GE Panametrics PT878 Ultrasonic Liquid Flow Meter

How to Operate the Panametrics PT878 Ultrasonic Liquid Flow Meter

A Theory of Operation on Ultrasonic Liquid Flow Meters Time of Flight

A How to Guide for GE Panametrics Ultrasonic Liquid Flow Meters

Applications

Sanitary Flow Measurement in a Dairy Plant
GE Sensing Panametrics PT878 This application note was written with the older PT868 in mind and as such it is equally applicable to the newer model the PT868 GE Sensing application note

Sanitary Flow Measurement of Juice
GE Sensing Panametrics PT878 This application note was written with the older PT868 in mind and as such it is equally applicable to the newer model the PT868 GE Sensing application note

Calculate the Efficiency of a Chilled Water System Using the temperature transducers and the flow meter you can measure the energy of a chilled water system. The flow meter can take a 4-20 mA temperature measurement of the water going into the a chiller and the temperature of the water coming out. From these measurements the logger can derive the energy figure for the system.

Log Water Consumption on Site
The flowmeter is attached to the incoming water line. However, because this is a remote site the PT878 flow meter must be connected to a remote dc source. To do this we use the standard charger supplied with the unit and an inverter. The unit plus an inverter draw 1.35 A so a 120 A/hr battery would last 3.5 days.

Measuring the Flow Rate of Diesel Fuel
You can use the GE Panametrics PT878 together with the small transducers to measure the flow rate of fuel in a diesel engine. The only possible problems here is staying within the temperature range of the transducer (-40 to 120°C) and knowing what sound speed of diesel actually is. The sound speed can be determined using the Sound Speed and Kinematic Viscosity table (pdf)

Also, if the pipe material is not amongst the standard pipe material pre-loaded in the device, you may need to use the sound speed information in the Pipe Material Sound Speed table (pdf)

Calculating Flow Rate for Different Valve Settings
The customer needed to check what the flow rate was for different valve settings. A PT878 was connected to the outfall of the tank. The flow was measured and recorded for each rotation of the valve. This was when the operation required a particular flow rate; this could be set by turning the valve the appropriate number of turns.

Ensuring There Is Flow in a Pipe Carrying Fuel Oil Prior To Welding
When oil pipe lines require repair it usually requires welding. Welding pipes which contain fuel oil can be very dangerous. The vapours from the fuel are the problem, not the fuel itself. If you are going to weld a pipe containing fuel oil the pipe MUST be full and flowing in order to ensure there is no gas present and to ensure there is no build up in heat. The GE Panametrics PT878 is a suitable instrument for the welders to attach to the pipe, ensuring there is flow and that the pipe is full.

Measuring Flow in a Pipe Carry Oxygen
The following are applications using the PT878 flow meter where oxygen flow has been measured:

Measuring Flow in a Pipe Carrying Compressed Air
The following are applications using the PT878 flow meter where compressed air flow has been measured:

Measuring Flow in a Pipe Carrying Nitrogen
The following are applications using the PT878 flow meter where nitrogen gas flow has been measured:

Measuring Flow in a Pipe Carrying Superheated Steam
The following are applications using the PT878 flow meter where steam has been measured:

Measuring Flow in Pipe Carrying Natural Gas
The following are applications using the PT878 flow meter where natural gas flow has been measured:

Nominal Sizes and Pipe Dimensions

Note: If you are using the PT878 to measure temperature for energy calculations, if it has NEVER been used for temperature measurement it needs to have the 4 mA and 20 mA levels calibrated.

The Energy Option also needs to be enabled as does the appropriate scaling of the analogue input. These are both under different items in the 'Program' menu. The calibration is done in the 'Setup>Calibrate' menu What you need to know...

1. Fluid Details

2. Pipe

3. Physical Layout (the flow must be laminar...)

If you cannot successfully answer the above questions then you cannot guarantee the operation of the PT878 flowmeters. However, these flowmeters will often work anyway. This technique has an advantage such that if it does work then you can believe the reading.

These are some additional comments from the PT878 manual
1. Fluid Problems

2. Pipe Problems

3. Installation Problems

Ultrasonic or Acoustic Couplants and Alternatives
The stuff we use (ECHOTRACE 9000) is water based so it is easier to clean up. Generally speaking most silicone oils & gels, greases, Vaseline (paraffin) and even some hair gels etc. can be used if the temperature is not sufficient to make it run out from under the transducers and or be workable in overhead applications. I have found that good quality high temp wheel bearing grease is usually a suitable alternative. Glycerin can give a few extra dB of coupling (it can sometimes help obtain useful readings when there seems to be no reason why it won't work) as its acoustic impedance is similar to plastics, but it can cause corrosion and or rusting so it must be completely removed.

Ultrasonic gel can usually be purchased from veterinary supplies or those larger pet warehouses. It is usually used for doing ultrasound testing on horses. Before purchasing, consider temperature and usability for overhead applications (viscosity) as some are very fluid at ambient temperature.

Additional Resources

Instrument Manual (pdf)
Power Point Introduction to the PT878 Flowmeter (pdf)
Gas Flow Meter Selection (Google Spreadsheet)
PT878GC Installation Requirements (pdf)
Nominal Sizes and Pipe Dimensions (pdf)