Design Codes - Pipework
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Design Codes - Pipework
This Technical Measures Document covers the use of piping standards and
the design and maintenance of piping systems. Reference is made to relevant
codes of practice and standards.
Related Technical Measures Documents are:
The relevant Level 2 Criteria are
Introduction
Piping systems are the most commonly used method of conveying fluids in
the process industries. The integrity of piping systems is dependent on
various considerations and principles that should be observed when
designing, constructing and maintaining process plant piping. Pipework is
made up of many components including pipes, flanges, supports, gaskets,
bolts, valves, strainers, flexibles and expansion joints. Such components
are available in a variety of materials, types and sizes and may be
manufactured to a national standard or maybe a manufacturers proprietary
item. Transmission pipelines are not included within the scope of this
General principles
The operator should demonstrate that it designs piping systems based on
the requirements of nationally accepted standards, and uses competent
persons to implement good design practices with respect to mechanical and
process design.
Some companies publish their own internal piping standards based upon the
relevant information from national and industry sector standards. These
internal standards often include materials selection and other items
required to specify pipes and piping system components for the specific
fluids handled by the company. Where this is the case the company should
demonstrate compliance with the standard, that the standard has been
produced by competent persons and that the standard is subject to periodic
Design - Implementation of Pipework standards
Pipes and piping components are normally manufactured to meet the
requirements of national standards such as ASME B31 Code for Pressure Piping
or BS 1560 Circular Flanges for Pipes, Valves and Fittings. Manufacture to
such standards ensures that the items are suitable for use under specific
operating conditions. Normally a standard defines the allowable stresses,
and temperature and pressure ranges under which the piping component may be
used. Additionally some industry sector groups publish standards for
handling specific substances. As examples Euro Chlor publishes standards for
chlorine piping systems and the LPG Gas Association publishes standards for
LPG piping systems.
Material selection
Whilst carbon and stainless steels are commonly used materials of
construction, increasing use is being made of non- metallic and lined or
plastic piping systems. The selection of the material of construction should
taken into account variation in process conditions that may occur under
foreseeable upset conditions. The strength of some materials changes
considerably at elevated temperatures. Typically the mechanical strength of
plastic pipework and bellows reduces considerably at elevated temperatures.
Steels may suffer from brittle fracture at low temperatures. The operator
should demonstrate that procedures are in place to ensure that deviations in
process conditions such as fluid temperature, pressure and composition are
identified and assessed in relation to the design of the pipework.
Corrosion / erosion due to fluid flow occurs in pipework. In practice for
pipes it is usual to select materials of construction which corrode slowly
at a known rate and to make provision for the material loss due to corrosion
/ erosion. All piping components such as gaskets and bellows must be
compatible with the fluid. The operator should demonstrate that it has
procedures in place to ensure the correct selection and use of materials of
construction in piping systems.
Exterior surface corrosion of pipework components and supports can appear
as pitting or crevice corrosion. Painting to an appropriate specification
will significantly extend the period to the onset of corrosion but the
durability of the paint finish is largely dependent on the quality of the
surface preparation. Improperly installed insulation can provide ideal
conditions for corrosion and should be weatherproofed or otherwise protected
from moisture and spills to avoid contact of the wet material on equipment
surfaces. Application of an impervious coating such as bitumen to the
exterior of the pipework is beneficial in some circumstances. Wrapping or
taping pipework to provide protection is also a common practice. Cathodic
protection is an electrochemical method of corrosion control which has found
widespread application in the protection of carbon steel underground
structures such as pipework and tanks from soil corrosion. The process
equipment metal surface is made the cathode in an electrolytic circuit to
prevent metal wastage.
The operator should demonstrate that it has inspection and maintenance
programmes in place for pipework systems carrying hazardous fluids and in
particular for lagged pipework.
Pipe joints
Pipe joints are often the point of leakage on pipework systems and the
number of joints in piping systems should be minimised where practicable.
Joints can be permanently welded for high integrity systems or reformable
types such as flanged, screwed or compression fittings may be used. Welded
joints should meet the requirements of a standard such as BS 2971
'Specification for Class II welding of carbon steel pipework for carrying
fluids'. Welds should be inspected by an appropriate method depending on the
application requirements. Radiography and ultrasonics are widely used where
high integrity welds are required. The operator should demonstrate that
procedures are in place to ensure the appropriate level of integrity is
provided by the jointing method employed.
Evaluation of stresses, reactions and movement
Lack of consideration of the stresses, reactions, and movement of the
piping and connected equipment at the design phase can result in failure of
supports, leakage at flanged joints, distortion of valve bodies, and failure
of in line items such as bellows. Notably the Flixborough disaster occurred
due to a bellows failure. The operator should demonstrate that competent
persons carry out the mechanical design of piping systems.
Routing and supporting
Piping containing hazardous fluids should be protected from damage by
external mechanical impacts, leaks from adjacent pipework and external
sources of heat. Pipework should be routed to take into account the
requirement for safe access for operation, inspection and maintenance. Pipe
supports and bridges should be designed with sufficient mechanical strength
for the loads exerted on them and for traffic impact resistance where
appropriate. Armco barriers or the equivalent should be used to protect pipe
routes close to roads.
For hazardous fluids, the piping should avoid 'dead legs' and be designed
to facilitate drainage to prevent trapping of fluid. Pockets should be
avoided in piping carrying slurries, fluids that can create blockages or
form corrosive condensate. The design of sampling systems should be
appropriate to the hazard of the fluid and have due regard for problems such
as freezing or solids / hydrate formation causing blockages. Double valving
or the use of high integrity proprietary sampling systems are likely to be
appropriate for the sampling of hazardous substances. The operator should
demonstrate that procedures are in place to ensure that the orientation and
routing of pipework minimises both the likelihood of loss of containment and
any subsequent loss of inventory of toxic or flammable substances, and that
measures are installed to protect pipework where necessary.
Operational demands
During design, the operation of each piping system needs to be clearly
understood not only under normal conditions but also those conditions
arising during start up, shutdown and as a result of process upsets. These
items should also be addressed during project HAZOP studies. The operator
should demonstrate procedures are in place to ensure that phenomena known to
cause problems in piping systems are considered and allowed for in the
mechanical design or designed out where practicable. These should include :
Pressure surge
Condensate hammer
Cavitation
Pulsations / vibrations
Cyclic loadings
Temperature gradients and cycling
Valving is the primary means of isolating process equipment and is
provided for both maintenance and emergency purposes. For maintenance it is
also necessary to consider the requirements for meeting isolation standards
(spectacle blinds, etc). Where isolation is provided it is possible to trap
liquid between closed valves and in some circumstances temperature changes
in the fluid can result in thermal expansion of the trapped liquid and loss
of containment. The location of isolation valves should be a prime
consideration during HAZOP studies. The operator should demonstrate that
procedures are in place to identify the requirements for the safe isolation
of process plant for emergency and maintenance purposes. Where thermal
expansion is a problem, the operator should be able to demonstrate that
training and awareness programmes have taken place and that pressure relief
has been installed where necessary.
Where fluid flows through a pipe static electricity is generated. The
conductive properties of the fluid and the pipework system affect the
charging process and in some cases it is necessary to restrict flow rates to
control static generation. There is a basic requirement for the earthing of
process equipment to prevent ignition of flammable vapours by static
discharge. The operator should demonstrate that procedures are in place to
ensure that pipework design meets the requirements of standard codes of
practice such as
for the control of
static electricity. Additionally procedures should be in place for the
periodic testing of the continuity to earth of pipework where necessary.
Construction and fabrication
Fabrication specification should specify welding and jointing procedures,
alignment tolerances, defect limits, extent of visual and non-destructive
testing. Pipework should be constructed in accordance with isometrics signed
off by competent persons. Pressure tests should be carried out to written
procedures to confirm adequate containment at process conditions.
Commissioning procedures should be in place to ensure that installed
pipework is inspected before use to identify any design faults that may have
been introduced at the construction stage and to confirm suitability for
Materials control
Stores control systems should be in place to ensure that only items
suitable for the particular process duty can be drawn for repair /
replacement work. Similarly purchasing controls should ensure that purchased
materials are suitable for the particular process duty. The operator should
demonstrate that robust systems are in place for controlling the purchase,
storage and issue of materials and items for use on hazardous process plant.
Changes to specification, etc should be considered under Change Control
Industry applications
Special steels are required for handling chlorine at low temperature to
avoid embrittlement and at high temperatures chlorine burns mild steel. The
flow rate of liquid chlorine through pipework is restricted to avoid
removing the ferric chloride coating on the pipe surface which protects
against erosion / corrosion. Wet chlorine gas corrodes mild steel and
ebonite lined steel is used for this duty. Where ROSOVs can trap liquid
chlorine pressure relief is installed on the pipeline.
For above ground liquid duty carbon steel seamless pipe is used and the
joints can be either flanged or welded. Screwed fittings are only
permissible on pipe diameters up to 50 mm and compression fittings can not
be used. Copper and polyethylene pipework are not permitted on liquid duty
but copper can be used on vapour duty for pipes of up to 15 mm diameter in
conjunction with compression fittings.
Ethylene Oxide
Mild steel or stainless steel maybe used with ethylene oxide, however
mild steel must be rust free to prevent initiation of exothermic
polymerisation. Flanged joints should have stainless steel spiral wound PTFE
joint gaskets or trapped Fluon gaskets. CAF is not suitable for use above
25°C and natural rubber is not permissible. Joints should be kept to a
Codes of Practice relating to Pipework Systems
There are a large number of British Standards covering the components
that may be present in a piping system, such as:
BS 3293 Specification for carbon steel pipe flanges (over 24in.
nominal size) for the petroleum industry.
BS 4504 Circular flanges for pipes, valves and fittings.
BS 2971 Specification for Class II welding of carbon steel pipework
for carrying fluids.
BS 6990 Code of practice for welding on steel pipes containing process
fluids or their residuals.
BS 6464 Specifications for reinforced plastic pipe, fittings and
joints for process plant.
Some of the more general standards and codes of practice of interest are
given below.
ASME B31 ‘Guide for piping and piping systems’.
This is a comprehensive standard for the design of pipework systems. In
section B31.3 the standard defines categories of hazardous materials
which are then used to define the standard of appropriate piping
components.
Code of practice for the
control of undesirable static electricity. Part 2 Recommendations for
particular industrial situations, British Standards Institution.
This document gives sound advice for the control of static electricity
in a wide range of circumstances. Specifically the use of piping systems
made of polymers for handling flammable materials is not recommended.
Fire precautions in the
chemical industries, British Standards Institution.
Section 38 provides advice on the design of piping systems for handling
flammable materials.
LPGA COP 22 LPG piping system design and installation, LP Gas
Association, 1996.
The code covers the installation of pipework in carbon steel, copper or
polyethylene for conveying LPG to BS 4250.
GEST 79/82, 'Choice of materials of construction for use in contact
with chlorine', Euro Chlor.
A typical industry sector standard containing specific guidance on the
use of materials of construction for chorine systems.
IGE / UP2 Gas installation pipework, booster and compressors on
industrial and commercial premises
Guidance on natural gas piping on industrial sites
Further reading material
Perry’s Chemical Engineers’ Handbook, Section 6, Transport and
Storage of Fluids, McGraw Hill.
Lees, F.P., ': Hazard Identification, Assessment and Control', Second
Edition, 1996.
Case studies illustrating the Importance of Design Codes - Pipework
HSE aims to reduce work-related death, injury and ill health.standardcodes是什么意思_百度知道
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standard codes标准码例句:1.3.1.4 All piping materials shall be tested as prescribed in the piping specifications and standard codes and practices and certificates of conformance shall be furnished for review and approval by employer. 3.1.4所有管道材料应按照管道规范、标准规范和惯例规定测试，且应提供合格证书以供业主审批。2.Throughout this standard the following standards and codes are referred to. 本标准参考了下列所有标准和规范。3.Compile or guide staff compiling standard documents such as technical codes, technical details an provide guidance for proper application. 编写与本专业有关的工艺守则、工艺细则、通用工艺等工艺标准文件，并指导焊接工艺人员正确应用。
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标准规定；法则On the basis of standard codes, corresponding revisal codes are also adopted toexpress the deviation from standard codes. 在此基础上，进一步确定曲线的修正编码，以表示曲线与标准编码的差异程度。~很高兴为您解答如有问题请及时追问，谢谢~~O(∩_∩)O
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出门在外也不愁What is an ISIC Code?
What is an ISIC Code?
The International Standard Industrial Classification of All Economic Activities (ISIC) is the international reference classification of productive activities. Its main purpose is to provide a set of activity categories that can be utilized for the collection and reporting of statistics according to such activities. It provides a comprehensive framework within which economic data can be collected and reported in a format that is designed for purposes of economic analysis, decision-taking and policy-making. The classification structure represents a standard format to organize detailed information about the state of an economy according to economic principles and perceptions.These economic activities are subdivided in a hierarchical, four-level structure of mutually exclusive categories, facilitating data collection, presentation and analysis at detailed levels of the economy in an internationally comparable, standardized way.How to Read an ISIC CodeThe ISIC is subdivided in a hierarchical, four-level structure. The categories at the highest level are called sections. The two-digit of the code identify the division, the third digit identifies the group and the fourth digit identifies the class.ExampleSectionCManufacturingDivision13Manufacture of TextilesGroup139Manufacture of Other TextilesClass1393Manufacture of Carpets and RugsHistory:Since the adoption of the original version of ISIC in 1948, the majority of countries around the world have used ISIC as their national activity classification or have developed national classifications derived from ISIC. ISIC has therefore provided guidance to countries in developing national activity classifications and has become an important tool for comparing statistical data on economic activities at the international level.ISIC Broad StructureSectionDivisionsDescriptionA01–03&Agriculture, forestry and fishingB05–09&Mining and quarryingC10–33&ManufacturingD35&Electricity, gas, steam and air conditioning &supplyE36–39&W sewerage, waste management &and remediationF41–43&ConstructionG45–47&Wholes repair of motor &vehicles and motorcyclesH49–53&Transportation and storageI55–56&Accommodation and food service activitiesJ58–63&Information and communicationK64–66&Financial and insurance activitiesL68&Real estate activitiesM69–75&Professional, scientific and technical activitiesN77–82&Administrative and support service activitiesO84&Public admini &compulsory social securityP85&EducationQ86–88&Human health and social work activitiesR90–93&Arts, entertainment and recreationS94–96&Other service activitiesT97–98&Activities of hou &undifferentiated goods- and services- &producing activities of households for own useU99&Activities of extraterritorial organizations and &bodiesWhat are ISIC Codes Used for?Wide use has been made of ISIC, both nationally and internationally, in classifying data according to kind of economic activity in the fields of economic and social statistics, such as for statistics on national accounts, demography of enterprises, employment and others. In addition, ISIC is increasingly used for non-statistical purposes.Used for providing a continuing flow of information that is indispensable for the monitoring, analysis and evaluation of the performance of an economy over time.Used to classify statistical units, such as establishments or enterprises, according to the economic activity in which they mainly engage.At each level of ISIC, each statistical unit is assigned to one and only one ISIC code.ISIC provides the internationally accepted standard for categorizing producing units within an economy, which allows for data comparison at the national and international levels.Why are ISIC Codes Important?Important tool for socio-economic statistics that need to be arranged in accordance with the productive system of the economy.ISIC&allows the gathering and analysis of data quickly and efficiently.ISIC has been recommended to countries as an international standard and model in the development and/or adaptation of their national activity classifications.ISIC has a central position among existing classifications of economic activities, as well as other economic classifications, such as those for products.