The first oddity I noticed was the noise from the vents associated with the individual reboilers. As Figure 6-1 shows, the expanding gas, used to drive the glycol pumps is also used as fuel to reboil the glycol. The excess gas not burned in the reboiler is vented under pressure control to the atmosphere. When… Read More »
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… Read More »
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… Read More »
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… Read More »
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,… Read More »
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… Read More »
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… Read More »
If the air flow existing from the tube bundle is hotter than the effluent gas, the chances are there is insufficient air flow to properly cool the gas. In particular, if the air temperature blowing out of the effluent end of the tube bundle is only 10°-15° cooler than the effluent gas, lack of air… Read More »
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… Read More »
1. Check interstage line temperatures to determine which valves have been removed from a cylinder. 2. Remove disabled valves, cages, and valves in ends taken out of service and replace with gaskets. This reduces parasitic pressure loss. 3. By-pass crank-end when not in use through fuel gas lines. Saves horsepower. 4. Is engine exhaust temperature… Read More »