Significant changes in altitude affects tire pressures when traveling from one elevation to another. Fortunately this influence is relatively small and can be easily accommodated.

Atmospheric pressure is the force exerted on objects by the weight of the air molecules above them. While air molecules are invisible, they have mass and occupy space.

However as altitude increases, atmospheric pressure decreases. For example, atmospheric pressure pushes against the earth at 14.7 pounds per square inch (1 kilogram per square centimeter) at sea level, yet drops to only 10.1 pounds per square inch at 10,000 feet as indicated in the following chart.

Altitude (ft.) Air Pressure (psi)
Sea Level 14.7
1,000 14.2
2,000 13.7
3,000 13.2
4,000 12.7
5,000 12.2
6,000 11.7
7,000 11.3
8,000 10.9
9,000 10.5
10,000 10.1

When it comes to measuring tire inflation pressure, it is important to realize there is a difference between atmospheric pressure and gauge pressure. Most pressure gauges (including all tire pressure gauges) are designed to measure the amount of pressure above the ambient atmospheric pressure.

Imagine removing the core from a tire valve and allowing the air to escape. Even after the air has completely stopped rushing out of the valve, the tire is still experiencing 14.7 pounds per square inch of atmospheric pressure. However, a tire pressure gauge would read zero pounds per square inch of tire inflation pressure because the pressure outside the tire is equal to the pressure inside.

Since a tire mounted on a wheel essentially establishes a flexible airtight (at least in the short term) pressure chamber in which the tire is shaped and reinforced by internal cords, it retains the same volume of air molecules regardless of its elevation above sea level. However, if tire inflation were set with a tire pressure gauge at sea level (where the atmospheric pressure of 14.7 pounds per square inch is used as ambient atmospheric pressure by the gauge), the same tire pressure gauge would indicate the pressure has increased at higher elevations where the ambient atmospheric pressure is lower. Those measured at the 5,000-foot level (where an atmospheric pressure of only 12.2 pounds per square inch is the ambient pressure) would indicate about 2-3 psi higher than at sea level. On the other hand, traveling from a high altitude location to sea level would result in an apparent loss of pressure of about 2-3 psi.

However, the differences indicated above assume that the tire pressures are measured at the same ambient temperatures. Since tire pressures change about 1 psi for every 10-degree Fahrenheit change in ambient temperature, the tire pressure measured in the relatively moderate climate typically experienced at sea level will change when exposed to the colder temperatures associated with higher elevations.

This means that in many cases differences in ambient temperature may come close to offsetting the differences due to the change in altitude. Depending on the length of their stay at different altitudes, drivers may want to simply set their cold tire pressures the morning after arriving at their destination, as well as reset them the morning after they return home.

Altitude and tire pressure was explained in an article on the Bridgestone U.S. website: http://www.bridgestonetrucktires.com/us_eng/real/magazines/02v7iss1/ra8.asp

PressurePro was nominated by Senator Claire McCaskill to represent the State of Missouri at a Green Summit in Washington DC June 17th.  One business represented each state and a majority of Senators were present.  Vice President Biden gave the opening remarks and each business had an opportunity to showcase their products and speak to Senators and representatives from government agencies.  We spoke with representatives from the Dept of Defense, Homeland Security, Dept of Transportation, EPA and more.  In light of President Obama’s directive to lower fuel use and carbon emissions, interest in our product was high.  We were approached by several Senators and agencies asking about our product.  I was very impressed with was a young man by the name of Van Jones who is Special Advisor to the President for Green Jobs, Enterprise and Innovation & White House Council on Environmental Quality.   He came to speak with me and is interested in our TPMS because it can assist in meeting the Obama Administrations directive to lower fuel use and carbon emissions in military and government vehicles as well as being an American made product.  There are opportunities in DC for PressurePro which would broaden our name and product recognition as well as validate PressurePro as the top product on the market.     

PressurePro is supporting two Universities in the Solar Car Challenge. http://www.wsc.org.au/welcome.html.  Duane and Carol Sprague of L&S (Distributors in Arizona) were contacted by the Michigan Universities Solar Team and we’re partnering with them to provide PressurePro on this vehicle.  

Written by Ryan Gray   
Friday, 20 November 2009 11:09

The National Transportation Safety Board responded to a fatal motorcoach crash last year by recommending mandatory tire pressure monitoring systems in all motor vehicles weighing more than 10,000 pounds, including school buses, and that motorcoach passenger safety be improved.  Earlier this month, NTSB ruled that an August 2008 motorcoach crash Texas that killed 17 and injured another 38 was in part caused by low tire pressure that resulted in the driver losing complete control of the vehicle. Also this month, Transportation Secretary Ray LaHood released a motorcoach safety action plan that addresses occupant safety.

Any requirement for tire pressure monitoring systems in large vehicles would come from the National Highway Traffic Safety Administration. NTSB also asked the Federal Motor Carrier Safety Administration to address tire pressure by requiring that it be checked during all commercial vehicles, pre-trip and roadside inspections.  The national specifications and procedures for school buses already says that drivers should inspect tires for under inflation, wear and damage as well as all valve stems and caps during a vehicle walk-around inspection prior to starting any student route or trip. Alexandra Robinson is the chair of the general operations writing committee at the 2010 National Congress on School Transportation. She said one proposed change to the national guidelines that will be submitted this month for review and comment by NCST delegates will relate to tire pressure checks conducted by drivers during the pre- and post-trip walk-around inspections and that operators be familiar with how tire pressure monitoring systems work if used on any school buses. She also said the school bus operations writing committee will also request that matter be taken up by the school bus specifications writing committee.

While tire pressure monitoring systems remain optional nationwide, local school districts can require them at their discretion. Robinson said that it is possible that the NCST delegates might consider a resolution on tire pressure monitoring systems, similar to recommendations it made to NHTSA five years ago on revising federal school bus standards to include integrated lap/shoulder seat belt systems for drivers and students.  “I think it would probably behoove the [school bus] manufacturers to start making those [systems] standard features,” she added.

NTSB also called on NHTSA to establish occupant protection standards for motorcoaches that account for frontal impact, side impact, rear impact and rollover crashes and require that overhead luggage racks remained anchored during crashes. Within two years of completing the performance standards, NTSB wants to see NHTSA require child safety restraint systems and improved roof strength requirements for all newly manufactured motorcoaches.  The recommendations stem from the NTSB crash investigation report released this month. Last summer, while traveling at 68 mph northbound on U.S. Highway 75 in Sherman Texas, a motorcoach right front axle failed after the low-pressure tire punctured and severe over deflection occurred, which resulted in tire sidewall, belting and body ply separations. As the driver lost control, the motorcoach overrode a seven-inch-high, 18-inch wide concrete curb and struck a metal bridge railing. The motorcoach rode the bridge railing for another 120 feet before plunging eight feet off the bridge. It fell about 8 feet and slid approximately 24 feet on its right side before coming to rest against a bridge abutment.

Drugs and alcohol also played a role in the crash. NTSB recommended that FMCSA establish a drug and alcohol clearinghouse to be used by all transportation operators when conducting driver background checks. In this case, the U.S. Department of Transportation is already out in front of the issue, as it previously has said the clearinghouse will be contained in the federal surface transportation reauthorization bill that is still in Congress.

Modular provides a robust interface between the IntelliMine® system and Advantage PressurePro. This interface automatically receives event and parameter information that is available in DISPATCH® and reporting utilities. OEM event information can also be viewed in detail remotely through the MineCare® system, including DISPATCH® information such as location and operator, with a snapshot of data before and after the event. Users can create their own alarms in the Trending Application or simply monitor data for post analysis. Equipment sensor values can be viewed live in graphical format with the MineCare® RealTime Monitoring Application.

Features

The ModularReady™ Interface to Advantage PressurePro is a powerful tool for machine management  that provides operators, service personnel and managers information on an onboard tire monitoring system. The PressurePro interface is developed to communicate MMS with the same onboard tire monitoring system. This Standard interface provides data to MineCare and DISPATCH applications. The PressurePro interface is responsible for receiving data packages, scaling parameters, creating events, and sending them to the MineCare Adapter. The PressurePro interface is responsible for receiving data packages, scaling parameters, creating events, and sending them to the MineCare Adapter. The PressurePro interface currently handles vital information from up to 34 tires with a total of 102 parameters and 208 events.

Advantages

Receiving information for machine management allows you to effectively monitor tire performance. With accurate, real-time data, users have the ability to make quick decisions regarding operator and equipment performance issues that affect safety and productivity. Proactive maintenance measures can be taken when abnormal conditions are observed. On Mining Trucks, PressurePro system is a tire monitoring system used to monitor pressure and temperature for Off-Highway Trucks. PressurePro system has 2 main components: An operator console mounted in the vehicle cab and battery powered wireless sensors

that are connected to each tire. The PressurePro interface allows MMS applications, such as DISPATCH and MineCare, to get vital sign information from the field equipment. The interface shall communicate with the Pressure Procontroller via serial rs232 protocol. PressurePro interface is responsible for processing this data, scaling parameters, creating events and sending them to Adapter. The current PressurePro interface handles 102 parameters and 208 events. Data handling and information integrity are improved because data is captured and stored as it occurs. Integrating this information with other data captured by the IntelliMine® system provides a comprehensive picture that allows you to see all factors affecting asset health and equipment performance.

 
Hardware Requirements

Each interface requires the following components:

• PressurePro controller via serial rs232 protocol

• A Modular ML Hub

• An external Generic Serial Processor (GSP) kit

• A cable to connect the two systems

 
Software Requirements

Minimum DISPATCH® code version: 5.4.5

This interface requires a site and unit license