The Effect of the Control Valve Noise on the Ultrasonic ... · PDF fileThe Effect of the Control Valve Noise on the Ultrasonic Gas Flowmeters ... The effect of the control Valve noise

The Effect of the Control Valve Noise

on the Ultrasonic Gas Flowmeters

Ahmad Mahdy Hammad - Bapetco

The effect of the control Valve noise on the Ultrasonic gas flow meters

The presenter Bio:-

Ahmad Mahdy Hammad

Bachelor Degree Of Electronic Engineering on 2004 .

Fiscal Metering Section Head at Bapetco.

Responsible for three metering stations (Ameriya – EPC – Crossover) at Bapetco (joint venture between EGPC & Shell).

Fiscal metering instructor at Enppi & OGS (Oil & Gas Skills Company).

Purpose:-

To illustrate the effect of noise caused by a regulating valve on the ultrasonic gas flow meters & find a suitable solutions with a case study from Bapetco.

The ultrasonic flow meter operation:-

Ultrasonic acoustic pulses transmitted by one transducer are received by the other one, and vice versa.

The ultrasonic flow meter operation:-

Without flow, they propagate with the same speed in both directions. If the gas in the pipe start to move with velocity ν, pulses travelling with the flow will move faster, while those travelling against the flow will move slower.

By calculation the time difference we can get the gas velocity then the volume of flowing gas.

So any acoustic noise can cause many problems to the meter.

The control valve noise:-

All control valves generate abroad spectrum of noise which maybe overlaps with the ultrasonic transducer frequency.

Researches reveal that most of the ultrasonic transducers operate at 100KHz which is in the same range of the control valves noise frequency.

The ultrasonic gas flow meter performance under the acoustic noise caused by a control valve:-

Simply the noise will reduce the SNR of the meter (Depending on the manufacture recommendations) which will lead to a measurement errors.

In some cases the noise is big enough to make the USM fluctuating between zero & 950MMSCF/D.

How to eliminate the acoustic noise :-

1- Put the control valve downstream the USM. The best position for the control valve is to be down stream the USM. 2- Install noise damping elements:-

Note:- Pipe reducer should be avoided as it will amplify the noise by ratio directly proportional to the reducer diameter ratio.


3- Changing the transducer frequency:- You can overcome the noise problem by changing the transducer frequency from 100KHz to 500KHz if it is possible. We already upgrade our transducers from 100KHz to 200KHz but still have some troubles.


4- Signal processing technique:- Signal averaging (Stacking) is very effective way to reduce the random noise but it will affect the USM response time It will make the USM slower so it will misread the rapid changes in flow rate. 5- The USM path length:- The short paths have more resistance to the noise. 6- Increase the transducer power:- Sure if the signal amplitude increased so it will lead to more noise resistance.

How to eliminate the acoustic noise :- 7- The coded multiple burst CMB:- Advanced excitation method where transducers transmit a burst signal instead of a single pulse. With Coded Multiple Burst (CMB) the transmitted signal consists of a time coded sequence of bursts. The received sequence of burst signals is sampled, decoded and the original pulse is reconstructed. This improve the noise resistance but sure it has a limit.

How to eliminate the acoustic noise :- 7- The coded multiple burst CMB:-


8- The control valve choice:-

All control valves generate enough noise to affect the ultrasonic flow meters but the ball valves are less noisy than other types.

9- Reduce the differential pressure on the control valve:-

If the diff. pressure to the pressure ratio larger than 0.25 it will generate noise.

So if the upstream pressure is 100 Bar so the differential pressure on the control valve shouldn’t exceed 25Bar.

Case study from Bapetco ultrasonic flow meter:-

(Elster-Instromet Q-Sonic 5 paths).

EPC station layout:-


The designed flow rate is 730 MMSCF/D.

The actual flow rate is 950 MMSCF/D.


Control Valve with designed CV=2500.

The actual working CV is about 2990.

The normal U/S P is 70 Bar & the D/S P is 67 Bar. (Noise has low effect).


Control Valve with designed CV=2500.

The actual working CV is about 2990.

The normal U/S P is 70 Bar & the D/S P is 67 Bar. (Noise has low effect).


The up normal conditions on USM:-

The U/S Pressure is 74 Bar & the D/S Pressure is 40 Bar.

The USM reading fluctuate between 0 & 950 MMSCF/D. (Trends lost).



When the high speed occurred or our customer had shutdown for any reason the PCV closed.

The pressure drop on the PCV was about 50 Bar & the temperature decreased to 0 C.

Then the operator started to open the PCV gradually till reaching the normal flow rate 950 MMSCF/D.

But with up normal pressure drop which was about 35 Bar.

The temperature increased to be 12 or 14 C.

The USM reading fluctuated between 0 & 950 MMSCF/D although our customer meter reading was 950 MMSCF/D.

All the 5 paths performance are 0% to 40%.

The USM returned back to the normal reading after the pressure drop reached 2 or 3 Bar.


Note:-

There are many problems occurred in this up normal process conditions such as:-

1- High acoustic noise.

2- High flow velocity. (33 m/s)

3- Icing & liquid content on the transducer due to the high pressure drop & the temperature decrease.

But finally all of them were a results of the high pressure drop on control valve which lead to the USM failure.


Case study from Bapetco ultrasonic flow meter:- Solutions:-

1- We upgraded the USM transducer to be 200KHz instead of 100KHz.

It didn’t solve our problem.

2- We upgrade the electronics to increase the flow velocity range from 30 m/s to be 40 m/s.

It didn’t solve our problem.

3- Enable the coded multiple burst (CMB) on the USM.

It improved the USM performance as the fluctuation was between 500 to 950 MMSCF/D but sure it still not accepted.

4- Installing s silencer or relocating the meter to be upstream the control valve. (Still under the engineering revision).

Also we will change the PCV with a new one which have CV=4000.

Presentation conclusion:-

The acoustic noise is a very important problem which can lead to the ultrasonic meter failure.

It is better to avoid it during the design phase but it can be also reduced after the flow meter operation.

It is a nightmare so try to avoid it in the installation phase.

Thanks

Any Questions

References:-

1- NEL technical report by Mr. C. Coull on 2003.

2- Elster-Instromet Q-Sonic manual.

Documents

The Effect of the Control Valve Noise on the Ultrasonic ... · PDF fileThe Effect of the Control Valve Noise on the Ultrasonic Gas Flowmeters ... The effect of the control Valve noise