INDUSTRY
Petro Chemical
OBJECTIVE
Provide monitoring and control of the
cycle water treating system from the
DCS or from the local panel.
SOLUTION
• Modicon
®
Quantum PLC
• Concept
TM
Programming
Software
• FactoryCast
TM
Software
BENEFIT
• Redundancy provides fault
toleration
• Seamless communications to the
DCS over standard protocol
• Access to process data via
standard web browser
• Easily expandable
Monitoring and control of a
cycle water treating system
Introduction
In 2000 this customer announced it would build a petrochemical complex. The
complex is centered around a cracker producing 1 million ton/year of ethylene.
Downstream products are 575,000 ton/year of ethylene glycol (EG), 400,000 ton/
year high density polyethylene, and 150,000 ton/year linear alpha olefins. Puffer-
Sweiven of Houston, TX was the Schneider Electric solution provider that
assembled the cabinets, programmed the PLCs and factory tested the equipment.
Application
A cycle water treating system which consists of two demineralizer trains with a
common vacuum de-gasifier after the cation exchangers. Each demineralizer
train consists of a cation exchanger, an aldehyde removal unit and an anion
exchanger. During normal operation the anion exchanger is regenerated after
3200 m3 has been treated (about 48 hours), the cation after 13,000 m3 ( about
192 hrs). The Aldehyde unit is normally bypassed, and is regenerated after 850
m3 has been treated ( about 12.8 hrs).
The PLCs communicate over Modbus
®
Ethernet to the DCS. The DCS then displays the system graphics and alarms.
The operator operates the cycle water treating system from the DCS or from the
local panel. The system has redundant CPUs and redundant Ethernet modules
to maximize run-time. All control resides at the PLC level (both discrete and
analog).
Objective
Provide monitoring and control of the cycle water treating system from the DCS
or from the local panel.
Solution
Two Quantum 140 CPU 534 14A running in IEC only contained the application.
Each primary rack also contained two 140 NOE 771 00 for redundant communi-
cations to the DCS via two NR&D QUCM-LE modules. The DCS communicated
via RS485 using Modbus RTU at 19.2 kBaud. The QUCM modules bridge to
Modbus TCP/IP. An additional 140 NOE 771 10 was added to each primary rack.
This is used for OFS communications to the plant LAN and also for the engineer-
ing workstation. A GPS module is installed in the RIO rack. This synchronizes
the PLC clock.
All analog I/O was pre-wired to custom terminal connectors via cable bundles to
a field marshalling cabinet. The analog signal terminal panels have HART filters
to allow for HART communications to the field instrument without interrupting the
analog control signal. The discrete signals were taken to terminal blocks.
Application Case
History
Application Case
History
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