union paper mills

8/8/2019 Union Paper Mills

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UNION PAPER MILLS

TRAINING REPORT SUBMITTED

BY

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CONTENTS

Union Paper Mills

1.1 Introduction

1.2 Products

Process and Working

2.1 Waste Paper

2.2 Pulping

2.2.1 Pulp

2.2.2 Re-pulping

2.2.3 Screening

2.2.4 Operational Parameters

2.3 Refiner

2.4 Paper Making

2.4.1 Stock Preparation

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2.4.2 Sheet Forming

2.4.3 Pressing

2.4.4 Drying

2.4.5 Sizing

2.4.6 Calendaring

2.4.7 Reel Slitting Machine

2.5 Boilers

2.5.1 Biomass

2.5.2 Fuel Launch System

2.5.3 Furnace

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2.5.4 Economiser

2.5.5 Multi Cyclone Deduster

2.5.6 Degasser

Maintenance

3.1 Pump

3.1.1 Gear Pump

3.1.2 Eccentric Screw Pump

3.1.3 Piston Pump

3.1.4 Centrifugal Pump

3.2 Bearings

3.2.1 Classification of Bearings

3.2.2 Selection of Bearings

Distributed Control System

Fire Safety and Control

Summary

Appendix 1 (Flow Charts)

6.1 Pulping Process

6.2 Paper Making Process

6.3 Boilers

Acknowledgements

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Union Paper Mills

1.1Introduction

1

UPM are the pioneers in manufacture of paper and paper boards, through the

environmentally green process of recycling waste paper, in the UAE. They are a part of a

major Dubai based business group viz. M/S M.A.H.Y. Khoory & Co.

Set up in 1988, the mill is the first of its kind in the region. Initially it was equipped

with a 100 tonnes paper making machine, a 500 tonne capacity pulping machine and four

diesel oil boilers. In 2005 it acquired a second paper making machine from Eu rope with a

capacity of300 tonnes. Recently the company has acquired 2 biomass boilers replacing the

diesel oil boilers. This change has got them several applauds as they make their intentions

for a greener environment. Apart from all the machinery, the paper mill also has a fullyequipped laboratory for quality control and to conduct research on raw material and

process.

1.2ProductsUPM has two machines operating twenty four hours every day producing 400 tonnes

of paper on an average daily basis. Different products include:

y Waste Based Fluting

y Waste Based Test Liner

y White Top Test Linery Unbleached Core Board


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Process and Working

2.1Waste Paper

2

The recycling process requires large amounts of waste paper each day for producing

pulp. The waste paper collected is strewn in with lots of reject material, thus the amount of

the actual raw material maybe less than the collected amount. UPM has a numbe r of

workers who are hired for collection of this waste paper across a number of cities. However

they also have to buy some fraction of waste paper from the markets to maintain a constant

feed for their machines.

Storage of raw material before being fed into the pulping machine


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2.2Pulping2.2.1 Pulp

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Wood and other lignocelluloses, such as straw or other annual plants consist of

many different cell types in which cellulose and hemicelluloses, and lignin are the main

chemical components. In the chemical digestion of lignocelluloses, lignin, which is

embedded predominantly between the wood fibres as a binder and i n the outer cell wall

layers, and the hemicelluloses are largely dissolved out of the fibre matrix. The cohesion of

the structural elements is lost in the process. The fibrous material obtained after digestion,

consisting principally of cellulose, is called pulp.

2.2.2 Re-pulping

UPM recycles paper; hence the only raw material needed in the pulping process is

waste paper and water.

The waste paper is fed into the drum rolls through a conveyor belt. The conveyor

belt ensures a steady supply of waste paper. It does so by constantly measuring the weight

of the raw material and accordingly adjusting the speed of the feed. The complete process is

controlled by manually initiating a set rate in accordance with the quantity of pulp required.

Also it is required to maintain a specific consistency. Hence, the required consistency is set,

and according to the amount of waste paper feed, respective amount of water is pumped in

from the storage tank.

Conveyor belt feeding raw material into the drum roll


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The entire length of the drum rolls is around 28.5 metres and has inclined plates

inside for beating of the paper. The rolls are rotated with the help of a 750KW upward push

gear motor. The paper beaten with the water forms pulp which is then diluted to get

required consistency and collected in a Bottom Vat Tank.

Drum rolls beating of waste paper with water to form pulp

From here the pulp goes through different stages of screening. At the end of the

screening processes, the pulp is then moved to the hydro drain where some amount of

water is removed from the pulp to increase its consistency. The pulp is finally stored in a

storage tank from where it sent for refining and paper making.

2.2.3 Screening

The waste paper contains a lot of reject material such as staple pins, plastics and

sand. To remove these and obtain pure pulp, it has to be passed through four stages ofscreening.

The first stage is relatively simple in which the large plastics and tapes are rejected.

This process occurs at the end of the drum rolls where the pulp is initially formed. Here

more water is added and the rolls have 10mm diameter hole all around its curved surface

area. So that the pulp is drained down to the Bottom VAT tank for storage and the large

impurities are rejected. After this process, the pulp undergoes more complicated screening


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processes. These processes follow a cascade system to minimize the amount of reject or in

other words to reduce wastage of pulp. The casca de systems for different screening

processes are also described below.

Coarse screening. In the second stage it goes through Coarse Screening Process.

Materials with dimensions of greater than 2.4 mm diameter are removed. The coarsescreener is a pressure screener. It consists of a rotating basket with the same rotational

velocity as the pulp. A rotating basket is used here as the reject material is large and by

rotation of the basket, the mechanical damage caused due to friction between the reject

particles and the basket is minimised, thus increasing the life of the screener.

The Coarse Screening Process consists of three screeners. The pulp init ially moves

into the primary screener whose reject moves to the secondary screener. The accept of

both these screeners moves to the Dump Chest where it is stored and sent for the next

screening process. The secondary reject moves to the tertiary screener. Tertiary accept goes

back to the secondary screener and its reject is finally thrown out.

Coarse screen basket with hole diameter of2.4 mm

Medium Consistency Cleaning.The accept from the coarse screening process then

undergoes Medium Consistency Cleaning. Here primarily sand particles are removed. The

MCC consists of a conical metallic flask. The pulp is pumped with high velocity tangential to

the cone curve. Due to gravity the pulp starts moving downward but rotating along the walls

of the cone. The sand particles being heavier stick to the walls whereas the pulp remains in


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the inner region. As the suspension moves down a fan pump a t the centre of the cone

pushes the pulp back up the cone and out through an opening on the top. The sand particles

move down and are rejected.

Cyclone screeners for removal of sand

Fine Screening. The pulp then goes to final stage; the Fine Screening Process. This

process rejects any particle with dimensions greater than 0.15 mm. It is also a pressure

screen in which inner propellants push the pulp outwards. However, here the basket is

stationary due to the small size of the impurity particles. Instead of holes, the basket in fine

screening has longitudinal slits of .15 mm width. This is necessary to avoid frequent

blockages in case of holes due to the extremely small dimensions. The pulp is now sent to

the hydro drain.


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Primary fine screener

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The cascade system of MC Cleaning and Fine Screening are similar to that of coarse

screening. However here, the accept of the secondary screeners moves to the primary

screener instead. Only primary accept is sent forward.

DCS image of Coarse Screen Cascade System


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2.2.4 Operational Parameters

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UPM has a pulping plant of about 500 tonnes. The feed rate of waste paper is about

17 -18 t/h. The consistency at the initial pulping stage is around 19%. Water is added in the

first simple screening process where the consistency drops to about 2 -3%. This is required

for minimal wearing of the machines during the various screening processes. After theCoarse Screening the pulp is diluted to around 1.1-1.2% consistency and after MC Cleaning it

is further diluted to less than 1% consistency. Total amount of water added in the complete

process is about 120 litres per second. Now, when the pulp moves to the hydro drain, water

is removed and a consistency 5-6% is maintained depending on the required gsm of the

paper product.

2.3Refining

After the pulp has been screened and its consistency increased, it is stored in the

receiving chest from where it then moves to the refining process. The objective of the

refining process is to break loose and fibrillate the fibres in the pulp. This process has a

marked influence on the quality of the pulp. The refiner shown below is a double disk

refiner.

Mechanical refiner


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2.4Paper Making9

Various quality requirements have to be met by various types of paper. The

machines and process for manufacturing different types of paper vary correspondingly.

However, the essential steps in the papermaking process that are sheet forming, pressing,

drying, sizing and calendaring are the same and have been unchanged for the past twomillenniums.

Paper consists essentially of fibres, either primary or secondary. The quality

characteristics of the finished paper sheet are determined by the fibre properties, which in

turn depend on the type of fibres and their treatment during pulping, the auxiliary agents

and additives and also the process conditions on the paper machine. Important quality

characteristics of the finished paper sheet are:

y The mass distribution on paper referred to as grams per square metre (gsm).

y The strength properties in machine direction and cross machine direction. Given as

the ratio between the two (MD/CD).

y The optical properties.

y The surface properties.

y Absorptive behaviour. Important here for printing purpose.

It must be noted that the most important working agent in the manufacture of paper

is water. Water is required to provide the individual fibres in the suspension with as much

free space for undisturbed movement, slowing down reflocculation. Water is required to

produce strength in paper which is a result of hydrogen bond form ation between fibres

during the drying process.

2.4.1 Preparingthe stock

During the process of paper making sometimes, due to a fault in the process or an

impurity, the paper breaks out before being dried completely. This paper falls into the brok e

tower which contains water. Also sheets of paper that are torn in the packing process are

manually thrown into this tower. The water-soaked paper from here is pumped into the

thickner where water is first removed and then added to get pulp of re quired consistency.

This pulp then goes to the broke chest where it is stored.

The pulp from the refiner chest is pumped into the Blender. In the blender, pulpcoming in from both refiner chest and the broke chest is mixed to get a pulp with uniform

consistency and is then pumped to the machine chest. A consistency of about 3 -4% is

maintained here. The pulp is then pumped to another screening process. The reject of the

primary screen goes to the secondary. The accept of the secondary is pumped back to the

primary and that of primary then goes to the paper making machine.


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Blender

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This screening process is carried out by pressure screens and is done to be

completely sure that there is no impurity present in the pulp to protect the headbox and

wires from any mechanical damage.

2.4.2 SheetForming

In the sheet forming stage a uniform sheet with definite properties should be

formed continuously. Here the water from the fibrous suspension is filtered off on a rotating

continuous wire to produce a water web. This system consists of stock approach, the

headbox and the wire.

Stock Approach System.It is responsible for metering the amount and type of stockcomponents used, mixing and for delivering the suspension in the required amount and

with the appropriate pressure to the headbox. The suspension delivered must be of

constant pressure, quantity and composition in order to ensure constant and uniform paper

quality.

Headbox. The headbox produces a jet of suspension which should have a largely

constant velocity, thickness and direction across width of the paper machine and be


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independent of time. Pumping the suspension to the headbox and their prior passage

through pressure screens creates a pressure variation. Thus pulsation dampers are used to

keep the velocity of the jet constant. The suspension which is delivered to the headbox

through a round cross-section is turned and distributed uniformly across the entire width of

the headbox. The suspension then flows out to the wires through a narrow slit. Important

here is that a suitable process for flow must be adopted to prevent any reflocculation of the

fibre.

Headbox and Wires

Wires. In the wire section, a fibre web is formed from the suspension. Primary

importance is given to three objectives; extensive separation of fibres from water or

dewatering, prevention of fibre flocculation, well-ordered deposition of fibres on the wire.

In the paper making machine used, dewatering is primarily being done by suction rolls.

These have an open shell and sometimes even vacuum is applied through the interior. The

water drained from here moves to the broke water tank.

2.4.3 Pressing

The objective of the press section is to increase the dry content of the paper web by

dewatering and to increase the strength of the web by compression before t he web enters

subsequent dryer section. This also saves energy consumed in the dryer section. The press

section usually consists of several successive press bi-nips. The web is transported between

one or two felts through the nip. The water removed f rom the web is stored and carried

away in the felt. It then moves to the back water storage tank. The most important

properties of the felt are the storage capacity under pressure, the water retention

behaviour on leaving the nip, which in turn, prevents rewetting of the web.


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Pressing section

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A newer technique known as shoe press is also employed in the pressing section.

The line of force here can be varied locally across the width. Thus desired properties of

paper can be varied accordingly.

2.4.4 Drying

As indicated, the water is removed in this section by heating. The heating effects in

fibre-fibre bonding via hydrogen bonds and the web strength is increased. Dry content of

the web after this section is above 95%.

The web is transported through a long course of steam heated cylinders. Dryer felts

press the web against the drying cylinder for better heat transfer. The dryer section is

aerated with hot air to carry off the water vapour generated and to i ncrease drying

efficiency. The entire dryer section is enclosed in a drying hood. Apart from this technique

used in the plant, forced convection drying and infrared drying are also used in the paperindustry.

During drying process, the paper web shrinks. The extent of shrinkage really depends

on the stock type, ie. degree of beating or the fibre orientation. Longitudinal shrinkage can

be controlled by stretching between individual drying groups. However shrinkage across the

width is non-uniform and higher at the ends than the centre of the web.


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Drying section

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The steam required for the drying process is produced in the boilers. Boilers are

discussed in section 2.5.

2.4.5 Sizing

During size press, starch, size or pigments are applied to the fibre matrix to increase

the strength of the paper and to modify the surface properties with respect to liquid uptake

during writing, printing, or coating.

In sizing, a thin layer of size is applied to the paper just before it moves into the roll

nip. As a result of the hydraulic pressure in the roll n ip, the paper web absorbs the sizing

liquor. The amount of size taken up by the paper depends on the dry content of the web. To

guarantee uniform size uptake across the width, the web must be pressed uniformly across

the width in the nip and must exhibit constant moisture content.


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Red pipe transferring the additives being sprayed on the paper

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The water applied in the size press is evaporated in the after -dryer section. This

section is similar to the initial drying section; however the temperatures of the steam are

kept higher in this section.

2.4.6 Calendering

The objective of this exercise is to produce a smooth paper surface which meets therequirement of printing and writing. Apart from increasing smoothness, calendering also is

used for thickness reduction. However apart from thickness; the opacity, tear s trength and

absorptivity of the paper maybe reduced to a certain extent.

The web is fed through counteracting cast-iron press rolls and in this process the

surface roughness of the web is levelled by the action of pressure. The web is passed

through the press nips of these rolls.

The level of smoothness that can be attained is greatly influenced by the type of

stock, the moisture content of the paper web, the temperature of the paper web, the

pressure applied by the roll nips, the retention time in the nip and also the surface

temperature of the roll.


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2.4.7 Reel-Slitting Machine

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In the reel-slitting machine, the paper web is cut to the width required for further

processing. The functions of a reel -slitting machine include:

1. Unreeling the roll present in the full paper machine width.

2. Cutting to the desire web width.

3. Reeling the individual rolls on to separate cores.

The web is cut with rotating circular knives of high alloy tool steel. At a defined

contact pressure, the disc shaped knives penetrate into the paper. the positioning of the

knives and, consequently, the adjustment of the roll width is performed manually or

automatically.

The most important requirements to be met by the cut rolls with regard to further

processing (printing, cross cutting) are uniform reel hardness across the width of the roll

and in the diameter, straight front surfaces, and absence of roll defects and roll damage.

Now the paper is ready to be packaged and sent to the storage hous es. From here it

is then delivered to the target industries.

Reel slitting machine


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2.5Boilers16

Temperatures of the cylindrical rollers in the dryer section vary from 80oC 110

oC.

These temperatures of the surface are obtained by passing superheated steam through

these hollow cylindrical rollers. For round the clock operation of the plant large amount of

steam is required in a continuous supply. This steam is produced by heating of water in largeboilers.

Initially there were four diesel-oil boilers catering to the steam requirement.

However these have now been replaced by 2 large bio-mass boilers. This move has greatly

reduced the emission of poisonous effluents produced by burning of diesel -oil.

Diesel oil boiler

2.5.1Bio-Mass

Bio-mass is a renewable energy source. It is biological material derived from living or

recently living organisms such as wood, waste, (hydrogen) gas, and alcohol fuels. Biomass is

commonly plant matter used to generate electricity or to produce he at. In this case,

biomass is used to produce heat which is transferred to water to convert it into superheated

steam.

The fuel used in the biomass boilers here mostly consists of old discarded wooden

crates, wooden furniture, branches of dead trees and so on. It is collected by the company

as well as bought from the market. Before being fed, these large pieces are first cut in a

machine. It breaks the pieces of wood into uniform sized chips which helps in better feeding

and control.


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inclination of approximately 15o. Apart from all this, additional fire safety equipment is

present in the Fuel Launch System in case of any back fire.

Boiler showing FLS, furnace, economiser and MCD

2.5.2Furnace

The furnace floor is lined with grates, where the fuel moves. It is primarily divided

into 5 stages. These are Drying, Pre-combustion, Combustion, Post combustion, and De -

ashing.

The furnace is lined with water columns and the fixed step grates below are lined

with a grid of water pipes. The heat generated in the furnace upon burning of the fuel isused up by the water in the water columns and is converted to steam. The temperatures

reached inside the furnace are of the range 650oC-800

oC. The water grid is placed to remove

local heat from the grates. This water is pumped in and thus it is known as forced cooling

system. As this water absorbs heat, its temperature rises and is thus useful in preheating in

the degasser.

Steam that is lower in temperature comes in from the paper machines and is stored

in the steam collector. From here it moves to the degasser. Water also is pumped into the

degasser where it is preheated in the presence of steam. This water then passes through the

economiser, the steam drum and finally to the water columns in the furnace. All this whilepreheating of the water is underway.

Now in order to continue combustion inside t he furnace, a constant supply of oxygen

is required. This is provided through two air fans. The primary air fan pushes air from

outside into air boxes that are lined through the furnace. The secondary air fan pushes air

through the grates.


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Steam generated then moves into the steam drum and then to the pipes from where

it is carried to the dryer section of the paper machines. The effluents on the other hand

from the furnace go to the economiser, where their h eat is used to preheat the water, and

then to the multi cyclone deduster. From the deduster the effluents free of dust particles go

the back filters and finally escape through the chimney.

2.5.3 Economiser

The economiser is long airtight container with a winding of pipes inside. Water, to

the water columns in the furnace, moves through these pipes. Outside these pipes, effluents

and dust produced during combustion; move in the opposite direction t owards the multi

cyclone deduster. The main object of the economiser is to save energy by preheating the

water by passing it through the hot effluent gasses, thus, utilising the heat energy of the

waste gasses. The economiser is also lined by soot blowers along its walls. These remove the

ash that gets deposited on the pipes.

2.5.4 Multi Cyclone Deduster

Effluent gasses and dust particles pass through the economiser and into the multi

cyclone deduster. The use of this is to remove the ash and dust particles mixed with the flue

gas before they can escape through the chimney.

The flue gasses and the ash particles enter the flue chamber horizontally. The flue

chamber is lined with conical funnel shaped dedusters. These are homogeneously spread

throughout the chamber by specific positioning. The gasses enter these cyclone dedusters

horizontally into their whirl chambers. Here the dust particles are brought into fast rotation

and due to centrifugal forces they are pressed to the outside walls. Now due to gravity,these particles steadily move downwards and through the bottom of the funnel they are

removed into an ashbin.

The flue gas on the other hand being lighter remains in the centre of the cyclone

deduster and with the help of a flue gas fan in the centre, they are pushed up through an

outlet from it rises through the inner tubes into the purified flue gas collector. These gasses

then go into the back filters where after further treatment they are discharged through the

chimney.

It must be noted that sealing is a very important parameter in the working of the

multi cyclone deduster. Even a small leak can cause a significant reduction in the efficiency

of the MCD.

2.5.5 Degasser

The water sent to the water columns is first passed through the degasser. Here

water is sprayed through tiny nozzles for maximum surface area between steam and water.

When water at saturation point comes in contact with steam, the oxygen escapes from the


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water into the steam by Henrys Law. Hence the solubility of oxygen in water at saturation

point is practically zero.

Henrys Law states that the amount of gas dissolved in a given type and volume of

liquid is directly proportional to the partial pressure of that gas in equilibrium with that

liquid.

The pulper, the boiler and the paper machines are broadl y the three different

sections that constitute the paper industry. Each of these has their specialised and

dedicated supervisors, operators and workers.

Boiler - the back filters and the chimney


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Maintenance

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All the machines used in the three different sections discussed above are very large

and involve a lot of moving and stationary parts. Thus there is a constant wearing down of

the components and their proper maintenance and care is essential. The Union Paper Millshas a detailed maintenance programme and a dedicated unit for this purpose. They have

regular maintenance shutdowns to replace parts that may damage the system and to keep

the machines running at their optimum potential. They also have a fully equipped

workshop, a large storehouse and even a laboratory to ensure their product quality is

maintained in accordance with standards. Discussed below are two very essential

components of any machine; pumps and bearings.

3.1PumpsA pump is a device used to move fluids, such as liquids or slurries, or gasses. A pump

displaces a volume by physical or mechanical action. Pumps fall into five major groups:

direct lift, displacement, velocity, buoyancy and gravity pumps. Their names describe the

method for moving a fluid. Each of these categories consists of a number pump types. We

will be discussing a few of them; some of which have been used quite commonly in the

plant.

3.1.1 Gear Pump

A gear pump uses the meshing of gears to pump fluid by displacement. They are one

of the most common types of pumps and have been used in a number of applications in the

plant. There are mainly two main variations; external gear pumps which use two externalspur gears, and internal gear pumps which use an external and an internal spur gear.

As the gears rotate they separate on the intake side of the pump, creating a void and

suction which is filled by the fluid. The fluid is carried in teeth of the gear to the other side of

the pump, where the meshing of the gears displaces the fluid. Th e tight clearances, along

with the speed of rotation, prevent the fluid from leaking backwards. The rigid design of the

gears and appropriate bearings used allow for very high pressures and the ability to pump

highly viscous fluids.


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3.1.2 Eccentric Screw Pump

External gear pump working

Internal gear pump working

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An eccentric screw pump transfers fluid by means of the progress, through the

pump, of a sequence of small, fixed shape, discrete cavities, as its rotor is turned. The

volumetric flow rate of the fluid thus depends on the speed of rotation and to the level of

shearing forces applied to the liquid.

It consists of a helical rotor and a two start, twice the wavelength and double the

diameter helical hole in a rubber stator. The rotor seals tightly against the rubber stator as it

operates, forming a set of fixed-size cavities in between. The cavities move when the rotor is

rotated but their shape or volume remains the same. The pumped material is moved inside

the cavities.

Often it is believed that the pumping occurs due to the dynamic effect of the drag, or

due to friction against the moving teeth of the screw rotor. However, this is not the case. It

is actually due to the sealed cavities, like a piston pump. It is thus able to operate at

extremely low rates, even to high pressure.


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3.1.3 Piston Pump

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The piston pump consists of a simple piston and cylinder arrangement. Here the inlet

valve is first opened to allow fluid into the cylinder. After filling, the inlet valve closes and

the piston pushes in. Now the outlet valve is opened and it pushes out the fluid from the

cylinder. After emptying the fluid, the outlet valve closes, and the piston moves out,creating a vacuum which is filled with fluid from the inlet valve again. The piston pump also

comes under the category of a reciprocating pump.

3.1.4 Centrifugal Pump

It consists of an eccentric rotor which rotates at a high velocity. The impellers are

mounted through a spring on the eccentric rotor. The length of the impellers is such that it

keeps the spring unstressed in the maximum radius region and compres sed inwards in the

minimum radius region. The impellers give a rotating motion to the fluid and push it

forward. The fluid is inlet into the larger radius region and is rotated to the discharge side or

minimum radius region. The difference in volume pushes the fluid forward.

In most centrifugal pumps, for pumping fluids with low viscosity such as water, the

minimum radius is kept to a zero to avoid any back flow. However in more viscous fluids and

thick oils, some tolerance is set to avoid jamming of the pumps.

3.2BearingsA bearing is a mechanical device to allow constrained relative motion between two

or more parts, typically rotational or linear movement. Bearings maybe classified according

to the motions they allow and according to their principle of operation as well as by the

directions of applied loads they can handle. The bearings that are discussed in the following

text allow rotational motion only. However, some of them can bear both radial as well as

axial loads.

3.2.1 Classificationofbearingsonthe basisofthe moving parts andloadhandled

y Ball bearings

y Cylindrical roller bearings

y Needle roller bearings

y Taper roller bearings

y Spherical roller bearingsy Toroidal roller bearings

y Thrust bearings

Each of these bearings has a number of variants. Such as the ball bearings may be

deep groove ball bearings or angular contact ball bearings. These may also be in a

combination with each other such as combined needle roller and angular contact ball

bearings or combined needle roller and cylindrical roller thrust bearings.


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3.2.2 Selectionofbearingtype

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Each bearing type displays characteristic properties, based on its design, which make

it more, or less, appropriate for a given application. Several factors have to be considered

and weighed against each other when selecting a bearing type. Some of the important

factors to be considered when selecting a standard bearing type are

y Available space

y Loads

y Misalignment

y Precision

y Speed

y Quiet running

y Stiffness

y Axial displacement

y Mounting and dismountingy Integral seals

Available space. In many cases, one of the principal dimensions of a bearing, thebore diameter, is predetermined by the machines design and the shaft diameter.

Loads.The magnitude and direction of load both play a vital role. The magnitude of

load usually determines the size of the bearing. Whereas depending on the load, ax ial or

radial, the choice of bearing may vary. Certain designs of cylindrical bearings and oroidal

bearings can support only pure radial load. Others may accommodate some axial load, and

thrust ball bearings may accommodate loads that may be purely axial. Certain types of

double row bearings can also handle a moment load.

Misalignment. Angular misalignment between the shaft and housing occur, for

example, when the shaft bends (flexes) under the operating load, when the bearing seatings

in the housing are not machined to the same height or when shafts are supported by

bearings in separate housings that are too far apart.

Precision.Bearings with higher precision than normal are required for arrangements

that must have high running accuracy as well as those applications where very high speeds

are required.

Speed. The permissible operating temperature limits the speed at which rolling

bearings can be operated. Bearing types with low friction and correspondingly low heat

generation inside the bearing are therefore the most suitable for high -speed operation.

Quiet running.In applications such as for household appliances or office machinery,

the noise produced in operation is an important factor and can influence the bearing choice.


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Stiffness.The stiffness of a rolling bearing is characterised by the magnitude of the

elastic deformation in the bearing under load. In most cases this deformation is very small

and maybe neglected.

Axial displacement. Shafts, or other rotating machine components, are generally

supported by a locating and non-locating bearing. Locating bearings provide axial locationfor the machine component in both directions. Non-locating bearings must permit shaft

movement in the axial direction, so that the bearings may not be overloaded.

Mounting and dismounting. Frequent mounting and dismounting requires easily

separable bearings.

Integral seals. The selection of a seal is of vital importance to the proper

performance of the bearings.


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Distributed Control System (DCS)

26

A distributed control system refers to a control system usually of a manufacturing

process or any kind of dynamic process, in which the controller elements are not central in

location; rather, they are distributed throughout the system with each component sub -system controlled by one or more controllers. The entire system of controllers is connected

by networks for communication and monitoring.

A DCS typically uses custom designed processors as controllers and uses both

proprietary (manufactured exclusively by the organisation installing the system, as with a

patent) interconnections and communications protocol for communication. Input and

output modules form component parts of the DCS. The proc essor receives information from

the input modules and sends this to the output modules. Input modules receive information

from the input instruments which in turn receive from it from the Human-Machine

Interface. The input modules then transmit these instructions to output instruments. Eachof the pulper, the paper machines and the boilers has their own dedicated DCS.

DCS of the Biomass boilers DCS of the Drum Rolls in the pulper


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Fire Prevention and Safety

27

The raw materials used by UPM as well as their finished product, are both

combustible substances. The waste paper used in the pulping process, the wooden chips

and waste used in the bio-mass boilers as well as the final paper product are allcombustible. The fire caused by or in any of these can be categorised as TypeA kind of fire.

A number of different varieties of fire extinguishers are available for initial response

to this type of fires. These include dry chemical powder extinguisher, carbon dioxide

extinguisher and AFFF foam type extinguishers. These h ave been placed at easily accessible

locations within short distances. Apart from these water hoses are also installed which draw

water from a ready water reservoir.

Main sections that need to be regularly monitored include the storage of raw

materials and the dryer section where the temperatures are very high. Being located in a

desert, the daytime temperatures soar extremely high which multiply the risk of large fires

in the raw material storage section. Heat and ample fuel make containing such fires difficult.

To prevent fire in the dryers, good housekeeping of the section is important. The plant

maintains a strict no smoking policy within the premises.

The electricity consumption, for non-stopping functioning of the machines, is also

high. Also an elaborate system of cables has to be installed for the DCS. Hence apart from

Type A fires, the industry also faces potential threats of electrical fires or Type C fires. A

separate fire fighting approach needs to be taken for this category of fires. Water or foam

type extinguishers cannot be used here. Only the dry chemical powder extinguisher and the

carbon dioxide extinguishers should be used. Main cause of such fires is improper insulation

and stacking of cables in a hazardous order.

To avoid confusion in testing situations, all the extinguishers are marked with their

compatibility of the type of fire. The plant engineers and workers are also i nformed about

the classes of fires and their first response action. A fire safety alarm system is also installed,

though it has yet to be tested. Fire fighting and safety equipment are yet to be installed in

the recently set up biomass boilers.

So far the plant has seen minor fires in the dryer section and a medium intensity fire

in the raw material storage system. Barring these few minor incidents, the plant has a goodfire prevention and safety record.


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Summary

28

Situated in Al-Quoz area of Dubai, Union Paper Mills is one of the largest

manufacturer of paper and paper products in the Middle East, serving the paper

requirements of the Middle East and regions of South East Asia since 1988. UPM producesc.400 MT ( utilising 100% production capacity ) of paper per day by utilising c.480 MT of

waste paper.


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Appendix1

Pulping Process

Waste paperthrough conveyor

belt + water pumpedfrom tank

Cascade Coarse

Screen

Hydro-Drain to

increase consistency

Paper Making Process

Headbox andwires

Sizing

Reel slitting

Drum rolls beat thetwo raw materialstogether to form

pulp

Cascade MC

Cleaning

Pressing

Drying at highertempratures

Initial screeningfollowed by storage

in Bottom VAT

Cascade Fine Screen

Drying at lowertempratures

Calendering

29


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Boilers

WoodenChips

Air

Boiler

Steam

Water

30


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Acknowledgements

31

I most sincerely thank the Union Paper Mills and its employees for their warm

support and guidance and for making my training at the plant an informative and enjoyable

experience. I would like to mention special thanks to:

1. Mr D Gandhi

2. Mr. T. Anjaneyulu

Ge w Works Manager

Produc Production Manager

Engine

union paper mills

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