Piping recommended velocities

Enough space must be available to properly service the flow meter and to install any straight lengths of upstream and downstream pipe recommended by the manufacturer for use with the meter. Close-coupled fittings such as elbows or reducers tend to distort the velocity profile and can cause errors in a manner similar to those introduced by laminar flow. The amount of straight pipe required depends on the flow meter type. For the typical case of an orifice plate, piping requirements are normally Hsted in terms of the P or orifice/pipe bore ratio as shown in Table 1 (1) (see Piping systems). 

Maximum Recommended Velocities Through Nozzle Connections, Piping, etc. Associated With Sheil and/or Tube Sides of Heat Exchanger... 

Piping systems should be designed for an economic flow velocity. For relatively clean fluids, a recommended velocity range where minimum corrosion can be expected is 2 to 10 fps. If piping bores exist, maximum fluid velocities may have a mean velocity of 3 fps for a 3/8-in. bore to 10 fps for an 8-in.-diameter bore. Higher flow velocities are not uncommon in situations that require uniform, constant oxygen supply to form protective films on active/passive metals. 

The number of jets is based on gas velocity. For 1-inch standard pipe, the recommended velocity permits a flow rate of 61,200 scfd per jet. Expressed as an equation... 

Magnetic flow meters are sometimes utilized in corrosive Hquid streams or slurries where a low unrecoverable pressure drop and high rangeabiHty is required. The fluid is required to be electrically conductive. Magnetic flow meters, which use Faraday s law to measure the velocity of the electrically conductive Hquid, are relatively expensive. Their use is therefore reserved for special situations where less expensive meters are not appropriate. Installation recommendations usually specify an upstream straight mn of five pipe diameters, keeping the electrodes in continuous contact with the Hquid. 

Oleum Equipment ndPiping. The traditional material of constmction for oleum is carbon steel. Relatively low oleum velocities must be used in steel piping to prevent excessive corrosion. The corrosiveness of oleum decreases with increasing SO concentration. Eor oleum concentrations <5% SO, carbon steel is not recommended because of excessive corrosion. Steel is borderline from 5% to about 15% SO, depending on temperature. 

Here are various recommended flows, velocities, and pressure drops for various piping services. 

The bend radii of pipes should be designed to be as large as possible. A minimum of three times the pipe diameter is recommended to maintain safe, economic flow velocities. 

Figure 1. Available pressure drop may in some cases dictate acceptance of a lower maximum velocity, but at least 75 m/s is recommended to insure good dispersion. Flare tips consisting of a simple open-ended pipe with a single pilot are subject to flame lift-off and noise problems at lower velocities, and should therefore be designed for a maximum velocity of 50 m/s.

The required pipe internal diameter can be calculated based on the volumetric flow rate and a maximum velocity. The maximum velocity may be the erosional velocity or a limiting value based on noise or inability to use corrosion inhibitors. In gas lines it is recommended that the maximum... 

The unit shown in Figure 4-49 has been used in many process applications with a variety of modifications [18,19,20]. It is effective in liquid entrainment separation, but is not recommended for solid particles due to the arrangement of the bottom and outlet. The flat bottom plate serves as a protection to the developing liquid surface below. This prevents re-entrainment. In place of the plate a vortex breaker type using vertical cross plates of 4-inch to 12-inch depth also is used, (Also see Reference [58].) The inlet gas connection is placed above the outlet dip pipe by maintaining dimension of only a few inches at point 4. In this type unit some liquid will creep up the walls as the inlet velocity increases. 

Do not grossly oversize compressor piping. Compressor manufacturers generally recommend gas velocities in the... 

Recommended methods for assessing the corrosivity of waters, including flowing potable waters, are described in ASTM 02688 1983. Three procedures are described in which test specimens in the form of wires, sheets or tubes are placed in pipes, tanks or other equipment. The test assembly for the first of these consists of three helical wire coils mounted in series on, and electrically insulated from, a supporting frame. The assembly must be installed so that flow is not disturbed and turbulence and high velocities, e.g. of more than 1 -53 ms , are avoided. A minimum test period of 30 days is recommended. Procedures for the other specimen forms are given in the standard. 

A critical shear stress, Tcril between 3 and 4 N m-2, has been recommended to prevent the formation of a thick biofilm. Melbourne and Metropolitan Boards of Work (1989) propose T = 3.4 N m-2. In a small diameter pipe (<0.4 m) this corresponds to a velocity about 1 m s-1. In a larger pipe with a diameter > 1 m, the velocity should exceed 1.2-1.4 m s-1. 

Hydrogen gas velocities in piping should not exceed the erosional velocity at peak conditions. Lower velocities are recommended. The erosional velocity, uc, is calculated by 1... 

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