Innova-Mass® Model 241 Improves process billing process for District Energy

Many large cities in the Northeastern US use central steam heating to heat buildings in the city center. Superheated steam is produced at a central facility, then piped to various buildings where it is used for heating water or for heating the building itself. Obviously, this steam is not free, so the various providers must find a means to measure its consumption and bill the users.

Since most of these steam systems have been in operation for many years (sometimes for almost a century) most cities in the Northeast used a legacy device called a shunt meter. This is essentially a turbine meter through which the steam is bypassed. This device has two major drawbacks. First, it is mechanical so the device wears out. Secondly, it is a volumetric device so additional temperature, pressure and flow computers must be installed to measure mass flow. The total system accuracy and repeatability is affected by the individual components. Further, process variables may be measured at different points. All of these factors together lead to poor accuracy typically around 5%.

A large Midwestern city’s district energy provider faced the same problems described above. Their old shunt meters were wearing out and leading to high maintenance costs and increased downtime. After considering several alternatives, including a standard vortex meter, the company settled on the Innova-Mass® Model 241 insertion multiparameter mass vortex meter as a cost effective replacement. The Innova-Mass® simultaneously measures three process variables: velocity, temperature and pressure (VTP) through one process connection. This allows for a real-time calculation of true mass flow.

While traditional vortex meters have been in use for many years, the typical device is a flanged in-line unit that measures only one variable (the velocity of the flowing fluid). Effectively, this makes all vortex meters volumetric. While mass flow can be calculated for a constant density fluid, it becomes much more problematic for gases and steam. The Innova-Mass® is a quantum improvement and somewhat unique in that it is an insertion device.

Insertion vortex meters have seen limited use (there are only 3-4 suppliers) because they are measuring the velocity at only a single point and are therefore greatly affected by flow profile. The Innova-Mass® solves this inherent problem by measuring the Reynolds number in real-time, calculating a dynamic flow profile and determining correction algorithms for the point velocity. This means a reliable insertion meter for very large pipes where an in line meter would likely be much too costly. Since everything is calibrated together, system accuracy is very high. Better than +/- 2.0% of reading accuracy and +/- 0.2% repeatability is the norm.

The Innova-Mass® provided a perfect solution. It was easily retrofitted into existing steam lines and directly measured mass flow with no extra equipment and no moving parts. By replacing the old shunt meters, the energy provider saved approximately 35% annually in maintenance costs and saw a 25% increase in billable steam flow previously unaccounted for.