Pressure and Air Sampling

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.

Pressure and Air Sampling

If water damage has occurred inside your home, especially to the drywall, a remediation company will probably suggest sampling the air to determine if hazardous mold has developed. The process can be rather straightforward and simply consists of pumping a specific volume of air near the area of concern into a container for laboratory analysis. For lower cost, the volumetric sample is obtained by timing a specific airflow for a fixed amount of time. Then the sample can be submitted to an offsite lab.

Air Sampling Equipment

In addition to mold spores, air sampling also can be performed for pollen, insect parts, skin cell fragments, fibers such as asbestos, fiberglass, cellulose, clothing fibers) and organic particulates including ceramic, fly ash, copy toner and more.

In a work or potentially hazardous environment, verifying compliance to regulations on a periodic or even continuous basis can dictate much more accurate and precise readings. In digitally controlled pumps, a built-in airflow indicator can allow adjustment of the airflow from a few (5) to several 1000 (typically 4000 to 5000)ml/min.

SKC's Pocket Pump

SKC’s Pocket Pump displays airflow and pressure and has both constant flow and constant pressure modes. In this case, the pressure is 28.94 inches of mercury (inHg).

For air sampling equipment, All Sensors TLAX Series 4 to 20 mA Output Transmitter can provide the necessary accuracy as well as improved overall long term stability. The sensors have operating pressure ranges of 0.5 to 30 inH2O differential and gauge and 1 to 150 PSI differential and gauge.

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Pressurized

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.

Pressurized

When subjected to sufficient pressure in a closed container, some gases become liquids at normal temperatures. Called liquified gases, common liquified gases include: anhydrous ammonia, chlorine, propane, nitrous oxide and carbon dioxide. Equilibrium inside the tank means that the contents exists in a liquid-vapor balance state. In contrast, some gases, called non-liquified gases, including oxygen, nitrogen, helium and argon, do not become liquid even at very high pressures. However, with lower temperatures as well as higher pressure, some gases, such as oxygen, can be converted to a liquid. The differences in these processes are used for scientific, industrial and commercial purposes. At or above its critical temperature, no amount of pressure will cause the gas to liquefy. The minimum pressure required to liquefy a gas at its critical temperature is called the critical pressure. When pressure is an essential part of the process, both the pressure and the temperature are controlled and monitored.

Carbon dioxide pressure-temperature phase diagram

Carbon dioxide pressure-temperature phase diagram. Source: Wikipedia.

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Oxygen Tank Pressure

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.

Oxygen Tank Pressure

For many reasons, patients that require additional oxygen use storage tanks with compressed oxygen to supplement their normal air intake.  The size and subsequent capacity of the tank may vary but the full pressure is typically about 2,000 psi and can go as high as 3,000 psi. With this pressure level in the tank, a regulator converts the supplied pressure to a lower, and much safer, level for the user. With newer aluminum and other materials instead of steel to avoid magnetism problems in situations such Magnetic resonance Imaging (MRI) tests, the pressure level is lower. Minimum pressure in tanks is around 300 psi with delivery systems operating at pressure below 400 psi. In contrast, the storage and delivery system of liquid oxygen in a hospital, pressures are usually around 50.0–55.1 psi. The amount of oxygen present inside the cylinder is measured by the pressure at the outlet nozzle.

PV/T = constant

where P is pressure in the cylinder,

V is the volume of the cylinder,

and T is the temperature

Applied Home Healthcare Equipment

Image courtesy of Applied Home Healthcare Equipment.

Normal clean air contains 19% to 21% oxygen. In contrast, a supply of 60% oxygen with 40% nitrogen is considered acceptable for most clinical purposes but usually high much higher content is available.

Portable oxygen cylinders often have flow and pressure gauges. They provide easy, on sight measurements for a user. However, remote monitoring can use microelectromechanical systems (MEMS) pressure sensors to provide an electrical signal that can be transmitted to one or more receivers.  With this information displayed remotely, a variety of healthcare givers can access and use the information.

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Safe Operating Pressures for Welding

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.

Safe Operating Pressures for Welding

Creating, cutting or repairing metal objects can involve welding. One type of welding uses an oxy-acetylene mixture of gases. Instead of air, pure oxygen is used to increase the temperature of the flame. The gases are stored separately in tanks and to monitor the gases, a pressure gage is installed on both the oxygen and the acetylene tanks. Before starting, each tank should read zero psi. To start the flame, the valve of the acetylene tank is rotated about a quarter of a turn to apply pressure to the regulator. Then the acetylene pressure is increased to 7 psi. Next, the oxygen gas valve is fully opened and then its regulator is adjusted to 40 psi. To start the flame, the acetylene valve on the torch is turned about ½ of a turn and an arc striker is used to ignite the acetylene. Then, the oxygen valve on the torch is opened to achieve a neutral flame or one without a hissing sound and where the flame goes from orange to blue. For safety, the acetylene is turned off at the torch and then the oxygen.  Similarly, at the tanks the acetylene is turned off first and then the oxygen. After purging the torch to make sure any gas residue is removed, the regulators are backed out and the final step is to check and make sure both tanks show zero pressure.

Acetylene tank welding torch

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