Pressure pipes

Shipments of concrete pipe in 1990 had a value of > 1.6 billion dollars. Much of this piping was for storm and sanitary sewers, culverts, and irrigation piping. Pressure piping sales were close to 300 million. There are a large number of manufacturers of concrete pipe since much of the pipe is produced reasonably close to the point of use. 

Piping pressure drop Optimum pressure drop... 

Straight tube loss See Chapter 1, Fluid Flow, Piping Pressure Drop ... 

All losses except for straight tube Straight tube loss 2- Ah = 2.9-4-N 2g See Chapter 1, Fluid Flow, Piping Pressure Drop ... 

Usually used where piping pressure drop is high and therefore natural circulation is impractical. 

When the predetermined system blowdown pressure is reached, the pilot valve closes, full system pressure is restored to the dome above the piston, and the piston is quickly moved to the closed position. The pilot valve pressure sensing point may be located in the main valve inlet neck, or on the shell of the vessel being protected. The valve is less affected by inlet piping pressure drop in the latter case, as described below. 

Multiply K by the empty-pipe pressure drop to obtain the pressure drop eaused by the Kenies mixer model installation. The theoretieal horsepower required by the Kenies mixer is determined by... 

In the sulfide stress cracking region, appropriate metallurgy is required in line piping, pressure vessels, etc. There is a listing of acceptable steels in the NACE standard. Steels with a hardness of less than 22 Rockwell C hardness should be used in areas where sulfide-stress cracking is a problem. 

Piping pressure ratings should be designed so that no matter which valve is closed, the piping is rated for any possible pressure it could be subjected to, or is protected by a relief valve. 

In order to cover all the lines in the facility, pipe and valve tables are normally included. Each pipe pressure class is assigned a designation. Sometimes it is necessary to assign two classes for a single designation. For ample, in Table 15-1 A, L, and AA are all ANSI 150 cl , but they contain different fluids. 

American Standards Association piping pressure classes are ... 

Quite often the mixing units or elements are installed in a circular pipe however, they can he adapted to rectangular or other arrangements. Pressure drop through the units varies depending on design and whether flow is laminar or turbulent. Because of the special data required, pressure drops should he determined with the assistance of the manufacturer. Of course, pressure drops must he expected to he several multiples of conventional pipe pressure drop. 

For two stages of compression, what should be the pressures across the cylinders if the intercooler and piping pressure drop is 3 psi ... 

If the drill string is thought to be a thin wall cylinder with closed ends, then the drill pipe pressure produces the axial stress and tangential stress given by the following formulas ... 

Find the tensile load capacity of 5-in., nominal weight 19.5-lb/ft, steel grade E, premium class drill pipe exposed to internal drill pipe pressure = 3,000 psi and rotary torque T = 15,000 ft-lb. 

Note that the drill pipe pressure is a sum of all the pressure losses in the circulating system. 

Where, of necessity, the vent pipe rises to a considerable height, excessive internal pressure on the tank may result, due to the pressure head of oil should an overflow occur. To prevent any possible tank failure due to such an occurrence a vent pipe pressure-relief device must be provided. It should be self-draining to reduce the risk of blockage, particularly when using heavy oil fuel. Codes require that these devices should not place any restriction on oil flow and must discharge within the bund area. 

Purge points shall be fitted at section isolation valves, at the end of pipe runs and at other suitable positions to facilitate the correct purging of pipes. Pressure test points should be fitted at the outlet of each section-isolating valve. 

When water (a Newtonian liquid) is in an open-ended pipe, pressure can be applied to move it. Doubling the water pressure doubles the flow rate of the water. Water does not have a shear-thinning action. However, in a similar situation but using a plastic melt (a non-Newtonian liquid), if the pressure is doubled the melt flow may increase from 2 to 15 times, depending on the plastic used. As an example, linear low-density polyethylene (LLDPE), with a low shear-thinning action, experiences a low rate increase, which explains why it can cause more processing problems than other PEs. The higher-flow melts include polyvinyl chloride (PVC) and polystyrene (PS). 

Acceleration due to gravity Thermal conductivity Length of pipe Pressure... 

The equations in the section Piping Pressure Drop are, of course, intended for use with full pipes. Reference 12 provides a rapid way to estimate whether a horizontal pipe carrying liquid is full. The criteria are... 

It should be noted that Equations 13.9 and 13.10 apply to smooth pipes, whereas the pipes used for transmission of fluids usually have some surface roughness, which increases the friction factor. However, for short fluid transmission pipes, the overall pressure drop is usually dominated by the pressure drop in the pipe fittings (valves, bends, etc). Thus, for short transmission pipes, there is little point in calculating the straight pipe pressure drop accurately. If the transmission pipe is long (>100 m) and straight, then the Fanning friction factor can be correlated as7 ... 

Euler number Neu. . A P Neu PV2 AP = pressure drop in pipe (Pressure energy)/ (kinetic energy) Flow in closed conduits... 

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