pickle mill

8/12/2019 Pickle Mill

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2006

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AUTHOR: Peter Hopf

Siemens AG

ThyssenKrupp Stahl AG (TKS) is part of the carbon

steel business unit of ThyssenKrupp Steel, which has

been operating a tandem rolling mill in Dortmund,

Germany since 1972. It produces quality steels primarily

for the automotive industry, including an increasing

proportion of the latest steel grades such as dual phase

(DP) and transformation induced plasticity (TRIP) grades.

Over the years, the company has been converting the mill

in several stages to increase its capacity. An important

step was coupling it with the pickle line in 1998. The

companys next goal was to equip the mill to produce thesame high-quality steel as TKSs continuous tandem mill

in Duisburg, commissioned in 2000.

When Siemens started the TKS modernisation project in

2001, the Dortmund plant had a mix of old and new

components. The main drives were 30-year-old DC motors

with analog controls. The converter-fed three-phase drive

units in the coupling section dated back to 1997.

Instrumentation made use of the latest 24V technology,

but also included some old 220V sensors and the process

peripheral equipment connected to the automation via

hardware couplings and bus systems.

Because of numerous minor conversions over the years,

the plant was using a variety of different automation

components, including automation technology from the

1990s. What is more, there was no central computer for

process automation; instead, the plant relied on several

computers from different vendors.

CONVERSION PLANNING

Siemens started by performing a detailed on-site review,

and then worked with TKS to devise the conversion

concept. As much work as possible was performed during

maintenance shutdowns to keep the main shutdown time

as short as possible. The hydraulic, cooling and lubrication

systems were converted in stages during maintenanceshutdowns before the main shutdown. Siemens also

directly installed ET200 components in existing

switchgear cubicles, preparing the ET200 on assembly

panels that could then be installed in the old cubicles in a

very short time during a maintenance shutdown.To minimise conversion time, the existing field bus was

retained, even though it included parts from another

manufacturer. Special bus connections allow the Simatic S7

to operate the Interbus. Siemens simply unplugged the bus

cable from the old automation device and connected it to

the new Siemens automation system during the shutdown.

In the coupling section, the three-phase supply drive

systems from Alstrom were also converted to the Siemens

bus standard quickly and easily by exchanging the bus

interface for a standardised Profibus interface. The

flatness measuring system was re-used by simply

replacing the interface connection with a Profibus card.To minimise costs expensive main drive power

components such as motors and thyristors were re-used

whenever possible. By connecting the plants 30-year-old

thyristors to new digital control system, a whole series of

analog cubicles were replaced by a single cubicle for dual

motor control.

The DC supply systems for the pickle line and the

Simatic S5 automation measurement and control

systems were left unchanged. Siemens linked the

tandem mills reused DC roller motors, including the

reused thyristors, to new all-digital Simoreg devices. The

old DC reeling machine, on the other hand, was

replaced completely by two new AC reeling machines

with an indirect converter. Exchanging the interfaces for

Siemens components allowed the reused DC and AC

drive systems in the coupling section to connect to the

new automation system.

The conversion also involved completely replacing the

basic automation system of the coupling section,

tandem mill and new run-out section, including all

technological control systems. This required an interface

between the remaining functions of the pickle line and

the new basic automation system. A new model-based

SIROLL process automation system that could handle

the entire plant replaced the old process computers. Thisresulted in a significantly simpler interface design. All

converted sections now feature standard display and

diagnostic systems.

With minimum downtime, Siemens modernised ThyssenKrupp Stahls coupled pickle line/tandemmill in Dortmund Germany, enabling the 30-year-old plant to rival the production quality of todays

most advanced facilities.

Modernising the coupled pickleline/tandem mill at TKS Dortmund


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SINGLE-OPERATOR CONTROL OF THE MILL

All components are based on Simatic PCS 7 with WinCC

as the standard control system for plant operation and

fault diagnosis. The Simatic S7 provides control and

regulation functions. New process peripheral equipment

is connected via the ET200. The Simatic TDC automation

system provides maximum computing power for

technological control.

Industrial PCs provide process automation. An open

communications system exchanges data between the

systems, using Profibus as field bus for peripheral

equipment. Fast Ethernet serves as the process bus,

backed by Simatic TDCs Global Data Memory for real

time data exchange between the system controls.

Siroll WinCC components were used for the joint display

system, which features central power-up capability and a

central signaling system that can be operated from anyplant monitor. The plant also relies on the versatile

Siemens thickness control concept, which uses the

extended mass flow technique to ensure tight tolerances

under all operating conditions. The flatness control

system makes use of neural networks that have a self-

learning function, enabling them to adapt precisely to

production requirements.

Siemens paid particular attention to the design of the

pickle line/tandem mills main control pulpit (see Figure

1). The high degree of automation in all operating modes

allows a single operator to control the intermediate

section, tandem mill and reeling machine, up to the

removal of the coil from the mill. The fault diagnostic

system provides the operator with relevant information in

an easily understandable form, supporting fast reaction

to changing situations.

INSTALLATION

Integration tests using plant simulation are essential to

success, especially in conversion projects. For theDortmund plant, Siemens exhaustively tested the entire

automation system, including all control consoles, in the

test department in Erlangen before shipment. Then, the

r Fig.1 Main control pulpit

a


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FINISHING PROCESSES

system was set up onsite in Dortmund two months before

the main shutdown. This gave Siemens time to train TKSs

operating and maintenance personnel. By carrying out

ghost rolling with all production shifts, Siemens

eliminated a host of problems that would otherwise have

gone undetected until the plant was started up.

Extensive preparation, proven systems, and expert

installation management allowed the plant to start up

ahead of schedule on 31 August 2003, after only a 34-

day production halt. After a few days, the plant exceeded

the planned production figures. Analyses in October

2003 showed production quality levels comparable to

those found in the most-advanced tandem mills. Figures

2 and 3 show the mill.

On 26 November 2003, a major fire destroyed the entire

tandem mill area, interrupting acceptance testing. The

blaze affected all five rolling stands, the ventilationsystem, the roller installation crane, and the hall roof.

Twenty different companies and 350 employees worked to

repair the plant. Siemens supplied all rolling stand control

panels, plus decentralised process peripheral equipment,

sensors and other components in the stand area.

Renovation specialists from Siemens Industrial Services

helped clean up all electrical equipment that was not

directly affected. This made it possible to avoid downtime

for many components.

Original estimates suggested the plant would not be

available for three months. However, the rolling mill

started up again on 31 December, 35 days after the fire.

Once production resumed in January, the acceptance

tests were continued, with final acceptance in February

2004. Now that the Dortmund plant been brought up to

match the state-of-the-art standards of TKSs Duisburg

facility, TKS has two pickle line/tandem mills advanced

enough to meet any customer requirement. MS

Peter Hopf is Project Leader, Siemens AG, IndustrialSolutions & Services, Erlangen, Germany

CONTACT: [email protected]

q Fig.2 View along the mill stands

r Fig.3 Exit section of the modernised mill

pickle mill

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