Safety for men and environment
Some parts of the former Dutch Steam
Decree 1953 as they were stipulated in Stoomwezen rules for pressure
vessels RToD G0203.
(Now superseded by the European Pressure Equipment Directive.)
The licence for putting into
operation of steam apparatus or vapour apparatus.
A licence for putting into operation of a steam apparatus
or a vapour apparatus may be granted by the official designated
pursuant to section 11, subsection 1, of the Dutch Steam Act only
after it has been found that use under the desired working
pressure and at the desired working temperature is to be
considered permissible on the basis of the results of:
- The assessment of the
materials used.
- The assessment of the
construction of the apparatus.
- The examination of the
construction of component parts and their connections.
- The pressure test, with the
understanding that in the case of vessels which are
pipelines the pressure test may be omitted, if the
"Head of the Dutch Service" considers that
there are sufficient grounds for this omission.
- The final examination, being
the examination with regard to the set-up, lay-out and
equipment of the apparatus.
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In the Steam
Decree is not stated that pipelines or piping systems
should be calculated. It states only that
it should be assessed, tested and examined.
It is generaly accepted that the assessment by
calculation is the best way to fullfill the Steam
Decree, how ever it is not stated as such in there.
If in doubt than the best way to find out if a piping
system requires Stoomwezen approval is to contact them prior
to spending a lot of money and effort.
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If we notice D1101 of
the Rules for pressure vessels we can determine the extent of the
analysis and the method of analysis of a piping system required
by Stoomwezen.
Paragraph 3 of D1101 states:
- Piping systems shall be
analysed for the effect of thermal expansion, pressure,
weight and wind loading for all applicable sets of
operating conditions.
- Analysis for weight and wind
loading may be omitted if there is no doubt about the
minor character of these loads.
- Analysis may be embodied if
the results are available of a previously executed
analysis of an identical or -in the judgement of the
competent body- comparable piping system.
The
above directives are approximate ones, and are intended primarily
for surveyable laid-out piping systems. The final decision as to
whether the assessment requires an analysis always rests with the
competent body.
Method of analysis
Analysis is almost exclusively performed by calculation.
The method of analysis shall satisfy the following requirements:
- Thermal
expansion, loads, displacements and constraints shall be considered in their
relation for the entire piping system. This entails that
even if the analysis is performed piecewise, the
compatibility and equilibrium conditions shall be
adequately satisfied throughout the piping system.
Pressure, weight loads and wind may be left out of
consideration when analysing for thermal expansion.
Thermal expansion may be left out of consideration, when
analysing for pressure, weight loads and wind.
- With the aid of the method of
analysis the course of displacements, forces and
moments of
the piping system shall be established, and also the
relative displacement of the ends of expansion joints.
- The elastic properties of the
piping components may be taken into account as follows:
- via
the elastic properties of straight pipe; bends
and other shapes shall be converted into
equivalent straight pipe in accordance with
appendix I of D1101;
- in
the form of a calculated or measured relation
between displacements and forces. The latter
often takes the form of a flexibility or
stiffness matrix.
- In so far as stress
intensification in piping components is present, this shall
be taken into account in accordance with appendix I of
D1101 (or ASME)
- The
load on attachments and structural parts attached to the
piping system,
and also the internal forces and moments at the location
of piping components (flange connections, valves and the
like) in the hot or cold condition shall be determined on
the basis of the hot or cold modulus of elasticity
respectively and with the introducing of cold pull and
relaxation.
- The
forces and moments in the piping system shall be determined in the same
way as the stress range, i.e. on the basis of the modulus
of elasticity at ambient temperature and without
considering the cold pull. Pressure, weight loads,
external loading and/or wind loads shall be included in
this calculation in special cases only.
