Operating Instructions

Dong IL Paper Mfg., Co., Ltd.
BM 1, (KURKI)
Air Systems/H. Suikki/PNä December 14, 2007 i

4 OPERATING INSTRUCTIONS

1 AIR DRYERS .......................................................................................................... 1

1.1 Air dryer for board grades .............................................................................. 1
1.1.1 The operation principle .................................................................... 1
1.1.2 Retraction and supporting devices .................................................. 2
1.1.3 Circulation air equipment ................................................................. 4
1.1.4 Gas burner ....................................................................................... 5
1.1.5 Burner output / combustion air regulation ........................................ 5
1.1.6 Burner control .................................................................................. 6
1.1.7 Operational conditions and interlockings for burner ........................ 6
1.1.8 Automatic purging in normal circulation condition ........................... 7
1.1.9 Operation during web break. Short circulation equipment ............... 8
1.1.10 Preheating ....................................................................................... 8
1.1.11 Exhaust air equipment ..................................................................... 9
1.1.12 Make-up air equipment .................................................................... 9
1.1.13 Alarms ............................................................................................. 9
1.1.14 Maintenance .................................................................................. 10

2 VENTILATION EQUIPMENT OF INFRARED DRYERS ....................................... 12

2.1 Ventilation equipment for gas-heated infrared dryers .................................. 12
2.1.1 Combustion air .............................................................................. 13
2.1.2 Circulation air ................................................................................. 13
2.1.3 Interlockings .................................................................................. 14

PowerDry Classic air dryers 4 Operating instructions
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instructionsOperating_instructions.doc

BM 1, (KURKI)
Air Systems/H. Suikki/PNä December 14, 2007 1

1 AIR DRYERS

1.1 Air dryer for board grades

1.1.1 The operation principle

The hot circulation air is fed to the nozzles through the ductwork in
the air dryer box. The nozzles are near the paper web. Hot air is
blown towards the web through slots which are crosswise in view of
the paper web.

The air dryer boxes consists of boxes, under which the paper web is
going and the retraction and supporting device for opening the
boxes.

Hot blowing air to the air dryer

Humid air back to
circulation air ducts

Air distribution ducts
Blowing nozzles

Figure 1 Air dryer box

The air dryer nozzles are of Impingement type.


BM 1, (KURKI)

Figure 2 Impingement nozzle

This cooled and humid air is extracted between the blowing nozzles
into the air dryer box where it is led by ducts outside the air dryer
and into the circulation air ductwork.

There are perforated plates between the blowing nozzles to prevent
bits of paper from going into the circulation air.

1.1.2 Retraction and supporting devices

The nozzle surfaces of the air dryer are very close to the paper web
when operating. The air dryer boxes can be opened for tail
threading, cleaning and maintenance.

The air dryers are equipped with pneumatic hoisting cylinders which
can move the air dryer away from the web.

For cleaning of the nozzle area the tending side edge of the air dryer
can be hoisted 200 mm.

The air dryers open automatically after the web break.

In the automatic system the air dryer can be opened and closed.
Pre-alarm with electric bell will be given before retraction.


BM 1, (KURKI)

Each air dryer has sensors which inform the automation system of
the close position of the air dryer.

The supporting devices are equipped with manual mechanical safety
locks by which the air dryers can be locked in the open position.

CLOSING THE AIR DRYERS CAN BE PREVENTED BY A
MANUAL MECHANICAL SAFETY LOCKING DEVICE. SAFETY
LOCKING MUST ALWAYS BE USED IF ONE ENTERS BETWEEN
THE OPEN AIR DRYER.

Cylinder

Air
Dryer

Locked Open

Figure 3 Manual mechanical safety locks


BM 1, (KURKI)

1.1.3 Circulation air equipment

The circulation air is taken from the return air (humid air) duct of the
dryer and led to the circulation air fan. By the fan the circulation air is
blown through the burner to the air dryer.

Circulation air ductwork

The circulation air duct is connected by exhaust and make-up air
equipment which discharge the humid circulation air and bring in
drier air.

The supply and return sides of the circulation air duct are connected
by a by-pass duct before the air dryer. In the by-pass duct and in the
circulation air duct on the supply and return sides there are dampers
equipped with an actuator. These dampers prevent the circulation air
from flowing into the air dryer during a web break. There is a more
detailed function description in Section "Operation during web break.
Short circulation equipment".

Circulation air fan

The circulation air fan can be started and stopped in manual mode, if
the combustion air fan is running. If the fan is in AUTO mode the fan
can be started by using group start function, in that case the fan
starts after certain delay when exhaust fan and combustion air fan
are running.

The blowing velocity in the air dryer nozzle affects the air dryer
evaporation efficiency. The circulation fan has an inlet vane control
damper. Its set value can be changed to change the blowing
velocity.

Inlet vane control damper

The inlet vane control damper is closed when the circulation air fan
stops. The automation system also opens the inlet vane control
damper with a short delay to the set value after the start.


BM 1, (KURKI)

1.1.4 Gas burner

The gas burner is installed near the fan in the circulation air
ductwork. It is a duct type burner where the expanded part of duct is
equipped with a burner head composed of modules, a lighter, flame
control equipment and a combustion air duct.

Gas is brought to the burner through a special safety valve group
whose safety, ignition and flame control functions are automatically
operated by the control logic of the burner.

Gas needs enough oxygen for complete combustion. The burner is
equipped with a combustion air fan which takes air from the fan area
and blows it to the burner.

1.1.5 Burner output / combustion air regulation

The temperature of the air blown in the air dryer affects the
evaporation efficiency of the air dryer.

The burner output is changed by an actuator which regulates gas
amount.

The circulation air temperature of the air dryer is regulated by
changing the burner output by gas control valve.

Burner needs constant combustion air pressure and there is
pressure control loop in automation system. Setpoint for pressure is
fixed and operator can´t change it.

Short circulation

When the short air circuit is in use (web break, service) the control
circuit of the circulation air temperature gets it’s measurement value
from the temperature sensor after burner in the circulation air
ductwork. The control system force the setpoint of air temperature to
100 °C during the short circuit.


BM 1, (KURKI)

Normal operation circulation

During normal operation and pre-heating period when the air dryer is
closed the control circuit of the circulation air temperature gets it’s
measurement value from the temperature sensor in air dryer. The
temperature sensor in the circulation air ductwork serves as a
temperature limit sensor. The maximum air temperature is 350 °C.

The automation system measures the circulation supply air
temperature for the normal operation and the temperature can be
read in the display of the automation system.

1.1.6 Burner control

The burner can be started and stopped either locally in the burner
control box or alternatively in the automation system. The choice of
the burner control, local / remote, is made in the burner control
panel.

Failures can also be reset either locally or in the automation system.
There are signal lights for different failures in the burner control
panel and all the failure information is given as alarms to the
automation system.

1.1.7 Operational conditions and interlockings for burner
1 Emergency stop closes the gas safety locking valves and thus
stops the burners.
2 The burner is ready to start if:
− the exhaust air pressure is sufficient
− the combustion air pressure is sufficient
− the circulation air pressure is sufficient
− (i.e. the fans are really running)
− the temperature after the burner is under the pre-set
maximum limit
− the gas pressure is over the pre-set minimum limit
− the gas pressure is under the pre-set maximum limit
− the pre-purging sequence is proceeding without any
interruption


BM 1, (KURKI)

3 The burner starts (ignites) if:
− the pre-purging sequence has been completed
− the gas control valve is in min. position (low fire position)
− the flame scanner is working
− the selection switch in local burner panel is in local position
or, in case the selection switch is in remote position, DCS
program control “burner ready to start”
4 The burner starts automatically after "burner ready to start" mode
has been achieved (pre-purging completed).
5 The burner is working (burns) if:
− the flame scanner continuously recognizes a flame
− the "pre-purging completed" - information is continuously
valid
− the burner control internal failure checkings are not indicating
malfunctions

If any of the operating conditions mentioned above is not at hand,
the running burner is shut off or the ignition sequence is interrupted
and the signal lamp in the control panel of the burner shows the
actual failure. When the burner shuts off the gas valve automatically
moves into the minimum position.

In case of web break the burner control valves move to low fire
position.

When the burner has ignited and burns with minimum flame (low fire
position), a signal lamp is lit and the burner effect can be adjusted,
by regulating the main gas valve, to the desired level.

1.1.8 Automatic purging in normal circulation condition

Before the burners can be ignited locally or remote, a so called pre-
purging has to be carried out, by which any possible gas in the
circulation air ductwork is exhausted. The pre-purging sequence
takes ab. 60 seconds. The burner must continuously get the "pre-
purging done" signal in order to burn.


BM 1, (KURKI)

The one-minute pre-purging for normal circulation starts
automatically when the exhaust air, the circulation air and
combustion air fans are running. During the pre-purging the shut-off
dampers opens and by-pass dampers closes automatically (so
called long circulation), the exhaust air damper opens 100% and the
circulation air damper opens 100 %.

If these conditions are fulfilled during the pre-purging sequence, the
condition "pre-purging done" is valid.

The "Pre-purging done" condition has to be valid in order to be able
to ignite the burners and to run them.

The "Pre-purging done" condition disappears if the combustion, the
exhaust, or circulation air fan stops. A new pre-purging of the system
must then be carried out by starting the fan which has been stopped.

1.1.9 Operation during web break. Short circulation equipment

The starting routines of the burner take several minutes due to the
control and purging operations connected with the gas burner. In
order to avoid unnecessary delays, it is practical to keep the gas
burner and the air circulation running during short breaks.

Web break opens the air dryers and the system goes to the short
circulation.

During the tail threading the air flows in short circulation circuit
(through the by-pass duct to the inlet side of the circulation air fan),
preventing it from blowing into the air dryer.

1.1.10 Preheating

After a longer production stop the air dryer boxes have to be warmed
up before tail threading.

Preheating is operated from the air dryer display.

The operator gives the temperature set value and preheating
temperature set value from the display.

Air dryer ready for coating information is displayed in the air dryer
display and it is one condition of station ready for coating which is
indicated with signal lamp in the control box.


BM 1, (KURKI)

1.1.11 Exhaust air equipment

When returning from the air dryer, the circulation air has cooled and
the water evaporated from the web inside the air dryer has mixed
with the air. To ensure a stable water content in the circulation air,
the water picked up by evaporation must be removed before the air
is blown back into the air dryer.

Circulation air is "dried" by exhausting a certain amount of humid
return air, removing the water mixed with it.

There is one common exhaust air fan at coating station. The exhaust
air is taken from the circulation air duct and led directly outdoors.

The exhaust air amount is regulated with the damper of the exhaust
air duct. The leakage air temperature corrects the air amount.

If the fans are started with group start, the exhaust air fan will start
first of all fans.The exhaust air fans can be started and stopped in
manual mode without any interlockings.

1.1.12 Make-up air equipment

The exhaust air is replaced by drier air. The make-up air is sucked
directly from the mezzanine floor into the circulation air system. The
duct is equipped with a local manual control damper.

1.1.13 Alarms
• Circulation air fan
− Circulation air fan MCC failure
• Circulation air temperature control
− air dryer temperature too high
• Circulation air temperature before fan/burner
− temperature too high
• Combustion air fan
− Combustion air fan MCC failure
• Exhaust air fan
− Exhaust air fan MCC failure


BM 1, (KURKI)

• Burner control
− high temperature
− low gas pressure
− high gas pressure
− low process air pressure
− low exhaust air pressure
− low combustion air pressure
− low fire micro switch open
− flame off
− emergency switch
− burner in operation
− burner in local control
• Air dryer retraction
− time alarm if the top box does not close or open in valid time
− pre-alarm with electric bell will be given before retraction

1.1.14 Maintenance

Cleaning

To ensure fire safety and faultless operation, the air dryer and the
blowing nozzles must be kept clean both outside and inside.

The outside of air dryer is washed clean. The inside is blown by
pressurized air.

The blowing nozzles and the suction holes must be cleaned as soon
as they have got dirty. They are cleaned by a brush or a wet sponge.
It is not recommended to clean them by a water jet because hot
metal parts may be damaged. If the nozzles are blocked, problems
can occur in the coating. Therefore the nozzles must be cleaned at
every washing shutdown.

The nozzle surfaces must not be scratched.


BM 1, (KURKI)

Control and regulationof an air dryer

The following things must be checked at least four times a year:
• The air dryers moven open/shut without obstacles both when
cold and when operating.
• The air dryer is in the closed position against stoppers so that the
clearance in the drawing is in the attaching parts of pneumatic
cylinders.
• Heat expansion of the air dryer has no obstacles across the web
on the tending side.
• The safety locking mechanism for the open position of the air
dryer works well.
• The nozzle surfaces are clean.


BM 1, (KURKI)

2 VENTILATION EQUIPMENT OF INFRARED DRYERS

Infrared dryers are used for heating a certain material aglow. The
glowing surface placed near the paper web transfers its heat energy
by emission to the water in the paper.

The temperature of the moist paper web can be raised quickly by
means of the big energy transfer of the infrared dryer.

2.1 Ventilation equipment for gas-heated infrared dryers

The ventilation equipment of gas-heated infrared dryers is shown in
the flow sheet:

REGULATION DAMPERS
FOR MAKE-UP AIR AND
EXHAUST AIR

PREFILTER

FINEFILTER

PRESSURE DIFFERENCE
ALARM OF FILTER GUARD

PDA CIRCULATION
AIR FAN

COMBUSTION TIC
AIR FAN
TEMPERATURE
PIC CONTROL

PIC
PRESSURE PRESSURE
CONTROL CONTROL

REGULATION
DAMPER

HSZ

Figure 4 Ventilation equipment for a gas-heated infrared dryer


BM 1, (KURKI)

The function of the ventilation equipment of all gas-heated infrared
dryers is the same. The capacity of the infrared dryer is directly
proportional to the combustion air pressure. The pressure is
measured in the infrared dryer. The automation system has a control
circuit which regulates the correct pressure by means of a damper
located in the combustion air duct.

2.1.1 Combustion air

The combustion air system produces to the infrared dryer the air
needed for gas burning. The combustion air is taken from the fan
room, filtered and blown to the emitters.

The cleanness of the combustion air filters can be watched by
a differential pressure gauge which gives an alarm to the automation
system when the filter is dirty.

Limit values:
• clean filter 45 Pa
• filter to be replaced 250 Pa

The type of combustion air filters:
• fine filter: Viledon AC50 EU5

2.1.2 Circulation air

The circulation air system intensifies heat transfer and discharge of
the evaporated water by circulating hot air between the web and the
emitter.

The make-up air of circulation air is taken from the fan room and the
exhaust air is blown to the existing heat recovery and outdoors.

The circulation air temperature is regulated automatically by means
of dampers located in the exhaust and make-up air ducts. If the
temperature exceeds the set value, the exhaust air and make-up air
dampers open. The dampers are regulated in parallel, or both of
them are always equally open.

The circulation air pressure is kept constant by the regulation of the
inlet vane control of the circulation air fan.


BM 1, (KURKI)

2.1.3 Interlockings

The pressure control of the combustion air must always be in AUTO
mode and the operator gives the desired set value of pressure. The
minimum position of the regulator output is 40%.

The temperature control of the circulation air must always be in
AUTO mode and the operator cannot set it to MAN mode. The
minimum position of the controller output is 25%.

The pressure control of the circulation air must always be in AUTO
mode and the operator cannot set it to MAN mode. The minimum
position of the controller output is 50%.

During the start-up the supplier of gas-heated infrared dryers
regulates the actuator operating ranges of the ventilation equipment
of the gas-heated infrared dryers by means of mechanical limit
screws. This limited operating range is set as limit values of the
output of the process control system in question.

The gas-heated infrared dryers are controlled according to the
instructions by the supplier of infrared dryers.


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