Archive for October, 2009

Troubleshooting At The Dehydration & Compression Station

Natural gas transported through common carrier pipelines must meet a moisture specification of 7 pounds of water per MMscf. Gas is usually dried to meet this requirement by scrubbing with a concentrated glycol solution. Figure 6-1 shows a standard glycol contactor tower, regenerator, and pump. Gas flows into the bottom of this tower where entrained …

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Process Cooling – Glycol Dehidrator Increase Gas Temperature

We invariably cool the compressor discharge prior to dehydration. Unfortunately, natural gas will be reheated—sometimes by 10°F — in a typical gas field dehydration contactor. This occurs because of two factors: • The circulating glycol may be 70° hotter than the contactor gas inlet temperature. • The heat of condensation or absorption of the water …

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Process Cooling – Excessive Gas Inlet Temperature

There are three factors which increase an air cooler’s inlet temperature: • The compressor valves are faulty. • The compression ratio has increased. • High pressure, high temperature natural gas is being produced from the wellhead. heat transfer surface area) a 10°F increase in compressor discharge temperature may increase the air cooler outlet temperature by …

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Process Cooling – Gas Side Problems

Whenever finned—tubed cooling bundles are arranged in parallel, as shown in figure 5-2, a potential exists for poor cooling due to gas maldistribution. A low gas outlet temperature from an individual bundle is indicative of lack of gas flow through that bundle. To correct this situation, measure the total pressure drop across the coolers. Next, …

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Process Cooling – Fan Blade Pitch

Air flow from a fan will vary considerably with the blade pitch. The pitch is adjustable. To save engine horsepower, an operator may set the blade pitch at 15° during the winter. During the summer, he may attempt to maximize air flow by setting the blade pitch up to maximum—22.5°. Almost all fan cooler blades …

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Process Cooling – Fan Tip Speed

Most fans are designed for a maximum fan tip speed of 14,000 feet per minute. To calculate the tip speed of the fan, do not calculate the fan rpm, from the pulley size and driver speed. The belts may be slipping. Measure the fan speed directly with a tachometer. Then calculate the fan tip speed …

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Process Cooling – Gas Cooling

Underground gas transmission pipelines are externally wrapped in a protective plastic type coating. Gas temperatures in excess of 130°F to 140″F can cause embrittlement and eventual failure of this coating. For this reason, the usual industry practice is to specify that natural gas discharging into a transmission pipeline be cooled to less than 120°F. Also …

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