the utilize of wedge flow meter in measuring low flow, high viscosity media


Thread Starter


Hi guys,

I come from a flow meter company in China, named Boocca Shanghai Industry Co.,Ltd. I am a new guy in this field. I wanna to discuss the utilize of wedge flow meter in measuring low flow, high viscosity media, such as bitumen.

My colleagues said wedge flow meter is a good choice in measuring low flow with high viscosity. Because wedge flow meter could handle media under very low flow velocity (about 0.01m/s). And the Reynolds range from 300 to 1000000 (6zero). Am I misunderstanding anything?

Hi there,

Please check your information again. I have never heard about a "wedge" flow meter before. Are you referring to a vortex meter?

If so what is your question about it? Please be more specific in what it is you are having problems with and what you need to know otherwise your mail will just be ignored.
The segmental wedge is a variation of the segmental orifice. Commercial units come mounted in a tube/pipe. A differential pressure drop is created across the wedge.

Although the general rule is that a wedge flow element can handle low Reynolds numbers typical of low viscosity fluids, the measurement is still DP. The flow conditions have to create sufficient DP to be read, and the DP transmitter (and its seals) has to be able to 'see' that DP and survive the operating temperature and pressure conditions, which are unstated.

Generally, suppliers of the wedge flow elements run (or provide) a sizing calculation using on your flow conditions to determine suitability. Google will find you numerous vendors.

It also isn't clear whether you expect a given metering installation to make flow measurements over the entire range of viscosities stated.

John Erskine

Hello Miss Cecelia - you are correct, wedge meter is useful for measuring very high viscosity media such as bitumen. Also the wedge meter can be made to any custom requirement, such as pipe size and wall thickness, pipe material, and flange rating. So for example it can be used in very high temperature media also. The other information posted here by others is correct, wedge meter is a "differential pressure" flow meter, and there are some different makers of those, including my company, Preso (USA).

For any application, the manufacturer will ask you some specific details about it, to make sure that the meter is sized properly and will deliver full accuracy in your customer's conditions. As to the low-end Reynolds number limit, 300 is sometimes specified but it is difficult to test under perfect conditions - other manufactures may say 400 or 500; and some say that going lower than these minimums will deliver a repeatable measurement, though accuracy may suffer.

Respecting the nature of these public forums I won't plug my company exclusively, but your information is correct and any wedge meter manufacturer will be able to help you from this point - good luck!

John Erskine
Hi John,

Thanks for your information. I also work in a flowmeter company. As I have been joining it for a short time, there are a lot of thing I have to learn. I found this forum accidentally, and I found most people in here are very professional.

About the wedge flow meter, it seems not very popular, or people call it in other name?

Best Regards

John Erskine

Hi Cecilia - thanks for your reply. Mainly I have heard it called wedge meter, or sometimes "segmented wedge", or "segmental wedge". Also, please note that wedge meter is one type of "differential pressure" flow meter, or "DP meter" for short. And finally, these are also referred to as "primary flow element". DP meter family includes wedge, Venturi, Pitot tube, and orifice plate; also some hybrid models such as V-cone. Compared to other types of DP meters, I think you are correct that wedge meter is not so popular, the main reason is that normally other types of DP measurement can be lower cost than wedge. #1 DP meter in terms of the number of units installed around the world is orifice plate. That one is very low cost, although compared with other types it usually has much higher pressure drop. For certain applications such as bitumen and other high viscosity fluids, wedge meter is one of the few that can do successfully.

Regards, John Erskine
Hi John,

Thanks for your reply.
There are a lot of DP meters, but could you tell me which one is the second popular? And the third popular? Take my company as an example, we have averaging pitot tube flowmeters, v-cone flowmeters, balance flowmeters. I am not sure I should promote which model to my EU and USA customers.

By the way, Could you tell me what do you think about Chinese flowmeters or China products? Because someone said that foreign customers thought China only supply cheap but bad quality products (of course, I don't think so), I don't know if they still think like that. is the best control forum I have found so far, do you know any other similar forum? Could you please give me some advice?

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