SpoolFab Weight Calculation - General

For calculations based on the volume of metal, a unit weight of0.2833 lb per cubic inch is used. This was adopted to give a material weight factor of 1.0 for carbon steel.

Pipes, Dummy Legs and BW Reducers

For pipes and dummy legs, the weight is based on the volume of metal calculated based on the nominal dimensions, times a weight factor for the material type. Reducers are treated like a piece of pipe of the larger size.

BW Elbows

BW Elbows are assumed to weigh 5% more than a piece of pipe with the same length as that of the elbow along its centerline.

BW Tees and Crosses

BW Tees and crosses are treated like three or four pieces of pipe, using the appropriate fitting dimensions and nominal wall thicknesses. Because this would underestimate the weights of larger tees, the result is factored as follows:

Up to and including 8 inch 1.0

20 inch and above 1.7

Between 8 inch and 20 inch linear interpolation from the above.

SW/TH Tees and Elbows

For SW/TH Tees and Elbows, the weight is taken from the master files. In the event that the master files show zero weight, the weight is assigned using formulae.

The formula for the weight of SW tees is as follows:
Weight = 0.286  x  NPS  x NPS x  FTR^1.266

Where NPS is nominal pipe size. FTR is based on fitting rating as follows:

FTR = 3 for 3000#
FTR=  6 for 6000#
FTR = 9 for 9000#.

Similarly, the formula for the weight of SW elbows is as follows:
Weight = 0.33  x  NPS  x NPS x  FTR^1.07

BW Connectors

Most of these will be nipples. Their weight is assumed to be that of a piece of pipe of the same dimensions.

Flanges, BW Caps, and Plugs

Items with codes SW, IF, CW, BW, WF, and SF have their weights taken from the master files. No formulae have been entered for these items, so if there is a zero entry in the master files, the weight will be taken as zero.

Miscellaneous Items

These include attachments plus certain in-line items like valves, gaskets and certain instruments. For miscellaneous items, the weight is initially taken from the miscellaneous items database but can be edited anytime.

You can check what weight SpoolFab has assigned to an item by calling up the item information window. Press shift-F11 and select Item Information. You can then use right and left arrow keys to go through each item in turn.

If you want to increase the weight of a spool without affecting the BOM:

Click in open space, select Standard Detail/Column Centre and pick one of the Dim Points. DO NOT PRESS ENTER.

You can press Shift-Down a few times to make the dim point less conspicuous.

Then press Ctrl-Enter. This makes SpoolFab treat it as an item rather than a detail.

Replace any existing description with "Blank" without the quotes, and enter the desired weight in the Wt box. Clear the User Code box and Accept. The description "Blank" prevents the item from appearing on the BOM, but its weight will still be included in the total spool weight.

The item tag will show on the drawing on screen, but will not show on printouts or pdfs.

Weight Estimate using SpoolFab Method

Where OAL=overall length, inches  PWPF=Pipe weight per foot, pounds

The SWF Weight Calculation Method – An Alternative

The main differences between the SpoolFab method and the SWF method are:

For CW (BW Caps) SpoolFab uses actual weights, SWF uses a formula.

For BS, KS, RS, CS (most SW fittings other than elbows and tees), the SWF usually gets a higher weight, esp. for 4 inch SW fittings.

For pipes, and other fittings the differences are small, with the exception of BW Tees larger than about 18 inch, for which SpoolFab gets higher weights.

‍Weight Estimate using SWF (Shaw Weight Formula)

‍Formulae use dimensions in inches and have a result in pounds.