HUALONG WCJ Series Drop Weight Tear Tester DWTT)0 pages

Drop Weight Tear Tester

DWTT

What is the drop-weight tear test?
Steel pipelines are widely used to transport energy in the form of liquid petroleum and
natural gas. The steel used in the manufacture of these pipelines must have high
strength and toughness, and high resistance to fracture. Over the last few decades, it
has become recognized that the drop-weight tear test (DWTT) better represents the
ductile fracture resistance than the Charpy test since it utilizes a specimen that has
the full thickness of the pipe and has a fracture path long enough to reach steadystate fracture resistance. The zones of ductile and brittle fracture during DWTT
characterize the quality of pipeline steels.
The drop weight tear test (DWTT), specified in API RP 5LR or ASTM E436, was
developed in the early 1960s at the Battelle Memorial Institute, USA, to overcome
some limitations of the 'Pellini' Drop-weight test. Drop weight tear testing is a material
characterization test aimed at avoiding brittle fracture and ensuring crack arrest in
pipelines (seamless or welded).

Overview
HUALONG WCJ Series is mainly used for drop weight tear test (DWTT) of Ferritic Steels, to
observe specimen fracture surface after impact within the temperature that fracture type is
converted from non-ductility to ductility. This test method is that hammer striker with some
weights is raised to some height then released. Free drop hammer impacts and tears the
specimen. After impact, proportions of ductile fracture (shear) and cleavage on the fracture
surfaces are measured.
Impactek data acquisition system is available to be introduced into DWTT tester, through which
can upgrade simple uninstrumented DWTT tester to an instrumented DWTT tester who is able to
measure the amount of force required to break a specimen, and this enables calculation of
separate values for initiation energy and propagation energy, those impact resistance information
gathered by doing instrumented testing can be used by Research and Development to evaluate
the effects of metallurgical variables such as composition, processing, heat treatment can have
on the fracture resistance of new or existing materials. Test results may also be used to indicate
particular steel’s suitability for use in a specific application.

Application range
This testing machine accords with the relevant requirements of Standards for DWTT such as:
Metallic materialsDrop-weight tear tests of ferritic steels.
1. API RP 5L3
2. ASTM E 436
3. EN 10274
4. GB 8363
The recommended practice API RP 5L3 issued by the American Petroleum Institute (API)
describes the testing procedure to be used on large-drop impact testers. A specimen supported
at both ends is impacted with a cold-press-fitted notch, with the point of impact opposite the
notch. Since the specimen thicknesses are very large sections of actual pipeline tubes, high
impact energies of up to 100,000 Joule are necessary to break the specimen.

Main features
1. Regulating impact energy by adjusting the lifting height and mass of the weights.
2. Very robust construction stands up to the rigours of high energy testing to provide high
reliability with a minimum of downtime.