This article is intended to answer some of the questions that come up about the subject of Line Numbers and Line Lists for a typical process plant project.
Some of the questions that come up about Line Numbering include: What is it? Why is it? What does it mean? Who does it? Another question is that is often asked “is there a common pipe line numbering system? Do engineering companies and clients have different line numbering systems? Another question is: Does ASME B31.3 or CSA (Canadian STDs), have a standard for line numbering?
These are all good questions and it is important for every piper to know the answers to each one. I could be wrong but I think it is safe to say there is no “common pipe line numbering system” in use in the process plant engineering and design world. There are just too many companies and people and clients and project types to be able to achieve such commonality. I don’t remember seeing anything in ASME B31.3 (or any other Code), but then again it is not the purpose of the B31 Code to dictate a line numbering system.
To properly discuss this subject we need to understand the purpose of the “Line Number.” We also need to acknowledge that some companies use the term “Line Designation.” Whether your company uses the term “Line number” or the term “Line designation” the purpose is still the same. It is the name for the line, it is for positive identification. It is the same as for you your name is the way to positively identify you. The pipe line identification is necessary through out the project and is used for many purposes by many different people or groups. The line numbering is an important aspect of the piping on a project and should only be created and controlled by the piping group for the project, specifically by the piping material engineer for that project.
As with any of the other “gray hair” pipers, I too have seen many different line numbering systems in my working past. Of all of them I have determined that while there are some similarities there is no totally common system.
Here are some details that I have been able to determine for myself. There are two basic areas that tend to govern line numbering. These are the line number method and the line number elements.
* Methods - There are two basic line numbering “methods.” The first method is based on the Purpose or Function of the line. The second method is based on the line “Size.”
* Elements - There are many potential line identification elements that may be included in a line numbering system. The elements that are most commonly included in a line numbering scheme are: Plant Location, Line Identity, Line Class (or Line Specification), Size, Insulation Type (when required) and Heat Tracing Type (when required).
Methods
The “purpose or functional” method of line numbering is where the line is best defined as a single line having an origin and a terminus consistent with a purpose or function. An example of this might be a pump suction line. It might come from a Storage Tank, a Tower Bottom or an Accumulator. It travels some distance and then splits and connects to the two pumps designated for that one service or function. This is one line, it serves one purpose or function therefore it has only one line number. Another example would be the pump discharge that leaves both of these pumps and join to form the single pipe line that runs to the next piece of equipment. This line also has one purpose or function therefore it has only one number.
The “line size” method is where the line number changes whenever and wherever the line size changes. When compared to the first (purpose or function) method, the pump suction line might have five line numbers instead of one. The pump discharge might also have five or more depending on what happens at the destination end of the line.
One or the other of these two methods becomes the “Rule” for a company, client or project. As we all know, for every rule you will always be able to find an exception. One exception that is common to both of these “Rules” is the rule of the change of line class (or line specification). The change in line class is most often caused by a change in pressure or material. A line might be the same size from one point to another but includes a pressure control valve that lets the pressure down to a level that allows a lower flange rating and or another material therefore a different line class. There are other line class change initiators but I think you get the idea. Any change in a lines conditions or material causes a mandatory change in the line number no mater which line numbering method is being used.
Elements
The elements of a line number might be arranged and look something like this:
10-1021-CA1A-12”- IH -ST
Where:
10 = the plant Unit or Area (mandatory)
1021 = the numeric line number (mandatory)
CA1A = the line class (mandatory)
12” = the line size (mandatory)
IH = Hot Insulation (only when required) (1)
ST = Steam Tracing (only when required) (2)
(1) Other types of insulation include IC = Cold Insulation, IS = Safety Insulation, IA = Acoustic (or Sound) Insulation, etc.
(2) Other types of tracing include: ET = Electric Tracing, CWT = Chill Water Tracing, TT = Thermon (Hot Oil) Tracing, etc.
* In this case the “10” refers to a physical plant area as defined by the project work breakdown structure document. Other Areas might be 20, 30, 40 or 11, 12, 13, etc.
* The “1021” represents the twenty-first line in this area. All line numbers on this project will be four place numbers starting with 1000 in each area.
* The “CA1A” represents the project piping material line class code for: 300# (C), Carbon Steel (A), 1/32” corrosion allowance (1) and a specific gasket type/material (A).
I have no doubt that there are other items of information that could be or are added in some form or another based on the preference of a specific company of client. My credo is “Keep It Simple.” The manner of arranging the Elements to form a line number is something that is also dictated by the Company and or in some cases the Client. The sequence that is shown above is in the order of information priority that I am used to.
The line numbering activity should only be done when the P&ID’s are well along in the development process. The more complete the P&ID’s are the less hours will be wasted and the better the results of the line numbering effort. The degree of P&ID completeness prevents recycle when new equipment or systems are added or when equipment or systems are deleted.
As the Piping Material Engineer (or designate) performs the line numbering of the P&ID he or she also initiates the first draft of the Line List (or Line Designation Table) data base. The resultant document from this data base will be extensive for a whole project but will be broken down by plant area.
In addition to the line identification elements (indicated above), the Line List (data base and document) will or should also include important information for the design process and construction process such as the following:
* The line commodity
* The phase (liquid or gas)
* The origin of the line
* The destination of the line
* The line pressure, both the normal operating pressure and the maximum operation (or Design) pressure
* The line temperature, both the normal operating temperature and the maximum operation (or Design) temperature
* An indicator code for Stress Analysis requirements
* PWHT requirements
* The insulation thickness (optional)
* The line schedule (optional)
The line list once initiated will have many additions, deletions and be used by lots of people throughout the project both in the design office and in the field.
One of the first and most important activities where the line list is used is when the definitive labor hour estimate is generated. The number of lines on a project has a direct bearing on the labor hours required. This is true for the piping design activities in the home office, the pipe fabrication shop and for the installation contractor in the field. So it is very important to get it right.
Checking or the Quality Assurance & Quality Control (QA/QC) in process plant piping engineering and design is a grossly misunderstood activity that is performed (or should be performed) by every piping group on every process plant project deliverable. Problems arise when checking is not done and when it is done it is often done incorrectly. When it is done incorrectly not only the end result (the document) suffers but the designer who created the document suffers and the checker who does the checking also suffers.
The document (the drawing or other deliverable) suffers because the "Check" was ineffective or incomplete. In some cases the checker "thinks" he or she is a better designer than the designer. So they turn the sheet over and redraw the configuration in "red" and send it to the correction group. The checker redraw is a document that in fact has never been checked. In other cases even after a normal check, mistakes may remain and this will cause another round of costs due to the re-checking, correcting (revision), approval, printing in the office to the cost of reissue handling in the field.
The document creator (the designer) suffers because he or she gets blamed for every "red" mark the checker finds on a document. The designer's reputation suffers and they get the feeling that the "Checker" is out to get them. The truth is that most (if not all) of the "red" marks on a check print are in fact not the designers fault. They are more often traced to late changes to P&ID, vendor drawings or data from another discipline.
The document checker suffers because he or she gets a bad reputation and people do not want to work with them. They do not learn to do it right so they keep making the same mistakes. As a checker you may ask the obvious question, how do you do it right? That is simple; when you (as a checker) find a "red" mark (indicating a mistake) you should dig deep and find out why is this "wrong." Is it really wrong and why? That is the real purpose of checking.
"Why doesn't it work like this?" and the second: "Why is there so much animosity between the designers and the checkers?" These are both very good and very valid questions. The answer to both questions is the same. The answer is the lack of training. There is not now nor has there ever been proper training in what checking is or how to do checking. Before you did your first checking did anyone give you receive any training or any simple instructions about how to check or what to check?
What kind of (checking) training should be given? Who should be given this (checking) training? The training given should include everyone in the piping design department. It must include the definition of what checking really is and what is the real target of the checking process.
Checking is really the last stage in the process normally called QA/QC. QA/QC stands for Quality Assurance and Quality Control. QA or Quality Assurance is the things that are done ahead of time during job set-up to assure that things will be done a certain way. This includes filing systems, procedures, and specifications governing the work as it proceeds forward. QA is also the proper follow through during the work to remain in compliance with the procedures. Example, you set up a filing system for vendor data and the first drawings that came in got filed in their correct places. But later when revisions came in they got "lost" and were not placed in the correct file. This is not good.
QC or Quality Control (Checking) is the verification of the product of all the accumulated data and work processes.
Our business is the process plant engineering and design business. In the process plant engineering and design profession the deliverables are drawings. For the piping design department the deliverables include piping plan drawings and piping isometrics. The piping plan drawing (or the 3D model) is important but it is just a means to an end. The isometric is the end product and must contain all the information necessary to purchase the correct material, fabricate the piping configuration, and install the line or system complete with testing and check-out.
The training for Piping Checking (QA/QC) should cover both the Purpose and the Process.
The Purpose
The purpose of checking as it applies to piping drawings in a Process Plant Project is to verify that all the specifications, drawings and other deliverables reflect the correct combination of the diverse issues impacting the end product. These include but are not limited to:
· Safety
· Function
· Operability
· Maintainability
· Constructability
· Mechanical integrity
· Mathematical Accuracy
Piping Design and the deliverables of the piping design effort is an important part of any process plant project and the checking of the piping drawings cannot be diminished in its importance.
With the above in mind:
· "Rule #1" all products and deliverables from the piping design group shall be checked.
· "Rule #2" checkers check the design, they do not do the design
· "Rule #3" all corrections shall be done by the original designer of the document (when ever possible)
The Process
The Piping Design Supervisor for a project assigns the responsibilities for checking to one or more individuals. These "checkers" are held responsible for checking all (or a specific assigned group of) documents. These checkers should be well trained and well experienced individuals who can be fair, who can focus on quality and have a firmness of conviction.
The process of checking includes:
1. Defining what is a "checkable" product
2. Freezing all work on the area that is in check
3. Becoming familiar with the assigned area
4. Defining what constitutes the source material for the assigned area.
5. Obtaining a copy of the current revision of each of all source material
6. Using a set (or standard) checking procedure
7. Diplomacy between the designer who made the drawings and the checker
8. Fairness when determining right from wrong
9. Proper correction of the drawing(s) based on the checker's direction
10. Proper backing and support of the Piping Design Supervisor
You may question "What does all this mean?" Let's take each of the items from this list and discuss them in detail.
"Defining what is a checkable product?"
This means that you should not spend hours/money checking work that is not ready for check. This is the responsibility of the piping design supervisor. If a drawing is not finished, not ready for check then it should not be placed in the checking group. A checkable product in piping would or should be all the piping plan drawings (or CADD models) and all isometrics that are complete. They have been through all the required reviews with all changes and comments incorporated. All activities involving other groups such as stress analysis, or instrument checks have been completed and comments incorporated. A checkable piping plan or isometric is a document that, in the absence of checking should be thought of as ready to go out the door. If it is not ready to go out the door then it is not ready to be checked. A checkable product is also a complete package of the check prints and all source material.
"Freezing all work on the area that is in check"
This again this is the responsibility of the piping design supervisor. When all or a portion of an area is placed in the checking group for check then all work on that portion should stop. It makes no logical or economic sense to be changing what the checker thinks he or she is checking. Too often a checker will have a question about something on an in-check drawing and they go and seek a clarification from the designer only to be informed that "Oh, its not like that anymore." This shows that the product was not ready for check, or there is a lack of communication between the supervisor and the checker or that there is a lack of support by the supervisor for the checker and the checking effort.
"Becoming familiar with the assigned area"
This is a joint responsibility of the piping supervisor and the checker. The checker (if done right) is someone who is totally new to the area being checked. This would be someone who has not worked on the specific assigned area drawings. They may even be someone new to the company or the project and as such they do not have the history of the area. The piping supervisor should provide (and the checker should demand) an overview of the area including the basics of the process, the operation, key maintenance issues and any constructability issues.
"Defining what constitutes the source material for the assigned area" This again is a joint responsibility between the supervisor and the checker. The source material to be used for the checking of the product (the drawing) should be the same material that was used when the last work was done to create the product (the drawing). Yes! There are times when a later revision of a source document (such as a structural drawing or an equipment outline) with changes will be received after the work was completed. These changes need to be reviewed by the piping design supervisor and a determination made as to whether the change requires pulling the drawings out of the checking group/process for modification. Remember checkers do not do the design. If the checker does the design then who checks the checker?
"Obtaining a copy of the current revision of each of all source material"
Having a copy of all the source material is one thing. Having the latest copy/revision of all the source material is an all together different matter. The checker needs to check with each discipline that created the source documents to determine what the latest revision is. The checker needs to check with the group responsible for vendor data to determine the current revision of drawings for each applicable piece of equipment. Once this is done and correct and up-to-date copies are in hand the checker should review the revisions of these drawings against the revision used to prepare the "in check" drawings. If it is found there are differences then the piping supervisor should be notified and a decision as to the suitability for check should be made.
"Using a set (or standard) checking procedure"
Using a standard checking procedure can be a company issue. Some may have very well defined guidelines for checking while others will have little or nothing. With or without the guidelines the checker himself or herself should follow a well structured and methodical procedure when checking piping documents. Piping documents as noted previously normally include piping plans and isometrics. The isometric is recognized as the defining deliverable of any piping effort. The checker should have a check list of normal things to check on the everyday isometric and any project specific items that exist.
"Diplomacy between the designer who made the drawings and the checker"
This is a two way street. Both individuals should be motivated by the same goal. That goal is the accuracy of the information, the quality of the product (isometric), the reputation of the company and the interests of the client. With the proper attitude about the common goals there needs to be open and constructive communication between the checker and the designer whose work is in check. It would not be proper for the checker to "attack" the designer when seeking insight into why something was done a certain way. It is also not proper for the designer to rebuff the checker or be flippant with answers to the checkers inquiries.
"Fairness when determining right from wrong"
This is the checkers responsibility. The checker is a checker for now on this job but on the next job they may be in a different position and making enemies by arbitrary decisions would not prove to be productive in the long run. When an apparent error is found the checker should try to find out where the "error" came from not who made the "error." What information did the designer use to create the document and what information did the checker use to check the document. There may have been a revision to the source information between the time the designer did the original work and the time of the check. Decisions about right and wrong should be made solely on the basis of the source documents and issues such as safety, functionality, operability, maintainability and constructability. When done with the checking the checker should sign and date the check print and forward it for correction.
"Proper correction of the drawing(s) based on the checker's direction"
The proper correction of the drawings includes who does the correction and how the corrections are done. The first choice of who does the correction is the person who made the drawing in the first place. This is not always possible but where possible the originating designer gains insight as to mistakes he or she might have made, thus doing the corrections becomes a learning experience. When the originating designer does the correcting it affords a chance to catch items that the checker was not aware of that were deemed important to the original design. "How" the corrections are done is of even more importance. The corrector is to do the corrections completely and exactly as marked by the checker. When the corrector has an issue with a mark or change made by the checker then the corrector should discuss it with the checker. This conversation should be conducted with the proper attitude on the part of both parties. When done making the corrections the person doing the corrections should sign and date the check print properly.
"Proper backing and support of the Piping Design Supervisor"
The Design Supervisor needs to remember he (or she) is responsible for all of what the designer has produced. If the design is bad then it is the Supervisor's fault not the designer's. The Piping Design Supervisor is the supervisor of all of the piping design not just the good stuff. Proper design supervision means that the Design Supervisor makes frequent and detailed reviews of what each designer is doing and how they are doing it. The Design Supervisor is also responsible for all instructions, data flow and communications effecting information related to the design work. Proper backing does not mean always taking the side of the checker. It does mean backing the checker when the checker is right. When there is an issue that seemingly cannot be resolved between a checker and originating designer, a corrector or anyone else, the responsible piping supervisor needs to get involved. He or she needs to determine the facts, review the supporting source documentation listen closely to both sides and make a decision consistent with the goals of the project.
If all of this is done, and done consistently everyone involved will benefit. The most important one to benefit will be the company. They will have a better trained, better functioning design group and they will be more likely to get repeat business from satisfied clients.