Steam flow meter

saussyHen

I am a little out of touch these days with new technology. Can anyone recommend a steam flow meter for the following conditions? 100psig saturated 3000 lbs/Hour max with an average flow1200 lbs/hour this is for revenue service so they are looking for better then 1% accuracy. I can intergrate the data in many ways so it does not have to be a totaliser.
Thanks

Brad White_203

Vortex Shedding

we do not specify as much in steam as we used to, but Vortex Shedding types seemed to be the most reliable. The device itself is simple, but the electronics to interpret the data is where the accuracy (and cost) is. Being a gas, it is compressible so measurement can be a challenge when accuracy is desired.

What we found is that the larger the main and more constant the load, the simpler it all is. (Makes sense.)

When reading varying peak and sub-peak loads, splitting the main into a 1/3-2/3 arrangement to read highs and lows was essential.

In the end, most times we investigated steam flow meters, the Owner would opt for tried and true condensate meter (Cadillac Meter). As a simple paddlewheel, it captured all steam use including line drips, so the utility could charge for all system and piping inefficiencies. That put the onus on the user to maintain their system and insulation.

saussyHen

thanks

I was leaning to the old tried and true my self and putting a mag flow on the pumped return and I have the computer power in the system to do the rest of the calculations. The volumetric type like the one you described is interesting I will look into and see if the case is pressure rated. Thanks

Tony Conner_2

The Cases...

... are not pressure rated. They are installed with a steam trap ahead of the meter, and the condensate gravity-dumps through them. They are deadly accurate, with an infinite turndown. They're no good for direct contact steam applications like humidifiers, etc, as the condensate MUST be available to go through the meter. If there are any steam or condensate leaks in the system ahead of the meter, then that won't get read. On the flip-side, if you're heating liquid with steam through a heat exchanger, and you develop a tube leak in a situation where the liquid is higher pressure than the steam side, the meter will happily read the other liquid as condensate. It has no way to know what the liquid is, or where it's coming from. This leads to VERY high steam bills, and customer complaints.

If you want to meter the steam itself, use a vortex shedding flow meter, WITH PRESSURE COMPENSATION. Without a pressure compensator, any deviation in steam pressure - up or down - will affect the accuracy. Higher pressures than the meter was set for will show up as low readings, lower pressure will read high. And the greater the pressure deviation, the bigger the meter error. DO NOT oversize the meter, as this will affect the turndown - you'll wind-up giving steam away at low loads. Use the smallest meter that will do the job. I'd guess the size at 1-1/2".

If you've got a condensate tank & pump and all of the condensate gets to the tank, I'd install a condensate meter just ahead of it. (Remember that these meters gravity dump, so they HAVE to be higher than what they're draining into.) If there's a district steam utility near you, they've usually got LOADS of condensate meters sitting around from old buildings that have been demolished. You could probably pick one up cheap. I've been involved in testing lots of these, and the vast majority were within a 1% accuracy range. I thought that that was pretty good, considering that all of those meters were made in the 1920's & 30's. There was one that was out about 5% (we scrapped it), but ALL were in the customers favour - not the steam utility's, so nobody had any grounds to complain.

Brad White_203

Well Said Tony!

That pretty much covers it on all accounts. Well said.

saussyHen

Tks.

Many thanks for all the good input folks.