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pipingdesigners.com Training
Seminar Section - VI, Pipe Fabrication IssuesB: Pipe Fabrication Shop Assignment Questions and ProblemsBy: James O. Pennock
The information below includes information the company should know about a pipe fabrication shop before an order is placed. It is also what the person needs to know about the shop and the pipe fabrication purchase order before he or she starts an assignment in the pipe fabrication shop.
What is the name and location (address) of the proposed pipe fabrication shop? What is the ownership of this shop? What is the organization chart (names and positions) for this shop? What is the name and title of the primary shop contact for this order?
What is the history of this shop? What is the performance history for this shop? Has the company contacted other companies (customers) who have had work in this shop?
How many production lines does this shop have and what is the break-down? Normally the different production lines are arranged by size and material. The size breakdown is based on the respective jigs, fixtures, cranes (or handling equipment), the welding procedures, the welding machines, the fitter and welder training and experience. The material separation is to insure that Stainless Steel and other alloys are not contaminated by carbon steel. Typically Stainless Steel lines will use nylon slings instead of chain to lift the pipe spools. The lines might be as follows: - Small bore (3” and smaller) Carbon
Steel What other pipe fabrication related capabilities does this shop have (i.e.: expansion joint fabrication)?
When will the shop order be placed? What kind of other services (internal cleaning, priming, finished painting, etc.) does the shop fabrication order include? What kinds of piping (material, sizes and schedules) will this order cover?
What is the shops standard stock categories (2” to 24” sch. 40 and 80 Carbon Steel only, etc.)? Will the shop buy all material or will the company purchase and supply some piping and non-piping material (i.e.: Thermowells)? What is the material market’s projected actual lead time for delivery of alloy and other non-standard stock materials? When will the “Buy” quality Bill-of-material summary be ready for issue? What is the intended quality of this B-O-M summary? Will there be a secondary MTO for shop material and an effective on-going program to identify new shop material requirements? Will there be limits applied to where the material comes from?
When is the planned start of isometric issue? What is the planned isometric issue duration? When will the actual isometric issue start? When will the company supplied material be delivered 100%? When is the first pipe spool required at jobsite? When is the last pipe spool required at jobsite?
Where is the jobsite? What is the planned method of shipping?
What are my company’s specific concerns
relating to this shop’s performance?
Below are some issues relating to execution,
coordination, cost and delivery that the company should address
to reduce costs and improve delivery.
In the past some engineering companies have insisted on having multiple priority categories, twenty or more, in some cases. This is just plain ludicrous. A shop, any shop has limited options for the handling of normal work and “Priority” spool pieces. They in fact have only three options. The engineering company needs to know and understand this and then keep things very simple. Option 1: “FIFO” This means that all phases (engineering, material allocation, production, NDE, PWHT, painting and shipping) are processed on a “first-in-first-out” (FIFO) basis. Engineering receives the customer isometric and prepares the required shop spool drawings. They then do a material take-off to check for material availability. If material is available then the spool drawing is released to the production floor. From there it is scheduled into the normal flow of work on the basis of FIFO for that specific (size/material) production line. This also means that the all work is done at the shop’s normal shift and work day hours. If the engineering company planned and scheduled their work properly and they gave the shop the right information about the requirements for pipe fabrication then this option should meet the needs of the order. Option 2: “Fast track” (or “Head-of-the-line”) This means that at all the normal work phases (listed above) an isometric and the resultant pipe spools are moved to the head of the line at any effected work station. This, however, still means that all work is done at the shop’s normal shift and work day hours. This option may or may not have a cost adder depending on how often it is imposed. It should not be used for more than 5% to 8% of the total order. Option 3: “Premium”
This means that all of the normal phases are still done but at the
“head-of-the-line” basis AND the shop agrees to work 24
hours (three shifts at 8 hrs or two shifts of 12 hrs) to finish
the “premium” work. All extra costs (labor and utilities)
incurred for “Premium” work is paid for by the client.
This option will indeed have a cost adder, and it will be significant.
This option should not be used for more than 2% to 3% of the total
order.
The late notice of new material requirements has a serious effect on the real engineering, fabrication and delivery duration. How do late notices of new material happen? The most common reason this happens is because material specs changed late in the project, long after the shop “Buy” MTO (Material Take-off) was completed. Another reason it happens is because there is always more than one way to do most things. The senior piper who planned on something being done one way (using specific material) has a junior or a novice piper who does that thing another way (using different material). This does not have a big impact on “shop stock” carbon steel material. However it does have a huge Impact on very high cost, long delivery alloy materials. Keep in mind for some sizes and schedules of carbon steel it may be possible to acquire and have delivery from over night to three weeks depending on where the shop is located and where the source is located. On the other hand for materials like P22 and P91 the delivery might be as much as 50 weeks or more. An important thing to remember is that
a shop will not and does not start fabrication on a piping “spool’
unless and until they have all the required material for that “spool.”
Here are two tables that shows the impact that missing material
may have on the overall delivery duration schedule (DDS). The numbers
shown here were taken from a real job.
(Here we are talking about large diameter/heavy wall pipe bends in pipe where the bend radius is more than the standard 1-1/2 D 90 degree fitting ell.) The effect of pipe bends on the production schedule can also have a major impact. To the shop a pipe bend is just another piece of material, much like a fitting. The shop might have its own bending line but it may be in another state, province or country. They need to have advance notice of all bend requirements. The pipe to be used for the bend needs to be purchased, received, inspected, logged in to the shops warehouse system then it needs to be scheduled into the bend shop. The pipe is then sent to the bend shop (or line) where it is bent, checked for accuracy then “Stress relieved” (PWHT) and returned to the fabrication shop for the balance of the operations required to finish the pipe spool. The ideal approach where large bends are required is for the original “buy” MTO to include a summary of these bends so the material can be purchased and bent ahead of time.
The effect on the shop schedule by company “HOLDS” on isometrics is a major problem. Consistently the engineering company will issue piping isometrics to the shop then weeks later they call the shop and place a “Hold” on the isometric and all the resulting spools. Keep in mind a typical isometric may contain anywhere from three to five shop spools. When the isometric/shop spools is placed on a customer “Hold” the shop releases all the material contained on those spools for other spools. These shop spools also lose their slot in the normal first-in-first-out flow of work. Typically what happens is one of the following: A) This isometric is mid-size
standard weight carbon steel material. As a result the company forgets
and this isometric is on “Hold” for a few weeks. Then
they remember the “Hold.” After some time they take a
new look at it and determine that there was no reason for the “Hold”
and releases it. The company then complains that these spools are
behind schedule. B) This isometric is also mid-size
standard weight carbon steel material. The company keeps this isometric
on “Hold” for period of time while they do a redesign.
The isometric is then revised and released with the “Hold”
removed. The shop now finds out that there is a minor dimensional
change to only one of the spools on this isometric. Again the company
complains that all these shop spools are behind schedule. C) The company revises the isometric
and proceeds to issue it in the normal manner. This isometric falls
in the realm of the 34 to 50 week material delivery. The revision
contains material that is “new” or not previously included
in the “Buy” MTO. The shop can do nothing but order the
“new” material and place the effected spool at the back
of the line. The engineering company now starts to complain that
the spools should only take 16 weeks to fabricate. D) In this case all (6+/-) isometrics
(and the resulting shop spools) for a complete system were placed
on “Hold” with no reason given. The material this time
was small bore stainless steel. The SS material was included in
the original “Buy” MTO and was purchased and delivered
to the shop. The “Hold” put a stop to all work on these
isometrics for many months. The “Hold’ was initiated by
a controversy about the material “life” in the alleged
strong corrosive atmosphere. When the isometrics were finally revised
and reissued the new material was a special Alloy 20 with a 50 week
delivery. The service for this piping was the same as what is found
around the average swimming pool for the chlorine system which uses
plastic piping. They could have installed plastic pipe and replaced
it every year for the next fifty years for far less than what this
new material and the delay cost the project. What is the answer to the problem created by late “Holds” by the engineering company? The easy answer is to disallow all “Holds” on shop spools. To do this the engineering company must do a number of things. They must do a better job of controlling the work on the design floor, Do It Once and Do It Right. They can also look at making any required changes in the field wherever possible. After all there are a lot of field welds all ready and a few more will not make as much of an impact on the field as it would on the shop. Some may cry Oh! You can’t do that! Well I suggest that you can and should. They can also do a better job of communicating with the shop when there is no choice but to place a “Hold.” They need to fully define the reason for the ”Hold” and what if any effect the potential change will have on material.
Dimensional differences in high-cost, long delivery fittings (WOL) at fitting make-up situations can cause major problems. The example I site has 8, 24” X 10” P91 Weld-O-Lets required for installations that were designed for fitting-to fitting. There was no flexibility for adjustment of dimensions. Six of the O-Lets came in from the manufacturer with the height dimension as stated in the catalog. Two of them were different from the catalog. The catalog dimension and the dimension used by the design team was 9.” One of the O-Lets had an 8” height and the other had a 10” height. This 1” short and 1” too long caused a major problem. The manufacturer claimed that there was no requirement for them to make all the O-Lets (of this size) at 9” and they would not warrantee the O-Lets if the shop modified them to fit. The suggested solution to this is to find out what fittings/dimensions are used in the design (and the electronic data base
Many shop fabrication orders include “customer” furnished items of material. Sometimes it is special alloy material and sometimes it is specific material items such as valves or weld-in Thermowells. Normally it is not a big problem for the shop to receive, warehouse and dispense this material. However there are methods used in the identification and purchase of this material that can and does cause major delays for the shop. The example that I have seen is where the “customer” furnished material was purchased with a specific “Tag” number identification. This “Tag” number item could only go in one specific place. Conversely only the correctly “Tag” number item could be installed in a specific pipe spool. This means that the shop must find that specific “Tag” number item before they can release that specific pipe spool to the production floor. Here is the story. The “customer” company purchased over 500 weld-in Thermowells for a pipe fabrication order. They had the thermowell manufacturer mark each well with a specific instrument “Tag” number. They were then shipped to the shop in small groups of 100+/- to 150+/- as they were completed. These groupings were received at different times, by different people and stored in different places in the warehouse. When a shop material person was sent to find a specific “Tag” number thermowell and did not look in all the right places thus not finding it, he or she stopped looking. A material shortage report was then turned in and a delay was created. This did not have to happen. These 500+ thermowells, although they had over 500 individual “Tag” number identifications came in only 5 sizes. Thermowells come in three basic types. These types have to do with how they are installed in the piping system. There are: A) Threaded wells for the normal low temperature and low pressure, non-toxic commodities. These are installed in the field. B) There are flanged thermowells (in various ratings) that are used for higher temperature, higher pressure and more hazardous commodities. These flanged wells are also normally installed in the field. C) Then there are the weld-in thermowells. These are used on very high temperature, very high pressure and or very toxic commodities. These wells are the only ones that would normally be installed in the pipe fabrication shop. Now all these thermowell types no matter whether they are threaded or flanged or welded-in they have one thing in common. That is they come in only a limited number of sizes. The sizing of all thermowells is based on the “U” dimension and the "stem length. The “U” dimension is the distance the well protrudes into the pipe past the base of the threads (threaded well), flange face (flanged well) or the inside diameter of the pipe (welded-in well). The 500+ thermowells in the example we are talking about here broke down to only one type (weld-in) and only five (5) sizes. They could have and should have been bought as a bulk item by the five sizes and identified on the isometric as just a “type/U-dimension/stem length” code. This would have had a great impact on the ability of the shop to find material and release spools faster. The bottom line here is to keep it simple, buy everything as bulk material when ever possible.
All information required to fabricate a pipe spool should be included on the isometric. That is a great statement and should be valid with only one exception. That exception would be the piping material specification that defines the specifics about the material on an isometric. That is fine; the pipe specs are sometimes the size of a small automobile. It is accepted practice for the shop people to have a full copy of the pipe specs and use them. However there is other information required by the shop that should be included on the isometric rather than having to find it among documents they are not familiar with. This information includes which lines need post weld heat treatment and the maximum operating temperature which impacts the type of post weld heat treatment. What is happening here is that the engineering company sends a line list (or line designation table) or other document to the shop and expects the shop to find the required information. The problem was that the shop was not familiar with these other documents and did not always have the current revision. Isometrics had been issued for lines that were not on the line list.
Some engineering companies ask the shop to do partial painting of pipe spools. This is sometimes done when a line will have safety insulation (therefore no paint) where it could be touched and painted where it cannot be touched. It also includes the carbon steel shoes on alloy or carbon steel lines that will be insulated. Trust me the shop will be more than happy to do this partial painting. And, trust this, they will charge you a hefty price for it. Painting of pipe spools is based on the weight of the total spool, not the square foot or meter of area painted. For total painting they normally have a flat rate price per ton. For partial painting they will discount the rate to (not by) 65% to 80% of the total rate. This means that you pay 65% to 80% of the full spool painting cost to paint only one 24” long shoe. This is not cost effective. There is always going to be painting touch-up in the field and shoes can be painted there at a far cheaper cost.
Another costly item is requiring paint touch-up of “dings” by shop prior to shipping. Pipe that is (fully) painted by the shop can and will get dings before the truck leaves the yard. Some engineering companies require the shop to touch-up these dings before the load leaves the yard. This is also not cost effective. The load is held in the shop until it can be inspected for dings and then they are touched up and re-inspected. This only delays the shipment and the load is going to get more dings in route. It will also get more while being unloaded, during storage in the field prior (to installation) and during handling at installation. The most cost effective way to handle dings in shop painted piping is as follows. First, at every step along the line do everything possible to prevent dings. Second, don’t reach for the paint brush every time you spot a ding. Third, after installation, when all the field welds are being painted, go ahead and touch up those dings.
Every fabricated pipe spool that leaves the shop must be identified for proper and timely installation. Who is responsible for the spool piece identification numbers? Every company has its own methods of operation and therefore some will add the MK number as a part of the isometric extraction process and others may produce plans and elevations then have the shop do the identification numbers. This identification is sometimes called the “Mark-number” and is normally shown as MK – * (numbered in sequence). The MK number is normally preceded by the purchase order (PO) number for the shop fabrication work, the line number (or the isometric number) and the sheet number. Therefore, for example the first pipe spool for line number 10-122A1A on PO # 9876543-2 would be P.O. 9876543-2 – 10-122A1A-Sht 1 - MK -1. This is a very simple identification method and if it is on every spool the field has no problems. However, what if you are on a job that has over 10,000 individual pipe spools and many (maybe all) arrived in the field not marked with the proper identification. This has happened! It is a very costly process in the field to sort out what the spool piece number is supposed to be. The delay is costly in both money and schedule. A clear understanding needs to be established between the design office and the shop, before the order is placed, as to what MK number method is to be used and who is responsible for initiating and controlling the numbers.
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