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Quotes - Engineering - SalesBonnet and Channel Head Options
Choosing the Front Head
The front head carries the tube-side nozzles, houses the pass partitions and closes the tube side against pressure. TEMA type B is a bonnet: an integral head that bolts to the shell as one piece. Type A is a channel with a separately removable flat cover.
The bonnet case. Fewer gasketed joints, less flange, lower cost and lower weight. At high pressure and large diameter these advantages compound, which is why bonnets dominate the upper end of the pressure range alongside D-type closures.
The channel case. Remove the cover and the entire tubesheet face is exposed with the tube-side piping still connected. On any unit that gets inspected, plugged or cleaned on a schedule, that saves real time repeatedly.
Pass partitions. Multi-pass tube sides need partition plates and a matching gasket rib. A partition gasket that leaks does not announce itself; it just short-circuits flow and quietly costs you duty. Reassembly detail matters here more than most people expect.
Typical Construction
- Bonnet (TEMA B): Integral head, bolts to shell as one piece
- Channel (TEMA A): Cylindrical section with separately removable cover
- Tube-side access, bonnet: Requires disconnecting tube-side piping
- Tube-side access, channel: Cover removal only
- Relative cost: Bonnet lower; difference grows with diameter and pressure
- Gasketed joints: Bonnet fewer; channel more
- Pass partitions: Plates with ribbed gasket in either head
- High pressure: Bonnet or D-type closure preferred
- Nozzle location: Tube-side inlet and outlet both on the front head
- Codes: ASME Section VIII, TEMA R, B or C
Bonnet and Channel Head Options
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Both Tube Nozzles Are on This End
Because a U-tube bundle returns the fluid to where it started, the tube-side inlet and outlet are both on the front head. That head is also the one you have to clear to withdraw the bundle.
Plan the piping so those connections can be broken without dismantling surrounding equipment, and leave the bundle-pull clearance in front of them. Otherwise the removable bundle is removable only on paper.
