SKZ Testing GmbH: Cracked Round Bar Tests (CRB) According to ISO 18489 for PE Pipes
Case Study
- Customer: SKZ - Testing GmbH
- Location: Würzburg, Germany
- Industry: Testing Services, Plastics
- Topic: CRB Test with ZwickRoell Testing Machine
March 2025
The SKZ Plastics Center (Würzburg) has added the innovative cracked-round bar test (CRB) according to ISO 18489 to its range of services. This procedure, carried out using a ZwickRoell LTM electromechanical testing machine, was successfully validated by extensive interlaboratory tests and assessed by the German Accreditation Body (DAkkS).
SKZ - Testing GmbH: Accredited Testing Laboratory for Quality, Safety and Certification in the Plastics Industry
SKZ - Testing GmbH, based in Würzburg, is an accredited testing laboratory that supports companies in the plastics industry with independent material and product testing, product monitoring and product certification. With state-of-the-art testing technology and many years of experience, the laboratory guarantees the highest quality and safety standards. The comprehensive testing services - from mechanical and thermal tests to environmental and longterm weathering tests - help manufacturers certify their products in accordance with national and international standards and make them marketable.
SKZ - Testing GmbH currently owns ten testing machines from ZwickRoell, which are used to test a wide range of properties of plastics, including tensile, flexural, compression and sliding/friction properties. The company not only carries out short-term stress tests such as impact bending or impact tensile tests, but also quasi-static and longterm tests, such as creep and relaxation tests. Dynamic tests complete the spectrum. The testing lab also runs comprehensive mechanical-technological tests on plastic specimens and component-related tests, as well as investigations based on physical-chemical methods such as spectroscopy and microscopy. In addition, they perform rheological, optical and electrical tests as well as fire and diffusion tests. A significant area is dedicated to the aging testing and lifespan estimation of plastics.
In addition, SKZ - Testing GmbH is involved in the areas of research, continuing education and the certification of management systems in order to support companies in the plastics industry not only in quality assurance, but also in the sustainable ongoing development of their products and processes. As a reliable partner to the plastics industry, the company plays a key role in driving forward innovative and sustainable solutions in plastics processing and supporting companies in complying with regulatory requirements.
The task
Cracked round bar tests (CRB) in accordance with ISO 18489 for stress crack testing of PE pipes.
Traditional methods for determining the stress cracking resistance of polyethylene pipes such as FNCT (full notch creep test), PENT (Pennsylvania edge notch tensile test) and NPT (notched pipe test) often reach their limits with modern PE 100-RC grades. These methods are time-consuming, often require over 10,000 hours without usable results and are heavily dependent on wetting agents, which influence the results and are environmentally questionable. The cracked round bar (CRB) test according to ISO 18489 offers a more efficient alternative by eliminating harmful wetting agents and extremely high temperatures, making it a more environmentally friendly and practical test method.
The ZwickRoell solution
Use of the LTM electrodynamic testing machine at SKZ Testing GmbH.
SKZ Testing GmbH has opted for the LTM electrodynamic testing machine from ZwickRoell to meet the challenges of modern materials testing. The machine offers high dynamic performance and is low maintenance, making it ideal for advanced material testing. The LTM is characterized by its enclosed design, lack of temperature control, and a 3 kN force sensor, which enables a precise, oil-free, and low-noise testing environment.
“The addition of the CRB test to our testing portfolio is further evidence of our ongoing commitment to excellence in materials testing. We are very proud to have received accreditation from the DAkkS for this. Special thanks goes to ZwickRoell for their excellent technical support on this project.”
Johannes Engert , Head of Department Pipe Testing, SKZ Testing GmbH
The result
Outstanding results since the implementation of the cracked round bar test (CRB).
The introduction of the cracked round bar test (CRB) according to ISO 18489 at SKZ - Testing GmbH shows outstanding results. Accreditation by DAkkS and optimized test performance, including standard-compliant specimen preparation, have led to a reliable and energy-efficient testing process. Since January 2022, the testing machine has not recorded any days of downtime due to defects, which underlines the high level of machine reliability.
