Pumps static head

Static Head. Fluid elevation above or below the datum line. For horizontal centrifugal pumps, static head is calculated from the pump center line with vertical pumps, it is taken from the eye of the first-stage impeller. 

Static Discharge Head The static discharge head is the vertical distance measured from the free surface of the hquid in the receiver to the pump centerhne, plus the absolute pressure at the hquid surface. Total static head hf, is the difference between discharge and suction static heads. 

Hs = Static head in feet (positive or negative) of the fluid level in the suction vessel to the pump centerline. 

The Hs, static head, is the static height in feet observed from the level in the vessel to be drained to the centerline of the pump. If the... 

The curve of the pump in this service should show a NPSHr of less than 14 feet at the duty point. The purpose of this pump is to drain this tank down to 14 feet below the pump without eavitating. Let s consider a second static head, Hs-, of-14 feet. The other factors would remain the same ... 

Hs Static Head. It is the level in the d-a tank above the pump centerline. This is normally about 12 to 15 ft. 

I. Hs - the static head, or the change in elevation of the liquid across the system. It is the difference in the liquid surface le el at the suction source or ve.s.sel, subtracted from the liquid surface level where the pump deposits the liejuid. The Hs is measured in feet of elevation change. Some systems do not have Hs or elevation... 

One component of the TDH is the Hs, the static head. In this example the surface level in the discharge tank is 115.5 ft above the pump centerline. The surface level in the suction tank is 35.5 ft above the pump centerline. The AHs, by observation is 80 ft. See Figure 8-6. 

For a saturated (bubble point) liquid, pipe vertically downward from the drawoff nozzle as close to the nozzle as possible. This gives maximum static head above any horizontal sections or piping networks ahead of the pump. 

Discharge static head H (from centerline of pump) Suction static head S, (actually -HS)... 

Figure 3-40A. Static head, overall = H + L. (Adapted by permission, Centrifugal Pumps Fundamentals, Ingersoll-Rand Co., Washington, N.J. 07882.)...

Note that both the discharge and suction pressures must be on the same base/units. These illustrations are for static head only, while overall (he pump has to work against the static and the pressure heads. (To be discussed.)... 

Static head is positive pressure of fluid on pump suction above its centerline (S), (4-). 

The discharge head of a pump is the head measured at the discharge nozzle (gauge or absolute), and is composed of the same basic factors previously summarized 1. static head 2. friction losses through pipe, fittings, contractions, expansions, entrances and exits 3. terminal system pressure. 

It is important to recognize that a cenlrijugal pump will operate only along its performance curve [10, II]. External conditions will adjust themselves, or must be adjusted in order to obtain stable operation. Each pump operates within a system, and the conditions can be anticipated if each component part is properly examined. The system consists of the friction losses of the suction and the discharge piping plus the total static head from suction to final discharge point. Figure 3-51 represents a typical system head curve superimposed on the characteristic curve for a 10 by 8-inch pump with a 12-inch diameter impeller. 

Qni = Flead at best efficiency point on pump curve, ft = Viscous liquid capacitv, GPM Q = Water capacity, GPM S =. Suction static head, ft, or height of liquid (static) above ( + ) or below ( —) the center line of the pump on suction side, ft, or,... 

Figure 5-5F. Lifter turbine is efficient for pumping large volumes against static heads of less than 36 inches. As shown, It Is used below a draft tube. Inverted, It is used above an orifice plane In tank bottom. Courtesy of Lightnin (formerly Mixing Equipment Co.), a unit of General Signal.

Figure 5-5U. Shrouded turbine for high pumping capacity. Usually used with low static heads, creates minimum of direct shear. Courtesy of International Process Equipment Co., Div. of Patterson Foundry and Machine Co.

When a fluid is flowing through a pipe, resistance to flow is caused by friction. The pipe bore selected for each section must be such that under any operating conditions, the initial head, either static head of oil in the supply tank or the pump delivery pressure, will be adequate to ensure the required flow rate. Additionally, any change of flow rate and consequent variation in loss of head must not adversely affect the operation of the associated oil-burning equipment. 

The absolute pressure at the inlet to the pump is usually the atmospheric pressure in the receiver, plus the static head from the water surface to the pump inlet and minus the friction loss through the pipes, valves and fittings joining the pump to the receiver. If his absolute pressure exceeds the vapor pressure of water at the temperature at which it enters the pump, then a net positive suction hand (NPSH) exists. If this NPSH is above the value specified by the pump manufacturer, the water does not begin to boil as it enters the pump suction and cavitation is avoided. If the water entering the pump is at a higher temperature, its vapor pressure is increased and a greater hydrostatic head over the pump suction is needed to ensure that the necessary NPSH is obtained. 

However, since in most cases pumps are supplied coupled to receivers and the static head above the pump inlet... 

Hs0 = Head at no flow, or shutoff, ft I4ms = Head of viscous fluid, ft Hw = Water equivalent head, ft hd = Discharge head on a pump, ft of fluid hs = Suction head (or suction lift) on a pump, ft of fluid hSL, hDL = Friction losses in pipe and fittings , subscript SL for suction line and DL for discharge line, ft of fluid hv = Velocity head, ft of fluid L = S = Static head, suction side, ft (Figure 3-38)... 

Centrifugal pumps, 181 Discharge systems, 187 Example calculation, 186 Flow friction losses, 185. 186 Friction losses, pipe, see Chapter 2 Friction, 188 Pressure head, 184—186 Static head, 184-186 Suction head, 184, 185 Suction lift, 184, 185 Suction systems, 186 Hvdroclones, 265—267 Application system, 267 Ignition, flammable mixtures, 493 Impellers, centrifugal, reducing diameter, 203 Impellers,... 

Avoid overheating FW tanks and the generation of steam in the tank. If the FW temperature is too high and there is inadequate net positive static head (NPSH) on the FW pump suction, the pump will not operate and cavitation problems may occur. 

The net head or pressure measured in ft. or m that causes a liquid to flow through the suction side of a pump, enter the pump chamber, and reach the impeller. When the source of liquid is above the pump, NPSH equals the barometric pressure plus the static head, less the entrance head, frictional losses in the suction piping and vapor pressure of the liquid. When the source of liquid is below the pump, NPSH equals the barometric pressure less the static head, entrance head, frictional losses in the suction piping and vapor pressure of the liquid. NPSH is specific for each pump design and application and must be supplied by the manufacturer. 

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