Controlling Coupling Guard Leakage by Improved Design

ME ROTIC Dubai Oct-12-14, 2021Eliminating Hydraulic Control and Trip Oil From

Steam Turbines Through Electrical Actuation AndSelf Contained Hydrostatic Trip Valves

By Kim Lovejoy; Lovejoy Controls & Abdulrahman Alkhowaiter; Saudi Aramco

Steam Turbines Require High Power Actuators For Steam InletWith High Response Speed; Governor Valves and Stop Valves

High Power Actuators are used:

Governor Valve Actuator:Must be of high force:Example, the Delaval 30,000HP turbines at UGP-SHGPhave an actuator rated at8500 Ibs. force, based uponcontrol oil system pressure.

The reaction time of actuatorto shaft speed commandinputs from governor must beno more than 0.01 seconds.

Trip Valves: The actuator istraditionally hydraulic, but isused as a static hold deviceagainst spring closing force.Main function is to maintainvalve in open position.

Governing Valves Require High Power Actuators with High Response Speed: Hydraulic Has Been Industry Standard Since 1903

Actuator Specifications Typical:

The actuator must be of highforce: Example, Delaval30,000 HP turbines have anactuator rated at 8500 Ibs.force, based upon control oilsystem pressure.

The response time of actuatorto shaft speed commandinputs from governor must beinstantaneous; no more than0.01 seconds.

The connection to valvelinkage and valve rack mustbe stiff, otherwise loosenessin bushings or flexibility willlead to non-linear reactionand poor speed control.

Governing Valves Require High Power Actuators: System Relies on Control Oil Systems from 150 to 1000 psig with Multiple Elements

Hydraulic Control Has Weakness of Many Elements:

The Hydraulic actuator is maincomponent; it can haveinternal wear due to dirty oil orwater contamination. It alsohas seals which can leak.

The control oil systemcomprises, pumps, filtration,piping, and coolers all of whichcan fail and cause actuatormalfunction. The control oilsystem may or may not havepumps; smaller systems usethe lube oil itself.

The control oil because of itshigh pressure & flammability,comprises a fire hazardgreater than lube oil.

Governing Valves Require High Power Actuators: Hydraulic Actuators Can Have Reliability Problems due to Contamination-Wear

Hydraulic Actuator Failure:

In Many cases installationhas both Master Pilot valveactuator and Slave largeactuator.

Both are sensitive to oilcontamination with water anddebris. Have multiplebushings which wear.Linkages wear is anotherfailure point.

With time, the actuatorresponse to speed variationloses accuracy and speedhunting occurs.

The high operatingtemperature environmentreduces lifetime.

Governing Valves Require High Power Actuators: System relies on Control Oil Systems at 150 psig or Higher & Accumulators

Typical Lubrication & Control OilSystem Skid:

The Control oil system istypically separate on largemachinery of 40 MW andabove.

For API-612 machines, it isusually a part of thelubrication system however itadds a PCV valve, additionalpiping, trip solenoid valves,instrumentation, and anAccumulator.

By eliminating the control oilsystem, all the above capitalcost and future maintenanceplus reliability-failure costsare eliminated.

Aftermath of Turbine Destroyed by Oil Fire From Control Oil Piping Leakage; Is it possible to Eliminate the Control Oil System?

Safety: Flammable Oils used in Hydraulic Control:

When high pressure oilleaks, it sprays out as ahighly flammable mist ignitedon hot turbine casings.

It is true that lubricationsystem oil can also ignitefires but Industry experienceshows majority of firescaused by control oil circuits.

Cannot eliminate thelubrication oil system but itis possible to eliminate thecontrol oil system.

The goal is higher safety andreliability, and this can beachieved by engineeringsolutions.

Three New Technology Improvements: 1-Newer Generation Hydraulic Actuators Woodward Varistroke Utilizes External Control Oil

Existing Manufacturers of Complete Control Systems:

Woodward has acted toretain market share bydeveloping newer hydraulicactuators and system.

The Varistroke actuator herestill uses the completeconventional external controloil system circuit.

Other manufacturers such asBHGE are advocating selfcontained hydraulic controlvalve and trip valves, toeliminate the control oilsystem. This is called“Hydrostatic” system.

However, electrical actuationhas superior advantages.

Three New Technology Improvements: 2- Electro-Hydraulic Actuators REXA Self Contained Hydraulic System Closed Loop Actuator

Existing Manufacturers of Complete Control Systems:

REXA USA has built a selfcontained hydraulic actuatorwhich needs no externalcontrol oil system.

The actuator here still doesnot need the completeconventional externalcontrol oil system circuit.

Turbine manufacturers suchas BHGE are also advocatingsimilar self containedhydraulic control valve andtrip valves, to eliminate thecontrol oil system. This iscalled “Hydrostatic” controlsystem. No external controloil system.

Three New Technology Improvements: 3-Development of High Power Roller Screw Electrical Governor Valve Actuators in 1990’s

Eliminate Hydraulics by Utilizing High Power Electric Actuators:

Exlar USA actuators are thefirst in market with very highforce, linear accuracy about0.0005 inch.

Utilizes an 440 volt electricalcontroller that receivessignals from conventionalelectronic governors.

Designed for outdoor usage at60 DegC environment.However we recommendedinstalling actuator in anenclosed cabinet with airvortex cooler.

With above, we have achievedzero failures after 8 yearsoperation at two gas plants.

New Technology Improvements: Upgrading to Electric Actuators Exlar High Force-Speed Actuators on 5 MW 6000 RPM Turbine

5 MW Steam Turbine with oldHydraulic control system:

This turbine is a 5 MW output6000 RPM Westinghousedriving 1200 RPM generatorthrough a 5:1 reduction gear.The unit was unreliable, poorspeed control.

The hydraulic governor valveservomotor was modified byanother company with apneumatic positioneradjusting the servo motorpilot, but the remainder of theservo motor retained.

The control failed; theydestroyed five couplings dueto poor speed matching.

Westinghouse 5 MW 6000 RPM Turbine Retrofitted by Lovejoy Controls Inc. Electronic Governor, Control Valve Exlar Electric Actuator

Retrofit 5 MW Steam Turbinewith Electric Actuator:

Lovejoy removed allhydraulic control elementsand upgraded the unit toElectric actuated governorvalve, and Electronicgovernor.

Installed vector servo driveand Exlar GSX40 linearactuator.

The start up was flawlesswith speed control stableand +/- 2 RPM at alltimes. The load control wasappreciated by the customerLouis Dreyfus Commodities.

https://www.lovejoycontrols.com

Saudi Aramco Gas Plant Feb-2021: Retrofitting 30,000 HP Turbine Governor Actuator From Hydraulic To Electrical By Lovejoy

Wasit Shin Nippon Turbine Several Speed Control Failures:

Picture: 30,000 HP TurbineVoith Hydraulic Actuator hadoil contamination relatedspeed instability andshutdowns: 2017, 2018.

Decision by Wasit Admin andEngineering to upgrade toElectric Actuators.

CAD Drawing showing newExlar actuator selected with1.15 force factor more thanexisting Hydraulic actuator.

We spent many hoursimproving the design of thesupport stand and weldedattachment to bar.

Gas Plant Feb-2021: Retrofitting 30,000 HP Shin Nippon KT-101 Control System Layout Before Modifications

Gas Plant Feb-2021: Retrofitting 30,000 HP Shin Nippon KT-101 New Control System Layout After Modifications

Emergency Trip Valves: These are Spring Powered to Fail ClosedWith Conventional Hydraulic Piston Setting and Oil Dump Valves

Emergency Stop Valves areSafety Devices:

The valve uses a spring forclosing but must be set byhigh force such as hydrauliccylinder-piston pressure.

The trip valve must be able tobe tripped suddenly in 0.5seconds max. This isachieved by Solenoid dumpvalves draining pressure.

Such valves can be reliable ifoil is clean, but aredangerous with watercontamination or dirt causingsticking and failure to trip.

Therefore it is worthwhile toeliminate the control oil.

Three Optional Designs: Wasit Gas Plant 2022 Modifying Shin Nippon Trip Valves to Self Contained Hydraulic System; by Lovejoy Controls

First Option: Retrofit Existing with Self Contained Oil Module:

These are small selfcontained hydraulic unitssuitable to provide thepressure and flow needed tomaintain the valves open.

Such self contained units areresistant to contaminationbecause will not allow dustentry or water contamination.Uses stainless steelreservoir and tubing.

By working with Lovejoy, weimproved overall design bysimplifying components,minimizing pump sizing, andeliminating the oil cooler andrelying on convection cooling.

Proposed Wasit Gas Plant 2022: Modifying Shin Nippon Trip Valves to New Self Contained Hydraulic System

Retrofit Existing with SelfContained Oil Module:

The drawing shows existingdual stop valves withcontrol oil feed.

It is not recommended toutilize two independenthydraulic self contained tripmodules; more reliable &lower cost-maintenance toutilize single system with 2x 100% pumps.

No modifications requiredto trip valves; the system isdesigned to feed proper oilflow, pressure. No safetyimpact; the same hydraulicdump solenoids are used.

EHTTV: Gimpel Makes Self Powered Hydraulic Trip Valve Installed: Jazan DR Steam Turbines Driving Air Compressors

Second Option: Purchase NewEHTTV Self Contained OilModule Trip Valve:

The pictures show theGimpel stand alone EHTTVinternal hydraulic module.

The cost of EHTTV may beprohibitive if replacing twoexisting Stop valves, butwill be a good solution ifonly replacing single valve.

From system point of view,the EHTTV trip-safety issimilar to the first solutionof adding self containedhydraulic module. Both aresafer than conventionalcontrol oil systems.

EHTTV: Gimpel Makes Self Powered Hydraulic Trip Valve Installed: Jazan DR Steam Turbines Driving Air Compressors

Second Option: Installation ofNew EHTTV Self Contained OilModule Trip Valve:

The CAD drawing shows theGimpel stand alone EHTTVstop valve installed atJazan Refinery DR turbines.

The advantage of the selfcontained trip valve allowedmanufacture to eliminatethe control oil systemcompletely, because he isusing pneumatic actuator atgovernor.

From system point of view,the EHTTV safety andreliability is higher thanconventional systems.

Eliminating Oil: New Mitsubishi Alternative Design Stop ValveUses Geared Motor Setting and Pneumatic Trip

Third Option: Mitsubishi Trip Valve Eliminates All Control Oil:

The green color trip valve islatest development by MHIwhich eliminates control oilsystem by electric actuatoron governor and new tripvalve power source.

The trip valve has a springand geared electric motor toset the valve stem. Thepneumatic piston is used todisengage between motor-gear shaft and stem.

These designs may requiredamping devices such ashydraulic damper to dampthe stem to plug drop.

Eliminating Oil: New Mitsubishi Heavy Industries Alternative Design Stop Valve uses Geared Motor Setting and Pneumatic Trip

Mitsubishi New Trip Valve:

CAD drawing shows new tripvalve with geared motorlinked to valve stem and bluespring compressed by motor.

When trip action is required,the trip signal is sent to asolenoid valve which causesair piston to disengage thegear shaft from valve stem.

Potential issue with thissystem is that it may havehigh wear at pneumatic tripcontact point, or sticking atthis juncture and fail to close,and no damping at closure.This can be solved by designimprovements.

Thank You Elimination of control oil was our first goal in the introduction of

Electric Actuators in 2010 to Gas Plants Feed Gas Turbines. We expect to achieve it fully at Wasit Gas Plant in 2022 when the self contained

Hydrostatic system developed by Lovejoy-Aramco is installed.

By Kim Lovejoy; Lovejoy Controls & Abdulrahman Alkhowaiter, Saudi Aramco