Yearbook 2013/2014 - ehedg

104 Material and design optimisation calculated by EHEDG: Tubing systems
After additional production steps, such as grinding,
annealing and leveling, the tubing must undergo eddy
current testing in order to ensure the quality of the longitudinal
weld seam.
3. The third method plays a role in refinery and power
plant technologies, which use tubing with wall thicknesses
exceeding 16 mm. Hot rolled steel is typically the
primary material. It is formed into tubing with the aid of
presses that exert hundreds of tons of pressure onto
the material and then longitudinally seam welded.
The mastery and exploitation of such manufacturing
processes means achieving optimal material properties. The
suitability of the material for further processing is equally
important. Analysis is made possible by the countless material
and surface testing procedures currently available. The most
well-known method is the measurement of Ra values. The
results of surface profile measurements, however, are limited
in validity because they do not provide information about
the microstructure. Additional inspections are necessary for
proving suitability of the tubing, for example, welding tests,
electrolytic polishing tests and microscopy.
Important: Materials selection
The right selection of suitable materials determines, among
other things, cleaning qualities and system life. Today, there
are a multitude of alloys on the market that possess the
necessary stable properties to stand up against different
types of corrosion. In order to fully utilise their properties,
however, they must be properly processed. The application
and its particular influencing factors, such as medium,
concentration, time and temperature determine the selection
of materials and surfaces.
Figure 2. Beyond standards: Example of a customised branch
solution.
Manifolds: Dead space minimisation is the
objective
Figure 3 shows a manifold with attached valve, for example,
for dosing an additive into a base fluid. Conspicuous here is
the short distance between the central tubing and the valve
base plate. As a result, a tiny dead space occurs when the
valve is closed. In comparison to conventional construction
with T-pieces, the potential dead space volumes are reduced
by approximately 38%; at the same time, the component is
clearly more compact (Figure 4).
Branch conduits: Know-how is in the details
The production of geometrically simple and frequently
used components, such as branches, demonstrates the
complexity of implementing EHEDG guidelines. This
begins with the selection of materials. This is the only
way that optimal welding can be ensured. Furthermore,
the processing methods must be adjusted to the future
application.
Different techniques (boring, saddle, and collaring
methods) are available for the processing of T-pieces, each
of which have their merits, but also their application limits.
Dockweiler uses the collaring method for branch conduits
with a diameter of 19.05 to 168.30 mm and also produces
special T-pieces, for example, with inclined or eccentric
outlets (Figure 2). The advantages are exact geometry and
complete drainability of the production system. Dockweiler
solely uses the Wolfram Inert Gas Process (WIG) orbital
welding method for producing components. Validated
documentation is available for all welding seams and
surfaces; depending on requirements, components are
electropolished after production. If desired by the customer,
pressure calculations or X-ray testing can be conducted for
critical components.
Figure 3. The minimisation of dead space is an important design
objective for many EHEDG-compliant tubing components.
Figure 4. Compact and hygienic: Short branch with valve base plate.