Research and Development

Continuous in-line bending process for jacketed high-pressure elbows

To increase the already high reliability and safety standards of BHDT‘s jacketed elbows for LDPE production further, an innovative process for continuous in-line bending of jackets was developed. The main benefit of BHDT’s new jacketed elbows is the ommision of weld seams on the elbow. The implementation of simulation models (finite elements methods) enables BHDT to predict the ovality and excentricity of the in-line bended jackets prior manufacturing. Surface temperature measurement on the high-pressure pipe during in-line bending avoids unintended microstructure changes in the high-pressure material and guarantees the required mechanical properties.

Caption 1: Temperature evolution on a jacket during in-line bending

Caption 2: Strain evolution on a jacket during in-line bending

Surface hardening of corrosion-resistant alloys

A new and highly innovative surface hardening process is increasingly applied at BHDT. Main applications of those modified materials are parts for highly corrosive and abrasive conditions mainly in the urea and ammonia production, e.g. valve seats and valve stems. Various corrosion and hardness tests confirmed the suitability of this technique for increasing the operating life time significantly. As a further benefit the fatigue strength of all surface hardened parts is elevated, too. The best results are obtained with all types of stainless steels and nickel-base alloys.

Welding automation

BHDT increasingly focuses on welding automation (e.g. orbital welding for pipe connections or pipe / flange connections) in its departments HDF (Urea & Fertilizers) and HDO (Oil & Energy). The main benefit of automated welding is an impressive improvement of quality and reproducibility of the welds. Moreover, automated welding yields to higher productivity, especially when highly alloyed materials are concerned.

Caption 3: Current density - potential curves of a Super Duplex stainless steel (orbital vs manual welded)

In-situ wall thickness measurement by means of ultrasonic testing during deep-hole drilling

A device for determination of wall thickness and centricity of high-pressure pipes during deep-hole drilling was designed. To achieve reliable results, it is crucial to apply correct values for the speed of sound in the investigated materials. For high pressure vessels and tubes it is common to use wrought high-strength, quenched and tempered steels (e.g. 1.6580) as well as martensitic corrosion-resistant steels (e.g. 1.4006). To reduce measurement uncertainty of wall thickness evaluation, the influences of chemical composition, microstructure, orientation and heat treatment condition on speed of sound of various materials were determined. Significant differences in sound velocities were obtained between normalized, quenched and quenched + tempered conditions. In addition, sound velocities in one austenitic corrosion-resistant alloy and one super duplex stainless steel after different heat treatments were obtained.

Results were utilized for calibration of the wall thickness measurement device in order to improve the accuracy of ultrasonic testing. As an outcome of this work, in-situ wall thickness evaluation during deep-hole drilling will be established as a standard characterisation method at BHDT GmbH.

References: M. Prohaska, M. Panzenboeck, H. Anderl, W. Kordasch, Influence of chemical composition and microstructural parameters on speed of sound of various materials used for high-pressure applications, 18th WCNDT, Durban, South Africa (2012), 1-12, paper no. 263

Failure analysis

BHDT offers its customers extensive failure analysis services in cooperation with national and international laboratories and institutes. After determination of the critical parameters and causes of failure, BHDT offers tailor-made technical solutions to avoid similar failures in future.

Caption 4: Cavitation corrosion and intergranular corrosion on a valve stem

Caption 5: Grain boundary