Altitude Test 101: An Ultimate Guide

Altitude testing simulates environments with varying degrees of reduced air pressure, allowing you to measure the impact high or low altitudes may have on your products or packaging systems.  In the commercial transportation industry, where products and materials are exposed to extreme altitudes through air and ground transportation, altitude testing is especially valuable.

If you want to learn about altitude testing, our guide is for you. It covers everything you need to know about altitude testing from definitions, importance, applications, and more. You’ll learn everything you need to know in this guide – let’s get started:

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1. What is an altitude test

The high-altitude simulation test is to put the test sample into the high-altitude test box, then reduce the air pressure in the high-altitude test box to the value specified in the relevant standards, and keep the specified duration for the test. Its main purpose is to test the environmental adaptability and reliability of instruments, electrical products, materials, parts, and equipment under low pressure, high temperature, and low temperature alone or simultaneously in aviation, aerospace, information, electronics, and other fields.

Altitude testing simulates products intended for operation or transportation at different altitudes. These tests typically simulate the low air pressure experienced when operating products at high altitudes, or when transporting products by air. It is also common to perform operations and transport simulations at altitudes below sea level.

However, tests that simulate high pressure underwater are often referred to as stress tests or intrusion protection (IP) tests. Also, tests performed at the extremely low pressures of outer space or near-Earth space are often referred to as vacuum tests rather than altitude tests.

In altitude testing, dwell times at each simulated altitude are typically between one hour and one day. It is also common to simulate ramp rates between altitudes that may occur during transport. Less commonly, very high ramp rate tests are performed to simulate rapid decompression, for example during an air travel emergency.

2. Why is altitude testing important?

Altitude testing (also known as low air pressure) simulates the reduced air pressure experienced at higher altitudes to assess the effect on your product or packaging system’s performance. When exposed to altitude pressures, sealed flexible packaging systems may fail. In fact, the altitudes experienced by trucking often exceed the levels experienced by commercial air transportation.

The stress of extreme altitudes can cause your products or packaging systems to fail. Damaged products can negatively impact your company’s profits and reputation. A product’s ability to safely traverse extreme altitudes can be determined by altitude testing. Proper altitude testing will look at many factors that components experience at extreme altitudes. These include:

1) Temperature

Average temperature drop of 3.5°F per 1,000 feet increase. Components designed for use in aircraft and aerospace equipment must not only withstand extreme cold, but also the rapid temperature changes experienced during takeoff and landing.

2) Humidity

As temperature changes, humidity also changes. Sensitive components must also be able to withstand these conditions. Commercial and military equipment require tight tolerances, so humidity testing is required to ensure they will always provide the required performance.

3) Pressure

In terms of pressure, MIL-STD-810, RTCA DO-160, and other standards define acceptable behavior for rapid decompression of interior and exposed aerospace equipment. Altitude testing helps you maintain compliance and provide a reliable product for any application.

Even if your application does not require compliance with MIL, RTCA, or other standards, taking the time to conduct proper testing can help your product stand out from the competition.

Many buyers view these standards as a guarantee of superior quality, delivering superior performance in any environmental or atmospheric condition. Your product can be effectively marketed by altitude testing to military standards in a crowded market.

Altitude testing is sometimes done at the same time as other tests. In order to better simulate high-altitude cold environments, altitude testing can be conducted concurrently with temperature testing. Alternatively, high-temperature testing of air-cooled equipment is sometimes performed without any reduction in air pressure as a low-cost way of simulating the reduced cooling effect of low-density air at high altitudes.

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3. Influence of low-pressure environment on equipment

Manufacturers of any airborne equipment should consider the impact that high-altitude or low-pressure testing may have on your products.

The impact of the low-pressure environment on the equipment is multifaceted: including the direct mechanical impact of the pressure difference caused by the decrease in air pressure, and the impact of the decrease in air density on the heat dissipation and thrust of the power equipment and the electrical performance. Additional effects and detrimental effects on volatile substances caused by damage to seals caused by pressure differences in electrical equipment.

1) Directly use the shell to destroy the sealed product

Under the action of low air pressure, the shell of the sealed product with shell will be directly damaged due to the excessive pressure difference between the inside and outside, and the existence of the pressure difference will also cause the seal to be damaged.

2) Reduce electrical performance

Under normal atmospheric conditions, the air is a better insulating medium, and many electrical products use air as an insulating medium. When these products are used at high altitudes or as airborne equipment, partial discharges often occur near electrodes with high electric field strength due to the reduction of atmospheric pressure.

What’s more serious is that air gap breakdown sometimes occurs, which means that the normal operation of the equipment is destroyed. Therefore, the low-voltage environment will also have an impact on the electrical performance of electronic and electrical products, especially for equipment that uses air as the insulating medium, the impact of low voltage is more significant.

3) Lead to a large temperature rise of heat dissipation products

The so-called heat dissipation product refers to the test product whose surface temperature at the hottest point is more than 5°C different from the ambient temperature after the temperature of the test product reaches stability under free air conditions and specified atmospheric pressure. A considerable part of electronic and electrical products are heat dissipation products, such as motors, transformers, etc.

These products consume part of the electric energy during use and convert it into heat energy, which increases the temperature of the product. The temperature rise of cooling products increases with the increase in altitude (decrease of atmospheric pressure). The temperature rise and altitude are roughly linear, and the slope depends on factors such as its own structure, heat dissipation, and ambient temperature.

4) Lead to the loss of volatile substances

The liquid’s boiling point is lowered as a result of this decrease in pressure. For those liquids whose saturated vapor pressure is high under normal atmospheric conditions at sea level, the low pressure causes them to vaporize or even boil. The evaporation process of liquid is an equilibrium process, that is, the number of liquid molecules volatilized into the air through energy is balanced with the number of molecules combined with air molecules hitting the liquid surface.

When the atmospheric pressure decreases, the density of the air decreases, and the possibility of the volatile molecules of the liquid entering the air being knocked back to the liquid surface is greatly reduced. Therefore, under low-pressure conditions, the rate of liquid evaporation will be greatly accelerated.

This is the case with lubricating oil or grease. The reduction of the pressure will accelerate the volatilization of lubricating oil (or grease), aggravate the friction of moving parts, and accelerate the wear of the surface of moving parts. Plasticizers in organic materials will also accelerate volatilization due to reduced air pressure.

The volatilization of plasticizers promotes the aging of organic materials, changing their mechanical or electrical properties. Volatilization of volatile matter will also pollute the product and its surroundings, causing the product or object to corrode or become contaminated.

Based on the impact of the above low-pressure environment on equipment, typical low-pressure environment effects include:

• Gas or liquid leakage from the sealed enclosure;
• Deformation, cracking, or explosion of the sealed container;
• Changes in the physical and chemical properties of low-density substances;
• Equipment damage caused by low-voltage arcs or corona discharges Faults or faults;
• Under low pressure, the heat transfer efficiency decreases, resulting in overheating of the equipment;
• The lubricating oil volatilizes;
• The engine starts and burns unstable, the thrust or traction decreases, and the airtight seal fails

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4. Common altitude test standard

Here are some common Altitude test standards:

• Combining Altitude and Temperature Testing
• high altitude riding
• ASTM D4169
• MIL-STD-810
• MIL-STD-202
• and other military and commercial standards

In conjunction with temperature or vibration testing, altitude testing can be performed with operating or non-operating units.

2) What factors will be considered in the altitude test?

Linkotest generates comprehensive and accurate results from our altitude testing service by considering several different factors. In addition to exposing a product or packaging system to varying degrees of reduced air pressure, our altitude testing simulates the temperature changes that cargo may face at extreme altitudes.

By considering multiple factors during altitude testing, we can more accurately replicate the environment a product or packaging system will be exposed to. The results produced by these altitude tests are very useful to manufacturers and designers to prevent product damage and optimize the shipping process.

3) What level should most altitude tests be done at?

Pressure differentials can create potentially harmful pressures on any enclosed air volume and can affect the product or packaging system. The decompression experienced by a product or packaging system during transport depends on the way it is transported.

Depending on the shipping method you intend to use, our altitude testing service simulates different altitudes. Typical altitude is 4,267m (14,000ft) and one hour is allowed. However, military standards and some European standards may require 12,192m (40,000ft)