Jabsco Pump Catalog

FEATURES • Versatile: The flexible impeller pump combines the priming feature of positive displacement type pumps with the general transfer ability of centrifugals. It will pump either thin or viscous liquids and can handle more solids in suspension than other types of rotary pumps. It operates at low or high speeds, can be mounted at any angle and pumps in either direction with equal efficiency. • Self-Priming: Pumps instantly with dry suction, lifts up to 10' (3m) — up to 25' (8m) when wetted. Permits cleaner, safer installations. No foot valve required. • Simplicity: One moving part — a tough, long-lived, wear-resistant flexible impeller, lubricated by the liquid being pumped. No metal-to-metal pumping action — no gears to jam, clog or become noisy. • More Capacity: Flexible impeller pumps, in general, require less space because they deliver greater flow for weight, size and price than other types of pumps. The data given for the engine cooling systems and pump selection is for guidance only. It does not cover high-performance engines. You should always consult the engine marinizer. It is important that Jabsco Engine Cooling Pumps and Systems are matched during the design of ships' engine installations. Once installed, safety margins must be safeguarded, i.e., the emphasis must be on preventive , not corrective maintenance. Cooling systems most commonly used for marine propulsion engines are: • Heat exchanger cooling • Keel cooling • Direct cooling PRESSURE RANGES Standard impellers Suitable for continuous operation up to the following limits: • 1/4", 3/8" and 1/2" port sizes to 40' (12m) head, 17.3 psi (1.2 bar). • 1" to 2" port sizes to 70' (20m) head, 30.3 psi (2 bar). Special high pressure impellers Available for certain models. Impeller life will be extended by operating in the lower portion of recommended pressure range. TEMPERATURE RANGE • 45° to 180°F (7° to 80°C) For fluids less than 45°F (7°C) consult with the factory. OPERATING SPEEDS Ball bearing pumps • 1/4" or 1/2" ports: 3600 rpm max. • 3/4" or 1" ports: 3000 rpm max. • 1-1/4" ports: 2200 rpm max. • 2" ports: 2200 rpm max. This is also known as a closed system, i.e., the primary cooling circuit is isolated from the surrounding atmosphere. A centrifugal pump circulates fresh, treated water through the cylinder block passages and around the tube stack of a heat exchanger. The Jabsco raw water pump draws raw water (from sea or lake) through the ship’s hull inlet and pumps it through the heat exchanger tubes where it removes the heat transmitted from the primary circuit before discharging overboard. The heat exchanger, which can be single-pass or two-pass type, should be capable of handling approximately 10% more than the maximum engine heat rejection rate and may be fitted separately or as an integral part of the expansion/header tank. This tank allows venting of air or combustion gasses absorbed by the cooling water during engine operation and provides a positive pressure on the fresh water pump inlet. This pump, fitted in the coldest part of the primary circuit, has a capacity which will maintain a water temperature differential of approximately 45°F (8°C) across the cylinder block at full load. The engine operating temperature is regulated by a marine thermostat to about 185°F (85°C) on most engines. To provide an adequate safety margin for commercial diesel engines, which may be expected to operate more than 2500-3000 hours per year, size and rpm of the Jabsco raw water pump should be selected to give a flow capacity of approximately 15 GPM (57 LPM) for every 100hp maximum engine load and rpm. If an exhaust manifold is fitted in the raw water or fresh water circuit, the raw water pump flow capacity should be 10-15% higher. Additional coolers, such as oil coolers or charge air coolers, must be fitted after the pump, but in a compromise between reliability, size and weight, and pump delivery. Head should be about 10-13 psi of water at maximum rpm. Safety margins in pump inlet systems are extremely critical, so any restrictions or bends, other than seacock and inlet strainers, are to be avoided at all costs (see Suction System page 97). Raw water from the exhaust manifold is often injected into the exhaust pipe ( after an exhaust elbow to prevent raw water flowback into the cylinders), which may then be ducted through areas where a hot pipe would create a hazard. This is known as a “wet exhaust” system. In addition, mixing of water with exhaust gases will reduce exhaust noise. However, on small engines the raw water flow should not be less than 2.5- 4 GPM (9.5-15 LPM) for adequate silencing. Heat Exchanger Cooling 95 11 Flexible Impeller Pumps Introduction