Basics of Pipe Stress - (2)

Continued from  BASICS OF PIPE STRESS - 1

3.0 Allowable stress:

From stress strain diagram of a material like carbon steel we know about yield strength as also ultimate tensile strength. For our design purpose and allowable stress value is fixed which is based on a certain factor of safety over the yield strength or ultimate tensile strength. For higher temperature applications creep strength also comes in picture. Various codes detail the allowable stress basis. The basis adopted in ANSI B31.3 and IBR are described herein. These two codes have the maximum usage among the Indian pipe stress Engineers for Petrochemical/ Refinery.

3.1 Allowable stress as per ACSI:

As per Petroleum refinery piping code ANSI B31.3 the basic allowable stress values are the min. of the following values.

a) 1/3 of the minimum tensile strength at room temp.

b) 1/3 of tensile strength of design temp.

c) 2/3 of Min. yield strength of room temp.

d) 2/3 of Min. yield strength at design temp.

e) 100% of average stress for creep rate of O/D 1% per 1000 hr’s.

3.2 Allowable Stress as per IBR:

As pe the Indian Boiler Regulations the allowable working stress is calculated as shown below:

i) For temperatures at or below 454 Deg.C, the allowable stress is the lower of the following values:

Et = 1.5 or R = 2.7

ii) For temperatures above 454 Deg.C the allowable stress is lower of the

Values:

Et = 1.5 or Sr = 1.5

Where

R = Min. tensile strength of the steel at room temp.

Et = Yield point (02% proof stress) at the temp.

Sr = Average stress to produce rupture in 100,000 hr’s. at a temp. and in

No case more than 1.33 times the lowest stress to produce rupture at temp.

Sc = Average stress to produce an elongation of 1% creep in 100,000 hr’s. All these values have been made available after carrying on repeated laboratory tests on the specimen.

4.0 Allowable stress range:

The stress of a piping system lowers within the elasticity range in which plastic flow does not occur by self-spring during several initial cycles even if the calculation value exceeds the yield point, and thereafter-steady respective stress is applied. Hence repture in a piping system may be due to low cycle fatigue. It is well known that fatigue strength usually depends upon the mean stress and the stress amplitude. The mean stress does not always become zero if self spring takes place in piping system but in the ANSI code, the value of the mean stress is disregarded while the algebraic difference between the maximum and the minimum stress namely only the stress range SA is employed as the criterion of the strength against fatigue rupture.

The maximum stress range a system could be subjected to without producing flow neither in the cold nor in the hot condition was first proposed by ARC Mark as follows:

a) In cold condition the stress in the pipe material will automatically limit itself to the yield strength or 8/5 of Sc because Sc is limited to 5/8^th of Y.S. therefore, Ye = 1.6 Sc.

b) At elevated temperatures at which creep is more likely the stress in the pipe material shall itself to the rupture strength i.e. 8/5^th

Sh = 1.6 Sh.

Therefore stress range = 1.6f(Sc = Sh)

However, the code limits the stress range conservatively as 1.25f(Sc + Sh) which includes all stresses i.e. expansion – stress, pressure stress, hot stresses and any other stresses inducted by external loads such as wind and earthquake, f is the stress range reduction factor for cyclic conditions as given below:

To determine the stress range available for expansion stress alone we subtract the stresses inducted by pressure stress and weight stress which itself cannot exceed sh.

Therefore the range for expansion stress only is

SA = f(1.25 Sc + 0.25 Sh)

VALUES OF FACTOR ‘ f ’

Total number of full ‘ f ’ factor

Temp. Cycles over expected life

7,000 and less 1

14,000 and less 0.9

22,000 and less 0.8

45,000 and less 0.7

100,000 and less 0.6

250,000 and less 0.5

5.0 Pressure & Bending Stress & Combination Application:

The code confines the stress examination to the most significant stresses created by the diversity of loading to which a piping system is subjected. They are:

i) Stress due to the thermal expansion of the line.

ii) The longitudinal stresses due to internal or external pressure.

iii) The bending stress created by the weight of the pipe and its insulation, the internal fluid, fittings, valves and external loading such as wind, earthquake etc.

 

5.1 Stresses due to the thermal expansion of the line:

Temperature change in restrained piping cause bending stresses in single plane systems, and bending and torsional stresses in three-dimensional system. The maximum stress due to thermal, changes solely is called expansion stress SE. This stress must be within the allowable stress range SA.

SE = Sb² + 4St²

Sb = I (Mb / Z) = resulting bending stress

Mt = (Mt ^//2Z) = torsional stress

Mb = resulting bending movement

Mt ^/ = torsional movement

Z = section modules of pipe

i = stress intensification factor

5.2 Longitudinal stress due to internal or external pressure:

The longitudinal stress due to internal/external pressure shall be expressed as P (Ai / Am)

Where Ai is inside cross sectional area of pipe, Am is the metal area, P is the pressure.

5.3 Weight Stress:

The stress induced, self weight of pipe, fluid, fittings etc. as given by SW = M/Z, Where M is bending moment created by the pipe and other fittings, Z is the section modules of the pipe.

The stresses due to internal pressure and weight of the piping are permanently sustained. They do not participate in stress reductions due to relaxation and are excluded from the comparison of which as the latter has been adjusted to allow for them with the following provision.

6.0 Flexibility and stress intensification factor:

Some of the piping items (say pipe elbow) show different flexibility than predicted by ordinary beam theory. Flexibility factor of a fitting is actually the ratio of rotation per unit length of the fitting in question under certain value of moment to the rotation of a straight pipe of same nominal diameter and schedule and under identical value of moment. The pipefitting item, which shows substantial flexibility, is a pipe elbow/bend.

One end is anchored and the other end is attached to a rigid arm to which a force is applied. The outer fibers of the bend/elbow will be under tension and the inner fibers will be under compression. Due to shape of bend both tension and compression will have component in the same direction creating distortion/slottening of bend. This leads to higher flexibility of the end as there is some decrease in moment of inertia due to distortion from circular to elliptical shape and also due to fact that the outer layer fibers, which are under tension has to elongate less and the inner layer fibers which are under compression has to contract less to accommodate the same angular rotation leading to higher flexibility. Piping component used in piping system has notches/discontinuities in the piping system, which acts as stress raisers. For example a fabricated tee branch. The concept of stress intensification comes from this and is defined as the ratio of the bending moment producing fatigue failure in a given number of cycles in straight pipe of nominal dimensions to that producing failure in the same number of cycles for the part under consideration. Both flexibility factor and stress intensification factors have been described in PROCESS PIPING CODE”(ASME B31.3) and is also included in the various pipe stress analysis computer programmes.

7.0 Equipment nozzle loading:

As explained earlier pipe stresses are calculated for various type of loading such as pressure, weight, thermal etc. and it is reviewed whether the stresses are within allowable limits. However in lot of cases pipe stress analysis becomes critical and rather complicated because it is not only stress of piping but the nozzle loading of the various equipment which has to be kept within allowable limits.

For rotating equipment’s like steam turbines, compressors centrifugal pumps,

various codes like NEMA SM-23, API-617, API-610 etc. give guidelines regarding the allowable nozzle loading. For the analysis of these piping connected with various rotating equipment, vendor also provide information regarding nozzle movements and allowable loads. It is the responsibility of the equipment engineer to ensure that the allowable loads as agreed by vendors are always equal to or greater the values as per the respective applicable code. Various computer packages now have equipment nozzle check features. However the pipe stress engineers are advised to study the specific applicable codes also as this will give them a further insight for solving specific problems related to equipment nozzle loading.

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Basics of Pipe Stress - (1)

1. Introduction:

Present day process plant piping systems use various fluids at various conditions of pressure and temperature. The piping engineer has to design the systems to ensure reliability and safety throughout designed plant life. The piping systems are subjected to combined effects of fluid internal pressure, its own weight and restrained thermal expansion. The elevated temperature also affects the pipe strength adversely. Therefore the task of the engineer is:

i) To specify an adequate wall thickness to sustain the internal pressure with safety.

ii) To select a piping layout with an adequate flexibility between points of anchorage to absorb its thermal expansion without exceeding allowable material stress levels, also reacting thrusts and moments at the points of anchorage must be kept below certain limits.

iii) To limit the additional stresses due to the dead weight of the piping by providing suitable supporting system- effective for cold as well as hot conditions.

All these objectives are achieved by:

a) Assuming adequate support to prevent excessive sag and stresses in piping system.

b) Incorporating sufficient flexibility to accommodate stress resulting from changes in pipe length due to thermal effects and movement of the connection at the ends of the pipe.

c) Designing the piping system to prevent its exerting excessive forces and movements on equipment such as pumps and tanks or on other connection and support points.

 

The stress engineer of a piping design department performs the necessary calculations to ascertain that the various requirements due to internal pressure, thermal expansion and external weight are satisfied. Various computer packages are available in the market, which perform the required rigorous analysis. These analyses are basically static analyses. There are situations where stresses are introduced into the piping systems due to dynamic loading situations like reciprocating compressor vibration, safety valve discharge etc. However it is the static analysis which most of the pipe stress engineers perform and are acquainted with. Now the present day computer packages that are being used (CEASAR-II, CAEPIPE, PIPEPLUS etc.) are quite comprehensive and if the piping configuration and pipe data are fed properly, comprehensive analysis are done through the computer packages. This has improved pipe stress analysis job productivity immensely. However sometimes this has led to a decline in the knowledge about the basics of pipe stress analysis especially in situation where the stress analysis engineer after acquiring some sort of skill in the use of the analysis package does not make effort to learn about the basics of pipe stress. Some of the ideas about the basics of pipe stress have been enumerated herein.

2. General ideas on failure of materials:

Failures of material can occur by:

a) Brittle fracture

b) Excessive elastic deformation

c) Excessive non-elastic (plastic or viscous) deformations

d) Thermal or mechanical fatigue.

 

2.1 Brittle Fracture:

Steel is generally considered to be a ductile material. However in certain cases steels sometimes rupture without prior evidence of distress. Such brittle failures are accompanied by but little plastic deformation, and the energy required to propagate the fracture appears to be quite low.

The three conditions, which control this tendency for steel to behave in a brittle fashion, include

(1) high stress concentration; i.e. notches, nickes, scratches, internal flows or sharp edges in geometry

(2) a high rate of straining and

(3) a low temperature.

The transition temperature for any steel is the temperature above, which the steel behaves in a predominantly ductile manner and below which it behaves in a predominantly brittle maner. Steel with high transition temperature is more likely to behave in a brittle manner during fabrication or in service. It follows that a steel with low transition temperature is more likely to behave in a ductile manner and therefore, steel with low transition temperature are generally preferred for service involving severe stress concentrations, impact loading, low temperature or combination of the three.

2.2 Elastic and non elastic deformation:

Elastic deformamations are deformations that disappear when the stress is removed. Plastic deformation is non-reversible. When the stress is removed plastic strain approximately remains unaltered. A look at the stress strain diagram of say a carbon steel material will clarify the concepts. However there is another kind of plastic deformation called creep where the deformation increases with time at constant stress. At certain temperature levels creep, which is the term, used to describe this progressive deformation may occur in metals even at stress below the short time yield strength or proportional limit. Thus the yield strength or proportional limit, which are determined by short time tensile tests do not represent satisfactory criteria for the design of piping systems over the entire temperature range CREEP RATE or CREEP LIMIT determination through a large number of long time tensile test of elevated temperature becomes necessary.

2.3 Thermal and mechanical fatigue:

Failure has occurred when the service become more severe than the conditions for which the piping was originally designed. Thermal or mechanical fatigue is usually the most common causes of failures in high temperature piping systems. Severe localized mechanical stress have caused or contributed to failures.

Thermal fatigue is caused by frequent change in operating temperatures of pipeline. Thermal expansion and contraction occur in all metal components by the change in temperature. Over a long period this results in thermal fatigue. Hence for best metallurgical conditions, the temperature of the high temperature piping systems should be maintained continuously and uniformly as far as possible.

Mechanical fatigue is caused by pipe movement, vibration, restraints preventing free movement or other conditions.

Continued to  BASICS OF PIPE STRESS - 2

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PDMS - REPRESENTATION

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The Database Listing Form

The Database Listing form is displayed when you select Utilities>DB Listing or Query>DB Changes from the main bar menu. This form lets you output all or part of the database, including element attributes, as a text file.

A simple procedure to create a DB listing:

<!--[if !supportLists]-->1) <!--[endif]-->Select Utilities > DB Listing

<!--[if !supportLists]-->2) <!--[endif]-->Navigate to the element that you want to list.

<!--[if !supportLists]-->3) <!--[endif]-->Select Add > CE from the DB Listing form.

<!--[if !supportLists]-->4) <!--[endif]-->Destination should be File. Accept the default filename, or give a path and filename of your choice, i.e. C:\temp\P1501A.txt.

<!--[if !supportLists]-->5) <!--[endif]-->Press the Apply button at the lower left corner of the DB Listing form.

<!--[if !supportLists]-->6) <!--[endif]-->Open the file in the text editor of your choice, i.e. NotePad, WordPad, etc., and edit any attributes such as names, positions, etc. Search and Replace can be used to change names throughout the file. Remember, names must be unique. Don’t forget to save the file.

<!--[if !supportLists]-->7) <!--[endif]-->In PDMS, navigate to the level of a legal owner (or below) of the element type that you have listed.

<!--[if !supportLists]-->8) <!--[endif]--> Display > Command Line

<!--[if !supportLists]-->9) <!--[endif]-->Key in: $M C:\TEMP\P1501A.TXT

It can be used in three different modes:

DB Listing: This outputs a listing of the specified parts of the database in its current state.

DB Changes: This outputs a listing of the changes to the specified parts of the database as a macro which can be run in to return the database to the state it was in at the given time or session. You can edit the macro file so that only the required elements are changed.

DB Differences: This outputs a listing of the specified parts of the database, with the old and new elements and attributes changed or added since the given time or session.

The mode affects which gadgets are active on the form. The mode is changed using the options under Control on the menu at the top of the form.

Destination:

You can send the output to the Screen or a File. If you select File, fill in a valid filename to output to the $PDMSUSER directory, or input a valid pathname to output to a different directory. Select New for a new file, or Overwrite or Append if the file exists: if you do not, you will be prompted to specify which one you want. If you select Screen, the Command Input & Output window will be displayed, ready to display the information when you press Apply.

Browse displays a file browser.

Elements:

This shows the list of elements that will be reported on when the Apply button is pressed. Clicking on any element in this list will navigate to that element.

Changes since
Differences since
DB Listing:

The active gadgets in this frame depend on the form mode, which is shown by the frame title. None of the gadgets are active in DB Listing mode. In DB Changes and DB Differences modes, you can select:

Savework, which will report on changes since the last Savework.

TimeDate, which will report on changes since the time and date given.

Time format is HH:MM on a 24 hour clock, e.g. 16:15.

Date format is DD Mon Year, e.g. 9 Feb 1998 or 30 Aug 97

Session, which will report on changes since the given session number. Set the other gadgets in this frame to the time, date, session number and session user of the last saved session of the current DB.

Extract, which is only active when the current element is in an extract database. will report on changes since the given session number. When you choose this option, the options in the Since Extract frame will become active, see below.

You can type in the session number, or change it using the + and - buttons.

Remember that each DB has its own sessions. The current DB is shown by Database Name at the bottom of the frame.

Note that TimeDate and Session are related: changing one will affect the other settings, and also display the correct Session User.

The More button shows a form with the Session comment for the given session.

Highlight Changes:

This button is only active when the form is in DB Changes or DB Differences mode in DESIGN. If switched on, the changed elements will be highlighted in all

the 3D graphics views in the colour specified by Colour>Changes. This option is useful after a Getwork to see the changes that other users have made.

Since Extract

The first drop-down list in the Since Extract frame will become activewhen you choose the Since Extract option in the DB Changes/Differences frame. It shows all the databases in the extract hierarchy above the current extract, with the Master at the top of the list.

The options on the next drop-down list are:

Only which compares the current database with the selected extract ancestor database

Latest which compares the database with the latest version of the selected extract ancestor database.

Session which compares the database with the selected ancestor extract since session nn of that extract.

Date which compares the database with the selected ancestor extract since the given date in a session of the ancestor extract.

The Apply button is only active when there are elements in the Elements list.

The Dismiss button dismisses the form and clears the Elements list.

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PDMS SYNTAX'S

The Construct Syntax

The construct syntax is described more fully in the Design reference manual and it is worth looking at it in more detail. CONST allows distances and angles to be calculated from the design data and is invaluable when you are writing applications. For example

• Q CONST ANGLE N AND W --->>>> gives 90°

• CONST A PIN1 TO PIN2 TO PIN3

• Q CONST DIST FROM P1 to P2 TO P2 OF/BOX1 --->>>> gives a distance
  

• CONST DIST FROM PA TO PL OF PREV

• $S QA=Q ATT --->>>> Create a synonym to query attributes

• Q EVAR PDMSUSER --->>>> Query the operating system location of user file directory PDMSUSER

REPORTING SYNTAX

You can create an array which includes a number of elements which all satisfy specific selection criteria, as defined by yourself. The syntax is:

VAR !Array COLLECT selection criteria

!Array is the name of the array that will be created to contain the elements selected.

The following general criteria can be used to define the selection:

• A class of elements or element types

• A logical expression to be satisfied at all selected elements

• A physical volume in whichall selected elements must lie

• A point in the hierarchy below which all selected elements must lie

Eg VAR !PIPECOMPS COLLECT ALL BRANCH MEMBERS

This would create the array !PIPECOMPS and set it to contain the reference numbers of every
piping component in the MDB. Logical expressions use the WITH and WHERE option; a volume is defined by the WITHIN keyword; and the hierarchy criteria is defined by the FOR keyword.

Eg VAR !ELBO COLL ALL ELBO WITH SPREF EQ /A300B/100

Evaluating Selected DB Elements

Using the facilities described here you can create an expression and have it evaluated for all elements which satisfy particular selection criteria. The results of the expression are then placed in a named array.

The command syntax is:

VAR !Array EVALUATE (Expression) FOR Select

!Array is the name of the array that will be created

(expression) is the expression that will be carried out for all elements that match the select criteria

Select is the selection criteria

Eg VAR !BOXES EVALUATE ( XLEN * YLEN ) FOR ALL BOXES

IF ALL ELSE FAILS!

As you can see, there are a lot of commands available to the PDMS user and the list above is only scratching the surface. Almost all of the command syntax is described in the reference manuals but in some cases you might find it difficult to compose the required command from these alone. In these cases, it might be necessary to build a command by using the query syntax itself, using $Q and $H syntax.

The command: $Q gives a list of all possible commands at any one time. On it's own, $Q gives a complete list of top level commands in any PDMS module. When applied in the middle of a command line, it lists the options available at that point.

E.G. the command:

• SETUP FORM --->>>> Yields an error incomplete command line

• SETUP FORM $Q --->>>> list_name as required

• SETUP FORM _FRED $Q --->>>> lists a number of options including:

• 'BLOCK/ING' 'RESI/ZABLE' 'AT' 'SIZE' 'COPY' and Newline

Each of the words in quotes can be used at this point. There may be further options after these words and the same technique can be used to find the way through. The characters before the '/' indicate the minimum abbreviation which may be used for each part of the command. The presence of the Newline keyword without the quotes indicates that the return key may be pressed at this point and the command is executed.

Another form of syntax querying is the $H command. $H is a slightly more sophisticated form
of $Q, which lists the available options numerically as the following example shows:

SETUP $H

1

SETUP $H1

'FORM'

SETUP FORM $H

UNAME

And so on.

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PDMS PSEUDO ATTRIBUTES

PSEUDO ATTRIBUTES

In order to get specific information directly from the database, a number of keyword or pseudo
attributes have been introduced. Pseudo attributes are not attributes as such, but they have
the ability to extract data when queried. For Example

• ELBO 1 --->>>> Go to elbo 1 of the branch

• Q PARAM --->>>> Query the parameters of the catref of the spref

• Q DTXR --->>>> Query the rtext of the detref of the spref_ can also use dtxs or dtxt

• Q MTXX --->>>> Query the xtext of the matref of the spref _ can also use mtxy or mtxz

• Q PSATTS --->>>> Query the list of pseudo attributes available for the CE.

A few useful pseudo attributes appear below:

General Queries

• Q LIST --->>>> Query what you can create below the current element

• Q OLIST --->>>>Query the type of elements which can own CE

• Q ORDER --->>>>Query the list position

• Q PROP DESC --->>>> Query the data element with the dkey equal to DESC in the component's dataset (Steelwork and Piping elements)

• Q PRLS --->>>> Query the list of properties in the component's dataset

• Q PURP XXX --->>>> Query the purpose attribute of the property XXX

Piping Attributes

• Q CHOICE --->>>> Query the answers of the selectors of the spref

• Q CHOICE STYP --->>>> Query the styp used to select the component

• Q PL BOP --->>>> Query the bottom of pipe elevation of the leave point

• Q PA INSU --->>>> Query the insulation thickness at the arrive point

• Q PGRAD 1 --->>>> Query the slope at ppoint 1

• Q ITLE --->>>> Query the length of implied tube (must navigate first by using 'IL TUBE' at a component)

• Q LBOR --->>>> Query the leave bore

• Q ABOR --->>>> Query the arrive bore

• Q APOS --->>>> Query the arrive position

• Q LPOS --->>>> Query the leave position

At Branch Level

• Q TULEN --->>>> Query the length of tube in a branch

• Q CLLEN --->>>> Query the centerline length through all components

Steelwork

• Q ODESP --->>>> Query the design params of the joint owner

• Q ADESP --->>>> Query the design params of the joint attached beam

• Q DRPS --->>>> Query the derived position of the beam start

• Q NWEI -->>>> Query the net weight (considering joint cut outs)

• Q GWEI --->>>> Query the gross weight (beam before cutting)

• Q NCOF --->>>> Query the net centre of gravity for the beam

• Q NSRF --->>>> Query the net surface area

• Q MIDP --->>>> Query the mid point

• Q POS PPLINE TOS START WRT /* --->>>> Query TOS of current element (SCTN)

• Q PPLINE TOS DIR --->>>> Query the direction of the TOS pline on a SCTN

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PDMS Creating & Deleting Elements

Creating Elements

• NEW BOX --->>>> To create anything in PDMS, you need to be at the right level in the hierarchy and use the command NEW followed by the TYPE of element you want to create.

• NEW EQUI /T-1101 --->>>> Create EQUI element and set the name attribute

• NEW ELBO CHOOSE --->>>> For piping components, you need to create the element and then link it to the catalogue via the spref attribute. The CHOOSE command allows you to select components from the specification by picking them from a displayed menu.

• CHOOSE ALL ---->>>> Allows you to see more detail about the component than CHOOSE on it's own.

Deleting Elements

• DELETE ELBO --->>>> To delete an element, the syntax is DELETE followed by the TYPE of element you are deleting.

• DELETE BRAN MEM --->>>> This deletes the members of an element (i.e. BRAN in this example) without deleting the element itself.

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PDMS Orientation Commands

Orientation Commands (General)

• ORI Y IS N AND Z IS U --->>>> This is the default orientation (wrt owner) for all elements that have an orientation attribute.

• ORI Y IS E45N --->>>> Specify that the Y axis is pointing E45N. When only one axis is specified, the other tries to get to it's default, so in this case, Z will default to UP.

• ORI P1 IS N --->>>> Rather than specifying an axis, this command specifies that a particular ppoint is to be orientated in the direction specified.

Orientation Commands (Piping)

• ORI --->>>> This command orientates the arrive of the element in the opposite direction to the leave of the previous element. It does not change the position.
  

• CONNECT --->>>> Perform an ORI, then position the arrive at the leave of previous.

• DIR S --->>>> This is a special command which is allowed to change the angle of a component. It first performs an ori, then adjusts the angle to ensure that the leave direction is in the direction specified.

• ORI AND P3 IS U --->>>> Used for valves, tees, etc., this command performs an ori and then points the ppoint in the required direction. It does not change the angle.

• DIR AND P3 IS U --->>>> This is another special command which is only used on tees with variable angles. (Usually for sloping lines.) In this case, the tee is orientated and the angle adjusted to allow p3 to point in the direction specified.
  

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PDMS Positioning Commands (Piping)

Positioning Commands (Piping)

NOTE: All the above commands can be used with piping components for exact positioning. The following commands are specific to piping because they use the implied direction of the previous component to determine the position. This implied direction is some times referred to as the constrained centreline and is simply a line drawn in the direction of the previous component. All of the following commands will move components along this line.

• DIST 300 --->>>> Position the current element 300mm away from the previous component. The direction is taken as the leave direction of the previous component.
  

• CLEAR 400 --->>>> Position the current element with a clearance of 400m between it and the previous element. For most types of component, this command gives a tube spool length equal to the clearance value. For some components such as level operated valves the clearance is likely to take the lever length as the obstruction length of the valve, so in this case the clearance might be more unpredictable.

• THRO N500 TO N500 --->>>> Position the origin of the CE along constrained centerline through N500 in ZONE coordinates.
  

• THRO PT --->>>> Position the origin of the CE along constrained centerline at the point where it intersects a perpendicular plane positioned at the branch tail.
  

• CONNect --->>>> Position the arrive point at the leave point of the previous component and orientate the component to suit.
  

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PDMS Positioning Commands (General)

Positioning Commands (General)

• At E300 N400 U500

• At E3333 N6000 U50 WRT SITE

• At N500W30U600 WRT WORLD

• AT N400 U500 E300 IN ZONE

• At N40 WRT /FRED

---->>> Position an element explicitly at the coordinates given relative to the element's owner. To position relative to some other element, wrt can be added, as shown above.

• BY N500 -->> Move the element north from it's current position by 500mm (This is relative movement.)
  

• CONN P1 TO P2 OF PREV --->>> Positions P1 at the specified point and orientates the element such that P1 is pointing in the opposite direction to the specified ppoint.
  

• CONN IDP@ TO IDP@ --->>> Connect a picked Ppoint on the current primitive to a picked Ppoint of another

• CONN P1 TO IDP@ --->>> Connect P1 of the current primitive to a picked
  Point of another primitive
  

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PDMS QUERY COMMANDS

Query Commands

• Q ATT - Query all the attributes of the current element

• Q POS - Query the position of the current element

• Q POS IN SITE (or Q POS WRT SITE) - Query the position of the current element relative to the site position

NOTE: Normally, the Q POS command gives the position relative to the element's owner.

• Q NAME - Query the name of the current element. This may either begin with '/' character. '/PIPING' or may be by a list position name (full name) such as:
  

ELBO 2 OF /P1/B1

• Q REF - Query the database unique reference number i.e. = 234/702. This is the best way of ensuring that you get to the element you want. Names can change but reference numbers are fixed so you always get the same element.

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SETTING PDMS ATTRIBUTES

Setting PDMS attributes

In principle, any attribute can be set by specifying the attribute name and value you want it to
take. The following are examples:

XLEN 200

DESC 'PLATE GIRDER'

HEIGHT 300

TEMP 120

NAME /FRED

PURP EQUI

ORI Y IS N

ORI Y IS N AND Z IS U

Navigation

Commands for moving around the PDMS database.

• /NAME - Move to an element by name

• =23/506 - Move to an element by its reference number

• END - Move up the database hierarchy by 1 level

• 6 - Move to the sixth element in the list of the current element

• NEXT - Move to the next element in the list at the same level

• NEXT 2 - Move to the second element after the current element

• NEXT ELBO - Move to the next elbo in the current list by passing any other elements

• PREV - Move to the previous element in the list

• PREV 4 - Move four elements back from ce

• SAME - Go to the previous current element

NOTE: NEXT and PREV commands work on the list according to the modes Forwards or Backwards. In backwards mode, the list is considered to be reversed so these commands have the effect of working from the opposite end of the list.

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PDMS SYNTAX EXAMPLES

PDMS Syntax Examples

Position>Move>Distance

Moves the element’s origin by a given distance in a given direction.

Ex.

MOVE N DIST 10’

MOVE S WRT /* DIST 5'

MOVE E IN SITE DIST 5'

Position>Move>Through

Moves the origin of the element in a given direction through a Reference Plane perpendicular to the line of travel that is passing through a picked element, p-point, or coordinate.

Ex.

MOVE N THRO ID@

MOVE N THRO IDP@

MOVE N THRO N46’

Position>Move>Clearance

Moves the element’s origin, p-point, or obstruction in a given direction with a clearance from another item’s origin, p-point, or obstruction.

Ex.

MOVE E DIST 10’ FROM /P-101

MOVE E CLEARANCE 10’ FROM /P-101

The options INFRONT, BEHIND, ONTO, and UNDER refer to a picked or named item’s physical obstruction, while the TO and FROM options refer to the item’s origin. INFRONT and TO refer to the near side while BEHIND and FROM refer to the far side of an item.


Position>Plane Move>Through

Moves the origin of the element in a given direction through a Reference Plane specified by the user that is passing through a
picked element, p-point, or coordinate.
Ex.

MOVE ALONG E PLANE N45W THRO ID@

• AT E3’ N30’ U10’ -- Position the current element at a specific coordinate (must specify all three coordinates)

• BY E6’6 -- Move the current element a relative distance in a given direction
  

• TO U12’6 -- Move a piping component to one specified zone coordinate along constrained centerline
  

• Q ATT -- Query all attributes of current element
  

• Q NAME -- Query name (or any specific attribute may be used) of the current element
  

• Q REFNO -- Query the reference number of the current element
  

• Q POS -- Query position wrt owner of the current element
  

• Q POS WRT ZONE -- Query position wrt zone of current element
  

• Q CE - Query the name attribute (or reference name) of current element
  

• Q MEM -- Query members of current element
  

• Q OWN -- Query the name of the owner of the current element
  

• NEXT -- Go to next element in list
  

• PRE -- Go to previous element in list
  

• SAME -- Go to the previous current element

• $Q -- Lists all valid commands

• MOVE $Q -- Lists all options for the MOVE command

• NAME /ANYNAME -- Set the name attribute of the current element

• DESC ‘ANY TEXT STRING’ -- Set the Description attribute of the current element to a text string.

• $S QA=Q ATT -- Create synonym to query attributes

• Q POS PPLINE TOS START WRT WORL -- Query TOS of current element (SCTN)

• Q EVAR PDMSUSER -- Query the operating system location of user file directory (%PDMSUSER%)

• NEW STRU -- Create new structure element (Note: CE must be a owner level (ZONE) or below

• NEW SUBS /MAIN-DECK -- Create new substructure element and set the name attribute

• POS E20’ N10’ U5’ -- Position CE at specified owner coordinates

• POS E20’ N10’ U5’ WRT /* -- Position CE at specified world coordinates

• CONN IDP@ TO IDP@ -- Connect a picked Ppoint on the current primitive to a picked Ppoint of another.

• CONN P1 TO IDP@ -- Connect P1 of the current primitive to a picked Ppoint of another primitive.

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STRUCTURE, EQUIPMENT & OTHERS Remaining Commands of PDMS

STRUCTURE COMMANDS

1. AXES AT POSE/S (end or start)

2. Q POSE WRT/*

3. EXTE END BY D 500 WRT/*

4. EXTE START BY U 500 WRT/*

5. EXTE END/START THRO ID@

6. EXTE END/START THRO IDPL@ (PL-Pline)

7. Q CUTL (To see length of section)

8. Q POS PPLINE BOS IN/* (BOS TOS NA)

9. ADD ALL STR

10. REM ALL STR

11. Q ATT

12. BY U//D/E/W/N/S 500

13. Q DRNS DRNE

14. DRNSTART S 45 E (Direction and angle)

15. DRNEND S 45 W (Direction and angle)




EQUIPMENT COMMANDS

1. ADD ALL EQUI

2. REM ALL EQUI

3. MOVE U THROU IDP@

4. MOVE E THROU IDP@

5. MOVE W THROU IDP@

6. MOVE N THROU IDP@

7. MOVE S THROU IDP@

8. REPR HOLES ON/OFF UPDATE

9. REPR OBST ON/OFF UPDATE

10. To Copy New Equipment

a. VAR1 NAME

b. NEW EQU COPY $V1 (To Include Equipment in another zone)

11. BY U//D/E/W/N/S 500

12. NEW BOX COPY PRE

13. NEW BOX XLEN 400 YLEN 250 ZLN 150

14. NEW CYL COPY PRE

15. NEW PYRE COPY PRE

16. NEW NOZZ COPY PRE

17. NEW BOX COPY PRE ROT BY 90 ABOUT Z THRO IDP@



OTHERS COMMANDS

1. For copy equip/sub equipment from one project to another project.

a. FILE /FILE NAME.TXT

b. OUTPUT CE

c. TERM

2. For pest equipment / sub equipment from one project to another project.

a. $M FILE NAME.TXT

3. For Undo Command

a. MDB NOUPDATE

b. EXIT

4. Mdb Update

a. MDB UPDATE

b. USER PROMQAMQA/MQA

c. /SUFN

d. EXIT

5. UNCLAIM CE

6. UNCLAIM ALL

7. ALPHA REQ CLEAR (To clear the command screen)

8. CREATE NEW ZONE/SITE/EQUI

9. ADD ALL WITHIN VOL CE 100

10. Q ORI (To see the orientation)

11. ALPHA LOG /C:/ANANT.TXT (To make command line file)
ALFA LOG END

12. SAVEWORK

13. Q US (User name)

14. Q MDB (Multiple data base)

15. Q REF

16. RECREATE DISPLAY /ABC.TXT (For save Display)

17. $M ABC.TXT (For restore Display)

18. Q UNITS

19. Q DISPLAY

20. Q BANNER (To Check the version number)

21. Q BANNER FULL

22. Q TEAM (PDMS user name)

23. Q USER (Logging name)

24. Q DBNAME (To check DB name)

25. Q DBTYPE

26. Q DBFNUMBER

27. Q DBFILE

28. Q LASTMOD

29. Q SESSMOD

30. Q SESSMODI

31. Q USERMODI

32. Q LASTMODI HIER

33. Q DRAW

34. Q DRAW COUNT

35. Q DRAW FULL

36. STATUS

37. SYSTAT (Gives you information about the current active Status of the project)

38. recre disp /gggg over (U can save as a display or u can do like this)
$m gggg

39. FILE /C:/AAA OVER
OUTPUT NEW CEV
TERM ENTER
$M /C:/AAA

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