Piping calculator delivers accurate results

On industrial/commercial mechanical piping projects that require a high degree of precision, accurate calculations are key to a fast, successful installation. Nowadays, mechanical contractors are often called upon to measure pipe to tighter tolerances than previously customary. A dedicated piping calculator that performs construction math can be a handy productivity-enhancing tool for pipefitters on the job, mechanics in the fabrication shop, and estimators in mechanical contracting offices. The numerical results when figuring non-standard angles, offsets, and fittings are faster and potentially more accurate than calculations made other ways.

Dedicated calculators are available that aid in calculating pipe length, pipe wall thickness, simple offsets, throat and heel dimensions for field cut elbows, rolling offsets with unknown bend angle, drainage drops and many other tasks.

For example, piping calculators are well suited to jobsite measurements at semiconductor, bio-pharmaceutical, and other industrial projects.

"Mechanics who are laying out jobs and cross-checking their engineering plans against site conditions and crunch math all day long save a lot of effort and help ensure accuracy using piping calculators," noted Jim Witt, a pipefitter since 1967 and the head of the CAD QA/QC Department at a large contractor active in the semiconductor/pharmaceutical industries. "There is a lot of detailed math involved in subtracting the fittings from the center to center measurement to get the end-to-end length of pipe and lots of lines that the calculator helps with."

Use of a piping calculator is also taught regularly to apprentices. For example, the Local 469 apprenticeship program has incorporated the Pipe Trades Pro into its curriculum.

"Unlike scientific calculators, which use decimals, piping calculators talk in our terminology of feet and inches," Witt explained. “It is much easier and less error prone to punch in calculations like 2' 10 ½" minus 1' 11/16" than doing it by hand or converting to and from decimals with a scientific calculator. It is a big timesaver on the job."

The calculator Witt uses in teaching, Pipe Trades Pro by Calculated Industries, www.pipetradespro.com, has more than 20 dedicated keys and functions, many identified by words like offset, travel, setback, angle/slope, pipe size, cos and sine right on the keys, so there is no mistaking the function being performed.

The calculator calculates for seven pipe materials: steel, stainless steel, brass, aluminum, cast iron, plastic and copper. When pipe material, type and size are entered, the calculator instantly displays pipe outside diameter, pipe internal diameter, pipe wall thickness, pipe weight per foot, filled weight per foot, (water by default, but any liquid density can be entered to calculate the filled weight per foot), and pipe internal area. Built-in functions also solve for off degree fittings; complex rolling offsets; percent grades and drops; parallel pipe cutbacks; flow rates, velocity, force and volumes; pressure loss for any pipe size, type or distance; and complete building, plumbing and metric unit conversions.

The company also uses the calculators in the fabrication shop when fabricating pipe sections.

"When we do take-offs from isometric drawings, we have to subtract fittings to achieve the end-to-end length for each pipe section as, for example, a length of pipe that goes between two 45s or two 90s,” said Witt. “Using the piping calculator eliminates a lot of the errors that can occur."

When preparing pipe for welding, the measurements have to be very precise, sometimes within tolerances as small as 1/32 of an inch, Witt pointed out. In semiconductor plants, specifications often call for electro-polished tubing, which is expensive, about $100 a foot for quarter-inch tubing. Any mistakes in cuts performed for weld fittings are very costly.

“There are a lot of difficult offsets where we cannot use standard fittings, so we have to custom bend the pipe,” said Witt. “The calculator comes in very handy to get our bends precisely right."

And, sometimes, the piping is massive, with perhaps 100 ¼-in. lines running side-by-side, each requiring rolling offsets. "We might have to make unique bends with the tubing. Using the calculator to calculate the arc length and a setback to make the bends speeds the processes," he said.

Here's how the Pipe Trades Pro handles that type of "rolling offset" calculation in the following example:

If the task is to calculate the travel and angle of elbow (Angle B) given a set of 7’ 3”, a roll of 3’ 6” and advance of 19’, here's how to solve it using the Pipe Trades Pro:

Witt, who is also an instructor for Local 469 of the Plumbers and Pipefitters Union, in Phoenix, teaches apprentices at the trade school how to use a piping calculator to expedite measurements for bends, angles and lengths on fittings.

Chris McCloskey, the chair and instructor of the Sprinkler System Installer Department, Trades and Manufacturing Technologies, Red Deer College, Alberta, Canada, noted that a piping calculator is expedient in sprinkler design/build and renovation projects, where there may be many changes during construction that necessitate new piping calculations by the layout crew.

The calculator makes it a lot easier to figure out routes in a building to bypass obstructions, to calculate flows and volumes ahead of time, and to calculate the weight of the pipe to determine the type of hangers, he explained. Any revamping and redesigning is, of course, submitted to the designer for review, verification and approval.

A piping calculator also comes in handy when trying to keep down job costs because we can now calculate hydraulic flow rates so accurately, we can use smaller diameter piping to achieve the same pressures and flow rates (gallons per minute and spray density), according to McCloskey.

"What we used to do in a sprinkler system with 6-in. pipe we can now sometimes do with 4-in. piping," McCloskey said.

Smaller diameter piping is lighter and easier to handle. By using the calculator to figure out weight per foot or filled weight per foot, contractors can size appropriate supports and, in some cases, can use lighter weight hangers, enabling, overall, a less expensive sprinkler system.

And, though specifications give flow rates, they might not spell out in detail pipe material and size, requiring the estimator to work backward to determine the appropriate size. The calculator helps with that, too, McCloskey added.

A mechanical engineer, Mike Diamond has been lead project engineer at Calculated Industries for nearly 20 years. Calculated Industries is a manufacturer and marketer of trade-specific calculators and digital measuring tools. For more information, visit: www.pipetradespro.com.