Cold Weather Preparedness Plant Winterization Lessons Learned & Best Practices

Transcription

1 Cold Weather Preparedness Plant Winterization Lessons Learned & Best Practices

2 Cold Weather Preparedness RF Criteria For Plant Visits: Generating facilities that experienced repeated freezing or cold weather related issues during the 2013 through 2017 winter periods. Multiple unit generating facilities that experienced freezing or cold weather related issues during the 2014 through 2017 winter periods. New generating facilities. 2

3 Onsite Visit Locations (all) 3

4 Cold Weather Preparedness Each Plant Visit Was NOT: A formal certification that the facility was fully and adequately prepared for winter operations. A comprehensive review of all plant systems, equipment and devices. 4

5 EQUIPMENT PROTECTION: Although some of the observations and practices were unique to an entity, the following can be generally applied: Installation of additional freeze protection. Erecting wind barriers. Fabricating new enclosures or modifying existing ones. Utilizing double insulation. Replacing damaged equipment with a more reliable design. Adding kerosene to fuel oil system to minimize gelling Treating coal and/or limestone systems with anti-freezing solutions. 5

6 Utilizing the system/equipment Resistance Temperature Detectors (RTDs) as ambient temperature indicators to confirm operation of area heaters during periods of unit shutdown. Ensuring that end-of-line heat trace indicators are installed on all plant piping susceptible to freezing conditions. Upgrading the original 3-watt heat trace design with a more effective 5- watt system. Remote monitoring and alarming of all transmitter enclosures exists from a Distributed Control System (DCS) display in the plant control room. Remote monitoring of heat trace circuit amperage from a dedicated display in the plant control room. 6

7 IMPROVING OPERATIONS: Although some of the observations and practices were unique to an entity, the following can be generally applied: Conducting meetings with staff to discuss lessons learned. Completing pre-winterization walk-downs of entire facility. Increasing frequency of operator rounds. Reviewing troubleshooting instructions between electricians and plant operators for heat trace panels/systems. Assigning a dedicated individual to monitor critical areas. Assigning contractors to observe and maintain portable heaters. 7

8 Commencing winter preparations in late summer/early fall to ensure sufficient time to address any deficiencies. Conducting additional winter pre-job briefs prior to beginning outside work to ensure personnel safety. Use of an Operator Actions Matrix to indicate and describe the necessary actions based on different ambient air temperatures. Use of plant staff for installing heat tracing who are more readily available and better understand the impact to plant operations instead of contractors. Use of a Heat Trace Equipment simulator for training personnel on proper installation and troubleshooting techniques. Although the winterization program has provisions for two-man operation based on ambient temperature, in order to ensure personnel safety, a corporate work-alone policy dictates the allowable tasks and responsibilities when operating staff are required to work alone. 8

9 Attempting to resolve inherent design issues with other vendors when the OEM is unable to provide a better or permanent solution. Effectively utilizing the knowledge and skills of a relatively small staff to accomplish all winter readiness objectives. Installation of a new 500 gallon kerosene tank to ensure an adequate supply of kerosene is available for all portable space heaters if fuel delivery is delayed. Design and installation of permanent enclosures surrounding the drum level transmitters with provisions to remove ceiling and floor when cold weather preparedness is no longer required. Ensuring that a formal and thorough heat trace and insulation audit was conducted to ensure winter readiness. Disabling of status lights and removing labeling on local heat trace panels for circuits that are not being utilized. To supplement the onsite emergency diesel generator, a portable generator is available for relocation to other areas of the plant site. 9

10 Review of lessons learned document and participating in post-winter recap meeting with the entire generation fleet. Changing the lubricating oil for the ID Fan Booster lube oil system to another type of oil with a lower operating point of minus 40 degrees F. Implementation of a Conservative Operations and Maintenance Activity during extreme weather events or other conditions which may impact the safety of plant personnel or reliability of the facility. Notifications that conservative operations are in effect are made throughout the plant. Building a roof over top of a Safety Shutoff Valve (SSOV) to prevent the vent from being blocked with ice/snow, causing failure of the CT cavity leak test and initiating a shutdown of the CT during startup. Use of removable metal enclosures on building ventilation louvers. Installation of heat trace and insulation on ID Fan control oil return lines. 10

11 Development of a Plant Freeze Protection Procedure which addresses the following: Areas not protected by the installed systems as well as when and what operator action is required in the event of installed system failure. Establishment of Control Points (points to be monitored in the absence of other obvious indications/alarms) Describing the heating area limitations of temporary heating sources. Directing the practice of maintaining water flow to larger areas or entire systems to prevent freezing. Directing the draining of water from system if feasible upon failure of freeze protection. Describing the heat trace protection boundaries of equipment/systems. Providing lay-up procedures to prevent freezing on idle equipment/systems. Heightening awareness to areas where cold weather readiness may create an undesirable condition: Operating air handling units which may create higher building temperatures during early winter periods when higher outside temperatures may temporarily occur. Closing of building ridge vents which may prevent the escape of hydrogen gas if a generator leak would occur. 11

12 Trough cover designed by plant personnel to prevent water overflow causing large ice formation which if broken free, caused line breaks, damage, and ice accumulation on equipment below. Typical heat trace cabinet located throughout plant site for monitoring, control and alarming of heat tracing circuits. 12

13 Newly installed insulated weather barrier in boiler room to prevent the entry of cold air which caused freezing of feedwater flow transmitter. Newly fabricated enclosure for feedwater flow transmitter. 13

14 Portable heaters are used to keep the HRSGs from freezing when off line to keep from draining the boilers. This also shortens the start up time since the boiler is kept warm. Replacement of various transmitter enclosures with improved design to maintain internal temperatures above freezing conditions. 14

15 Positive Observations/Best Practices Remote monitoring and alarming of all transmitter enclosures from Distributed Control System (DCS) display in plant control room. Remote monitoring of each heat trace circuit amperage from a dedicated display in the plant control room. 15

16 Permanent enclosures surrounding the steam drum ends for site glasses and transmitters. The floors and ceilings of the enclosures are only installed in preparation for winter readiness. New O Brien Heat Trace system with exterior clamps. Old design utilized metal clamps that were internally secured to the transmitter sensing lines and directly connected to the structural steel which acted as a heat sink and resulted in freezing of the sensing lines. 16

17 Temporary heaters and ducting utilized to prevent the formation of ice and snow on the surface of the air inlet filters. Specially designed heated blankets are used to prevent the demineralizer lines from freezing. These blankets use Velcro fasteners to attach to the hoses. They can be removed to prevent damage to the blankets during the summer. Lessons Learned and Best Practices slides are posted on the rfirst.org website under the Learning Center tab: Plant Winterization Best Practices ppt 17

18 Configuration of Inlet Bleed Heat (IBH) System used to divert a portion of the combustion turbine compressor hot air from interstage to inlet filter boxes. Lessons Learned and Best Practices slides are posted on the rfirst.org website under the Learning Center tab: Plant Winterization Best Practices ppt 18

19 Disabling the Heat Trace Status lights and removing labeling for circuits not-inuse which aids in the troubleshooting process and avoids confusion if a status light is illuminated for a non-existent circuit. 19

20 Roof built over top of the SSOV actuator to prevent exhaust vent from blocking with ice/snow. 20

21 Removable metal enclosures over the wall louvers in the area of the auxiliary boiler. 21

22 Insulation and heat trace on the ID Fan hydraulic control oil return line. 22

23 Placed Thermometers inside all outside boxes as well as all buildings housing critical components 23 Boxes that did not have glass installed, they drill the box to provide a temperature reading. Without opening the box

24 Pushing this button the operator can visually check if all indicator lights are working properly All indicator lights lit up 24

25 RF Cold Weather Lessons Learned Plant trip Two of three IP drum level transmitters froze causing a lowlow-low drum level indication. Gas turbine and duct burners tripped after 15 second time delay. Two of the three transmitters were in a separate enclosure. Enclosure heater powered from heat trace on instrument tubing. Only wiring for the enclosure heater shorted and failed. Exposed heat trace within the enclosure provided sufficient heat during higher ambient temperatures giving appearance of acceptable operation. Enclosure heater thermostat was not wired to heater circuit which allowed uncontrolled operation and ultimate damage to wiring due to overheating. 25

26 RF Cold Weather Lessons Learned Heat trace system checked once per shift when ambient temperature is below freezing. Normal expected current is 10 amps. Recorded current was 3 amps. No heat trace system alarms existed. Three alarm functions are high & low current, and ground fault. Low current alarm set at 1 amp. Since circuit failed open, ground fault alarm did not register. Ground fault alarm occurred when technician disturbed wires when removing cover. Heat trace circuit was rewired and thermostat properly connected. 26

27 ERCOT 2017 Weatherization Workshop December 18-19, 2016 Issues: Eight (8) generators experienced outages or derates. ERCOT followed up with spot checks. 27

28 ERCOT 2017 Weatherization Workshop Lessons Learned Plant 1 trip Ten critical components froze due to incomplete list of critical components: GT performance heaters (2) Compressor bleed valve air regulators HRSG HP flow transmitter sensing lines (2) HRSG LP flow transmitter HRSG HP attemperator HP bypass Condensate hotwell level flow transmitter Instrument air compressor coalescing filter and air dryer 28

29 ERCOT 2017 Weatherization Workshop Lessons Learned Plant 2 trip Steam seal pressure transmitter froze due to lack of heated wind break enclosure. Plant 3 derate HP superheater attemperator valve froze to the valve seat due to a loose connection on the associated heat trace cable. Plant 4 trip Two of the three main turbine throttle pressure transmitter valve bonnets froze due to inadequate insulation. Plant 5 trip One of the four drum level transmitters froze due to tripping of main breaker in heat trace sub-panel for a ground fault on one of the circuits. Plant 6 trip BFP suction strainer differential pressure due to damaged power connection boot for the heat trace cable on the root valves and heat stress cracks and brittle heat trace cable around the root valve. Plant 7 temporary derate frozen instrument air line caused a pressure transmitter to show a false low reading due to mechanical room louver vents being left open with vent fan in manual and space heaters not working. 29

30 ERCOT 2017 Weatherization Workshop Lessons Learned Plant 8 trip Deaerator level transmitter froze due to heat trace circuit failure as a result of corrosion on termination to fuse block. 30

31 ERCOT 2017 Weatherization Workshop Lessons Learned January 6-7, 2017 Issues: Six (6) generators experienced outages due to cold weather. ERCOT followed up with spot checks on three of the units. 31

32 ERCOT 2017 Weatherization Workshop Lessons Learned Plant 1 trip BFP suction strainer differential pressure transmitter sensing line froze due to heat trace failure causing a pump trip signal and subsequent unit trip. Plant 2 derate Lower steam coil developed a leak inside the FD fan intake resulting in ice forming on the bottom side of steam coil which damaged the fan blades. Plant 3 trip HRSG HP steam flow transmitters froze due to failed heat trace panel control modules resulting in two heat trace circuits not being energized. Plant 4 trip Deaerator flow transmitter sensing line froze creating a false high flow rate and causing the DA level control valves to close which allowed the DA level to drop resulting in a MFT. 32

33 ERCOT 2017 Weatherization Workshop Lessons Learned Plant 5 trip Loss of instrument air was caused by freezing of the air dryer pre-filter which restricted instrument air flow resulting in closure of the gas trip valve. Plant 6 trip HRSG HP feedwater high range flow transmitter, low side sensing line froze. Contractor that performed the fall audit on heat trace did not correctly terminate the associated heat trace circuit in a junction box. 33

34 Questions & Answers Forward Together ReliabilityFirst 34