Fluid Components International MT86, MT86HT General Information

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

Doc. No. 003162 Rev. F 1 - 1

Models MT86, MT86HT

FLUID COMPONENTS INTL CHAPTER 1 - GENERAL INFORMATION

Flow Transmitter

The flow transmitter measures the voltage differential (DV) produced by the temperature differential (DT) between
the active and reference RTDs for each individual sensing point. The flow transmitter amplifies the DV signal and
converts it into a signal that is temperature compensated and linearized. The linearized signals from the sensing
points are then averaged together and converted into the final output signal (4-20 mA, 0-5 Vdc, 0-10 Vdc, etc.) as
specified by the customer.

The flow transmitter has a diagnostic alarm. If a problem exists with a sensing point, a Light-Emitting-Diode (LED)
on the control board will flash to notify the customer.

Technical Specifications

• Process connection

2 inch male NPT or 2 inch 150 lb. raised-face
carbon steel flange.

• Number of sensing points

Up to and including 8 sensing points.

• Insertion length

The duct dimensions at the measurement site
determine the insertion U-Length.

• Material of construction

All wetted parts are 316 stainless steel with nickel­braze, per MIL-B-7883 using AMS 4777

• Local enclosure (flow element
terminal strip enclosure)

NEMA 4 enclosure with 1 inch female NPT
connection ports.

• Operating pressure

Standard MT86 is 0-50 PSIG or higher on
application.

• Operating temperature

Standard flow element: -50 to 350°F (-46 to
177°C).

High temperature (HT) element: -50 to 850°F
(-46 to 454°C).

• Remote enclosure (flow transmitter
control circuit enclosure)

NEMA 4 enclosure with 1 inch female NPT
connection ports.

• Input power

Standard 100-130 Vac or 200-270 Vac, 50/60 Hz,
50 watt maximum. Optional 24 Vdc, 50 watt max.

• Output signal

4-20 mA current loop capable of driving a 1000
ohm load. Optional:

10-50 mA, 400 ohm load max.
0-5 Vdc, 2 mA current max.
1-5 Vdc, 2 mA current max.
0-10 Vdc, 2 mA current max.

• Interconnecting cable

24 AWG (min.) 8-conductor shielded cable with
PVC insulation (100 feet maximum). Longer
distances are possible using a heavier gauge wire
for the heater circuit (see Table 2-1).

• Turn down ratio

2:1 to 100:1 within flow element range customer
specified.

• Accuracy

Flow transmitter: 0 to +150°F (-18 to 66°C) with
LCD or -50 to 150°F (-46 to 66°C) without LCD.

• Flow range

0.25 to 150 fps in gas under standard conditions
(14.7 PSIA @ 70°F).

• Flow element assemblies

± 3% of full scale at the temperature of calibration;
±5% of full scale with temperature compensation
over a range spanning 200°F. Manufacturer
determines the accuracy for specific duct
configurations upon submittal of a fully completed
Multipoint Mass Flowmeter Application Data
Sheet.

• Repeatability

May have 1, 2, 3 or 4 separate flow element
assemblies. Must contain a minimum of 2 sensing
points per flow element.

• Approvals

± 1% of full scale.

F.M., C.S.A., and CENELEC approvals are
available for all MT Series Multipoint Mass
Flowmeters.

Models HT86, HT86HT 1 - 2 Doc. No. 003162 Rev. F