MTO means Material Take-Off. This is the action of counting of the pieces and parts needed to fabricate, purchase and or construct something.
BOM means Bill of Material. This is normally a listing of only the material shown on an individual specific drawing such as a piping Isometric.
BOQ means Bill of Quantity (also called Material Summary). This is the totaling of all the quantities from all the BOMís from all the project to send to a piping supplier for pricing or purchase.
There are normally three material take-offs sessions during a process plant project. These are preliminary, secondary and final.
Preliminary MTO: A preliminary MTO is a material take-off very early in the design process when only a limited amount of information is known and very little detail has been developed. A preliminary MTO is normally done for two reasons. The first is to assist with the early "order-of-magnitude" (+/- 10%) estimate for the overall project. The second reason is to issue early order of magnitude Request for Quote for piping materials.
The preliminary MTO is only possible when there is a Plot Plan that is "Approved" by the Client or has been issued to the client for approval. This is done long before there is any detailed work started on the 3D design model.
A preliminary MTO is best done by very strong well experienced senior piping designers who are familiar with the project.
For the preliminary MTO we used a formatted form on which we could indicate the number or amount of material required for each line. On the form I would identify the line number along with the line class. I would then look at this line on the P&ID and on the Plot Plan and determine the routing of the pipe. Then in the boxes (on the form) I would then mark the amount of pipe required for each size required for that line. Then I would count the number of fittings required, starting with 90 degree elbows. Then continuing through all the other inline fittings and online fittings. After the fittings I would count all the flanges by size. Then I would count all the valves from the P&ID. The high point vents and low point drains would be made last based on an educated guess. Then I would take another form and do another line. As I did each line I would "Yellow" off the line on the P&ID so at the end all the lines are accounted for. As the forms were completed they would be reviewed by the Area Supervisor and then forwarded to the Material Control Group who would process the data to produce the RFQ's.
Each Isometric drawing indicates the bill of material required for that pipeline.
These are entered into excel sheet, according to the size and specification of the pipe.