9 replies to this topic

[abbaschemical]

Dear All,
May i know why there is no flow meter placed in any flare header in industrial practice ? A flow meter placed in a flare header can alert the DCS personal in case of any valve passing or relief valve passing or any other malfunction? Can anyone help me in this regard?

[Art Montemayor]

Abbas:

I don’t know where you obtained your information or where your industrial application is located, but here in the USA environmental laws dictate the accountability of ALL gases flared. Depending on the design and operational philosophy of the installation, design may incorporate individual meters on each flare source in order to have operational knowledge and control of any leakage, venting, or process upsets. Or, if regulations permit, one flow meter placed in the main flare entrance. However, bear in mind that such a meter would have to have an approved accuracy over a very wide span of flows – something that may not be available. That is why I am accustomed to seeing individual metering of flare gases. The total gas flared is the sum of the parts.

[Robert Montoya]

Dear all, typically during the design is not common to install flow meter, valves due that at any time could interfere with the passage of flow, pressure drop and liquid form could reach the Flare, it is not wanted. Now I have seen that type ultrasonic meter is used in the main header since the drop pressure with these meters the is zero. But install meters in the sub-head or head each principal brings an increase in costs. The measurement of the flow going to the gas by the following two reasons: due to custiones regulatory or implementation of a strict control system losses in the plant.

[kkala]

Attachement (from http://siteresources...Measurement.pdf '> http://siteresources...Measurement.pdf ) deals with the subject and confirms (see post 2) ultrasonic flow meter as quite suitable for continuous monitoring of flared gas flow. Location downstream of knock out drum is recommended.
This must be a new trend internationally. In local (Greek) refineries regulations are not so strict (yet). I was informed that monitoring of continuous flow emissions (e.g. from stacks) is going to be mandatory in near future (not of intermittent flows, e.g. from PSVs).
Flare header should not contain flow "restrictions" (as once read in API) and some flow meter types can be characterized so. But other types (like ultrasonic flow meters) do not fall in this category.

Attached Files

•  Guidelines_Flare_Vent_Measurement.pdf   378.47KB   183 downloads

[ankur2061]

abbaschemical,

Quite a long time back (5 years back) Ihad raised a query on ultrasonic flowmeters in flare headers and I had got some fantastic responses from the very knowledgable members of "Cheresources". The link is provided below:

http://www.cheresour...are-gas-header/

Regards,
Ankur.

[jr31]

Ultrasonic flowmeter is possibly the best option for Flare Gas monitoring due to high rangability requirements although there are other options like thermal mass flow meter.

For sensing the Safety valve leakage Flow switches again Thermal dispersion type (eseentially Yes Flow/NoFlow sensing) can be installed on sub headers.

Cheers!

[jrtailor09]

<sup>Flow meter requirement generally decide on case to case basis. If you have provided individual flow meter to each & every unit oulet connected to main flare header then it is not required to place a common flow meter at main inlet flare header.

I have seen separate flow meter provided at inlet of flare system to take invetory of daily flare gas burned.

See attached file for your understanding.

Regards,</sup>

Attached Files

•  Utltrasonic mass flow meter for flare1.pdf   426.94KB   111 downloads

Edited by jrtailor09, 15 October 2012 - 06:13 AM.

[abbaschemical]

Dear All,
Thanks for all your valuable and useful feedback. Had been really useful

[T.S.MURALI]

SICK intelligence probes -gas mass flow meters are employed suitable for T=250 Deg C, for such an application.

[wojtar]

Could anybody kindly explain the following:

 

How such flare "knows" that there is a flow in header or there is not when we don't have flowmeter installed?

In other words: I'm interrested how to connect the flare with process. It should burn only in emergency situations. Normaly only pilot burners are ignited. Is ultrasonic flowmeter the only solution?