Fluid Components International MT86_MT86HT Manual General Information - Manual

Doc. No. 003162 Rev. F 1 - 1 Models MT86, MT86HT
CHAPTER 1 - GENERAL INFORMATION FLUID COMPONENTS INTL
1. General Information
Description
The MT86 and MT86HT is an air and gas mass multipoint flowmeter that incorporates a flow element(s) that is
connected to a flow transmitter. Together they are designed to measure the mass flow in pipes, ducts or stacks. The
flowmeter accurately measures the irregular flow profiles found in pipes, ducts or stacks. An MT86 or MT86HT
measures flow from up to eight individual sensing points. An average of the individual flow signals gives an output
signal that represents the total mass flow. This output signal will operate up to four different output modules of
choice.
Operating Principles
The flowmeter has flow elements containing sensing points that are connected to the flow transmitter (control circuit
boards) by a wiring harness. The flow elements and the flow transmitter are usually separated by some distance that
in some cases can be up to 1000 feet (300m). The output that comes from the flow transmitter goes to the customer's
applications, such as valve control circuitry, alarms or meters. The operational theory of the flow element sensing
points and the flow transmitter are as discussed below.
Flow Element
The flow element consists of 2 to 8 sensing points. Each sensing point has two pairs of thermowells (metal tubes) of
the same size and shape. Each pair of thermowells is welded together. One thermowell pair has a heating element
placed in one tube and an active Resistance Thermal Detector (RTD) placed in the other tube. The other thermowell
pair has a reference RTD placed in one tube and an empty thermowell tube that is for mass equalization. See
Figure 1-1 for a cut away view of one sensing point.
The two pairs of thermowells are physically separated by a distance that allows the process media to flow between
them and yet prevents thermal interaction between the two pair.
Figure 1-1. Cut-Away View of One Sensing Point