Piping bends

The thickness of pipe bends shah be determined as for straight pipe, provided the bending operation does not result in a difference between maximum and minimum diameters greater than 8 and 3 percent of the nominal outside diameter of the pipe for internal and external pressure respectively. 

Ri = bend radius of welding elbow or pipe bend, in (mm)... 

Corrosion involving nonoxidizing acids can be highly sensitive to flow. Thus regions of high flow and turbulence are often more severely attacked than more quiescent regions. Weirs, lips, and other flow obstructions increase turbulence and thus corrosion. Pipe elbows, tees, and joints are frequently attacked. Outer curves at pipe bends often are more severely wasted than inner bends. 

For determining the frictional head, refer to friction loss in pipes, bends, elbows and reducers and valves as provided in Tables A.I and A.2 ... 

PIPE BENDS AND FLANGED OR BUTT-WELDING 90° ELBOWS... 

The resistance coefficient. Kb, for pipe bends other than qo° may be determined as follows ... 

The K coefficient values for each of the items of pipe, bends, valves, fittings, contractions, enlargements, entrance/exits into/from vessels are additive as long as they are on the same size basis (see Table 2-2 and Figures 2-12A through 2-16). Thus the resistance equation is applicable to calculate the head or pressure loss through the specific system when the combined Rvalue is used. 

Slabs, pipe sections, pipe bends, beveled lags. 

Sentinel holes are used as a simple form of thickness testing. A small hole of about I - 6 mm diameter is drilled from the outer wall of the piece of equipment to within a distance from the inner wall (in contact with the corrodent) equal to the corrosion allowance on the equipment (Fig. 9.11). The technique has been used even in cases where the corrodent spontaneously ignites on contact with the atmosphere. The philosophy is that it is better to have a little fire than a big one which would follow a major leak from corrosion through the wall. When the sentinel hole begins to weep fluid a tapered plug is hammered into the hole and remedial maintenance planned. Siting the sentinel holes is somewhat speculative although erosion at the outside of a pipe bend is often monitored in this way. 

Water is flowing at 5 m/s in a 50 mm diameter pipe which incorporates a 90° bend, as shown in Figure 2.8. What is the additional force to which a retaining bracket will be subjected, as a result of the momentum changes in the liquid, if it is arranged symmetrically in the pipe bend ... 

Design of vessel and vent line pipe supports is very important because very large forces can be encountered as soon as venting begins. Figure 4 shows the equations and nomenclature to calculate forces on pipe bends. The authors have heard of situations where vent line bends have been straightened, lines broken off, or vent catch tanks knocked off their foundations by excessive forces. For bends, the transient effects of the initial shock wave, the transition from vapor flow to two-phase flow, and steady state conditions should be considered. Transient conditions, however, are likely to be so rapid as to not have enough dura-... 

Water is flowing in a horizontal pipe bend at a velocity of 10 ft/s. The radius of curvature of the inside of the bend is 4 in., and the pipe ID is 2 in. A mercury manometer is connected to taps located radically opposite each other on the inside and outside of the bend. Assuming that the water velocity is uniform over the pipe cross section, what would be the manometer reading in centimeters What would it be if the water velocity were 5 ft/s Convert the manometer reading to equivalent pressure difference in psi and Pa. 

Water flows through a 30° pipe bend at a rate of 200 gpm. The diameter of the entrance to the bend is 2.5 in., and that of the exit is 3 in. The pressure in the pipe is 30 psig, and the pressure drop in the bend is negligible. What is the total force (magnitude and direction) exerted by the fluid on the pipe bend ... 

Water is flowing through a 45° pipe bend at a rate of 200 gpm and exits into the atmosphere. The inlet to the bend is 1 in. inside diameter, and the exit is 1 in. in diameter. The friction loss in the bend can be characterized by a loss coefficient of 0.3 (based on the inlet velocity). Calculate the net force (magnitude and direction) transmitted to the flange holding the pipe section in place. 

From Table 3 it can be seen that by optimizing the configuration of pipeline, it is possible to reduce pressure loss, air flow, transport velocity, and hence, pipe/bend wear. Depending on hardware requirements and reliability, which would to some extent govern the maximum operating pressure of the system (e g., say, 400 or 500 kPag), Pipeline Nos. 5 or 6 could be selected for this long-distance application. However, if diverter valves are required at the end of the pipeline, it may be more convenient to select Pipeline No 5 (i.e., D1 = 154 mm instead of 203 mm). 

By employing accurate test-design procedures (Pan and Wypych, 1992a), it is possible to model and design each pipe branch separately so that the system ultimately is well balanced. However, such a system may not be reliable over time due to uneven wear in the pipes/bends, changes in material property and/or on-site conditions. 

Reaction components acting on a pipe bend due to the change in fluid momentum... 

PL-2.8 ANCHORAGE FOR BURIED PIPING PL-2.8.1 Pipe Bends or Offsets... 

Di, = outside diameter of branch Ri = bend radius of welding elbow or pipe bend r = see definition in para. 304.3.4(c) and Table 10-48 r2 = mean radius of matching pipe s = miter spacing at centerline... 

---