Staying Competitive to Win Big
“HART is simply
the only way to go for quick start-up, re-ranging and troubleshooting,”
says Jim Weinstein of V-F Controls, Inc. (Mentor, Ohio). “The
fact that it is a standard is so important when systems involve
different vendors’ products.”
V-F provides flowmetering systems to chemical, rubber, petroleum
refining and steel-making companies and to the district-energy market
for custody transfer. They use HART Communication to stay competitive.
“Often a customer does initial piping, installation, and wiring
of our systems, then we assist in commissioning,” says Weinstein.
But sometimes process conditions aren’t as originally anticipated,
which means initial set-up of the instrument must be changed. “HART
allows us to make changes in minutes, compared to hours if we used
analog electronics.”
“One of my first HART installations was a steam-flow metering
system with differential-pressure, pressure, and temperature transmitters.
The signals were sent to a flow computer,” he says.
Accessibility to the transmitters was difficult because they were
located on the piping near the ceiling of a high-bay building. “The
customer had done the installation and wiring, and then called to
tell us that the transmitters were indicating totally erroneous
readings on the flow computer,” says Weinstein. “When
we visited the site to troubleshoot, we agreed.”
Reducing Troubleshooting Time
“I thought this would be a good time to try our new HART
communicator. I hooked it up to the pressure-transmitter terminals
on the flow computer, and established communication with the transmitter,”
says Weinstein. “It came back and said, ‘I am a temperature
transmitter.’ ”
Within minutes, Weinstein found that his customer had incorrectly
wired the two transmitters. “Troubleshooting with HART is
a dream. Without the HART-enabled devices, it would’ve taken
much longer—probably an hour just to get 50 feet in the air
to start.”
Weinstein says that HART adds loop-validation functions to V-F’s
applications like the ability to identify the transmitter at the
end of the loop or driving a 4-20mA signal in the loop to verify
proper response at a flow computer, chart recorder, or indicator.
“These capabilities not only identify proper wiring terminations,
they help us find potential ground-loop issues and configuration
errors in the transmitter or secondary electronics,” he says.
“I’am not aware of any other standard for digital communication
on a 4-20mA loop. As proprietary protocols fall by the wayside,
more instrument manufacturers jump on the HART bandwagon. Why carry
two or three communicators, when you can carry just one?”