Best Practices Steam Turbines

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Copyright: Reliance Industries Limited, India

BEST PRACTICES FOR STEAM TURBINES

Please send your comments and suggestions to the author. This document is intended for guidance purpose and may be adopted with minor modifications by any functional department within RIL group of companies. Reproduction of this document or parts thereof in not allowed unless written permission is obtained from the Approving authority.

Prepared by: UK Upadhyaya Checked by: K Gopalakrishnan Approved by: A Venkatraman

Group Manufacturing Services Engineering Services Dept

DOC. No: GMS/RP/35

Page: 1 of 24 Date: 10-May-07 Revision no.: 0.0

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INDEX Sr. No

Description

Page No

1

Introduction

03

2

Scope

03

3

Definition

03

4

Applicable Standards

03

5

Steam Turbine Types

04

6

Steam Turbine Classification

04

7

Selection Criteria

05

8

Specification

06

9

Installation & Commissioning

06

10

Monitoring during operation

08

11

•

Special purpose turbine(large)limit Monitoring

08

12

•

Lubrication system monitoring

08

13

•

Bearing temperature monitoring

09

14

•

Vibration monitoring

09

15

•

Thermal expansion of casing

10

16

•

Steam parameter monitoring

11

17

•

Operation guideline

11

18

Steam Turbine Maintenance

11

19

Special Tools

15

20

Spares Management

16

21

Documentation

17

22

Annexure

18

23

References

24

Prepared by: UK Upadhyaya Checked by: K Gopalakrishnan Approved by: A Venkatraman

Group Manufacturing Services Engineering Services Dept

DOC. No: GMS/RP/35

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1.0 INTRODUCTION Steam Turbine is widely used in power plants and in all industries like Refinery, Petrochemical, Chemical, Fertilizers, Paper industries etc where power and /or heat are needed for the processes. Steam turbine began to overtake the steam engine for electric power generation from beginning of year 1900 onwards. Gradually Steam Turbine efficiency and reliability improved as the time passed. Life extension, Design improvement, & developments of materials, operations, maintenance, performance monitoring, diagnostics and machine protection have helped very much in this. The use of Steam Turbines for Power Generation in Power Plants, for drives for critical Centrifugal/Axial Compressors in Refineries, Fertilizers & Petrochemicals and as drive units for pumps, fans, show the wide acceptance & importance of Steam Turbines

2.0 SCOPE The purpose of this document is to detail best engineering and maintenance practices with regards to the selection, operation and maintenance of Steam Turbines used as driver to rotate connected driven machines. It covers General Purpose (Auxiliary service) as well as Special Purpose Steam Turbines. Purpose of this document is to help: a. Plant /field maintenance personnel b. CES/CTS personnel c. Project personnel d. Newly joined personnel By implementing best practices failures and costly downtime can be avoided and will also help in reducing corrective maintenance costs. 3.0 DEFINITION A steam turbine is a prime mover that derives its energy of rotation due to conversion of the heat energy of steam into kinetic energy as it expands through a series of nozzles mounted on the casing or produced by the fixed blades. Steam Turbine functions due to: • Steam at high temperature and pressure contains the potential energy. • Potential energy of the steam is converted into a mechanical work through expansion in a nozzle and impact and/or reaction with a blade. • Mechanical Work of many sets of blades attached to a shaft produces rotational power.

4.0 APPLICABLE STANDARDS • API-611 4th Edition: General Purpose Steam Turbines for Petroleum, Chemical, and Gas Industry Services • API612- 5th edition: Petroleum, Petrochemical and Natural Gas industries-Steam Turbines -Special Purpose Applications • NEMA standards SM 23 / SM24

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Site approved standards

5.0 STEAM TURBINE TYPES 5.1 General purpose Turbines API 611 defines as : “General Purpose Turbines are horizontal or vertical turbines used to drive equipment that is usually spared, is relatively small in size (power), or is in non-critical service. They are generally used where steam conditions will not exceed a pressure of 48 bar (700 lbs g) and a temperature of 400 Deg C (750 Deg F) or where speed will not exceed 6000 rpm.”

5.2 Special purpose Turbines API 611 defines as : “Special Purpose Turbines are those horizontal turbines used to drive equipment that is usually not spared, is relatively large in size (power), or is in critical service. This category is not limited by steam condi tions or turbine speed.” API 612 defines as: “Horizontal mounted (or installed) turbines used to drive equipment that are usually not spared and are used in uninterrupted continuous operation in critical service.

6.0 TURBINE CLASSIFICATION Turbines as fundamentally classified as “Impulse” or “Reaction” type by how the steam expands through a nozzle and impact a blade. Impulse Stages are often compared with waterwheels, reaction stages to a rotary lawn sprinkler. There are different ways to classify the turbine based on A. By the action of steam a. Impulse b. Reaction c. Impulse and reaction combined B. By the num ber of step reductions involved a. Single stage b. Multi-stage c. Whether there is one or more revolving vanes separated by stationary reversing vanes. C. a. b. c.

By the inlet steam pressure High Pressure Medium pressure Low pressure

D. By the final pressure a. Condensing b. Non-condensing

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7.0 SELECTION CRITERIA Minimum requirements for a selection of Turbine are Requirements • Inlet steam pressure and temperature • Exhaust steam pressure • Driven Equipment power (rated max. -min.) • Driven equipment speed (rated max.-min.) and maximum allowable over -speed for trip • Speed control (manual or type of process signal) • Site conditions: indoor/outdoor and ambient conditions • Cooling water data (pressure, temp and cleanliness) • Any off-normal steam or driven equipment operating conditions • Type of driven equipment and service: o centrifugal or positive displacement o normal or quick start o continuous or standby duty o site electrical rating (if electrical accessories are involved) • Specifications: o customer required scope and turbine shop tests o API-611/612 (API data sheets required) o steam cost evaluation o sound level requirements Criteria The relative value of thermal to electric energy has much to do with the motor/turbine selection. In industries where electric power costs are high, turbine dominates as the driver selection. In a competitive and energy saving environment turbine selection also helps to achieve the same. Many industrial plants require both electric and thermal energy at the same time, thermal energy in the form of steam. If the steam is used for generating the power before its normal use then the generating power cost will be less. Efficient Plants are using steam for producing full electrical demand before its process requirements. Requirements can be distinguished as below • Steam demand predominates then steam can be supplied to the user by way of Pressure Reducing Station. •

Electrical demand predominates or where the electric power that can be generated in back pressure operation does not fulfills the requirement then balance power must be drawn from external source or generated in condensing operation within the plant itself.

Back-pressure Type Back-pressure Turbines are used in those industrial plants where the heat requirements are approximately the same as the electrical demand. The turbine normally operates against a constant back-pressure, demand fluctuations being compensated by parallel operation with the external power grid.

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Back-pressure turbines can be used when a large quantity of process steam is required. The turbine exhaust steam is supplied to the process and the electric output is dependent on the demand for the process steam. These turbines can als o be used as top turbines to supply exhaust steam to existing units; this improves the entire plant's thermal efficiency. Back pressure turbines with uncontrolled extraction A back pressure turbine with uncontrolled extractions is particularly suitable when two steam systems operating at different pressures are to be supplied and the extraction flow is less than the exhaust flow. Extraction back-pressure turbines can be used when two or more kinds of process steam are required. High-pressure steam is supplied through the extraction openings and low-pressure steam is supplied through as the turbine exhaust. Condensing Turbine The main field of application for condensing turbines in industrial plants is where cheap fuel is available in the form of waste products or waste heat derived from the manufacturing process. Condensing turbines are used increasingly as prime movers for the turbo compressors. The turbine and compressors can be designed for the same speed over a wide power range. Straight-cond ensing turbines are advantageous, especially when large quantities of a reliable power source are required or an inexpensive fuel, such as process by-product gas, is readily available. Extraction -Condensing Turbine Extraction-condensing turbines generate both process steam and stable electric power. Process steam, at one or more fixed pressures, can be automatically extracted as needed. This type of turbine has the flexibility to satisfy wide variations of process steam at a constant pressure and to meet electric power demands . 8.0 TURBINE SPECIFICATIONS Specifications: • customer required scope and turbine shop tests • API-611 4 th Edition: General Purpose Steam Turbines for Petroleum, Chemical, and Gas Industry Services • API-612- 5th edition: Petroleum. Petrochemical and Natural Gas industries -Steam Turbines -Special Purpose Applications • steam cost evaluation • Sound level requirements 9.0 INSTALLATION & COMMISSIONING Proper installation of Steam Turbine will contribute to long trouble free operating life with minimum maintenance and reliable operation. Below is the checklist of tasks to complete prior to placing the new machine into operation: • • • •

Unpacking and inspection Cleaning of shipping preservatives Inspection and preparation of foundation Leveling of turbine and pre-alignment checking with driven machine

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Grouting of machine base frame Aligning turbine and driven machine Connect auxiliary piping Check piping stain of steam inlet and exhaust piping Connect steam inlet and exhaust piping Provide insulation on steam lines and casing Preparation for initial starting and start -up

Above given guidelines are general and it is recommended to follow Turbine manufacturer installation guidelines while installing. 9.1 Acceptance Criteria Before starting-up the turbine either it is first start-up or after overhauling it is advisable to make sure that all connected systems and interlocks are working properly. This check-up is necessary particularly for the Emergency Stop Valve, control valves as well as the other safety devices, safety interlocks, since it is related with machine operation, safety of machine, plant and personnel depends. 9.2 Turbine No Load Trial Once the turbine installation /major overhauling completed, it is advisable to have turbine no load trial to ensure machine smooth running, interlock functioning, and overspeed trip checking before putting on load trial. • • • • • • • • • •

Follow turbine start-up instruction and startup cycle. Check journal and thrust bearing temperatures and shall be within the design limit as given by the machine vendor. Check Rotor axial displacement and casing expansion and shall be within the design limit as given by the machine vendor. Check vibration level and shall be within the design limit as given by the machine vendor. Check for steam leakage, oil leak if any. Check machine for any abnormal sound, machine should be free from any abnormal sound. Check turbine’s over speed trip and shall be within the allowable limit as given by the machine vendor. Check safety devices and interlock functioning before stopping. Check piping support of inlet and exhaust piping for any abnormality. Piping shall have proper support to take care of piping expansion. Check functioning of lube oil, cooling water system for its normal performance.

9.3 Turbine Load Trial Once the turbine no load run completed, machine with the driven machine will be coupled and made ready for load trial. § § §

Follow machine start-up instruction and startup cycle. Check journal and thrust bearing temperatures and shall be within the design limit as given by the machine vendor. Check Rotor axial displacement and casing expansion and shall be within the design limit as given by the machine vendor.

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DOC. No: GMS/RP/35

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Check vibration level and shall be within the design limit as given by the machine vendor. Check for steam leakage, oil leak if any. Check machine for any abnormal sound, machine should be free from any abnormal sound. Check safety devices and interlock are healthy. Check piping support of inlet and exhaust piping for any abnormality. Piping shall have proper support to take care of piping expansion. Check functioning of lube oil, cooling water system for its normal performance.

10.0 MONITORING DURING OPERATION The principal criteria of monitoring, which can indicate a dangerous condition d uring normal operation are as follows: • Oil and Bearing Temperatures • Bearing housing and Shaft vibrations • Shaft axial displacement • Steam Parameters • Oil Quality 10.1 Special Purpose (Large) Turbine Limit Monitoring Generally all large turbines are equipped with supervisory, safety and protection devices whose function is to prevent or give warning of operating conditions which are dangerous for the turbine operation: • • •

Supervisory devices are for identifying plant operating conditions and/or any deviations from set-point conditions. Safety devices are for identifying and eliminating conditions which are undesirable for operation of the turbine. They are designed and adjusted so that they operate before the relevant protection device and its trip and therefore contribute to avoiding plant trips. Protection devices are for shutting down the turbine itself or parts of the plant as soon as conditions arise which endanger the machine.

The principal criteria which can indicate a dangerous condition during normal operation are as follows: • Lubrication • Bearing Temperatures • Bearing housing and Shaft vibrations • Relative shaft vibration and absolute casing expansion • Steam Parameters

10.1.1 Lubrication System Monitoring The oil supply is critical to satisfactory operation of the turbine. It lubricates cools and controls in order to ensure that it performs these functions properly. The pressure and temperatures must be monitored continuously during normal operation, start-up and shutdown, and if necessary during turning-gear (barring) operation.

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The journal bearings support the turbine rotor in a central position in relation to the fixed guide blade carrier and outer casing. Damage to the bearings can result in serious damage due to internal metal to metal contact and s ubsequently involves repair and outage cost. An essential precondition for trouble free turbine operation is an adequate supply of lubricant to each bearing at all time. Lube oil supply to journal bearing is important, as the load carrying capacity of the oil film in the bearing is dependent on the viscosity of the lube oil used. In turn, however, it is equally dependent on the temperature of the oil film. Therefore in addition to the lube oil pressure it is important to maintain the lube oil temperature generally between 45 – 50 deg. C outlets of the lube oil cooler. The oil temperature at the outlet of the cooler must be monitored continuously. The cleanliness of the oil system is extremely important if the turbine and its driven equipment are to operate reliably and without interruption over long periods. Any contamination results in premature wear in components and to sudden operational disturbances and failures. The cleanliness must therefore to be checked at specified intervals. 10.1.2 Bearing Temperature Monitoring The temperatures of the journal bearings and thrust bearing are measured either as oil outlet temperatures directly at the bearing or as bearing metal temperatures immediately below the white metal lining of the bearing shells/tilting pads and thrust bearing pads. The bearing metal temperatures can vary widely even when the oil inlet temperature remains constant. With a thrust bearing the variation depends on the magnitude of the residual thrust. In the case of journal bearings the changes can be due to variations in the direction and magnitude of the bearing loads exerted by the shaft journal influenced by steam flow conditions. Any spontaneous increases in bearing temperatures above the normal measured maximum are always an indication o f some irregularity. Consequently, a thorough bearing inspection should follow such change.

10.1.3 Vibration Monitoring The purpose of vibration monitoring is to monitor the running condition of the turbine and detect any change with time. The objectives of vibration monitoring are to • Protect the machine and its surroundings against damaging vibration. • Identify the causes of excessive or changed vibration • Provide the basis for rectification when undesirable vibration occurs. The vibration monitoring gi ves an indication of • Changes in the running parameters due to broken blades, deposits, erosion, misalignment, shaft distortion, temperature sensitive unbalance. • Dynamic overstressing, especially in the bearings, which causes premature depletion of the bearing carrying capacity. • Elimination of the radial clearances, which are important during non-steady state operating conditions, especially start-up.

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DOC. No: GMS/RP/35

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When starting up and loading a turbine, especially from cold, it is to be expected that there will be some temporary vibration due to thermal unbalance which will considerably exceed the normal value measured when turbine is at operating temperature. However if an increase in vibration occurs suddenly for no apparent reason at a load or phase of the start-up procedure when abnormal permanent or temporary vibration is not anticipated, it is most likely to be due to damage or other malfunctioning, even when limit values are not attained.

10.1.4 Thermal Expansion of Casing In the case of Large Steam Turbine, at the time of installation, all stationary and rotating turbine parts kept aligned with respect to each other and all measuring devices to their respective neutral positions. Taking that zero position as reference, all parts of the turbine which are exposed to elevated temperature, such as casing, bearing housing and rotor are going to expand in both axial and vertical direction. Because of the diverse temperature levels and the distinct properties of material of construction, the resulting expansion may attain different values. Radial Expansion Through appropriate measures taken by Turbine design, it has been ensured that the changes in radial play due to differential radial expansion of stationary and rotating parts and then causing potential hazard for the turbine will be kept within limits. Axial Expansion More critical than radial expansion is elongation, the change of dimensions in the axial direction. The turbine casing, which is secured at its rear end (Drive end) to a fixed point, can yield in the axial direction under the influence of elevated temperatures only by sliding forward on the casing support together with the supporting front bearing support (Non-drive end). As holding down the bolts of the casing brackets at the front end permits free movement of the brackets in axial direction even after having tightened. This explains the importance of making sure, especially during the start-up and shutting down, that the washers of the bracket hold down bolts are easily movable by hand. Relative Expansion As mentioned above that turbine casing will expand in the axial direction under the influence of the high steam temperatures with the result that the front bearing housing, which serves as support for the turbine rotor, is being pushed forward. This bearing housing incorporates the thrust bearing by which the axial position of the rotor is fixed. By the elongation of the casing, this fixed point will therefore be shifted too. The rotor, when heated up by the steam which is flowing across it, is likewise going to expand, but in the direction opposite to the elongation of the casing. The difference between the elongation values of the turbine rotor and casing have been defined as relative elongation. Relative expansion under steady state conditions may be caused by: •

Different Thermal expansion coefficient of the rotor and casing material of construction.

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Different mean temperature values of rotor and casing.

The permissible limit values for relative elongation, which have been employed in the design of the turbine, include an additional margin of safety. These limit values must not to be exceeded in the operation of turbine.

10.1.5. Steam Parameters Monitoring A. Temperature The satisfactory functioning and life of the various components of the turbine are to a large extent dependant on the absolute main steam temperatures and temperatures fluctuations. Consequences of exceeding the permitted tolerances are: • • • •

A shortening of the life the affected components. A build up scale in guiding and sealing devices. Permanent distortion of housing and casings. Temporary or permanent changes in radial clearances.

B. Inlet Steam Pressure Monitoring The objective of Inlet Steam Pressure monitoring: • Maintain the inlet steam pressure within the permitted toleran ce. • Keep the initial steam pressure as constant as possible during steady state operation. • Match the initial steam pressure to the requirement of power output. • Maintain the pressure and changes during start-up as far as possible in accordance with the actual casing temperatures. C. Wheel Chamber pressure Monitoring Wheel Chamber pressure monitoring is a good indication of rotor condition. As this pressure is direct function of steam mass flow. If the measurement indicates higher values at constant mass flow then it is an indication of deterioration of turbine operation. All operating conditions need to be checked. 10.1.6. Operation Guidelines To ensure the trouble free operation, the turbine must be: • • • • • •

Operate as per specified operating parameters Maintain Proper lubrication Protective devices in line& functioning Operate as per SOP Regularly inspect/maintain as per Vendor guidelines Turbine steam quality to be ensured for trouble-free operation. The build up of deposits in turbine due to impurities in the steam can cause both thermodynamic and mechanical problem which can lead to blade failure.

11.0 TURBINE MAINTENANCE Steam turbines also require periodic maintenance and service. Scheduled preventive maintenance is essential for continued optimum performance and long service life of the

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turbine. Maintenance requirements and the corresponding schedule will vary with the application and service conditions. Turbine used for the stand-by service should be operated at regular intervals to minimise the problems normally associated with the idle equipment and to ensure that the turbine is operable when needed. The following maintenance and inspection guidelines are recommended for turbine operated under normal conditions, but it is recommended to follow the guidelines as recommended by the machine manufacturer. Auxiliary Turbine Daily • Visually inspection for leakage, external damage, abnormal noise • Check oil level in the bearing housing and governor, add oil if required.

Monthly • Check lube oil condition, if require replace. • Check that oil rings rotate freely and smoothly • Follow overspeed trip check frequency as recommended by manufacture, many are recommending for monthly check. • Check throttle/control valve, overspeed trip linkage for looseness, wear and freedom of movement. Yearly • For Woodward governor drain oil, flush and clean and re-fill with fresh oil. • Remove and clean the steam strainer. • Inspect internal component of the throttle/control valve for wear, replace if required. • Thoroughly inspect the governor linkage and overspeed trip linkage for wear, replace if required. • Inspect, clean and flush bearing housings, oil reservoirs and cooling water jackets. • Inspect carbon ring for wear -remove, clean and assemble, replace if required. • Check thrust bearing play. • Remove sentinel valve and check for operation • Check alignment • Check calibration of all measuring instruments. Special Purpose Turbine’s Major Inspection Manufacturer recommendation is the final for major inspection or overhaul. The frequency of this inspection/overhaul will depend on the turbine service conditions, its maintenance history, and convenience of scheduling a shutdown, and the user’s experience with similar machines. The turbine must be regularly monitored, particularly in the case for all protective, limiting and monitoring devices. The turbine plant is equipped with supervisory, safety and protective devices whose function is to prevent or give warning of operating conditions which are uneconomical or dangerous for the turbines

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•

Supervisory devices are for identifying plant operating conditions and /or any deviations from set-point conditions.

•

Limiting devices are for identifying and eliminating conditions which are undesirable for operation of the turbine. They are designed and adjusted so that they operate before the relevant protection device and its trip and therefore contribute to avoiding operational trips.

•

Protection devices are for shutting down the turbine itself or parts of the plant as soon as conditions arise which endanger the turbine.

The principal criteria which can indicate a dangerous condition during normal operation are as below: • Oil and bearing metal temperature • Bearing Housing and Shaft Vibration • Relative Shaft vibration and absolute casing expansion • Steam pressures and temperatures • Speed • High axial displacement • Wheel Chamber pressure The task of monitoring equipment is to keep the operating personnel constantly informed of the turbine’s operating condition. If measured values then depart form their normal operatin g range, the operating personnel will be able to take measures to return the turbine to its normal condition or to compensate for a deviation from the optimum operating condition, before a limiting or protecting device responds. Preventive maintenance must be performed on the turbine at certain intervals. Each manufacturer has its own fixed intervals; some of the leading turbine vendors recommendation on machine inspection are given in Annexure as reference. Overhaul Plan Overhaul plan shall be made ready so that fine tubing can be made at the time of actual job execution. Attached below a sample activities plan prepared for turbines overhaul and on the same basis a detailed plan can be made specific to the machine. Activities plan Sr. No

Activities

Activities Time

1

Coupling Jobs

1.1

Coupling Guard Removal/Oil Piping Removal

3

1.2

Coupling Spacer dismantling

3

2

Float & Alignment Checking

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Total Time 6

6

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2.1

Check Turbine rotor axial float & alignment with Compressor

6

3

Rear (DE) Bearing Removal

3.1

Vibration Probe & Thermocouple removal

1

3.2

DE Bearing Housing top cover removal

2

3.3

JB temperature thermocouple removal

1

3.4

JB Top half removal

1

3.5

Check Shaft run out at shaft journal

4

Front (NDE) Journal, Thrust bearing removal job

4.1

Vibration Probe & Thermocouple removal

1

4.2

Check clearance between trip lever and shaft from inspection window before removal of top half bearing housing

1

4.3

Bearing housing top half removal

2

4.4

JB top half removal

4.5

Thrust bearing removal

4.6

Check axial float without thrust bearing

5

Rotor Centering Checking (Follow Rotor Radial Position sheet of Protocol (0-3600-8544-40 sheet no. 7+)

5

6

0.5 1 0.5

8 4

5.2

Install centering fixture on Front Casing (NDE) and check reading Install centering fixture and check reading in thrust collar.

5.3

Install centering fixture on Rear (DE) Casing and check reading

2

6

Rotor Axial Position Checking (Follow Rotor Axial Position shee t of Protocol (0-3600-8542-40 sheet no. 8+)

6.1

Check Rotor axial position with respect to Casing

7

Dismantling of Casing & Removal of Rotor

7.1

Removal of Turbine Steam Inlet and Exhaust piping Removal of interconnected lube oil and governing oil piping.

24

7.2

Loosening of Casing Flange Bolts

36

7.3

Removal of top half of casing

4

7.4

Removal of Turbine rotor

3

5.1

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2 2 67

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8

Governing system overhauling (Parallel Activity), (ESV Control Valve, Trip Gear and Servomotor overhauling) & Rotor & Casing top half installation

8.1

Cleaning of Casing diaphragms

48

8.2

Rotor Installation

8

8.3

Installation of Casing top half

8

8.4

Casing Stud bolt tightening

8

9

Rotor Centering Checking (Follow Rotor Radial Position sheet of Protocol (0-3600-8542-40 sheet no. 8+)

72

8

9.2

Install centering fixture on Front Casing (NDE) and check reading Install centering fixture and check reading in thrust collar

9.3

Install centering fixture on Rear (DE) Casing and check reading

10

NDE Journal, Thrust bearing and collar assembly job

10.1

Install Thrust bearing

4

10.2

Install Thermocouple

2

10.3

Install Top half of JB

1

10.4

Check axial float

1

10.5

Install top half of bearing housing

3

10.6

Install Vibration Probes and Thermocouple

2

11

DE bearing/coupling Assembly Jobs

11.1

Install thermocouple

2

11.2

Install Top half of JB and bearing housing

4

12

Piping connection, Alignment checking & Coupling Job

12.1

Steam Inlet and Exhaust piping installation Governing and oil piping installation

24

12.2

Check alignment with Compressor while connecting piping

12

12.3

Preparation to be made for Turbine no load run

12.4

Refit the coupling spacer after No-load trial/cooling down

3

12.5

Box-up coupling guard and oil piping

3

9.1

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6

42

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12.0 SPECIAL TOOLS Special tools availability is very much important especially in case of Large Steam Turbines, non-availability may affect total overhaul/repair schedule as it may involves new tools manufacturing. Care should be taken that special tools shall be part of purchase order in case of new turbine procurement whereas if it is not available then it shall be procured after discussion with the Turbine vendor . Following tools are common ones and shall be stored in proper preserved condition so to have in good condition whenever needed; • • • • • • • • • • • • • • •

Rotor Lifting device Rotor lifting device require for bearing fitment Casing bolts opening device like electric coil heating Casing lifting jack bolts Guide Pins required for safe lifting of casing Rotor centering checking fixtures, generally supplied by OEMs Special measuring tools like small dia dial gauges Rotor supports required to place it during overhauling, if not supplied can be fabricated locally Special slings to match load of the components Alignment fixture Dowel pin removal fixtures, can be made ready before overhauling job, this is small tool but non-availability can lead to long delay Coupling hub removal and installation hydraulic kit in case of hydraulic fi t coupling Caulking tool for caulking wire Measuring instruments Other machine specific tools as recommended and supplied by the Turbine OEM.

13.0 SPARES MANAGEMENT Spares requirement for Special Purpose Turbines shall be decided based on the machine criticality, service, and stand-by availability. Spares requirement review shall also be carried out based on maintenance experience. Following insurance spares are recommended and shall be procured during initial procurement stage along with the machine : • • • •

Rotor (properly preserved) Journal bearings Thrust bearing Coupling

Other spares like gland fins, bearing housing oil seals, control valve and stop valve spindles, various oil seals, packing, casing jointing compounds, casing bolts, gland carrier etc requirem ent shall be reviewed and decided based on the site experience. Similarly spares requirement for General Purpose Turbines shall be decided based on the machine criticality, service, stand-by availability, number of similar machines installed. Spares requirement review shall also be carried out based on maintenance experience.

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Group Manufacturing Services Engineering Services Dept

DOC. No: GMS/RP/35

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Following insurance spares are recommended and shall be procured during initial procurement stage along with the machine: • • • • •

Rotor (Quantity shall be decided based on number of similar machines installed at site) Set of Journal bearings in case of sleeve bearing Thrust bearing in case of tilting pad type Coupling Governor assembly (Quantity shall be decided based on number of similar models installed at site)

Other spares like carbon glands, bearing housing oil seals, control valve and stop valve spindles etc requirement shall be reviewed and decided based on the site experience.

14.0 DOCUMENTATION Following documents shall be maintained for Steam Turbines: • • • • • • • • • •

Assembly protocols Datasheet Test reports Machine Alarm/Trip records Special tools list Spares List Lifting plan required during overhauling List of Special measuring instruments Equipment drawings Maintenance Records like filled SMP, overhauling report

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ANNEXURE I Preventive maintenance must be performed on the turbine at certain intervals. Each manufacturer has its own fixed intervals; some of the leading turbine vendors recommendation on machine inspection are given below as reference. 1.0 M /S SIEMENS Mainte nance Instructions Maintenance of the turbine during normal operation or short shutdowns is mainly restricted to the equipment and component mentioned in the introductory remaps. The object is to maintain the efficiency and to protect the high value of th e plant. The instructions sometimes mention devices and equipment which the operator mus t supply in order to facilitate the maintenance work. Preventive servicing and maintenance must be performed on the turbine at certain intervals, some of which is laid down by the insurance company - see also documentation 5-1000, Overhaul of Steam Turbines. The following intervals between overhauls are recommended. • • •

Minor overhaul after not more than 4 years or 20,000 to 25,000 equivalent operating hours Major overhaul after 6 to 8 years or 40,000 lo 50,000 equivalent operating hours. Major overhaul after 12 to IS years or 100.000 equivalent operating hours. If possible this overhaul should be carried out in the manufacturer's works or with his assistance; it is advisable to make early arrangements with Ihe nearest Siemens representative.

The turbine and all related ancillary equipment are tested and reconditioned during overhaul or, when necessary or advisable, worn parts are renewed. 2.0 M/S MAN TURBO Maintenance Maintenance comprises all measures which serve to maintain the desired condition of the machine unit Service and Maintenance schedule Correct maintenance of machine unit depends on numerous factors. Maintenance is influenced amongst other things by • Ambient condition • Quality of live steam • Quality of consumables • Number of startups • Standstill periods • Required availability of the machine units • Maintenance philosophy of operator/ user MANTURBO recommended an individual maintenance strategy jointly with tec hnicians of our after sales service. This is the one way to make sure the safe and economical operation. Moreover the MANTURBO after sales service offer individual training for correct maintenance of the machine unit.

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Maintenance activities on machine unit that have to be done, are listed in table Frequency Maintenance work Daily Weekly

Carry out the process checking of oil level in the oil tank --------

Monthly

Carry out the process testing automatic cutting in of auxiliary oil pump

Every three months

Compare the recorded operating valves from the operating record throughout this period to determine trends

Every Six Months

----------

Annually

Carry out inspection stages 1-3 in accordance with the inspection concept

3.0 M/S DRESSER RAND Daily • Visually inspect the turbine for external damage. • Check oil level • In reservoir • To oil level line on bearing case(ring oiled system) • In Wood ward mechanical governor Weekly 1

•

Check operation of auxiliary oil pump (on turbines with this equipment.

•

Chock operation of all low oil/air pressure shut down defect(s).

•

Drain small quantity of oil from system and conduct an oil analysis. Determine need for oil change. If system is equipped with an oil filter element, change the element at time of oil change.

•

Lubricate governor lever connection.

Monthly •

Check overspeed trip

Annually Shut down the turbine and perform the following. •

Remove and clean steam Strainer. Replace every three years.

•

For turbine with a Woodward mechanical governor- drain oil, flush and clean. R e-fill with new oil

•

Remove top half of turbine casing and

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• •

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o

Clean scale and foreign materials from wheels, buckets and nozzles.

o

Check carbon rings for wear and remove, clean and re assemble

o Check thrust bearing and end play. Remove sentinel valve and check for proper operation using air pressure. On a turbine with a pressure system, drain water and clean foreign materials from oil reservoir .

4.0 M/S COPPUS (TUTHILL) Maintenance and Inspection Schedule Maintenance requirement and the corresponding schedu le will vary with the application and service conditions. The following maintenance and inspection guidelines are recommended for turbines operated under normal conditions . Suggested Maintenance and inspection Schedule

Frequency

Daily

Maintenance or Inspection Procedure Check oil levels in bearing housing and governor. Add oil if required. Check for smoothness of operation, unusual noises, or other changes in operation conditions. WARNING Do not attempt to measure coupling temperature while the turbine is running Check overall appearance of turbine for steam, oil, or coolant leaks, and for external damage.

weekly

Test the overspeed trip system both by gradually increasing turbine speed until the trip speed is attained, and by manually actuati ng the trip lever. This exercise will not prevent sticking of the overspeed trip valve and linkage due to corrosion or steam deposits Check throttles valve and valve linkage for freedom of movement. Sample the lubricating oil and replace it, i f necessary.

Monthly

Check Bearing housings for sludge, sediment, or water (condensate). Flush and refill as required. Check that oil rings rotate freely and smoothly. Check the throttle and overspeed trip linkage for looseness, wear, and freedom of movement. Change the oil in the Woodward TG Governor.

Yearly

Remove and clean the steam strainers. Inspect internal components of the throttle valve for wear, replace if required. Replace valve stem seals . Clean and inspect the overspeed trip valve. Replace worn parts. Replace valve stem seals . Thoroughly inspect the governor linkage and overspeed trip linkage for wear. Replace as required. Inspect, clean and flush bearing housings, oil reservoirs, and cooling water

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chambers. Inspect carbon ring gl and seals. Replace as required. Check operation of the sentinel warning valve . Check alignment and foundation . Check calibration of all instruments . 5.0 M/S ELLIOT Frequency

Daily

weekly

monthly

Annually

Scheduled Maintenance Guidelines Maintenance Description Check all oil levels and add oil as necessary. Check bearing and lubricating oil temperature. Check turbine speed. Check smoothness of operation. Investigate sudden changes in operating conditions and unusual noise changes . If daily shutdown is doing, check the trip valve by striking the hand trip lever. Exercise trip valve to prevent sticking due to deposits or corrosion. If on a continuous operation schedule, exercise the trip valve by striking the trip lever. Reset the trip lever after the turbine speed decrease approximately 80% of the rated speed. Sample lubricating oil and renew as required Check governor linkage for excessive play, renew any worn parts Check the overspeed trip by overspeed the turbine, (if the driven machine permits) Check all clearance and adjustments Remove and clean the steam strainer, if the strainers are exceptionally dirty clean every six month Inspect the governor valve seat. Hand laps the valve seat if uneven wear exist. Replace the governor val ve stem packing Clean and inspect trip valve. Replace the worn-out parts and hand lap if required. Disassemble, inspect and clean the overspeed trip linkage. Inspect trip pin and check for easy of operation Check Journal bearing and rotor locating bearing and for wear and replace if required. Inspect and clean bearing housing oil reservoirs and cooling chambers. Lift turbine casing cover and inspect rotor shaft, discs, blades and shrouding. Inspect carbon rings and replace as necessary. Remove rotor assembly from casing and inspect reversing blades and nozzle ring. Check operation of sentinel valve. Adjust and check the overspeed trip when turbine is put back in operation

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6.0 M/S TRIVENI Recommended maintenance schedule Scheduled preventive maintenance is essential for continued optimum performance and long service life of the turbine. Turbines used for standby service should be operated at regular intervals to minimise problems normally associated with idle equipment and to ensure that, the turbine is operable when needed. The following are general requirements for scheduled maintenance. Weekly • Check for leakage(Steam, water and oil) • Check turbine oil level Monthly • Check for moisture in oil. • Check operation of turbine(if standby unit) • Check over s peed trip • Verify oil pressure(if pressure lubricate) • Take oil sample for examination Quarterly • Calibrate pressure and temperature switches(if installed) • Clean and lubricate all linkages • Check freedom of movement of all linkages • Take oil sample for examination Annual • Replace oil filter elements(if installed) • Inspect governor valve for scale • Check torque of bolting • Clean steam strainer Operation condition can cause variation in above schedule, for example, operation in desert region, humid regions etc…

7.0 M/S MURRAY (TUTHILL) Use this section to structure a regular program of inspection and maintenance. Murray turbines are manufactured in various frame sizes and model numbers. Special features plus variations in local conditions make it impossible to standardize on a general maintenance schedule that would apply equally to all situations. Therefore, this section is designed to help operators to begin and customize a maintenance program and help to establish guidelines for periodic inspections and maintenance. Monthly inspection Check the overspeed trip by accelerating the turbine to trip speed

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Quarterly (3 months) inspection •

Clean all linkage systems and Inspect for wear, Clean and oil or grease all the moving parts. (Fulcrum points) For units with Inlet operating temperatures above 500deg F high temperature grease should be used to lubrication on linkage parts . (DuPont Krytox GPL407, Bostic Never-Seez #235210 NHTC14 0r equivalent)

Six month inspection •

Remove and inspect the bearing. Inspect the radial contact surfaces (journal) and the axial contact surfaces thrust faces). Make sure that there is no signs of overheating , excessive wear (including dents , grooves or tears ), or dirt.

•

Check the effectiveness of all drains

•

Disconnect couplings- Remove oil grease and sludge and then flush. Inspect the hub and cover teeth. Then dry and replenish with high quality grease.

•

CHECK THE SENTINEL AND RELIEF VALVES TO ENSURE THAT THEY ARE OPERATIONAL. The relief valve should start opening when the sentinel valve opens and should completely open when the pressure in the casing is 10% above normal pressure.

•

Operate the turbine without a load and inspect governor operation and vibrations.

Yearly inspection •

Drain the governors Oil if applicable, while it is hot; flush the gove rnor's pump clean with the lightest grade of the same oil. Replace with high quality oil of the recommended grade and viscosity.

•

Remove and clean the governor valve and internal steam strainer. Make sure there are no leaks.

•

In pressure lubricating turbine , drain and clean the reservoir. In reservoirs with large capacity, where the cost of oil is a consideration. It may be convenient to check the sample of the oil before decide to change.

8.0 M/s M ITSUBISHI MAINTENANCE MANUAL General It is recognized h t at the internal inspections must be scheduled to suit plant load demand. However it is obvious that for economic reasons and to reduce forced outage for corrective maintenance general knowledge of the internal condition of the turbine at all times is desirable. A systematic check during operation to detect the significant change in this condition is a valuable guide. A complete and detailed “case history” starting at the time of installation should be complied for each turbine. The history should include a description and analysis of any unusual circumstance during its operational as well as any noteworthy condition found during

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inspection: Also a statement of the corrective measures taken or planned. The first complete inspection of a new turbine forms the most valuable datum point in this history and we recommend that a very thorough inspection be made at the end of operation. We recommended before the turbine out of service for inspection the following should be checked and the “case history” reviewed to determine items requiring especial attention and investigation. • • • • • • • • • • • • •

Check increase in vibration and make careful of any increase and the location Check oil leakage from the piping, bearing oil seal rings and the operating mechanisms Check steam leakage from the joint and valve stem Is the control system stable Are there control devices operating satisfactorily? Does automatic overspeed trip function at correct speed? Does the trip and throttle valve close promptly when tripped? Does the trip and throttle valve stop the unit when tripped? Does the governor valve close promptly when tripped? Are the rotor glands sealing properly? Has there been any change in lubricating system oil pressure? Has white metal or other metal been found on oil screens? Has there been any change in bearing outlet oil temperature?

15.0 References • • • • •

API-611 4th Edition: General Purpose Steam Turbines for Petroleum, Chemical, and Gas Industry Services API-612- 5th edition: Petroleum. Petrochemical and Natural Gas industries-Steam Turbines -Special Purpose Applications NEMA SM 23 / SM24 Site specified standards Various Turbine vendors web-sites

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