Square pitch

Square tube pitch provides for the insertion of a flat cleaning tool between the outsides of the tubes. This may be done continuously in either of two directions. In one arrangement, the tubes are in line with the flow. In the diagonal, square pitch, the tubes are staggered, causing the flow to divide as it meets each tube. 

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Tubes are most commonly arranged on an equilateral triangular pitch. Tubes are arranged on a square pitch primarily for mechanical cleaning purposes in removable-bundle exchangers. 

Tube exteriors with square pitch cleanable yes, mechanically or chemically chemically only yes, mechanically or chemically yes, mechanically or chemically yes, mechanically or chemically... 

Propeller Pitch pitch is the advance of the fluid per revolution on the basis that a propeller is a segment of a screw. Normally "square" pitch is used i.e., a pitch value equal to the propeller diameter. 

The jets are laid out on an approximately square pitch, with spacings in both directions varying between roughly 450 mm and 600 mm. A first approximation of the required spacing is obtained from Eq. (3)... 

Tube holes cannot be drilled very close together, since this may struc-tually weaken the tube sheet. The shortest distance between two adjacent tube holes is called the clearance. Tubes are laid out in either square or triangular patterns as shown in Figure S-.i. The advantage of square pitch is that the tubes are accessible for external cleaning and cause a lower pressure drop when shell-side fluid flows perpendicularly to the tube axis. The tube pitch is the shortest center-to-center distance between adjacent tubes. The common pitches tor square putienis arc i-in. OD on... 

In Figure 3-5e the square-pitch layout has been rotated 45, yet it is es,sentially the same as Figure 3-5a. In Figure 3-5d a mechanically clean-able modification of triangular pitch is shown. If the tubes are spread wide enough, it is possible to allow the cleaning lanes indicated. 

Corrosion allowance Tube diameters Square pitch cleaning lane Mm. shell thickness Transverse baffle and support plate thickness Min. thickness longitudinal battles... 

From Table 3-4 for 1-in. OD, 114-in. square pitch, fixed tube sheet, four passes, shell ID = 29 in. 

Can be pitched at various angles, most common is three blades on square pitch (pitch equal to diameter). 

The circulating capacity of 3-blade square pitch propellers is theoretically of the magnitude given in Figure 5-9. The speed ranges indicated may be grouped as [2] ... 

In-Line Square Pitch. Popular for conditions requiring low-pressure drop and/or cleaning lanes for mechanical cleaning of outside of tubes coefficient lower than triangular pitch. 

Diamond Square Pitch. Popular arrangement for reasonable low-pressure drop (not as low as in-line square), mechanical cleaning requirements, and better coefficient than in-line square pitch. 

Full Circle Tube Layouts Floating Head Exchanger / O.D. Tubes on 1-in. Square Pitch... 

For square pitch tubes, the shell-side equivalent diameter is... 

For plain tubing, the nominal O.D. replaces de. The volumetric equivalent diameter does not distinguish between square pitch and square pitch rotated by 45°. 

Figure 10-56. Equivalent diameter for tubes on shell side of exchanger taken along the tube axis, (a) Square pitch, (b) triangular pitch on 60° equilateral angles. (Used by permission Kern, D. Q. Process Heat Transfer, V Ed., 1959. McGraw-Hill, Inc. All rights reserved.)...

Boiling on shell side usually negligible unless tubes are very small and close together. For preferred 45° rotated square pitch with 1.25 d , Ap will be low. 

D-D Square-pitch marine propellers with 3 None, (i) shaft vertical at vessel axis, (ii) shaft 10 0.13 2.2-4.8 0.16-0.40 10 0.9... 

TWo tubular heat exchangers are available each with a 0.44 m i.d. shell fitted with 166 tubes, 19.0 mm o.d. and 15.0 mm i.d., each 5.0 m long. The tubes are arranged in two passes on 25 mm square pitch with a baffle spacing of 150 mm. There are two passes on the shell side and operation is to be countercurrent. With benzene passing through the tubes, the anticipated film coefficient on the tube side is 1000 W/m2K. 

Calculate the shell-side equivalent diameter (hydraulic diameter), Figure 12.28. For a square pitch arrangement ... 

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