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2nd Bolt Connection Conference 2014 - speaker Frank Hohmann

VDI 2230, part 2 presented on the Bolt Connection Conference 2014


The new updated version of the fundamental German bolting guideline VDI 2230, part 2 was highly anticipated by the audience of the 2nd Bolt Connection Conference in Meschede, Germany. This topic and more lectures about the calculation, control and design of bolted joints found a very positive response by nearly 80 participants from Germany, Austria, Switzerland and Denmark.


Meschede | Germany.

The focus of the 2nd Bolt Connection Conference 2014 was to explore the latest insights of technical innovation in optimizing the design of bolted joints larger than M20 (3/4''). The topics of the well-known speakers from all over Germany covered the whole spectrum of the "process chain bolt connection":

  • Technical design of bolted joints
  • Bolting method (Bolting tools and equipment)
  • Fasteners design
  • Bolt integrity (control mechanisms)



The updated bolting guideline VDI 2230, part 2

Nearly 80 participating engineers and technicians in the audience followed one lecture with very special interest: Prof. Dr. Willfried Lori's "The updated guideline VDI 2230, part 2". No wonder: This guideline VDI 2230 contains fundamental calculations, methods and rules for the technical design of bolted joints.

The VDI is the German Association of Engineers (Verein Deutscher Ingenieure) and well-recognized for their work in standardization. 

Being the chairman of the VDI 2230 Prof. Dr. Lori gave both competent and first-hand information, as the print-version of the VDI 2230 will be released not until December 2014.

Prof. Dr. Willfried Lori mediates the VDI 2230, part 2

Quick view on the VDI 2230

  • Part 1 Focuses on the systematic calculation of cylindric single bolt connections (ESV).
  • NEW: Part 2 focuses on the systematic calculation of multiple bolt connections (MSV). In this case designers need to idenfify the one bolted joint, which is subjected to the highest stresses. After that this one bolt connection can be calculated according to the definition in part 1.
  • The updated part 1 also includes a higher level of precision designing of single bolt connections (ESV). The calculations now consider special conditions of relative strength, bending loads and torsion loads of single bolt connections.
    For this update new insights were used which came from a FEM-calculation (Finite element method). The system and process design of FEM calculation in general where updated as well, which are defined in VDI 2230 part 2

New chapter 5: Hydraulic, friction- and torsion-free tensioning

  • For the first time the VDI 2230 will clearly separate between "turning" (torquing) and "pulling" (tensioning) bolting methods. 
  • The new and extra chapter 5 deals with "hydraulic, friction- and torsion-free tensioning" with bolt tensioning cylinders
  • Thererfore the guideline separates between 
    bolt preload F VM (initial assembly preload, generated by bolt tensioning cylinder and a run-down nut) and
    assembly preload F M (residual assembly preload after releasing the pressure). 
  • Hydraulic tensioning will also be considered in Table A8, which includes the tightening factors Alpha-A for all major bolting methods.
  • Alpha-A factor, quote from VDI 2230: “The tightening factor Alpha-A takes into account the scatter of the achievable assembly preload between FMmin and FMmax. It is determined while taking into account the tightening and adjusting techniques and if need be the coefficient of friction classes (Table A5) according to Table A8.”

Hydraulic, friction- and torsion-free tensioning: Our video explains the method in 48 seconds.


During his presentation Prof. Dr. Willfried Lori summarized: "Fundamental calculations were improved and extended comprehensively. The calculations are more clear and they are closer to every-day practice".


Possible corrective factors in the VDI 2230

Follwing the report of the VDI 2230 ITH president Frank Hohmann looked ahead at possible future developments of the guideline, speaking about "Relative elastic resiliences of the bolted joint". 

"The results of our experimental study show, that in some cases the theoretical calculations of the VDI 2230 referring to resiliences appear to have a deviance which is too high", Frank Hohman explained and suggested: "It should be considered to add a corrective factor for the formular". 

Frank Hohmann speaks about resiliences on the 2nd Bolt Connection Conference 2014

Being well known and recognized for this sceptical mind Prof. Dr. Willfried Lori could agree only partly. Both speakers discussed further options and did not forget to include the audience into their share of thoughts, which was appriciated by the participants. However in the end both speakers agreed on further research work on this topic and considered further cooperation.


"Maintenance Free Bolting" and ultra-sonic bolt measurement


The results of the survey among the participants showed the speech of Dipl.-Ing. Ulrich Uphues "Maintenance Free Bolting Solutions" was well received. Uphues presented the results of a 18-month long-term study of 2.5 MW wind turbine  tower bolts and did not forget to implement practical recommendations how to design bolted joints.

The long-term study was based on valid results from the use of the ultra-sonic bolt measurement system (USB-System). Concluding all facts Uphus showed that all measured preloads were above the required minimum target preloads by using IHF Fasteners together with ITH Bolt Tensioning Cylinders. 

That precision is the reason why maintenance intervals on these bolt connections can be called "Maintenance free". Reduced maintenance intervals lead to significant cost reductions - especially on offshore applications.


Share of minds: Thinking beyond

During the practical part "Hands on Tools" the engineers gained an impression of the latest innovations

"One of our ideas to organize the Bolt Connection Conference was that we wanted all participants to find the time to share their minds and thoughts on bolting technology", explained Jörg Hohmann who leads the company ITH together with his brother Frank Hohmann. "This is usually very productive for all participants. From direct conversations and the survey we know that this is well received. The exchange makes you think beyond".  

"Furthermore not many institutions worldwide deal with research on bolt connections bigger than M16. But that is just what we focus on: finding solutions to improve these bolt connections. Fortunately we have had some important research projects over the last years", Jörg Hohmann added. "We wanted to share this information to offer our participants advanced technical knowledge".


Positive response


"The results of our survey among the participants were very positive", Frank Hohmann said after the conference. "I would like to thank everybody involved. These results will set the standards for the next Bolt Connection Conference".

Also the practical part "hands on tools" the day before the conference was well visited. Nearly 90 % of all participants took their time to gain an insight on the latest bolting tools and solutions.  



Complete speakers & topics in the program

ITH recommends to use the latest versions of Microsoft Internet Explorer or Google Chrome for best compatibility using PDF files online.

As the conference language was German ITH offers to give you a  technical presentation at your site in other languages. 

Contact us for an appointment or regarding all questions regarding bolt connections.


2nd Bolt Connection Conference: Related information

  • Up to 40% higher preloads allow to use smaller bolt dimensions or designing bolt connections more compact. Both save costs.
  • Maintenance free bolt connections on wind turbines: The innovative IHF Fastener system substitues conventional bolt connections.
  • Testing and calibrating bolting tools with mobile ITH test devices and digital documentation and control systems.

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