flared gas metering 4

[mohamem]

hi

i want to ask is it essential to measure the flared gas flowrate & why .

Can I depend on interface system between the ESD SYSTEM & the PCS system to measure the flared gas flow without any flow measuring device.

the ESD system will advice the PCS of a blowdown and the PCS will perform a calculation of the actual quantity of gas blow down based oin the known piping volume , gas pressure & temprature at the start of the blowdown .

 

[dcasto]

At some point you will need to know with some certainty the amout that was flare. Either for permits, corporate loss or risk control, or even financial reasons.

There are threads here that discuss this. Non intrusive ultra sonic meters, pitot tubes, Venturi meters, vortec sheading as well as others are all viable options.

Trying to do a mass balance to get blowdown in realtime will be onerous at best. The programming will cost more than a dedicated meter.

 

[mohamem]

thanks a lot .
i am convinced with your opnion and i want to know what do you mean by Non intrusive ultra sonic meters

 

[dcasto]

The non intrusive actually goes with all the meters listed. The problem with flares is that they are designed with absolute minimum pressure drop and they must be sealed so that air doesn't get in. Orifice plates have high pressure drops and require some form of inspection.

Ultra sonic meters can be install externally for fairly accurate readings or internally for very high accurate readings. There is no pressure drop and external ones can be inspected with out taking the flare apaart.Also, turndown needs to be considered in your selection. Ultrasonic have a wide range of turndown, but that may not be a concern.

This is anexample of questions you can pursue in finding a system right for your plant.

 

[JLSeagull]

Pressure safety valves normally discharge to the flare header. Often units are unaware that they are releasing product to the flare. The flare requires flow measurement to accommodate flow somewhat in excess of the sweep gas - and for the blowdown events.

It is rare for the main flare header to be taken out of service. Thus external non intrusive flow measurement technologies are desirable for flare applications. GE Panametrics and Siemens Controlotron may be among the manufacturers to consider. Other technologies also exist.

 

[JoeWong88]

Flare gas metering has been discussed in CheResources. Read this thread.

Agree with the advices by dcasto & JLSeagull.

Ultra sonic flowmeter has the following benefits / advantages compare to other type of flowmeters ;

- Low TURNDOWN (can be as low as 2750-to-1)
- "Zero" pressure drop)
- No internal, insertion and moving parts
- Can tolerate certain amount of condensed liquid
- Take higher operating temperature **
- Not affected by gas composition
- No maintenance

** My personal experience upto 260 degC.

Read the following basically answer most of your queries.

* The Future of Flare Gas Measurement
* How much do you flare? How to measure flowrates of flare gas accurately and reliably
* Use Ultra-Sonic Flowmeter in FLARE Gas Header for emission monitoring