Instrumentation Articles

QUESTIONS AND ANSWERS FLOW_INSTRUMENTATION

QUESTIONS AND ANSWERS FLOW_INSTRUMENTATION

QUESTIONS AND ANSWERS FLOW_INSTRUMENTATION

A factor that influences measurement accuracy in magnetic flow meters is:

  1. Excessive fluid
  2. Signal distortion
  3. Temperature fluctuations
  4. Solids in the fluid

What does the magnetic flowmeter measure?

  1. Fluid velocity through the meter
  2. Density of the process fluid
  3. Specific gravity of the fluid
  4. Density, viscosity and specific gravity of the material

What is the relationship of voltage to the magnetic field and the velocity of the conductor?

  1. Voltage is inversely related to the magnetic field intensity and the conductor velocity
  2. Voltage is directly proportional to the magnetic field intensity and the conductor velocity
  3. Voltage is proportional to the magnetic field intensity only
  4. Voltage is proportional to the conductor velocity only

The best types of material to be used in the metering section should be:

  1. Metal
  2. Magnetic
  3. Nonmagnetic
  4. Nonporous

What name is given to the straight length of the pipe where the process fluid passes through the magnetic field?

  1. Electrode
  2. Conductor
  3. Faraday’s field
  4. Metering section

What type of problem is associated with using a magnetic flow meter?

  1. Signal distortion caused by noise
  2. Relatively high thermal conductivity
  3. Fluctuating heat capacity
  4. Sound waves or vibrations

What is a disadvantage associated with a magnetic flow meter?

  1. It can only measure specific Reynolds number profiles
  2. It can only be used to measure flow of conductive liquids
  3. It can only be used with low viscosity fluids
  4. You must shut down the process to use a magnetic flowmeter

Which of the following is compatible with a magnetic flow meter?

  1. Gas applications
  2. Ultrasonic systems
  3. Electronic control systems
  4. Flow measurement applications with low velocity fluid

A factor that has the largest influence on measurement accuracy in magnetic flow meters is:

  1. Slurries in the process fluid
  2. Variations in density
  3. The Reynolds number
  4. Coating of the electrodes

The Coriolis force is the result of:

  1. Volumetric flow rate
  2. Specific gravity
  3. Density of liquid
  4. Acceleration acting on a mass

Define mass.

  1. Mass is a measure of the quantity of matter
  2. Mass is a measure of the proximity of the molecules of a substance
  3. Mass is a measure of the density of a fluid
  4. Mass is a measure of how rapidly a substance flows

Which property has an affect on calculating the true mass flow rate of a substance?

  1. Viscosity
  2. Density
  3. Reynolds number
  4. Velocity

In a mass flow meter, what is the relationship between the sensing element and mass flow rate?

  1. Reaction of the sensing element is dependent upon the composition of the fluid
  2. The velocity and the density of the mass flow rate is proportional to the sensing element
  3. Reaction of a sensing element is proportional to the mass flow rate
  4. The mass flow rate must be a measure of the Reynold’s number profile

A factor that affects the measurement accuracy of mass flow rate is:

  1. Temperature of the process fluid
  2. Slurries in the process fluid
  3. The Reynolds number
  4. Variations in density

 

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GENERAL METHODS OF PROTECTION OF INSTRUMENTS

GENERAL METHODS OF PROTECTION OF INSTRUMENTS

GENERAL METHODS OF PROTECTION OF INSTRUMENTS

The general methods of protection of instruments shall include but are not limited to:
(1) Insulation of the instrument including tubing and piping to prevent heat loss or gain.
(2) Tracing the instrument including tubing and piping
• All tracing of instruments shall account for Manufacturer recommendations regarding maximum temperature of operation.
• Where tracing is to be used, care shall be taken to ensure that overheating of the process fluid does not occur.
(3) Purging or flushing the instrument including tubing and piping to prevent undesirable liquids, solids or gases from entering the instrument or impacting its performance.
(4) Isolating the instrument from the process fluid through the use of a diaphragm seal.
(5) Isolating the instrument including tubing and piping from the process fluid through the use of a sealing liquid, noting the following:
• Sealing liquids shall be immiscible/ compatible with the process fluid.
• Water may be used as a sealing liquid where the only purpose is to protect against the entry of the process fluid.
• An instrument may be sealed with a liquid having a low freezing point (e.g.: dibutyl phthalate at –35°C or 50%, ethylene
glycol in water at –36 °C).
• Instruments with a low (negligible) displacement may be sealed without the use of seal pots.
Instruments with appreciable displacement require seal pots with special piping arrangements for control of the seal liquid level in order to prevent hydrostatic errors.
• Instruments that have sealed leg installations should only have legs filled by qualified personnel. Warning labels should be attached to vent/drain connections.
(6) Isolating the instrument and piping from entrained fluids by use of vapor/liquid separators.
Special consideration shall be given to protection method(s) used, where hazardous/toxic fluids are handled. Protection philosophy in these cases shall be to contain the process fluid as close to the process (e.g. piping/vessels) as possible, even when the instrument system materials do not necessarily require protection.
(8) Design and installation of systems shall be such that pockets, crevices, etc. are minimised in order to prevent undesirable build up of hazardous/toxic material.
(9) In some cases, a suitable means of flushing or purging may be required (either continuous or intermittent).

(10) Enclosing the instrument in an insulated housing (where possible equipment shall be specified for the appropriate climatic conditions).

(11) Care shall be taken to ensure temperatures at the instrument to be kept within manufacturer’s tolerances.
(12) Where necessary, personnel protection shall be applied to instrument piping.
(13) Sunshades shall be provided where levels of solar radiation could cause excessive heat within an instrument and affect
its operation or accuracy. Other methods of protection may be used.
(14) The use of NACE compliant trims for corrosive services where applicable.

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