Another PSI Sighting: Pressure Shows Up Everywhere

Welcome to All Sensors “Put the Pressure on Us” blog. This blog brings out pressure sensor aspects in a variety of applications inspired by headlines, consumer and industry requirements, market research, government activities and you.

Another PSI Sighting: Pressure Shows Up Everywhere

While I could be more sensitive than many other people, any indication of the need to measure and/or control pressure in everyday situations usually catches my attention. A recent observation was the number on a neighborhood fire hydrant – in big letters it stated 200 psi. It turns that this is a common working pressure design criteria for residential fire hydrants.

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Conducting flow and pressure testing measurements require a pitot gauge and a fire hydrant cap gauge. Pressure measurements on fire hydrants are performed primarily using analog gauges with a 0 to 300 psi range although digital instruments do exist with one digital gauge specifying 0.5% accuracy. Static pressure is the normal pressure existing on a system before the hydrant flow valve is opened. Local requirements vary but in one case, normal minimum water pressure in a distribution system cannot be below 35 psi when a fire hydrant is opened downstream and the minimum water pressure (residual psi) cannot be below 20 psi. Observed pressure requirements include: 75 psi for larger cities and 50 psi for smaller cities.

In addition to the pressure range and accuracy, environmental aspects for a fire hydrant pressure sensor include the ability to withstand the contact of water and possibly other materials. Properly specifying the “designed for” and other operating pressures and environmental requirements are just the beginning of getting the right pressure sensors for testing fire hydrants or measuring the pressure of any flowing/static liquid.

What do you think/Comments?
Do you have a pressure sensing question? Let me know and I’ll address it in an upcoming blog.
-Dan DeFalco, Marketing Manager, All Sensors Corporation (ddefalco@allsensors.com)

What does a psi matter anyway?

Welcome to All Sensors “Put the Pressure on Us” blog. This blog brings out pressure sensor aspects in a variety of applications inspired by headlines, consumer and industry requirements, market research, government activities and you. In this blog we’ll look at why a PSI or two matters.

What does a psi matter anyway?

Underinflated footballs created a viral controversy before Super Bowl 2015.  Measurements of air pressure of 10.5 pounds per square inch (psi) instead of the minimum 12.5 were the issue. Rather than just talk about the issue (a.k.a. Deflategate), engineers performed calculations and more. One company conducted experiments as well.

In its testing, HeadSmart Labs found that on average, footballs dropped 1.07 psi from temperature change in a 75°F room to a 50°F room. Exposing the football to water resulted in an additional 0.75 psi pressure drop. With the combined effects, the footballs’ pressure decreased by an average of 1.82 psi to a max of 1.95 psi.

Richard P. Binzel, professor of planetary science at MIT, calculated that a 5 to 10% drop in temperature could create a drop of 0.5 to 1.5 psi, in a football’s air pressure. Equally important, he noted that the accuracy of the meters used to measure the footballs is unknown.

The bottom line for this or any critical pressure measurement is that for accurate measurements, especially at lower pressures, temperature changes are among the operating environment aspects that should be taken into account and accurate meters need to be used.

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What do you think/Comments?
Do you have a pressure sensing question? Let me know and I’ll address it in an upcoming blog.
-Dan DeFalco, Marketing Manager, All Sensors Corporation (ddefalco@allsensors.com)

Tire Pressure: Not all Measurements are the Same

Welcome to All Sensors “Put the Pressure on Us” blog. This blog brings out pressure sensor aspects in a variety of applications inspired by headlines, consumer and industry requirements, market research, government activities and you. In this blog we’ll look at tire pressure measurements.

Tire Pressure: Not all Measurements are the Same

The proper tire pressure in passenger cars and trucks provides optimum safety and efficiency.  Since drivers did not check tire pressures as frequently as they needed to, the U.S. Department of Transportation’s (DOT’s) National Highway Traffic Safety Administration (NHTSA) Transportation Recall Enhancement, Accountability, and Documentation (TREAD) Act of 2000 requires a tire pressure monitoring system (TPMS) on every new vehicle (all passenger cars and light trucks under 10,000 lbs. Gross Vehicle Weight) sold in the U.S. after November 2006.

Not all tire pressure measurements are the same. Car tire pressures are typically 30 to 35 psi with truck values running slightly higher. If you have an ATV, the tire pressure could be more like 8 psi max with some being as low as 2.7 psi and some as high as 10 psi. If you ride a road bicycle, the pressure can range considerably and depends on your weight with tire pressures of 95-105 psi for 110# riders to 125-135 psi for a 230# rider suggested from one source.

You can find tire pressure measurements in some unusual places. The Shipwreck water slide at SeaWorld uses large tires to carry several riders. The tire bumps into the sides of the slide to provide added excitement to the ride. For safety purposes, a maximum rating of 2.9 psi or 0.2 bar is recommended.

Shipwreck water slide uses large tires

The variety of tire pressure readings means that a single pressure sensor cannot provide the required accuracy and precision for all applications.

What do you think/Comments?
Do you have a pressure sensing question? Let me know and I’ll address it in an upcoming blog.
-Dan DeFalco, Marketing Manager, All Sensors Corporation (ddefalco@allsensors.com)