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Back pressure is the term used for the hydraulic pressure required to create a flow through a chromatography column in high-performance liquid chromatography, the term deriving from the fact that it is generated by the resistance of the column, and exerts its influence backwards on the pump that must supply the flow.
Back pressure can force an undesirable contaminant to enter potable water piping. Sources of back pressure may be boilers, heat exchanging equipment, power washing equipment, fire sprinklers, or pumps in the water distribution system. In some cases there may be an almost continuous risk of overcoming the static water pressure in the piping.
The silt density index is a measure for the fouling capacity of water in reverse osmosis systems. The test measures the rate at which a 0.45-micrometre filter is plugged when subjected to a constant water pressure of 206.8 kPa (30 psi). The SDI gives the percent drop per minute in the flow rate of the water through the filter, averaged over a ...
As a water conservation measure, many water purification plants recycle filter backwash water and other product streams from sludge treatment processes back to the beginning of the plant. [ 4 ] : 22.40–22.43 [ 5 ] : 242–3 On June 8, 2001, the USEPA released a final regulation governing acceptable practices for recycling backwash water. [ 10 ]
where the pressure loss per unit length Δp / L (SI units: Pa/m) is a function of: ρ {\displaystyle \rho } , the density of the fluid (kg/m 3 ); D H {\displaystyle D_{H}} , the hydraulic diameter of the pipe (for a pipe of circular section, this equals D ; otherwise D H = 4A/P for a pipe of cross-sectional area A and perimeter P ) (m);
Backflow occurs for one of two reasons, either back pressure or back siphonage. [1] Back pressure is the result of a higher pressure in the system than in its supply, i.e. the system pressure has been increased by some means. This may occur in unvented heating systems, where thermal expansion increases the pressure. Back siphonage is the result ...
g w is the unit weight of water (kN/m 3), = / d w is the depth of the water table (m), and the pore pressure at depth, z, below the surface is: = (), where: p u is the unsaturated pore water pressure (Pa) at point, z, below ground level, z is depth below ground level.
If the fluid is a liquid, a different type of limiting condition (also known as choked flow) occurs when the venturi effect acting on the liquid flow through the restriction causes a decrease of the liquid pressure beyond the restriction to below that of the liquid's vapor pressure at the prevailing liquid temperature.