Pressure sensors with integral overpressure protection are designed to withstand pressure values beyond their normal operating range without sustaining damage or compromising performance.
These sensors are suitable for use in challenging applications where pressure spikes, surges, or fluctuations are possible. The overpressure protection feature helps to prevent damage to the sensor and ensures reliable and accurate pressure measurement even under extreme conditions.
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Overpressure refers to a condition where the pressure value exceeds operational limits or a threshold pressure. This can occur due to various factors, such as equipment malfunction, process upsets, or unexpected pressure surges. Overpressure can have significant consequences, including:
- Sensor Damage: Excessive pressure can damage the sensor’s sensing element, diaphragm, or other internal components, leading to inaccurate readings or complete failure.
- System Failure: In critical applications, overpressure can lead to system failure, resulting in costly downtime, production losses, or safety hazards.
- Compromised Safety: Overpressure can create hazardous conditions, potentially leading to equipment damage, leaks, or even explosions.
Overpressure occurrences can be detected by setting up an instrument alarm condition on a process to warn an operator that a limit has been exceeded, or to trigger a switch to operate a pressure relief valve. It is also common to incorporate mechanical overpressure protection device to protect vulnerable systems and components, such as burst discs and automatic pressure relief valves.
Overpressure Protection Types
Overpressure in industrial and research applications can pose a significant risk to pressure sensors, potentially leading to damage, inaccurate readings, or even complete failure. To address this challenge, pressure sensors with built-in overpressure protection have been developed. These sensors incorporate design features that enable them to withstand pressure values exceeding their operational limits without sustaining damage or compromising performance.
On most manufacturer’s pressure sensor data sheets you will find an over-pressure or proof pressure rating. This is the maximum pressure that the pressure sensor will tolerate without damaging the diaphragm or putting it outside specification tolerances.
The overpressure or proof pressure rating is mainly a guideline for determining whether a pressure sensor will be protected when there is a system failure and a pressure is applied which is over and above the normal operating conditions.
Under-Ranging
One design approach is to under use the range of a particular diaphragm rating e.g. use a 100 bar diaphragm to measure 50 bar effectively doubling the overpressure rating (e.g. PD39X). The main drawback of this method is that the accuracy and output sensitivity are compromised so the high output and linear sensing technologies such as semiconductor strain gauge tend to be favoured when using the down ranging method.
Mechanical Stops
A more complex approach is to incorporate mechanical stops behind the diaphragm to prevent the diaphragm from being over-stressed. This leads to a more expensive and bulkier mechanical design. A sensing technology that has a large enough degree of travel is also required in order to make setting the distance of the mechanical stop to the correct over-pressure rating practical. Alternatively for sensing technology that does not have a high degree of mechanical movement it can be integrated into an oil filled capsule with a non-sensing diaphragm (e.g. XMD) that will yield in an over pressure condition to allow enough movement in another non-sensing diaphragm so that it bottoms out onto a mechanical stop and thus prevents any further increase in pressure and protects the sensing diaphragm.
Pressure Relief
Introducing pressure relief into the pressure sensor design is another elaborate way to protect the sensing diaphragm from over-pressure (e.g. DPS). Either self activating mechanical pressure relief valves or electrically activated valves controlled by the pressure sensor output can be utilised to vent and isolate the pressure sensor from an over pressure condition.
Help
Accuracy over 100% of range
I just want to learn that if I have a pressure transducer with a 0 – 250 psi range, can I use it for higher pressures such as 310 psi? Can you advise whether it is ok or the transducer is not going provide the correct reading, as I have used it beyond its range?
Most pressure transducers are not calibrated beyond 100% full scale so you cannot rely on the accuracy of any readings over 100%. Also if the over-pressure rating has been exceeded the accuracy below 100%FS may have been affected.
Related Help Guides
- Symptons and Causes of Damage to Pressure Transducer Diaphragms
- What is difference between working, burst and over pressure
- Selecting a pressure range for optimal service life and accuracy
- Protecting a pressure sensor from high pressure spikes
Related Technical Terms
Glossary of Pressure Range technical terms
- Absolute Pressure
- Barometric Pressure
- Bidirectional
- Burst Pressure
- Compound Pressure Ranges
- Differential Pressure
- FS – Full Scale
- Gauge Reference Pressure
- Hydrostatic Pressure
- Negative Gauge Pressure
- Rangeable
- Reference Pressure
- SG – Sealed Gauge
- Static Line Pressure
- Suction Pressure
- Vacuum
- Vented Gauge
Help from Pressure Range resources
- How do you choose the correct pressure range for a pressure sensor
- What is the difference between sealed gauge and vented gauge reference?
- Measuring vacuum with negative gauge or absolute ranges
- What is the difference between gauge and absolute pressure measurement
- What is difference between working, burst and over pressure
- What is the difference between vacuum and absolute pressure
- Can you measure vacuum using a gauge pressure range
- What does negative and positive gauge pressure mean
- Measuring negative pressure using a positive differential pressure range
