Lufkin and Pi-Cobra are the two main brands of diameter tape measures that we carry. If you’re a regular user of these unique and useful tape measures, you know their special skill: measuring the diameter of pipes or other cylindrical items.
The pipe diameter tape measure is normally used by pipeline workers and inspectors. They wrap it around the circumference of the pipe, and read the
diameter size on the tape. Now this useful tape can take on a new use during the COVID-19 lockdown.
For those of you who are forced to stay at home every day, you may have discovered the comforting appeal of the refrigerator. It’s always there with food for when you are hungry. It’s even there when you are not hungry, but just need some comfort. If you have a bathroom scale, you may have noticed that the spring might be getting weaker this month. Or, could it be that you are actually putting on weight?
A Lufkin pipe diameter tape measure can be a fun way to try to prove that your bathroom scale might be broken. Wrap it around your waist or your arm, and see for sure if you are getting too chummy with the Frigidaire.
My customers don’t want one with my company logo on it.
Here are my answers:
The “outside diameter tape” is used by plumbers, pipeline workers, electricians, car and boat repairmen.
All you do is wrap it around the pipe, and read off the diameter.
It compares to the price of many other pocket tapes.
Maybe so, but you would have to correct for the fact that you can’t readily see the zero mark. You would have to use the one inch or two inch mark, and subtract that from the total, then divide by pi. A pipe diameter tape measure has the zero conveniently located away from the end of the tape, to make it easy to line up.
Your customers would love a gift with your corporate logo. It would be a symbol of your generosity.
Diameter tape measures are made for wrapping around pipes and poles, to find the diameter. That’s a good enough reason to keep one in your tool box, garage, and vehicle. But there’s one feature that no one talks about, until now….
The other side of the diameter tape measure is a regular tape measure, in inches or centimeters. It measures length, not diameter. So, even though it is a special tape, it is also a handy every day tape, too. Lufkin, and the other manufacturers, thought of everything when they designed these handy pocket tapes. Everyone should have one or two.
There are distance measuring apps out there, but measuring the diameter of a pipe presents a unique measuring situation.
Calibration. There will need to be some way of checking to see if the app is working correctly. You will need to measure a known standard to see if the app is measuring right. If not, there needs to be some way of calibrating or adjusting the reading, to make it accurate. In other words, if you measure a 2 inch pipe, and the app says 2.1 inches, you need a way to adjust the setting to read 2.0 inches. Otherwise, when you measure a 3 inch pipe or any size pipe, the measurement would be off.
Calibration should be done with different sizes of pipe, to make sure you will get an accurate reading at any of those sizes.
The curvature of the pipe needs to be considered. You aren’t taking a picture of a 2D object. The pipe is 3D, so your camera may not see the top and bottom of the pipe as being 180 degrees away from each other. If you are too close to the pipe, you wouldn’t see the full 180 degrees. So your measurement would be too small.
Resolution of measuring. A pipe diameter tape measure normally has a resolution of 100th of an inch diameter. Can a smart phone app be that accurate?
The nearness of the object. For calibration, we would need some standard distance from the cell phone. Maybe this could be accomplished by using an object like a 12″ ruler, placed between the pipe and the phone. Hopefully, a less mechanical method will pop up.
If you know of an app that can accurately measure pipe diameter, please let me know. If one does not exist, I’m sure it will be invented in the near future.
Lufkin® has a world-wide reputation for making high quality tape measures. They used to make them in the USA, but they have shifted the production facilities to Mexico. Some of the tapes are made out of a cast case, which is highly polished and chrome plated, like the w906pd. Others, like the w606pd have a stamped case, which is shiny and chrome plated. A third type of case is black plastic, like the asw616pd. However, the tape blade inside is the same in all 3 types of cases. It is capable of measuring diameters up to 23 inches.
Pi-Cobra is a brand name for diameter tapes made with
a cast case which is chrome plated. It can hold a longer tape blade, capable of measuring diameters up to 38 inches. The case is very durable. These are manufactured in China.
Various other Chinese manufacturers make versatile OD tapes like the 416-04-024-P. The back side of the tape measures diameter up to 24″ in 100ths of an inch or 610 mm. The case is plastic, and has a key ring attached to it.
The UT-56675 is made in the USA. It is capable of
measuring pipes up to 45 inches in diameter. This is a belt tape, not a pocket tape. The calibrations are in tenths of an inch diameter.
Pi Day is March 14. This year you can help celebrate by answering the question at the bottom.
Pi is the constant ratio of a circle’s circumference to its diameter, no matter what size the circle is. This is useful knowledge when you work with water pipes or oil or gas pipelines, and you need to replace part of it. You can measure the circumference and divide by pi. But there’s an easier way to do that.
Let a Lufkin Diameter tape measure do it for you. You just wrap it around the pipe, and read the diameter. Mathematicians call pi an irrational number, since it goes on for an infinite number of decimal places, but using a diameter tape is a very rational and easy way to find the diameter of a pipe. To see a little video on How to measure the diameter of a pipe, just click here.
This time, we won’t get into the geometry theory of pi that we had in high school. The magic of a pipe diameter tape measure is its simplicity of use. Here are the 3 steps to find the diameter of a pipeline:
Clean the pipe surface. Soil and any other contamination, of course, will make the pipe seem bigger than it really is.
Wrap the diameter tape around it, with the diameter scale visible to you.
Simply read off the tape. This will be the diameter, even though the tape is wrapped around the circumference. That’s all!
Some things to watch for…..Some OD tapes (diameter tapes) are marked in 100ths of an inch. Some are marked in 64ths of an inch. On the 64ths of an inch tape, 32/64 would be 1/2″. 16/64 would be 1/4″. 24/64 would be 3/8″. For convenience, you can use a magic marker to mark some of these common, but confusing measurements.
A diameter tape measure can save you a lot of time and frustration when you want to find the OD (outside diameter) of a pipe, post, or tree. This special tape has the inch scale (or metric scale) stretched out by a factor of pi (3.14159). So, if you wrap it around the pipeline, you will not see the “circumference”. You will see its diameter. You don’t need to divide your answer by 3.14159.