If you calibrate devices that contain water, oil, or gas, you could have problems if the wrong substance or even grit gets in your system.  This can lead to frequent repair and maintenance issues and can cause irreparable damage to the inside of the instruments. It can damage a calibrator in a number of ways, clogged valves, worn-out parts, difficulty maintaining pressure, and worse.  If the contamination gets into the sensor, it can actually change the behavior and throw off your readings. Pressure calibration is very important.

What Does A Contaminated Standard Do?

If a contaminated standard is used to calibrate a gauge, transmitter, or other devices, it may pass the contamination to the device under test.  Which in turn causes even more problems.  Devices like these can damage easily and affect performance.

Preventing Contamination

There are some simple steps that you can take to avoid contamination in pressure calibration.

• Always inspect the device under test before you connect it to the calibration system.
• Be sure to clean the device after use if needed.
• Since some devices are hard to clean and missing, just one will cause problems. To supplement your inspection and cleaning routine, you can purchase an external device to help trap or separate the contaminated fluids from the standard.

Traps and Separators

There are a few different types of devices that you can purchase to help with keeping containments out.

• Dirt/Moisture Trap – These provide an effective barrier against the transfer of moisture and dirt from an instrument under test.  It will prevent unexpected particle contamination or fluid inside the device under test from entering the system.
• Self-Purging Liquid Trap – This communicates with the pressure controller to purge liquid from the device under test at the appropriate time.  Without requiring manual intervention. It uses gravity to make any liquid fall out of suspension with the gas as it goes through the trap. A purge valve at the bottom of the trap lets you remove the liquid.
• Separator – A separator separates the fluid in the device under test from the fluid in the calibrator. This method adds some error or uncertainty to your calibration because of the head height difference and the location.  However, it is something that anticipation and compensation in the calculations will fix.

Prevent Vacuum Pump Contamination

If you are concerned about vacuum pump contamination.  You can look for one that is equipped with an auto vent valve.  When you turn off this type of pump, it vents the vacuum or lets the atmosphere into the system and releases the vacuum.  Thus preventing the oil from the vacuum pump from getting sucked back into the controller.

Using a filter does have its potential downside.  A filter can add error to your calibration because the filters restrict flow and if you have a flow restriction with flow across it, you can have a pressure drop across the restriction.                                                                                                                                                  

Work with a Reputable Experienced Company

Many times, it is the little things that can make or break a calibration.  One way is to err on the side of caution and purchase your pressure calibrator and accessories from a company that understands pressure calibration and works with quality manufacturers.  SRP can help you find the best instruments for your lab’s specific needs with one of the largest pressure labs across Canada.