Engineering guide
The BV29 module calculates tubesheets, covers and the associated bolted connections of shell-and-tube heat exchangers to TGL 32903/29. It covers the split design with a separate tubesheet and bolted cover as well as channels of integral (non-split) construction; in addition, the elasticity coefficient to ST RGW 3649-82 can be determined, which describes the interaction of tubesheet, tube bundle and shell.
The TGL 32903 series is the pressure vessel code of the former East Germany (GDR) and is needed today primarily for the re-rating and assessment of existing plants that were originally designed to TGL. Anyone who needs to calculate a tubesheet to TGL 32903/29, or to verify an older unit as part of periodic inspection, will find here the code-compliant implementation of the original calculation sheets. For new designs, EN 13445, the German AD 2000 code or ASME Section VIII are generally used today.
Typical applications are modifications, upgrades and remaining-life assessments of heat exchangers in existing chemical and power plants, where the original design calculation has to be reproduced.
Scope
- Tubesheets and bolts (split design)
- Covers (split design)
- Chambers of unsplit design
- Elasticity factor according to ST RGW 3649-82
Typical workflow
Select the design type
First the design type is chosen: split construction with a tubesheet and a bolted-on cover, or an integral (non-split) channel. The design type determines which calculation sheets of TGL 32903/29 apply and how gasket and bolt forces are accounted for.
Enter loads and boundary conditions
Design pressure, temperature and the gasket geometry are specified. In the split design, the bolted joint introduces additional edge moments on the tubesheet, which enter the strength verification.
Determine the elasticity coefficient
The elasticity coefficient is determined according to ST RGW 3649-82; it captures the supporting effect of the expanded or welded-in tube bundle on the tubesheet. It reduces the effective bending load on the perforated plate.
Verify tubesheet and cover thickness
From pressure, boundary conditions, the ligament efficiency of the perforated area and the allowable stress, the required wall thickness of tubesheet and cover is obtained and compared with the actual thickness.
Verify the bolted connection
For the bolted joint, the bolt loads are determined for the assembly, operating and test conditions, and the required bolt cross-sections are compared with those actually provided.
Frequently asked questions
May I still design a new heat exchanger to TGL 32903/29?
For new designs within the scope of the Pressure Equipment Directive, the TGL standards are no longer a harmonized basis; EN 13445, the AD 2000 code or ASME Section VIII are the usual choices. The TGL calculation, however, remains the method of choice when existing equipment that was originally designed and documented to TGL has to be re-rated, assessed or modified — only in this way can the original design be reproduced consistently.
What distinguishes the split design from the integral design?
In the split design, the tubesheet and the channel cover are separate components, bolted together with a gasket. This allows the channel to be opened for cleaning, but introduces additional bolt and gasket forces as well as edge moments on the tubesheet. In the integral design, the channel is permanently connected to the tubesheet, which simplifies the calculation but restricts access.
What is the role of the elasticity coefficient to ST RGW 3649-82?
The elasticity coefficient describes how strongly the tube bundle elastically supports the tubesheet. A stiff bundle acts like a distributed elastic foundation and relieves the plate, so that smaller tubesheet thicknesses can be verified. If it is neglected, the calculation conservatively treats the perforated plate as freely spanning, and considerably larger required thicknesses result.
Technical content source: LV-Solved-Problems-Content 628d313247e7