home button icon
Text Heading
Flow Finder Icon

Article #4:  Identifying Bad Resistive Flow TDs

July 10, 2006
In our first Tip of the Week we mentioned that Flow Finders help technicians verify resistive flow transducer readings. In this article we'd like to explain the specific method we use to determine whether or not technicians can rely on these flow transducers for accurate readings.

Are your resistive flow transducers calibrated? It has been our experience that when flow transducer readings at air pipe manifolds don't add up to the flow measured at the pipe alarm panel, one or more bad flow transducers may be the problem. This possibility becomes even more probable if the pipe alarm panel reads 45 Standard Cubic Feet per Hour (SCFH), for example, and the total sum of the flow readings in the field is only 20 SCFH. If the cause of this discrepancy is not a bad flow transducer, it could be a leak in the air pipe, a cheater hose, or a ghost manifold. Whatever the reason, Flow Finders will help to solve the mystery.

How do you determine what's causing the difference in flow readings? The simplest and quickest way is to install Flow Finders at key locations on the pipe route. We recommend that you install a 0-47.5 SCFH or 0-95 SCFH Flow Finder at the pipe alarm panel (the correct one depends on the pipe's current flow rate) and a 0-19 SCFH Flow Finder between the air pipe and each of the manifolds. That's assuming, of course, that you are using old style air pipe manifolds and not the System Studies Flow Finder Manifolds, which are equipped with built-in Flow Finders. The Flow Finder at the pipe alarm panel will verify the reading provided by the panel's flow transducer. If the readings aren't the same, part—or possibly all—of the problem can be identified before you even leave the office. The Flow Finders in the field can then be used to verify individual manifold flow transducer readings and whether or not there are other problems in the system.

In addition, PressureMAP users may want to check the pipe alarm panel flow transducers on routes that have a low System Quality Index (SQI). By investigating the flow monitoring device, you may find that the cause for a low SQI is something other than a leak. Think of all the money you'd save by not looking for a leak that doesn't exist!

If you have any questions on how Flow Finders can be used in your area, give us a call at (800) 247-8255. We'd appreciate hearing from you.