Specific gravity pumping

Liquid Condition Specific Gravity Pump Material... 

Displacer units are tolerant of specific gravity shifts within their range, require no power to operate, are intrinsically safe, and can be easily field cahbrated. A single displacer unit can control up to three alarm set points or up to three pumps with different spans. They can be caHbrated for set points or pump spans from 0.15—30 m from the top of the vessel mounting. 

Thermal Dispersion. Thermal dispersion level switches are used on appHcations where multiple shifts inhquid characteristics are present. The unit is responsive only to a change in the thermal conductivity of the Hquid and ignores shifts in specific gravity, dielectric, density, temperature, and pressure. Units are used for alarm signal however, pump control maybe obtained using two units with a latching relay. 

Head. The tme meaning of the total developed pump head, H, is the amount of energy received by the unit of mass per unit of time (14). This concept is traceable to compressors and fans, where engineers operate with enthalpy, a close relation to the concept of total energy. However, because of the almost incompressible nature of Hquids, a simplification is possible to reduce enthalpy to a simpler form, a Bernoulli equation, as shown in equations 1—3, where g is the gravitational constant, SG is specific gravity, y is the density equivalent, is suction head, is discharge head, and H is the pump head, ie, the difference between H, and H. 

Table 6. Specific Gravities and Viscosities at Pumping Temperatures...

FIG. 10-31 Typical pump performance curve. The curve is shown for water at 85 F. If the specific gravity of the fluid is other than unity, BHP must he corrected. 

Change process to adjust specific gravity to design value, or throttle pump to reduce horsepower requirements. This will not correct problem with some vertical turbine pumps that have a flat horsepower-required curve. 

In the graphie below (Figure 1-5), these three pumps arc developing the same discharge pressure. In this ease they develop different heads inversely proportional to the specific gravity of the fluids. 

Where H = head in feet generated by the pump Q = flow recorded in gallons per minute sp. gr. = specific gravity 3960 = constant to convert BHp into gallons per minute... 

If the specific gravity at pumping temperature were not equal to 1.0, then the water horsepower would be adjusted by the spceifie gravity. 

Debris particles that are heavier than water migrate to the outer wall area and slither down into a collection bowl that is periodically blown down. Very little water is lost. Typical performance is 97.8% of solids with specific gravity exceeding 1.2 down to 45 microns. Side stream filtration is more common in cooling tower applications. The scheme uses a small dedicated pump to draw dirty water from the sump, direct it through a filtration device and sent it back to the basin. 

---