ExxonMobil Control & Instrumentation Engineer Interview Questions and Answers

Instrumentation is the science of measuring and controlling physical variables.

• Instrumentation involves the use of various instruments and devices to measure and control physical variables such as temperature, pressure, flow, and level.

• It is used in various industries such as manufacturing, oil and gas, and healthcare.

• Instrumentation plays a crucial role in ensuring the safety and efficiency of industrial processes.

• I c...read more

4-20 mA signal is preferred over 0-20 mA signal due to its ability to detect faults and provide a clear zero point.

• 4-20 mA signal has a clear zero point, making it easier to detect faults in the system.

• It allows for a wider range of measurement values, as the 0-4 mA range can be used to indicate faults or out-of-range conditions.

• 4-20 mA signal is less susceptible to noise and interference compared to 0-20 mA signal.

• It ...read more

An orifice tab is used to accurately measure the flow rate of a fluid through a pipeline.

• It creates a differential pressure across the orifice plate, which is proportional to the flow rate.

• The tab is placed upstream of the orifice plate to ensure accurate measurement.

• The tab can be designed in different shapes and sizes depending on the application.

• It is commonly used in industries such as oil and gas, chemical, and wa...read more

An orifice in a pipeline can be identified by measuring the pressure drop across it.

• Measure the pressure drop across the pipeline using a differential pressure transmitter

• Compare the pressure drop with the expected value for the given orifice size

• Use a flow meter to confirm the flow rate through the orifice

• Inspect the pipeline for any markings or labels indicating the presence of an orifice

Orifice tap is provided to measure the pressure drop across the orifice plate.

• Measures pressure drop

• Helps calculate flow rate

• Used in flow measurement systems

Orifice tab is provided to indicate the size of the orifice and its flow rate.

• Orifice tab helps in identifying the size of the orifice and its flow rate.

• It is used in flow measurement devices like orifice plates, venturi meters, etc.

• The tab is usually made of stainless steel and is welded to the orifice plate.

• The tab is marked with a number or letter to indicate the size of the orifice.

• The flow rate can be calculated u...read more

RTD measures temperature using resistance while thermistor uses resistance-temperature relationship.

• RTD has a linear resistance-temperature relationship while thermistor has a non-linear one.

• RTD has a higher accuracy and stability compared to thermistor.

• RTD is more expensive than thermistor.

• RTD is commonly used in industrial applications while thermistor is used in consumer electronics.

• Examples of RTD include platinum,...read more