bkW) split-shaft gas turbine driver (Solar Division of International Harvester)

Application Considerations The application of gas turbine drivers can vary from a simple driver for one pump operating at constant flow and discharge pressure to a multiplicity of units operating at variable speed on a pipeline. For the purposes of this discussion, it is assumed that the pumping system has been analyzed, a pump selection has been made, and all possible operating conditions have been analyzed so brake horsepower (brake kilowatt) and speed requirements are known.

The brake horsepower (brake kilowatt) output of the gas turbine must equal or exceed that required by the pump. This output can be determined by the use of specific performance curves similar to Figure 7 as corrected for elevation (Figure 8). Gear losses as necessary are added to the brake horsepower (brake kilowatt) required by the pump. Intermediate brake horsepower (brake kilowatt) and speed requirements should then be checked against a gas turbine output versus speed curve (Figure 4).

A torsional analysis of the combined unit is made (usually by the gas turbine manufacturer) to ensure the absence of any critical speeds in the operating range. Table 1 is a typical data sheet recommended for use when purchasing a gas turbine to drive a centrifugal pump.

TABLE 1 Typical data sheet for gas turbine driven centrifugal pump

Information from purchaser

Pumping requirements

Service_

Liquid_

Pumping temp._

Capacity (total) normal/max_/_

No. pumps operating_

Specific gravity at pump temp._

Viscosity at pumping temp._

Total head_

NPSH available_

Pump type, materials, and accessories

Site conditions

Range of site ambient temperature

Dry bulb Wet bulb

Atmospheric air

10 mm and above, ppm_

Corrosive constituents: Sulfur, ammonia, ammonium salts, salt or seacoast, other_

Noise specifications City, state, federal, other_

Emission specifications

City, state, federal, other_

Utilities available at site Steam: Pressure, lb/in2

Electricity

Cooling water

Source_quality_

Supply temp._min_max

Supply press, lb/in2

Information from manufacturer

Pumping requirements

Service_

Liquid_

Pumping temp._

Capacity (total) normal/max_/

No. pumps operating_

Specific gravity at pump temp._

Viscosity at pumping temp._

Total head_

NPSH available_

required _normal _max

Speed, rpm _normal _max

Efficiency _normal _max

Pump type, materials, and accessories

Gas turbine excluding gear

Design Max Min

Dry bulb temp.,

Total utility consumption

Electric power, kW ac/dc_

Compressed air, standard ft3/min (m3/min)_

Shipping data

Aux.

Turbine items

Information from purchaser

Information from manufacturer

Fuel

Gas_

Analysis attached

_liquid_

Accessories included (as required by purchaser)

Accessory items required (see list in right-hand column)

Inlet air filter Inlet air silencer Exhaust silencer Exhaust duct Starting equipment Load gear (if required) Driven pump Coupling

Fire protection system Equipment enclosure Baseplate or soleplates Combined turbine-pump Lub. oil system Main lube pump Auxiliary lub. pump Lub. reservoir Lub. filter Lub. oil cooler Unit control panel Auxiliary motor Control center

_yes

Source. Adapted from API Standard 616.

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