Chemical Engineering

A screen analysis is the one passes solids through various sizes of screen mesh. This is done to get a particle size distribution. A group of solids is first passes through fine mesh and the amount that passes is noted, then a little larger mesh and the amount recorded and so on.

The relationship shown below is valid for Reynolds numbers in the range of 2100 to 106. For smooth tubes, a constant of 23,000 should be used rather than 20,000.

You can use the Weymouth equation to estimate the gas flow. Below is the equation. The compressibility should be evaluated at Pavg shown below. Nomenclature is as follows: Q = flow rate, Million Cubic Feet per Day (MCFD) Tb = base Temperature, degrees Rankin Pb = base pressure, psia G = gas specific gravity (reference air=1) L = line length, miles T = gas temperature, degrees Rankin Z = gas compressibility factor D = pipe inside diameter, in. E = Efficiency factor E=1 for new pipes with no bends E=0.95 for pipe less than a year old E=0.92 for average operating conditions E=0.85 for unfavorable operating conditions

Try this handy little equation: Horsepower = (GPM)(Delivered Pressure) / 1715 (Efficiency) GPM = Gallon per minute of flow Delivered pressure = Discharge minus suction pressure, psi Efficiency = Fractional pump efficiency

1. Capacity varies directly with impeller diameter and speed. 2. Head varies directly with the square of impeller diameter and speed. 3. Horsepower varies directly with the cube of impeller diameter and speed.

The minimum flow that a pump requires describes the flow below which the pump will experience what is called "shutoff". At shutoff, most of the pump's horsepower or work is converted to heat that can vaporize the fluid and cause cavitations that will severely damage the pump. The minimum flow of a pump is particularly important in the design of boiler feed pumps where the fluid is near its boiling point.

The following method, developed by M.W. Kellogg, gives results within 3.5% of most manufacturers’ curves. Eff % = 80-0.2855H+3.78x10-4HF-2.23x10-7HF2+5.39x10-4H2-6.39x10-7H2F+4.0x10-10H2F2 H = Developed head, ft F = Flow in GPM (gallons per minute) Applicable for heads from 50 to 300 ft and flows from 100 to 1000 GPM

The motor amperage should be measured in the field with the pump discharge valve wide open. Subtract about 10% from the pumps maximum rated amperage. Then the maximum impeller size can be determined from A2 = A1 (d2/d1)3 A2 = Maximum amperage minus 10% A1 = Current operating amperage d2 = Maximum impeller diameter d1 = Current impeller diameter

The specific roughness for welded, seamless steel is .0002 ft. PVC has a specific roughness of 0.000005 ft. You may also want to consider using the Hazen-Williams formula, which lists a coefficient of 130-140 for cement-lined cast iron piping. You need to decide which is more conservative for your application.

Typically straight-through diaphragm, clamp or pinch, and full-port ball valves with cavity fillers are the preferred type of slurry valves. In general, gate, needle, and globe valves are NOT recommended for slurry services.

If possible, slurry lines should indeed be sloped. Generally, to slope the pipes 1/2 inches for every 10 feet of pipe is recommended.

Bypass lines should be placed ABOVE the control valve so that the slurry cannot settle out and build up in the line during bypass.

Any device that restricts the flow to perform measurements is not recommended for slurries. These devices include orifices and dampeners. These devices can lead to liquid/solid separation and they can lead to excessive erosion. Instead, measuring devices that do not restrict the flow should be used. One example of such a device is the magnetic flow meter.

This application is nearly perfect for a turbine regenerative type of pump. Factors that immediately identify your application and pump type are the small flowrate, low NPSHa, and high temperature. The regenerative turbine was specifically developed for these conditions and one more: high discharge pressures. The high discharge pressure may not be necessary, but the regenerative turbine can give you an NPSHr of 0.5 feet with ease. They are particularly suited to saturated boiler feed water and your application is similar, albeit not in pressure. You can visit the site below to learn more about these types of pumps.

The accuracy of vortex flowmeters can be within 1% so long as they're being operating within their recommended flow range, have a steady stream, and you have 10 pipe diameters of straight pipe behind the in front of the flowmeters. Outside of these parameters, these flowmeters are not accurate.

Gear pumps are a type of positive displacement pump that are appropriate for pumping relatively high pressures and low capacities. Advantages include the ability to handle a wide range of viscosities, less sensitivity to cavitation (than centrifugal style pumps), relatively simple to maintain and rebuild. Disadvantages can include a limited array of materials of construction due to tight tolerances required, high shear placed on the liquid, and the fluid must be free of abrasives. Also, note that gear pumps must be controlled via the motor speed. Throttling the discharge is not an acceptable means of control.

If Q/d2.5 is greater than or equal to about 10.2, then the pipe is said to full. In this case, Q is in GPM (U.S. Imperial gallons per minute) and d is in inches. Reference: Pocket Guide to Chemical Engineering, ISBN: 0884153118