BTU Meter

[mechengr24]

We are looking at submtering multiple buildings and floors for a campus.

What is the advantage/disadvantage to using the following types of BTU meters:
1. Paddle wheel type
2. Ultrasonic
3. Electromagnetic

Which manufacturers do you recommend for a reliable meter?

 

[quark]

Metering nonaggressive liquids is not that difficult. Accuracy of 1% or less is possible at measured flowrates.

Positive displacement meters are accurate even in partial pipe flow conditions as the their basic principle of operation is fixed volume displacement. Nevertheless, the liquid should be clean.

Both ultrasonic and mag flow meters consider full pipe CS area for volume flow computation in all cases. Though some mag meters have option to detect partial flow, the flow indication is still erratic.

If you are using these for chilled water system (AHU chilled water flow), you should select a type of meter with wider turndown ratio.

E+H, Emerson (Rosemount) and Yokogawa, all are good.

 

[danw2]

Paddle wheels are cheap. And their maintenance reflects their price and lack of durability. The axles break and the paddle flows down the pipe. No meter, junk in the line, have fun.

Turbine meters look like paddle wheels but are in a higher class of performance. They still need care and maintenance, the bearings do wear out.


Magmeters have good turndown and are mature, reliable products. But installation involves a lot of cutting and welding/threading.

All of the above technologies are flow meters only and require the separate purchase and integration of high accuracy RTD's and a BTU (electronic calculating) meter/box (or AI's to a BMS, DCS, SCADA, DAQ and a BTU algorithm in whatever it's called in your field).

I can't imagine in-line ultrasonic for utility metering (too costly), so you must mean clamp-on ultrasonic. Controlatron (now Siemens) has an 'energy' model that includes very high accuracy RTDs (several different styles, external clamp-on or insertion) for the Tin and Tout measurements and a BTU calculation as part of the electronics package. Easy installation, no cutting, not welding. I was impressed with the turndown on the meter I dealt with, it would see clearly register the flow from a single toilet flush at 3:00am in the morning. The only downside is a yearly check of the clamp-on fixtures and the sonic goop. But at least that's all outside the pipe.

I haven't priced them out but I suspect that the complete clamp-on is close to the price of a mag and RTDs and a BTU meter.

My 2 cents: never a paddle wheel,
turbine, eh . . .
toss up between mag and clamp-on, leaning toward the clamp-on because it's on the outside and there's no messing with the pipe for installation.

Downtime for meter installtion can be a real serious consideration in some cases, trivial in others.