OPERATING AND MAINTENANCE MANUAL

FOR

CONTINUOUS MESH BELT HARDENING AND TEMPERING PLANT

CLIENT

STEEL ACCESSORIES LTDBANGLADESH

TABLE OF CONTENTS

S.No. Description Page No.

1. INTRODUCTION 03

2. TECHNICAL SPECIFICATIONS. 06

3. PLANT DESCRIPTION. 09

4. PREVENTIVE MAINTENANCE. 19

5. TROUBLE SHOOTING 21

6. SAFETY INTERLOCKS 24

7. DRAWINGS 26

8. CALIBRATION 27

9. ACCIDENTS - HOW TO AVOID THEM? 29

10. ESSENTIAL SPARES 31

11. LIST & MAKES OF BOUGHT-OUT COMPONENTS 34

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1. INTRODUCTION

The intent of this manual, appendixed documents, and drawings is to provide the necessary instructions to install, operate and maintain Fluidtherm’s continuous mesh belt plant. It is recommended that these instructions be read carefully before installing and operating the furnace and its related equipment.

WARNING

PERSONAL INJURY MAY RESULT IF THIS EQUIPMENT IS OPERATED OR MAINTAINED BY UNTRAINED PERSONNEL WHO ARE NOT PROFICIENT IN THE FUNCTIONS OF ALL OF ITS SYSTEMS NOR IN THE HANDLING OF MATERIALS BEING PROCESSED. THE FOLLOWING MUST BE OBSERVED TO AVOID PERSONAL INJURY.

1. Refer to the instruction manual and supplied drawings before operating or maintaining the equipment.

2. DO NOT remove or bypass any safety items or electrical circuits.

3. Avoid contact with hot surfaces and electrical cables and connections.

4. Disconnect all electrical power suplies to any item being serviced before doing any maintenance work on it.

5. Shutting off the furnace at the control cabinet DOES NOT mean that the power supply is disconnected from the control cabinet. Personnel must be thoroughly trained in the proper methods for disconnecting power in order to do maintenance work.

6. Always use EXTREME CAUTION when working with or near volatile or noxious atmospheres or gases.

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2. CAUTION

1.0 Never use Flowmeters as shut-off valves. Shut-off protection is provided elsewhere on the furnace.

2.0 Be sure all operators of this furnace are well trained in the use of all atmosphere safety systems in order to avoid accidental harm to personnel or to any equipment.

3.0 Do not open hot furnace roofs as this will burn the roof seals & any piping/wiring in the vicinity & expose immediate area to intense high heat. Provide suitable protection for fire prevention of building, electrical wiring, lights, gas lines, building heaters, hoists and sprinkler heads.

4.0 This furnace must be grounded according to local electrical codes.

5.0 Do not touch or handle bare thermocouple junctions. Human body salts and oils adversely affect thermocouple performance and durability.

6.0 Thermocouple leadwires must be kept separate from any and all other wires or power leads. Running them through a separate conduit is a convenient way to ensure this.

7.0 Never load parts in excess of 160 Kg per square meter of belt. The belt width becomes narrower as it ages.

8.0 Never load parts in excess of 330 Kg/Hr.

9.0 Do not bypass any safety interlocks provided.

10.0 Do not remove covers on ignition transformer leads. High voltage when ignition occurs could damage transformer and surrounding parts.

11.0 Always maintain correct oil levels in the gearboxes. Don't over or under fill.

12.0 Replace blown fuses across the PLC and never short them. This will damage the input & output modules and cause long term shut down.

13.0 Furnace fans are to run clockwise looking from top downwards on the pulley. Never run anti clockwise as it will damage the fan.

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14.0 The furnace belt is provided with a mech oxid stopper at the entry. An overload situation may raise the counter weight roller when the roller meets the stopper it will trip on unload.

15.0 Never operate the plant at low oil level in the quench tank. Low level creates an explosive situation.

16.0 Always have entry & exit on burning off exhaust gases.

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2.0. TECHNICAL SPECIFICATIONS

(Note: Minor variations / adjustments may occur duringdetailed engineering)

HARDENING FURNACE

Capacity : Depends on component geometry

Typ 330 Kg/ Hr through hardening @ belt loading of 160 Kg/SqM (reference belt speed – 40 mm/min.) and a residence time of 100 minutes (approx).

Operating temperature : Max. 950°CNormal 920 + 10°C

Belt material : SS 314Belt width : 850 mmEffective upturn / side : 25mmInlet height : 200mmBelt hot length (effective) : 4500mmBelt speed range : 20 – 100mm / minuteNo. of control zones : 3 off

Connected load

Heaters : 67.5 + 45 + 45 kWBelt Drive : 1 x 0.37 kWSuction blower : 1 x 0.187 kW

QUENCH TANK

Tank capacity : 13,100 LitersConveyor width : 900 mmConveyor speed range : 616 mm/minPreheating of oil : Through dummy charge

Connected load

Conveyor drive : 1 x 0.75 kWPump for heat exchanger : 1 x 3.75 kWQuench sludge transport : 1 x 1.5 kWPump for cascade : 1 x 3.75 kW

POST WASH MACHINE:6

Belt width : 900mmCapacity : 6223 Ltrs

Connected load

Conveyor drive : 1 x 0.75 kWSpray pump : 1 x 3.75 kWHeaters : 27 kWSkimmer pump : 1 x 0.375 kW

CONTINUOUS TEMPERING FURNACE:

Capacity : 330 Kg/hr typ. at a belt loading of 160 Kg/ Sq.m, belt speed of 26mm/min and a total residence time of 5 hrs.

Belt speed : Variable 11to 83 mm/minOperating temperature : 600°C (max)

230°C (Normal)No. of zones : 3 offType of thermocouple : “K” type

Connected load

Heaters : 59.8 + 34.45 + 26.5 + 39.75 kWBelt drive : 1 x 0.37 kWFans : 5 x 3.75 kW

Width : 1300mmHot zone length : 8000mmInlet height : 200mm

Total plant kW : 379.5 k W + 10%

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GENERAL FEATURE

Provision for purging Media hardening : Nitrogen/LPG

Shell painting : Al. Paint

PLC – I/O Module : 10% Extra

Prov. Constant preheat time : with Icons

Furnace opening height : 200 max

Control hardening furnace &Tempering furnace : PID Thyristor & ON/OFF respectively

Drip trays : Yes

Time temperature Recorder : Via Flash card

Over all floor space : 33m x 6.5m

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3. PLANT DESCRIPTION

DESIGN BASIS :

THIS PLANT IS SPECIFICALLY DESIGNED FOR BEARING RACES AND ADDRESSES THE SPECIFIC ASPECTS OF ;

1. DISTORTION. A special quench design restricts ovality even on large dia thin wall rings.

2. MICROSTRUCTURE. A consistent and precisely controllable dissolved carbide content with good surface integrity.

3. RETAINED AUSTENITE. With the optional intermediate cooling tank, very low levels of retained austenite are obtained.

4. QUALITY CONSISTENCY. A very high Cpk value is obtained due to the consistency of properties of all bearings processed in the plant.

These furnaces, meant for processing of bulk produced parts are designed specifically with a view to reduce distortion, improve consistency in hardness ensure good surface chemistry and operate continuously in harsh production conditions with minimum manpower and maintenance expense. To achieve all this the plant is equipped with the following features.

Energy saving is coupled with reduction in distortion in all furnace models by the use of a HOT BELT RETURN system. The majority of the heat contained in the outgoing belt is efficiently transferred to the incoming belt + components, which will consequently consume less energy for heat up. An auxiliary benefit of such preheating is that component distortion is also reduced.

A narrow “deep throat” entry design reduces the gas consumption.

The hot belt preheating coupled with the deep throat design combine in keeping out residual lubricant vapor from the hot zone. As the velocity of the outgoing gases increases in the constricted deep throat it drives residual lubricant vapor (emitted from the preheated components and belt) out of the hot zone.

The furnace shell is welded gas tight and all leadouts are through sealed ports. Radiant tube heaters are disposed horizontally above and below the belt.

The radiant tubes are designed for side extraction and replacement “on the run” without having to shut down or open the furnace.

The plant design enables belt replacement from outside without having to open the furnace.

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Distortion is reduced by a special system that reduces the momentum of the quenched rings coupled to preheating for stress relief.

The quench tank comes with cascade spray in the chute area, strategic agitation headers and a chute shoe that ensures positive component seating on the conveyor.

The chute and quench tank are of a special design to reduce distortion, prevent component mix up which in turn reduces the idle time when component types are changed.

Components preferably washed before and after they are hardened and for this purpose several types of washing machines are available. The most common is a single / double chamber tank with a conveyor; spray system on the conveyor and a water blow off blower at the discharge end.

Several levels of automation are available for the control of the furnace and auxiliary equipment varying from manual supervision with push button and switch control through to total process automation via a PLC and various sensors, all working through a SCADA process control software, operated on a man machine interface unit with graphic display, data & event recording and reporting in Windows Excel spreadsheet format.

AN IMPORTANT FEATURE OF THE OVERALL DESIGN IS THE HIGH CONSISTENCY OF OUTPUT QUALITY. A Cpk OF AS HIGH AS 4.11 HAS BEEN RECORDED WITH FLUIDTHERM WIRE MESH BELT FURNACES.

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FURNACE ENTRY ARCH WORK

6-12 2 - 4 4 - 12 10 - 20

START OF FURNACE PREHEAT SECTION

END OF UNHEATED PREHEAT SECTION

START OF FURNACE

HOT ZONE

QUENCH DROP POINT

840C to 900C

400C to 600C

300C to 500C

MINS. MINS. MINS. MINS.

2.0 Fluidtherm Continuous mesh belt furnace:

Construction features:

Structure: The bottom resting frame of the furnace and the entry (charging) section are constructed from rugged, hollow, sections duly aligned and painted.

Shell: The furnace shell is made in mild steel plates duly stiffened & painted, with ports for radiant tubes (to a terminal box), rollers, thermocouples, fans etc. Flanged opening are provided for access into the furnace from the rear, sides and the top. View ports are provided at the rear and top. The shell is welded gas tight & pressure tested before insulation.

Entry hood: A hood is provided at the front end of the furnace to trap outgoing fumes and atmosphere gases. A pilot torch and flame curtain is provided to burn off outgoing gases.

Insulation: The bottom and the side walls are made up of refractory bricks while the roof is ceramic fibre lined. The refractory profile is computer designed for reduced wall losses and skin temperature.

Radiant tube heaters: Heaters are made in NiCr wire bundles threaded into and spaced by high alumina ceramic formers. Each bundle is inserted into an alloy 310, tube with special ALOX coating with a flange at one end and a welded cap on the other. Gas tight seals are provided for fixing the tubes to the shell. Heaters in each of the control zones will be parallel connected across a transformer.

Conveyor belt: Made in heat resisting steel (314) alloy. The belt weave will be appropriate to the components being processed.

Belt return roller: The rollers are made in HK grade centrifugally cast heat resistant steel and are driven at a surface speed equal to the belt speed.

Belt support rollers: The belt is supported by a series of rollers (alloy HK centri cast) driven at a surface speed equal to the belt speed.

Belt drive: The drive package consists of an AC motor and gear box fitted to chains & sprockets which impart motion at the desired RPM to the belt as well as to all the furnace rollers. The belt speed is infinitely variable through a variable frequency AC drive unit (Allen Bradley). A belt tensioning system is provided. A belt tracking (straightening) arrangement with bearings mounted in the entry section is also provided.

Temperature control: Temperature in all control zones is thyristorised (phase angle fired EUROCON) and controlled by means of microprocessor based multifunction PID controllers (FUJI) with an accuracy of + 3 %, auto tuning of PID values, two auxiliary relay outputs and thermocouple break error warning.

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Overtemperature control is provided from the second set point of the main temperature control.

Quench chute: A chute lined with alloy 310 plates is provided below the belt return roller for passage of components to the quench tank.

Atmosphere feed system: An atmosphere panel is supplied with streams for Nitrogen & LPG. 5 flowmeters 3 for Nitrogen , 2 for LPG wil be provided with hand valves, solenoid valves for LPG line, pressure gauges and switches, pipe fittings and piping, all mounted on a frame furnace attached.

Conveyorised Oil Quench Tank:

Shell: Mild steel duly stiffened and painted.

Conveyor: High Carbon Wire mesh belt type conveyor with bolted on slats and side walls. The belt width is greater than the width of the belt of the companion austenitising furnace. The belt is fastened to cross bars terminating in rollers that travel on profiled channels mounted on a removable framework.

Belt drive: This consists of one top mounted driven roller and one bottom mounted idler roller. The drive is effected by a AC motor & gear box and the conveyor runs at a fixed speed.

Quench shoe : A cowl is provided over the belt and around the quench chute of the furnace that ensures that components do not fall outside the conveyor belt.

Anti impact & distortion device : Anti impact distortion device is supplied to break the momentum of the parts falling through the furnace chute and eliminate the impact of the parts on the quench conveyor.

Quench cascade : A horizontal centrifugal pump is provided for quench cascade in the chute.

Quenchant cooling : Cooling is effected with a horizontal centrifugal pump which pumps the quenchant through a shell tube heat exchanger. All piping, valves, etc between the tank and heat exchanger are supplied.

Quenchant level indication: A floating ball with visual level indication for low, very low and high oil levels is provided.

2.1 POST WASH MACHINE (DUNK & SPRAY TYPE):

This consists of a heated & insulated tank with a mesh belt conveyor with slats. The components upon exiting the prior conveyor fall through a chute onto the conveyor within the heated wash tank. This consists of an endless belt going around two rollers one of which is immersed under the liquid level and the other above. The conveyor

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has upturned edges to prevent component spillage. A set of sparge pipes with nozzles are provided to spray hot cleaning media onto the components as they travel up. Controls are provided for tank heating and spray. Controls are provided in the central plant control panel.

Anti impact & distortion device is supplied to break the momentum of the parts falling through the quench chute and eliminate the impact of the parts on the postwash conveyor.

Control: All plant controls are incorporated in the central plant control panel.

Piping & cabling: The equipment is completely prewired upto junction boxes suitably located on the equipment to which client has to lay cables form the control panel. The equipment will also be prepiped upto boundry limits on the furnace to which points client will have to lay pipes from the respective source points.

1.3 CONTINUOUS TEMPERING FURNACE:

Design basis: As heat transfer is primarily by convection at tempering temperatures, the furnace internals (convection path) and fan design has been done with computational fluid dynamics software.

Shell: The shell is sturdy construction and painted. This is supported on legs to provide a convenient operating height.

Insulation: A combination of light weight refractory brick and low thermal mass fibre insulation are provided. The insulation profile yields low skin temperature. Constricting vestibules are provided at each end of the furnace.

Heating: Mains connected, alloy wire heaters are provided. These elements are positioned on the top of the conveyor. The elements can be removed for replacement without a plant shut down.

Convection fan: High velocity convection turbine fans are provided in all heating zones for maintaining the temperature uniformity by effective air circulation.

Air guide: Profiled air guides are provided below the convection fan assembly to guide the air flow such that it uniformly washes all the components across the width of the conveyor.

Conveyor belt: A special conveyor in stainless steel AISI 304 of the pintel design will be provided. This is suitable for especially heavy belt loads. Belt travels on SS capped skid rails.

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Conveyor Drive: The conveyor is driven by sprockets complete with AC motor and gear box. The speed is variable by means of an AC frequency drive. Tensioning of the belt is effected by take up units mounted on the end rollers.

Temperature on/off controllers (FUJI) are provided, one per furnace control zone.

Over temperature control is provided through the second set point of the zone temperature controllers.

2.3 Central Plant Control Panel : A free standing control cabinet built to international standards is provided. The cabinet is dust & vermin proof and provided with internal illumination and ventilation. All control switchgear and instruments are housed in the panel. Component parts of the control panel are

1. Control panel (RITTAL)2. Mains isolation switch (L&T)3. Voltmeter (AE)4. Voltmeter selector switch (Siemens) 5. Ameters for the different zones of controls (AE) 6. Ameter selector switches (Siemens)7. Controllers for the different zones of controls – FUJI8. VFDs for the hardening & tempering belts (Allen Bradley)9. Thyristors for the hardening furnace (Eurocon) 10.Heater contactors , one per zone of control (Siemens) 11.MCB’s for less than 2 HP for motors not connected across drives (Siemens)

Electronic overload relays for pump motors higher than 2 HP (SAMWHA) 12.CTs (AE) 13.Control transformer (Tamilnadu transformers) 14.A set of fuses (Siemens) , relays (Siemens), MCBs (Siemens), Connector

blocks, lamps (Siemens), switches (Siemens) , push buttons (Siemens) & wires (Finolex & ECI)

15.Buzzer (Market) 16.Switches across inductive load elements like contractors (Siemens)

NOTE: All motors will be Crompton Greaves proximity switches will be OMRON

Special Feature

Power control

Limits the connected load of the 1st control zone of the hardening furnace to a lower value when slow heating rates are required. This is done by varying the percentage output of the first zone temperature controller settable through its scroll buttons.

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Piping: All internal piping and fittings between the atmosphere feed panel and the furnace will be supplied, duly leak tested and colour coded. As per drawing No.FTL-376-1-3-0-2 incoming pipe line to terminal points on the gas panel and other sections of the furnace are to be provided by the client from their source of supply . Inter connecting cabling from the control panel (laid in trenches) upto individual equipment will be supplied to the extent required in the attached layout drawing No. FTL-376E-05-10/11. Extra cabling due to change of control panel position will be charged extra.

Paint shade: The plant will be painted as per the client's shade choice and if not specified in heat resisting aluminium and black for the furnace and siemens grey for the gas & control panels.

Documentation: Two off operation & maintenance manuals complete with spare part list, component manuals & test certificates, mechanical assembly & brick work drawings, electricals circuit drawings, piping circuit drawings & installation/foundation floor plant will be supplied along with the furnace.

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PLC WITH SCADA PROGRAMMING(LEVEL 1.5):

A PLC (Allen Bradley Micrologix 1500) and touch screen HMI (Panel view 600) is offered for performing the following functions on all supplied equipment.

Power control: In communication with the first zone controller and thyristor of the hardening furnace to limit connected power in that zone of control.

Temperature control: In communication with PID & on/off temperature control modules/controllers for each zone of control of the hardening & tempering furnace and all other equipment like quench tank and washing machine.

Drives control: The control of AC drive of all supplied equipment is interfaced through an RS 485 module in the PLC. The speed of the drive can be independently varied to match the furnace through put.

Monitoring / Control: The system will monitor/control the following devices connected to the PLC.

Monitor belt speed and upload setpoints to the PLC Monitor temperature and upload setpoints to the PLC Monitor water flow to jackets Monitor low conditions of gas flows

Data Collection: For the following parameters:

All zone temperatures All belt speed

Production Log : Maintain log of belt speed and zone temperatures.

Alarms : The system notifies the user in event of an unplanned change in process variables. A log of alarms is also maintained with the condition that caused the alarm. The system will offer the following alarms:

Belt speeds Zone temperatures Water flow failure Process low gas flow conditions.

Microporous insulation:

One layer of imported microporus insulation in the hardening furnace reduces skin temperature & causes consequent energy saving.

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Scale tolerant package of measures:

This set of measures makes the plant more tolerant to scale caused by heating & cooling in air. This typically consists of;

Additional pump for sludge transport Higher rated line filters with back up, bypass & clog indication Special design heat exchanger with prefilter & settling tank Gas tight man holes for scale removal from the furnace hearth Special design of quench tank for bottom tapping for periodic

de-sludging.

vertical pumps (3) in quench tank & wash machine.

3.8 DISTRIBUTION BOARD WITH BUS DUCT CONSISTING OF ;

S.No. Description Qty. Specification Make

1. Voltmeter 1 No. 0-600 V, 96 Sq.mm AE

2. Ammeter 1 /Zone Hardening furnace

Z1 0-150/5AZ2& Z3 0-100/5A

Prewash 0-50/5A

Tempering

Z1 0-150/5AZ2 & Z3 0-75/5AZ4 0-100/5A

AE

3. Voltmeter SI. Switch 1 No. 10 A / 415 V, Rotary Siemens

4. Ammeter SI.Switch 1 /Zone 10 A / 415 V, Rotary Salzer

5. Control fuses 1 No. 4 A, NS Siemens

6. Current transformer 3 /Zone Hardening furnace Z1 150/5AZ2& Z3 100/5A

Prewash 50/5A

Tempering

TNSG

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Z1 150/5AZ2 & Z3 75/5AZ4 100/5A

5VA

7. Switch fuse unit (MCCB)

1 No. 630 A L & T

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4.0 PREVENTIVE MAINTENANCE

4.1 Daily Schedule :

4.1.1 Check the conveyor movement of all equipments if found rubbing on the sides. Necessary adjustements to be done. (Follow instruction given in section 11 under heading conveyor belt installation instruction” sub heading “Tracking the belt”)

4.1.2 Physicaly touch all motors, pump & gear box and check for raise in skin temperature.

4.1.3 Check for any abnormal noise in the drive mechanisum of the hardeing furnace.

4.1.4 Check for the function of the level indicator in pre/post wash, OMQT, Post cooling.

4.1.5 Physically check the oil level in OMQT - if below safety level top up.

4.1.6 Check the function of the panel air conditioner.

4.1.7 Check float movement in the flowmeters.

4.1.8 Check for any gas leak’s if leaks observed attend immediately.

4.2 Weekly check (In addition to daily check)

4.2.1 Check for oil leak from gearbox.

4.2.2 Check for oil level in gear boxes if found below safety level top up.

4.2.3 Check all electrical terminal connection in side and out side the control panel.

4.2.4 Lubricate all transmission chains.

4.2.5 Clean the filter of dew point meter.

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4.2.6 Clean all hydro cyclone and strainers of pre/post and cooler tank.

4.2.7 Check for gas leaks in the complete plant.

4.3 Monthly (inaddition to daily and weekly)

4.3.1 Check the tightness of mounting fastners of all gearboxs, motor, pumps, blower, RT, bearing.

4.3.2 Check the tension of ‘V’ belts.

4.4 Half yearly (in addition daily, weekly and monthly)

4.4.1 Clean the oil separation units.

4.4.2 Check curtains condition

4.4.3 Check oil quality for desired properties.

4.4.4 Check thermocouples conditions.

4.4.5 Check all sprocket condition.

4.4.6 Remove all spray nozzles and clean

4.5 Yearly maintenance : Cool the furnace

4.5.1 Remove the top plate and check the following:

a. Condition of the belt if required replace.

b. Condition of rollers

c. Condition of insulation if any damage found rectify

d. Conditon of chute cast place.

e. Remove all fallen components

f. Condition of fans.

g. Drain water from pre/post, cooler tank and paint all wetted parts with

corrosion resistant plant.

j. Clean the cascade spray slots in OMQT

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5. TROUBLE SHOOTING

5.1 Atmosphere

5.1.1 Low Atmosphere Pressure

5.1.2 The following items should be checked:

A. The supply pressure has decreased or not available.B. The pressure regulator has been turned down.C.The pressure switch is defective or misadjusted.

5.1.3 The following corrective action should be taken:

A. The supply will have to be checked.B. The regulator should be set to the pressure rating on the flowmeter.C.The pressure switch will have to be replaced or readjusted.

CAUTION: If the low gas pressure alarm was for the Nitrogen and combustible gas was in the furnace, all personnel must be kept clear from the entry end of the furnace.

5.2 Burner Pilot Out

5.2.1 The following items should be checked:

A. The supply gas have to be correct. Flame sense rod must be defective.B. The Nitrogen from the furnace is extinguishing the flame.

5.2.2 The following corrective action should be taken:A. The gas should be adjusted with the burner valves.B. Flame sense rod should be replaced.C. The gas volume should be increased into the burner.

NOTE : The pilot(s) must be ignited before any introduction of combustible gases will be allowed.

5.3 Belt

5.3.1 The belt stops moving but the drive drum is still turning.A). The belt must have cut B). Counter weight is not enough.C). Belt must be over loaded

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5.4 Parts are Decarburised

5.4.1 The following items should be checked:A. Oxygen and dewpoint profiles should be run in the furnace

to see if there is too much oxygen and moisture in the furnace.

5.4.2 The following corrective action should be taken:A. The dew point and the oxygen inside of the furnace

should be decreased. The most probable cause is air infiltration through a flange, entry end etc.,

B. Small amounts of Propane/LPG should be injected.

5.5 Red rust formation on the heat treated parts

It is a low temperature oxidation (about 600°C) forming FeOH2O.

Causes

A. High dewpoint in endogasB. Leak in variocoolC. Frequent processing of parts with forging scales

Remedies

A. Check the endogas dew point and maintain better than +3°CB. Tighten the various flanges of variocoolC. Ensure N2 purge for variocool blower shaftD. Parts with forged scales to be shot blasted before chargingE. Ensure the exhaust suction pump working, which removes moisture from

quench tank/cooling section.

5.6 Hardness low or poor microstructure

Causes:

A. Belt speed too highB. Over loading the furnaceC. Furnace temperature is low

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Remedies

A. Adjust the belt speedB. Set the ram loader to correct direct time to maintain charge density less

than 80 Kgs/M2

C. Check all thermocouples

5.7 Parts mix up

Too frequent changes within short internals

Remedies:

A. Sufficient gap between part change over. (Note: During loading on empty belt, components tend to roll in the belt to a distance of 500 to 1500mm depending upon the shapre of the part)

B. Remove any part of the previous charge from ram loader. (parts tend to stick to ram loader due to heavy oil present.

5.8 For bought out items , the individual operating manuals carry extensiveTrouble shooting procedures which is available in volume II.

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6.0. SAFETY INTERLOCKS

A. Plant Interlocks

1. Furnace zone over temperature shuts down heaters of respective zones.

2. Active gas entry into the furnace is not possible if the furnace temperature is below 750 Deg C.

3. Flame failure at entry and exit of pilot burner initiates alarm.

4. Furnace belt is stoppage initiates alarm after time delay.

5. Quench conveyor stoppage initiates alarm.

6. Quench oil excess temperature starts circulation pump.

7. Oil level low initiates alarm.

8. Post wash belt stoppage initiates continuous alarm for every 2 minutes till it is attended.

9. Post wash water excess temperature cuts off wash heaters.

10.Postwash water level low cuts off postwash heaters and initiates alarm.

11.Tempering zone over temperature cuts off respective zone heaters.

12.Tempering belt stoppage initiates alarm.

13.Tempering fan stoppage initiates alarm.

B. Conveyor Stop conditions

1. Furnace belt will not run if the aux conveyor in QT is not running (sensed by

proximity on aux conveyor).

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2. Furnace belt will not run if emergency PB is pressed.

3. Furnace belt stops if the quench cascade pump overload occurs.

4. Furnace belt stops if the quench tank oil level is very low.

5. Post wash belt stops if the tempering belt is not running.

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7.0 DRAWINGS

1. Plant Layout FTL-423-1-1-0-2-3

2. Civil layout FTL-423-1-2-0-2-2

3. Field wiring FTL-423E-05-10/11-0

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27

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8.0. CALIBRATION

All instruments required in processing need to be calibrated to ensure product and

process integrity. Periodicity of calibration is a function of instrument usage and

accuracy of measurement called for by the process.

It is common practise for many organisations to evolve a calibration schedule based

on their experience, requirement and accuracy levels aimed for.

Given below are calibration schedules for measuring equipment on this furnace, to be

used as a guideline.

Item Periodicity

Thermocouples Once a month.

Temperature controllers Once in 6 months.

Flow meters Once in 12 months.

Belt speed monitor Once in 12 months

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Procedure and sources for calibration of instruments

Thermocouples : These are to be calibrated with a master thermocouple, whose

calibration status should be traceable to National standards. Calibrating tubular

furnaces for thermocouples and RTD’s are manufactured by Electronic Equipment

and Company, Mumbai.

Controllers : Controllers are calibrated by using a millivolt reference source, to read

a preset value of temperature.

Flow meters : The flow meters on the gas panel can be calibrated at the following

addresses :

a) Instrumentation Engineers P.Ltd.Plot No.1-3, Phase IIIIDA, Jeedimetla,Hyderabad - 500 055.Ph.No.040 - 3095147 / 3096401.

b) Institute of Design of Electrical Measuring InstrumentsS.T.Tope Marg (Eastern Express Highway)Chunnabatti, P.O.SionMumbai - 400 022.Ph.No. 022 - 5220301Fax No.022 - 5229016

c) Fluid Control Research InstituteKantikode WestPalaghat - 678 623, Kerala.Ph.No.566120Fax No.568326

d) Endee Engineers P.LtdD-122, Ansa Indl.EstateSaki Vihar RoadPost Box No.8945Mumbai - 400 072.Fax No : 022-8521615

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9.0. 9.0 ACCIDENTS AND HOW TO AVOID THEM ?

10.1 Carry out preventive maintenance as per schedule. This will to a large

extent, ensure safe operation, time after time.

10.2 Do not bypass any interlocks.

10.3 Insist on operators wearing safety goggles, boots, helmets & heat resistant

gloves.

10.4 Always ensure that the valve on the burn off tube is open whenever a process

is started.

10.5 Make sure the UPS works.

10.6 Make sure genset power is available to the plant.

10.6 Furnace shall be adequately purged with N2 before admitting ENDO and

similarly if N2 purging is essential while shutting down the furnace. ENDO

shall be completely removed before the furnace temperature drops to 800C.

10.7 Ensure adequate N2 is available for N2 auto purging if endogas supply is

affected.

10.8 Furnace atmosphere hazards :

Furnace atmosphere contribute one of the major safety hazards involved in

heat treating. Generally these hazards fall into three groups.

a) Fire

b) Explosion

c) Toxicity

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a) Fire :

When atmosphere contain more than 4 % of combustable gases, it is

classified as flammable. The combustable gases H2, CO, CH4 and other

hydrocarbon fuel gases should never be admitted to the furnace below 750 C

without proper inert gas purging.

b) Explosion :

At some point mixtures of air and combustable gases will explode when

ignited. When the furnace chamber is properly gassed with the chamber

temperature at or above 760C, it is likely they burn off before creating an

explosion hazard.

The positive flow of this atmosphere through the furnace and adjoining the

cold chamber can be burned. An ignited effluent from the atmosphere furnace

is an immediate visual sign that a safe condition prevails.

c) Toxicity :

Ventilation of the building containing atmosphere generators and atmosphere

furnaces is a major safety consideration.

10.9 Check the quenchant level regularly.

10.10 Always have the printer connected and analyse faults, alarm and temperature on a daily basis.

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10.0LIST OF ESSENTIAL SPARES

HARDENING FURNACE :

S.No. Description Minimum quantity reqd.

1. Radiant tube with flange and gasket

3 off

2. Heating element with ceramics completely assembled

4 off

3. Thermocouple - Simplex 2 off

4. Ceramic end brick for RT 12 Sets

5. Top rollers (alloy steel) 2 Nos.

6. Flame curtain entry 1 off

7. Flame curtain - Hot zone 1 off

8. Ceramic fibre blanket

a) 64 kg/m

b) 96 kg/m

c) 128 H

2 Rolls

2 Rolls

2 Rolls

9. Ceramic cup lock and washer 25 Nos.

10. Alloy washer 25 Nos.

11. Sealing rope 5 kg

12. Gasket assorted 2 sets

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TEMPERING FURNACE :

S.No. Description Minimum quantity reqd.

1. Heating elements (coil) 2 off

2. Ceramic collar tube for serial No.2 2 off

3. Thermocouple - Simplex 1 off

4. Curtain 1 off

OIL QUENCH TANK :

1. RTD Probe 1 off

2. Level indicator 1 off

GAS PANEL :

1. Pressure gauge 1 off

2. Glass tubes & floats (1 set consisting of 4 Nos.)

1 set

3. Opto sensors 4 off

4. PCB for Opto sensors 1 off

5. Gaskets assorted 2 sets

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PLC & AC DRIVE :

1. AC Drive 1 No.

2. Digital input module 1 No.

3. Relay output module 1 No.

PRE/ POSTWASH :

S.No. Description Minimum quantity reqd.

1. Immersion heaters 6 off

2. RTD probe 2 off

3. Spray nozzles 10 off

4. Level indicator 1 off

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11.0 LIST & MAKES OF BOUGHT-OUT COMPONENTS

S.No. Components Make

1. Ceramic fibre MMCF

2. Refractory bricks Maithan / Valley

3. Thermocouples Radix

4. Contactors ABB

5. Temperature controller (element excess) Viral/ Fuji

6. Ammeter / Voltmeter AE

7. AC Drive Allen Bradley

8. Motors Crompton Greaves

9. Gear box Shanti

10.Pumps KSB

11.Flowmeters IEPL

12.Solenoids Avcon

13.Valves Leader / Swastik

14.Heating elements Kanthal

15.Level switch Switzer

16.Blowers Continental Thermal

17.Mesh belt R.D.Ashar

18.Dew Point Meter ENDEE / SHAW

19.Chains T.I.Diamond Chains.

20.Heat resisting castings Magnatherm Alloys.

21.PLC & MMIC Allen Bradley

22.Overtemperature controller VIRAL

23.Panel A/C Werner Finley

24.Energy Meter BHEL

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12.0 CATALOGUES

37