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aReturn-line Capacity (lb/hr) with Pressure Drop (psi) for 100 ft of Pipe at a Velocity of 5000 ft/min.

Table 6.12 shows a typical pressure-capacity table extracted from a manufacturer's catalog. The use of such a table can be illustrated with the following example.

Example: A steamjacketed platen press in a plastic lamination operation uses about 500 lb/hr of 30-psig steam in normal operation. A 100-ft run of 1-in. pipe returns condensate to a receiver pressurized to 5 psig: the receiver is located 15 ft above the level of the trap. From the capacity differential pressure specifications in Table 6.12, select a suitable trap for this application.

Using a factor of safety of 3 from Table 6.10, a trap capable of handling 3 x 500 = 1500 lb/hr of condensate will be selected.

To determine the system back pressure, add the receiver pressure, the piping pressure drop, and the hydraulic head due to the elevation of the receiver.

Entering Table 6.11 at 30-psig supply pressure and 5-psig return pressure, the pipe pressure drop for a 1-in. pipe is just slightly over 2 psi at a condensate rate somewhat higher than our 1500 lb/hr; a 2-psi pressure drop is a reasonable estimate.

The hydraulic head due to the 15-ft riser is 2 psi/ft x 15 = 7.5 psi. The total back pressure is, therefore,

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