A.B. Hopkins Generating Station Circulating Water System

A. B. Hopkins Generating Station

OPERATING PROCEDURE

A.B. Hopkins Generating Station Circulating Water System

August 1 2014 Operating Procedure Unit 2 HP2A

TABLE OF CONTENTS

Section Page

1.0 Introduction 1

1.1 Purpose and Scope 1

1.2 System Identification and Scope Definition 1

2.0 SYSTEM STARTUP 2

2.1 Preoperational Procedures 2

2.1.1 Prerequisites 2

2.1.2 Prestart Requirements 2

2.2 Precautions and Limitations 2

2.3 Steam Turbine System Block Flow Diagram 7

2.3.1 Steam Turbine Startup 7

2.4 Prepare Steam Turbine for Startup 10

2.5 Cold Startup Procedure 13

2.6 Hot Startup Procedure 18

3.0 SYSTEM NORMAL OPERATION 22

3.1 System Routine Checks 22

3.2 Turbine Valve Testing 24

3.3 Steam Turbine Protection Device Testing 25

4.0 SYSTEM ABNORMAL OPERATION 26

4.1 Water in the Turbine 26

5.0 SYSTEM SHUTDOWN 28

5.1 Steam Turbine Shutdown 28

5.2 System Post-Shutdown Checklist 29

5.2.1 Short Term 29

5.2.2 Long Term 29

6.0 ALARM RESPONSES 30

6.1 Summary of Alarms 30

7.0 CHECKLISTS AND TABLES 51

Table 1 - Power Supply Checklist 51

Table 2 - Prestart Valve Lineup Checklist 51

Table 3 - Local Indicating Instruments 54

Table 4 - Control Room Indicating Instruments 56

8.0 REFERENCES 56

8.1 P&ID 56

8.2 Electrical One Line Diagrams 57

8.3 Control Diagrams 57

8.4 Instrument Loop Diagrams 57

8.5 Instruction Manuals 60

8.6 Miscellaneous 60

Draft Page i

A.B. Hopkins Generating Station Steam Turbine System

August 1 2014 Operating Procedure Unit 2 HPA

1.0  Introduction

1.1  Purpose and Scope

The purpose of this operating procedure is to provide the operator with specific procedures for operating the Steam Turbine System. The operating procedures include those detailed procedures required to start up, operate, and shut down the Steam Turbine System in a logical, efficient, and safe manner. The Steam turbine System supplies the rotational energy required by the generator to create electrical energy. The operating procedure includes the following sections:

Ø  Section 2.0 - System Startup

Ø  Section 3.0 - Normal Operations

Ø  Section 4.0 - System Abnormal Operations

Ø  Section 5.0 - System Shutdown

Ø  Section 6.0 - Alarm responses

Ø  Section 7.0 - Checklists and Tables

1.2  System Identification and Scope Definition

The Steam Turbine System takes the steam from the boiler and converts the thermal energy into mechanical energy to be used by the electric generator. The system contains the following subsystems and major components:

a.  Steam Turbine

Ø  HP/IP Turbine

Ø  Throttle Valve/Steam Chest Assembly

Ø  Reheat Stop and Interceptor Valves

Ø  LP Turbine

Ø  Control Block

Ø  Turning Gear

b.  Lubrication/Control Oil System

Ø  Lube Oil Reservoir

Ø  Lube Oil Coolers (2)

Ø  Main Lube Oil Pump

Ø  Auxiliary Lube Oil Pump

Ø  Turning Gear Lube Oil Pump

Ø  DC Emergency Lube Oil Pump

Ø  Lube Oil Reservoir Vapor Extractor

Ø  Lube Oil Transfer System

Ø  Lube Oil Conditioning System

Ø  Control Oil System

c.  Gland Steam System

Ø  Gland Steam Condenser

Ø  Gland Steam Exhausters (2)

Ø  LP and HP Supply Control Valves

Ø  Spillover Control Valve

Ø  Gland Steam Desuperheater

2.0  SYSTEM STARTUP

2.1  Preoperational Procedures

2.1.1  Prerequisites

a.  The 125 VDC electrical distribution system is in service.

b.  The 480 VAC electrical distribution system is in service.

c.  The compressed air system is in service.

d.  The circulating water system is in service.

e.  The generator and main transformer system is ready for service.

f.  The fire protection system is in service.

g.  The main steam system is in service.

h.  The steam generation system is in service.

i.  The condensate cooling system is in service.

j.  The condensate and feedwater systems are in service.

2.1.2  Prestart Requirements

a.  All clearances are released and the equipment is in safe operating condition.

b.  The power supply lineup is correct per Table 1.

c.  The prestart valve lineup is correct per Table 2.

d.  All system instrumentation is available per Tables 3 and 4.

e.  All turbine supervisory instrumentation recorders are turned on, set to the proper time, and marking legibly.

2.2  Precautions and Limitations

THE FOLLOWING PRECAUTIONS ARE SYSTEM SPECIFIC OPERATIONAL CONSIDERATIONS THAT MUST BE CLOSELY FOLLOWED. FAILURE TO FOLLOW THESE PRECAUTIONS MAY RESULT IN PERSONNEL INJURY OR EQUIPMENT DAMAGE.

a.  The turbine lube oil must be maintained within 110°F to 120°F at the coder outlet while at synchronous speeds. Operation outside these design temperatures may cause high vibrations or inadequate bearing lift at the journals.

b.  The turbine oil tank vapor extractor must be in service whenever any lube oil pumps are running. Without the slight system vacuum, oil and/or oil vapors could escape causing a potential fire hazard.

c.  Some of the turbine bearings and lube oil piping are located close to the high temperature turbine parts and/or piping. Turbine lube oil is a flammable product and therefore any leaks, especially in the high temperature areas could cause an immediate fire. The oil flash point temperature is approximately 375°F. Report and repair any lube oil leaks immediately.

d.  The lube oil tank level should be monitored closely. If any dramatic change in level (up or down) has occurred, notify the shift supervisor immediately.

e.  Use caution when working on or around air operated control valves and rotating equipment. They may move or start without warning.

f.  Clean up any lube oil leaks immediately to prevent unsafe, slippery conditions.

g.  All pumps must be properly vented for proper operation and efficiency.

h.  All oil level bulb/indicators are filled to the proper operating level (50 to 75% full).

i.  Minimize the use of the exhaust hood sprays during startup to avoid water impingement damage to the LP turbine blades.

j.  Avoid operating the turbine at extremely light loads for any considerable period of time to prevent overheating the exhaust end turbine blades of the LP turbine sections.

k.  Do not operate the vacuum pumps without gland steam to avoid drawing air through the turbine gland seals. (The vacuum pumps are discussed in detail in the Condensate System.)

l.  Place the turbine on turning gear before admitting steam to the turbine gland seals. Sealing steam must NOT be admitted to a turbine which is completely stopped. Uneven heating will occur which could result in bowing of the turbine shaft.

m.  Never roll the turbine until eccentricity is normal.

n.  Maintain vacuum as high as possible during the starting period to avoid undue heating of the LP turbine. Excessive heating can cause unnecessary stress due to expansion of the LP turbine internal components.

o.  During shutdown periods, maintain the turbine on the turning gear whenever possible to minimize rotor distortion.

p.  Do not operate the turbine at critical speeds.

q.  Adhere to all recommended heat soak periods to ensure even warm-up of all turbine components.

r.  Avoid running the DC lube oil pump for extended periods when an AC pump is available.

s.  Allowable temperature and pressure variations recommended by Westinghouse are as follows:

Ø  Main Steam Pressure - The pressure at the turbine throttle valve inlet flange should be controlled so that it does not exceed 105% of rated pressure. During abnormal conditions, the main steam pressure may exceed rated pressure momentarily by 30%, but the aggregate duration of such momentary switch shall not exceed 12 hours per 12 month operating period.

Ø  Reheat Steam Pressure - The steam pressure at the turbine reheat admission is not controllable so no limits for switches or transients are necessary. The pressure at the exhaust connection of the HP turbine should not be greater than 25% above the high pressure exhaust pressure existing when the HP turbine section is passing the maximum calculated steam flow at normal operating conditions.

Ø  Main Steam Temperature - The main steam temperature at the turbine throttle valve inlet flange should average not more than rated temperature over any 12 month operating period. In maintaining this average, the temperature should not exceed rated temperature by more than 150°F.

During abnormal operation conditions, the temperature at the turbine throttle valve inlet flange should not exceed rated temperature by more than 25°F for operating periods not more than 400 hours per 12 month operating period, nor rated temperature by more than 50°F for swings of 15 minute duration or less aggregating not more than 80 hours per 12 month period.

In maintaining the temperatures specified in the preceding paragraph, the steam delivered through any turbine main inlet flange must be within 25°F of the steam delivered simultaneously through any other main inlet flange. During abnormal conditions, this difference may be as high as 75°F for periods of 15 minutes maximum duration providing such occurrences are at least four hours apart.

Ø  Reheat Temperature - The steam temperature at the turbine reheat admission should not average more than rated reheat temperature over any 12 month operating period. In maintaining this average, the reheat temperature shall not exceed rated reheat temperature by more than 150°F.

During abnormal conditions, reheat temperature should not exceed rated reheat temperature by more than 25°F for operating periods totaling not more than 400 hours per 12 month operating period, nor rated temperature by more than 50°F for swings of 15 minutes duration of less, aggregating not more than 80 hours per 12 month operating period.

In maintaining the above reheat temperature averages, the steam delivered through any hot reheat inlet zones in the turbine must be within 25°F of the steam delivered simultaneous through any other hot reheat zone.

During abnormal conditions, this difference can be as high as 75°F for periods of 15 minutes maximum duration providing the occurrences are at least four hours apart.

t.  Other Limits and Settings established for Unit 2:

Ø  Rotor eccentricity should not exceed 0.003" double amplitude movement.

Ø  Bearing temperatures:

·  Up to 185°F considered normal

·  210°F alarm

Ø  Thrust bearing metal temperatures:

·  Up to 185°F considered normal

·  210°F alarm

Ø  Vibration limits (double amplitude - mils)

·  3.0 mils - satisfactory

·  5.0 mils - alarm

·  10.0 mils - trip

Ø  When starting the unit from a cold condition (Initial impulse chamber metal temperature below 250°F), steam should be admitted with a minimum of 100°F superheat to the turbine at the main inlet, but not more than 800°F total temperature.

The reheat inlets may be kept at a lower temperature, but this should not be more than 150°F lower than the main steam inlet temperature at zero load and 50°F at maximum load.

Ø  Controlled start thermocouples provide guidance for operation of the turbine as discussed below:

Starting and loading recommendations are designed to protect the rotor against thermal cracks resulting from rapid changes in steam temperature. Thermal stresses in the rotor are developed during startup when the rotor surface is suddenly exposed to hot steam, and during load changes when the internal blade path temperature changes with load and inlet steam conditions. Starting stresses depend on the mismatch between rotor metal and steam temperatures, and load-changing stresses depend on the amount of load change and the rate at which it is performed.

For hot start conditions, refer to the Starting and Loading Instructions which specify the recommended time to bring the rotor to speed as a function of initial rotor temperature and inlet steam conditions. (Thermocouples are provided in the impulse chamber to measure the inner cylinder metal temperature; this will approximate the rotor temperature in this area.)

The temperature difference between the horizontal flange and the bolts of all cylinders other than LP elements should not exceed 250°F. Experience indicates that this differential temperature limit will not be exceeded under normal startup and load changes if the Starting and Loading Instructions are closely followed.

Ø  During cyclic load operation, changes of load and steam conditions should be controlled in accordance with the Starting and Loading Instructions.

Ø  During normal unit operation, if the throttle steam pressure falls below 80% of normal, or if normal throttle or reheat temperature drops 150°F, load should be removed from the unit and the unit tripped.

Ø  Turbine exhaust steam temperature should not exceed 175°F for continuous operation or 250°F for periods of more than 15 minutes.

When operating with high exhaust temperature, particular attention should be paid to differential expansion, vibration, bearing metal temperature changes, etc.

The temperature limitations listed above are for periods when the exhaust hood sprays are out of service. The sprays are regulated to limit the maximum exhaust hood temperature to 170°F.

Ø  Steam supplied to the turbine glands should contain not less than 25°F superheat.

Ø  The vacuum trip is set to trip the unit in the range of 17" - 18" vacuum.

Ø  The overspeed trip is set at 3,960 rpm.

Ø  The unit may not be operated with the reheat stop and/or interceptor valves open on one side and closed on the other side. This restriction does not apply for very short periods of time such as when the valves are tested for stem freedom.

Ø  It is recommended that the minimum load for normal operation be 5% of rated load.

u.  Operation at less than 5% rated load should be avoided. However, when necessary auxiliary load may be carried indefinitely on the main generator following rejection of the main load provided:

Ø  LP turbine exhaust temperature does not exceed 175°F (with the exhaust hood sprays out of service).

Ø  All supervisory instrument readings are within allowable (alarm) limits. Particular attention should be given to differential expansion readings. Rapid or continued changes in readings may require timely action to avoid exceeding allowable limits.

v.  The turbine-generator unit should not be motored for any extended periods. It is recommended that such motoring operation be limited to less than one minute to prevent overheating of the turbine blading due to windage and lack of ventilation.

w.  Passing steam through the turbine with the rotor at rest is to be avoided.

x.  Avoid undue heating of the low pressure portion of the turbine beyond what is required for operating under vacuum. This is to avoid: