Auxiliary Equipment

The condensate injection piping should be conservatively sized based on the maximum injection flow requirements to obtain a low pressure drop between the injection source and the seal injection control valve. These control valves may be equipped with limit stops to prevent full closure and enable a continuous cool injection to the seals under almost all operating conditions. In some installations, isolating lines are furnished around the valves to enable a continued injection flow even during control valve maintenance. The valves can also be designed to remain open during a failure, such as a loss of station air to the pneumatic controls, and to close only with an air supply. Injection control systems that are not properly maintained might result in cold water entering a hot pump. Should this problem occur while a boiler feed pump is in the hot standby mode or when turning gears, thermal gradients will occur, leading to contact among the close running fits within the pump. Proper maintenance and operation of the injection control systems is necessary to ensure reliable operation of the pump itself. The air supply filter regulators for each control must be furnished with relatively dry clean air at station supply pressure.

The condensate injection supply to the seals must be clear and free of foreign matter to prevent damage to stuffing box components. It is therefore necessary to install filters in the injection line prior to the control valve. To keep damaging fine mill scale, oxide particles, abrasives, and other materials from entering the small seal clearances, several pump manufacturers recommend 100-mesh (150-micron) dual strainers. If dual strainers with isolating valves are used, each filter can be cleaned without interrupting injection flow during pump operation. Pressure gages should be installed before and after each filter to permit the operator to monitor filter pressure drop. A differential pressure switch and alarm for each filter are preferable to alert the operator to clean the strainer when pressure drop becomes excessive.

The condensate injection shaft seals should always be filled with cool water before and during pump operation, even during reverse pump rotation. Some pump manufacturers stipulate that condensate injection must be continuous without any interruption during all operation modes.

The clearances in the condensate injection shaft seal may double over the service life of the internal wearing parts. With double clearances, the leakage will approximately double. This factor should be considered when sizing the return drain piping back to the plant condenser if frictional losses are to be kept to a minimum. The drain line should be pitched at least a quarter-inch per foot (20 mm per meter). The collecting chamber at the pump stuffing box is vented to the atmosphere, and the only head available to evacuate the chamber is the static head between the pump and the point of return. This head must always be well in excess of the frictional losses (even after the leakage is doubled). Otherwise, the drains may back up, the collection chambers may overflow, and the adjacent bearing brackets may flood, with subsequent possible intrusion of water into the pump bearings and lubricating oil.

The seal collection chambers have especially large connections to assure proper drainage, provided no back pressure exists. Two types of condensate drain systems can be used to dispose of the drain coming from the collecting seal chambers. One system uses traps that are piped directly to the plant condenser if sufficient static head exists for positive drain flow. The second system collects the drain in a condensate storage tank into which various other drains (from other pumps shaft seals and so on) are also directed. As this vented storage tank is under atmospheric pressure, it must be set at a reasonable elevation below the pump centerline so that the static elevation difference will overcome fric-tional losses in the drain piping. A separate condensate transfer pump, under control of the storage tank liquid level control system, can then pump the condensate drains from the storage tank into the plant condenser. The storage tank should have its own overflow protection system that enables outside drainage if, for some reason, proper drainage cannot be achieved. For example, the top of the tank vent pipe should be below the pump centerline to help preclude the possibility of drainage backing up to the level of the pump seal collection chambers. Note that this storage tank should also be large enough for an adequate drainage collection to help prevent backups.

Renewable Energy 101

Renewable Energy 101

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. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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