Pressure Safety: How to Protect Devices from Overpressure

02/20/2020
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In the pressure calibration industry, dealing with highly sensitive pressure applications is a daily occurrence. The best calibration practices require the device under test (DUT) to be as close to the reference instrument as possible, which allows for both readings to sense pressure changes at the same time.

However, this practice also introduces the possibilities of pressure spikes to be sent to the DUT inadvertently because there is no buffer to protect the DUT from absorbing the rapid change. Just like breaker boxes and surge protectors keep electronics safe during a thunderstorm, sensitive DUTs need to be protected from pressure spikes.

Many sensitive devices lack the real estate to contain a self-protecting pressure relief system, so they must rely on an external source for overpressure protection. This could be a manual pressure regulation valve, a pressure regulation system or an automated pressure calibrating controller like the CPC6050. Each provides a multi-layer set of safeguards against unwanted pressure on the DUT. The first line of defense in these systems is intelligent software, a common feature of automated regulators or controllers. The software constantly monitors pressure rates and changes, and activates protection sequences to vent the system. Additionally, in the event of a power failure, the automated controllers are mechanically triggered to vent the controlling ports.

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One of the most common ways to protect pressure devices is using secondary relief mechanisms such as a relief valve or a burst disk. There are a wide variety of relief valves that assist in guarding devices ranged as low as a tenth of a psi up to thousands of psi in pressure. These can be strategically placed throughout the calibration system, in sensitive elements of the measuring chain like the reference sensors, or shared on a manifold between multiple DUTs. The relief valves are set to specific values that protect the internal transducers from overpressure exposure and damage. When chosen correctly, the DUT range can be matched with the reference devices, which will allow the internal relief valve to not only protect the controlling system but the DUT as well. Burst disks are typically employed at higher pressures and essentially cut off the pressure supply to the system when overpressured.

ReliefValvesExamples of relief valves present in Mensor instruments

Another application that requires overpressure protection is differential pressure. These systems typically require a reference, also known as line pressure, and measure port of a DUT to be pressurized at the same rate to a specific set point. Once this reference pressure set point is achieved, the measure port is then used to monitor or control pressure changes in relation to the line pressure. A dual differential relief valve, when plumbed to the reference and pressure ports, ensures the differential sensor never exceeds its range limits in positive or negative pressure direction.

Overpressure is one of the primary causes of transducer failure on the reference instruments and malfunction in DUTs, which can lead to expensive repair costs and downtime for factories. Using sophisticated software, mechanically designed fail-safes, and strategically placed relief valves, Mensor controllers and external hardware can provide reliable safety to almost any range of pressure devices.

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