6.2.3 Methods of manufacture and construction - part 7
Condenser tube support plates serve a number of purposes. They support the tubes in order to control vibration, and provide means for bowing the tubes to assist drainage. Also, they provide a convenient method of reinforcing the shell against the external pressure forces.
The spacing of support plates is controlled by the criteria governing tube vibration, but usually the maximum dimension does not exceed 60 tube diameters. With the introduction of titanium tubing, the spacing can be as low as 35 tube diameters which satisfies the criteria of freedom from fundamental frequency vibration from both machine and steam-flow-induced sources.
Where support plates are used as inherent stiffness members for shell reinforcement, the plate strength and attachments receive consideration as edge-loaded perforated diaphragms and are stiffened to avoid buckling, if required. The plate thicknesses can vary from 16 mm to 38 mm, depending on the design criteria. The tube hole drilling is carried out by multi-spindle numerically-controlled drilling machines, and it is common practice to 'stack drill' up to seven support plates at a time.
Branches, connections and reinforcement
Ordinarily, reinforcement may be dispensed with because plate thicknesses are in excess of those that require compensation. Details of any opening or branch connection to the shell which requires compensation and reinforcement must comply with the standards set out in BS1500 .
There are mandatory requirements for hydraulic tests on the components of the condensing plant, and these are summarised in Table 4.4.