PROS & CONS OF DIFFERENT GAS FLOW MEASUREMENT TECHNOLOGIES

PROS & CONS OF DIFFERENT GAS FLOW MEASUREMENT TECHNOLOGIES

This blog will try to highlight the pros and cons of different gas flow measurement technologies available in the market which will help process instrumentation engineers to effectively choose the?best flow metering technology?for defined applications which results in optimum results w.r.t cost versus performance ratio.

BELOW ARE FLOW MEASUREMENT TECHNOLOGIES AVAILABLE :

1. DIFFERENTIAL PRESSURE-BASED ORIFICE/AVERAGING PITOT TUBE/VENTURI/AEROFOIL?

2. THERMAL MASS – INSERTION TYPE

3. CORIOLIS

4. VORTEX

5. TURBINE?

6. ULTRASONIC – CLAMP-ON TYPE

The process instrumentation engineer’s task is to identify which of the above will be the best suitable technology.?

BELOW ARE SOME IMPORTANT FACTORS TO BE CONSIDERED & EVALUATED WITH COMPARING TECHNOLOGIES FOR OPTIMUM SELECTIONS:?

• Pipe sizes?
• Process conditions such as flow rate, pressure, temperature, density, viscosity, dirt & moisture, etc.?
• Installation conditions such as horizontal, vertical, or inclined & available straight lengths, time & efforts, etc.?
• Accuracy & repeatability needed
• Process turndown ratio needed
• Budgeted price

Based on the above factors we will try to summarize the PROS and CONS of different flow technologies & their possibility for selection. However, the ultimate choice is of the process engineer who has some specific technologies dominance and/or experience.??

1. DIFFERENTIAL PRESSURE-BASED FLOW METER (ORIFICE / AEROFOIL / VENTURI / PITOT?TUBE)

PROS

• Established Standard BS-1042/ISO5167 for Volumetric flow measurement
• Suitable for 15mm to 10mtrs or higher?pipe sizes
• Rugged designed for any process conditions of industries
• Any orientation possible?
• Highly Repeatable
• Low budget up to 300mm pipe size
• Site calibration easy?

CONS

• Higher pressure drop
• Needs periodic maintenance?
• Lower Accuracy 3% FSD & may drift from time to time
• Lower turn-down ratio 4:1?
• ?Lower flow sensitivity
• Susceptible to clogging
• High wear factor

2. THERMAL MASS FLOW METER – INSERTION TYPE

PROS

• Works on constant temperature anemometry (thermal dispersion)?
• Pipe sizes suitable 15mm to 10000mm
• Insertion is rugged and works up to 400?C & 16bar or more?
• Any orientation possible
• Better accuracy ±2%RD
• The highest turndown ratio is 100:1 or better
• Insertion type is adjustable & versatile
• Insertion has the lowest pressure drop?
• The low initial cost above 100mm pipe sizes

CONS

• Mechanically vulnerable to damage?
• Susceptible to turbulence & vibrations
• Flow straightener recommended??
• Affected by high moisture (>10%Vol.) & dirt/dust needs periodic cleaning or purging system

3. CORIOLIS FLOWMETER

PROS

• Works on Coriolis effect by oscillating tube provides direct mass flow rate
• Suitable from 2mm to 300mm pipe sizes
• Suitable for high pressure up to 400bar or more
• Any orientation possible?
• Highest accuracy (±0.1%- ±0.5%RD) & Repeatability (±0.02%)
• Highest turndown ratio is 100:1 or more

CONS

• High-pressure drop
• Not suitable larger pipe dia than 300mm
• Not suitable for higher temperatures above 120?C?
• ?Sensitive to vibrations
• High Initial Cost

4. VORTEX FLOWMETER

PROS

• Derives volumetric flowrate by vortices frequency measurement principle
• Suitable from 15mm to 300mm??
• Horizontal or vertical orientation is possible
• Suitable up to 300?C temperature & pressure up to 40bar
• Better accuracy up to (±1.5%RD) & Repeatability (±0.02%)
• Low Initial cost up to 80mm size

CONS

• Higher pressure drop
• Lower turn-down ratio 10:1
• Installation needs utmost care
• Susceptible to vibrations & turbulence
• Needs periodic maintenance
• High Initial cost 100mm & above size

5. TURBINE FLOWMETER

PROS

• Derives volumetric flowrate by moving rotating turbine frequency?
• Pipe sizes suitable: 6mm to 300mm
• Suitable for high pressure 250 bar & temperature up to 200?C
• Horizontal or vertical orientation is possible
• High accuracy up to ±1% RD & repeatability ±0.25%?
• Low initial cost

CONS

• Gas must be dry and clean
• Susceptible to vibrations & turbulence
• Moving parts needs periodic maintenance
• High wear factor

6. ULTRASONIC FLOWMETER – CLAMP-ON TYPE

PROS

• Derives volumetric flowrate by ultrasonic beam transit-time measurement – Non-Intrusive &?Fixed Type
• Pipe sizes suitable: 10mm to 1600mm
• Suitable for high pressure 200 bar & temperature up to max 200?C
• Horizontal or vertical orientation is possible
• Better accuracy up to ±1%-3% RD & repeatability ±0.25%?
• Turn down ratio better than 100:1
• Low Installation cost

CONS

• Gas must be dry and clean
• High Initial Cost
• Installation needs good technical knowledge
• ?Not suitable for pipes with inner lining?

*NOTE:?ABOVE ARTICLE DON’T CLAIM ACCURACY AND IT IS FOR GENERAL GUIDANCE ON FLOW TECHNOLOGIES AS PER PRACTICAL EXPERIENCE THERE MAY BE IMPROVEMENTS OR DIFFERENT CONFIGURATION POSSIBLE FROM DIFFERENT MANUFACTURERS WHICH MAY ELIMINATE SOME DISADVANTAGES.?

Considering the above Pros & Cons of different flow measurement principle user can be able to understand its need and compare basic important parameters which will ensure optimum selections. Hope this will help in your future decisions. Pls.do write us a comment on the same.

LEOMI, A make-in-India start-up registered company manufacturing Insertion Thermal mass flowmeter which has many inherent advantages in terms of performance versus cost ratio.?