GAS TURBINE & RECIPROCATING ENGINE
DECISIONS UPDATE
April 18, 2017
McIlvaine Company
TABLE OF
CONTENTS
Circor
provides Valves and Desuperheater Systems
HRST has
Steam Conditioning Solutions
Advanced
Valve Solutions Cooled Desuperheater
AECC
replaces CEMS with Predictive System for Seven Gas Turbines
NV Energy
Partners with Wipro on EWAM Program
Laborelec
(ENGIE) has Remote Monitoring and Niche Expertise Capability
Laborelec
provides IIoW on Intake Filers and Water Quality for Power Plants
Ethos
Energy Operates Monitoring and Diagnostic Center
Remote
Monitoring of Compressor Station Engines with Rockwell PlantPAx
Gas turbine attemperator problems provide a good
opportunity to demonstrate the value of IIoT empowered by IIoW (Wisdom).
Continuous sensing and data analytics need to be empowered with wisdom generated
by HRSG user group meetings, publications such as CCJ and the interconnection of
knowledge systems demonstrated by multiple Mcilvaine services.
Attemperator problems are at the top of the list for gas
turbine operators. Valves are playing an important role in the solutions.
Equally important is the control logic and continuous evaluation of conditions,
so we will be regularly covering developments in the Gas Turbine Decisions
Updates and posting articles in the intelligence system.
59D Gas Turbine and Reciprocating Engine Decisions
We will be conducting recorded interviews. Some will be for general
access. Others will be just for BHE Energy as part of our
4S01 Berkshire Hathaway Energy Supplier and Utility Connect.
Coverage in the IIoT & Remote O&M newsletter, webinars and intelligence system
will be expanded.
N031 Industrial IOT and Remote O&M
In fact we would like to bring together some of GE IIoT
experts such as Peter Spinney who gave a presentation on Sootblower optimization
in one of our BHE webinars and explore a similar approach to valve controls for
attemperators with people such as Michelle York.
The selection of valves for attemperator related service is
in one of 5 high performance valve decision guides being continuously analyzed
in
High Performance Valves and IIoT.
On GE Day at the 25th annual 7EA Users Group meeting, Nov
1-3, 2016, Michelle York of GE lead discussions on HRSG issues of which
attemperators were the component causing the most problems. CCJ editors covered
the event with the following editorial:
ATTEMPERATORS:
HRSG enemy No. 1
CCJ has published more editorial pages on attemperators
over the last 13 years than any other periodical serving the generation sector
of the electric power industry. These can be easily retrieved through the CCJ
search engine. CCJ is unique in its provision of analyses which can affect
decisions. McIlvaine believes the CCJ template can be beneficially expanded
across the power industry.
Bob Anderson (who organizes the HRSG forum) says that most
“internal-trim” attemperators in F-class combined cycles have been replaced with
more reliable equipment and have not been installed in new HRSGs for several
years but the newer designs have not solved all the problems.
If spray water leaks from the attemperator nozzle during
periods when steam flow is low, or zero, it will fall onto the internal surface
of the steam pipe and cause thermal-quench damage, and significantly increase
the quantity of water that must be drained during the next startup.
Anderson says he often sees evidence of leaking during a
review of operating data. “Sometimes the cause is insufficient inspection/repair
of the block valve, but mostly it’s due to the use of master control
valve/martyr block valve control logic. In my view, it’s not possible or
necessary to maintain tight shutoff at the control-valve seat if the block valve
maintains long-term tight shutoff.
“Master control valve/martyr block valve logic causes many
unnecessary block-valve open/close cycles and virtually ensures both valves will
leak after only a few runs. You can prevent leakage by arranging the logic to
open the block valve only once during startup — when exhaust temperature
increases to around 95°F—and to close only when the exhaust temperature
decreases below 95°F during shutdown.
McIlvaine poses the question of whether better logic
control is possible with the IIoT and better sensing of valve health, leakage,
corrosion, temperature, etc. which is monitored and analyzed remotely.
“Overspray occurs when more water is injected into the
steam than can be evaporated before reaching the thermocouple located downstream
of the attemperator. If the steam temperature downstream of the attemperator
decreases to within 30°F of saturation, damage to pipes, headers, and tubes may
result. Control logic should be arranged to prevent the control valve from
opening any further when this overspray limit is reached.”
“Most attemperators in use today use spring-loaded
variable-area spray nozzles which provide good atomization over a wide range of
flows; however, they depend on free movement of a poppet to work properly.
Oxidation of the poppet stem or guide and fouling by debris in the spray water
can cause nozzles to stick open or closed.”
“Attemperator manufacturers have worked to eliminate
oxidation issues by changing materials. Most now recommend installation of a
strainer upstream of the block valve to prevent valve and nozzle fouling.
Routine inspection of nozzles is important. When in doubt about a nozzle’s
condition, replace it with a new one and send the suspect nozzle to the
manufacturer for refurbishment.”
Circor says that they can deliver cost effective, reliable
performing steam conditioning solutions. The Aeroflow SCV is a Severe Service
Control Valve System that minimizes end user ownership. The Aeroflow SCV product
offers zero leakage, steam assisted desuperheating and multiple actuation
options in a competitive package.
Aeroflow SCV offers six models; two for Steam Control, two
with its Laval Nozzle using steam assisted desuperheating, and two utilizing a
spray ring header for desuperheating. All models offer ZERO leakage.
The Aeroflow Steam Assist Desuperheating models (SCV-LC/LD)
utilize the features of the Aeroflow Steam Control valve with the addition of a
Laval Nozzle. The Laval Nozzle atomizes attemperating spray water by using steam
assist technology. The performance benefit is excellent controllability and
rangeability with final temperature met immediately downstream of the
desuperheater (within 3 pipe diameters). The installed cost is lower due to
requiring very short run of special desuperheater piping.
The Aeroflow Steam Conditioning Spray Ring Header models
(SCV-RC/RD) utilize the features of the Aeroflow Steam Control Valve with a
traditional attemperator solution, which is customized for application
requirements. The performance benefit is good controllability and rangeability
with final temperature met within 10 pipe diameters. The spray ring portion can
also be used as a stand-alone unit for attemperation when pressure reduction is
not needed. The Aeroflow SCV is well suited for a variety of severe service
applications including:
Desuperheaters from CIRCOR Energy come in a variety of
configurations including probe style with fixed or variable nozzle, venturi and
double venturi. With a design that ensures finely controlled water spray, the
desuperheaters from CIRCOR Energy are highly effective in controlling steam
temperature close to saturation point over a broad set of steam conditions.
Circor has several divisions involved with desuperheaters.
They include: Leslie Controls,
Spence, and Schroedahl. Pibiviesse serves the oil & gas, petrochemical, water
transportation and power industries, providing ball valves available in side
entry, top entry and all welded construction in sizes up to 60 inch and in
pressure class up to ANSI 2500 and API 10000.
HRST helps turbine owners solve problems with engineering
support and training. Lester Stanley has many years of experience solving
attemperator problems. In one user group meeting he explained the sequence of
events at startup that often causes avoidable damage. When feed pumps are turned
on, he said, there’s a high differential pressure across closed attemperator
valves which often leak because of cycling wear and tear.
Water leaking by the valves enters the steam piping when
there is no, or low steam flow and minimal vaporization. Absent positive
drainage, water runs down the pipe to the superheater tube panels. The rapid
cooling caused by spray water entering the harps can warp and crack tubes and
damage headers. The same scenario may be repeated in the reheat circuit.
The leakage problem typically is easy to correct. Add a
tight-shutoff, fast-opening isolation valve upstream of the attemperator control
valve if one is not installed. If a block valve is installed and it is leaking,
upgrade to a quarter-turn ball valve with a metal seat at a minimum. Use smart
control logic and keep the isolation valve closed when desuperheating is not
necessary. Also look into the possible use of condensate pots if they are not
installed and consider a double-block-and-bleed arrangement in the spray-water
line. Check for leak-by during rounds and plan for valve service when required.
HRST also has a hardware solution. Combustion turbine
start-up and low load can damage HRSGs by high exhaust temperature and high
attemperator spray water flow. High spray water flows can damage steam piping,
superheaters, and reheaters. High turbine exhaust temperatures, especially those
at or above 1200°F, can cause oxidation and creep damage to the HRSG inlet duct
non-pressure part materials. These materials include liner plates, tube ties,
flow distribution plates and gas baffles. This leads to costly repairs and
unscheduled maintenance.
With the patent pending HRST QuenchMaster® Air
Attemperator, these problems can be avoided. This system enables safe low load
HRSG operation by reducing or eliminating attemperator spray water flow. Based
on HRST experience, this technology enables plants to run in emission compliance
with an additional 10-20% reduction in CT load. The HRST QuenchMaster Air
Attemperation System also avoids low load superheater and reheater steam
temperature control challenges.
There are applications for steam coolers in very complex
situations. One common example is if a cooler is not working continuously and
only has to function occasionally. This can occur, for example, during startup
and shutdown or in case of an emergency to protect the main steam lines. In this
instance the nozzle section will become very hot. The moment the cooler is
required to start, thermal shock will occur and the cooler will be permanently
damaged. In practice a very limited number of cycles can be expected before the
cooler is damaged.
Advanced Valve Solutions and HORA have developed a solution
for this particular problem, the “cooled desuperheater”. To avoid thermal stress
in the cooler valve body, the temperature differential between the cooling water
and the superheated steam temperature should be significantly reduced. A
temperature reduction of the valve body to the saturated steam temperature,
instead of superheated, will bring the temperature differential down to figures
which will not lead to thermal shock. The cooler is now suitable for numerous
starts and stops.
A limited amount of saturated steam is bypassing the
superheater and is brought into a “cooling jacket”. This saturated steam is
cooling the valve body, keeping it on saturated temperature. The saturated steam
leaves the jacket and will mix up with the super heated steam. The saturated
steam flow to the cooler is controlled by a small control valve and a manual
stop check valve. The use of cooled desuperheaters in Marchwood CCGT Power
Station is saving £200,000 per year.
At AECC in Little Rock analyzers that monitor emissions on
seven multi-stage gas turbines needed replacement. The company considered
options to either replace their analyzers with new, costly analyzers or replace
their hardware-based continuous emissions monitoring system with an alternate
solution. AECC recognized that replacing their current system with another
hardware-based CEMS would require a significant capital investment. In addition,
the ongoing maintenance needs of a hardware CEMS would produce considerable
expenses over its lifetime.
AECC thoroughly evaluated the option to implement a
software-based system and chose Software CEM from Rockwell Automation to help
achieve its emissions compliance requirements. The model-based, Predictive
Emissions Monitoring System (PEMS) utilizes powerful hybrid models of the
process with real-time sensor validation to provide predictive emissions values
with unparalleled accuracy. The use of hybrid modeling, through empirical models
and first principles knowledge, gives AECC the best representation of its
process behavior.
The project has been successful and the system was
certified through a Relative Accuracy Test Audit (RATA) as per 40CFR Part75.
Software CEM certified its initial RATA at better than 7.5% relative accuracy
and surpassed the U.S. EPA, CAMD requirements of +/- 10%.
A partnership between Wipro and NV Energy, an electricity and gas utility based
in Nevada, resulted in a successful Enterprise Work and Asset Management (EWAM)
program., NV Energy had to contend with dozens of legacy systems to support its
work and asset management functions. Actions taken were:
The first phase of NV Energy’s EWAM program, which focused on capital
construction for distribution assets, began in mid-2007. Before it selected
Wipro as its systems integrator, NV Energy had already chosen IBM’s Maximo (for
core asset and work management) and Ventyx Service Suite (for mobile workforce
automation). A critical aspect of Wipro’s bid was its knowledge of Maximo, which
NV Energy told us was better than IBM’s.” NV Energy had some very specific
requirements that were not available in the core Maximo product, and so needed
an integrator partner with a deep understanding of the software to make some
significant customizations and enhancements.
Phase one went live in late 2010. Phase two, which focused on NV Energy’s
compliance with DIMP and other gas regulatory requirements, went live in 2012.
This project was NV Energy’s first major IT initiative to use a global delivery
model, where a significant amount of work was done offshore. A strong IT partner
was vital, as NV Energy’s internal IT department lacked the resources to deliver
such a large-scale project. In fact, EWAM was run by staff from the operations
side rather than IT. As with many multi-year projects, there were unforeseen
barriers. During the project, some internal political challenges arose, and one
of the biggest hurdles to overcome convincing employees of the long-term
benefits of the EWAM program. Ultimately, it was time, persistence, and patience
that helped Wipro and NV Energy overcome these obstacles. The EWAM
implementation has helped NV Energy gain a lot of experience in large-scale IT
transformational projects.
Laborelec offers the full range of power plant monitoring services, including
remote monitoring. Experts follow up on alarms, anticipate problems, immediately
inform plant operators of potential issues, and advise them on the necessary
maintenance interventions.
Laborelec is a research and competence center in electrical
power technology. It was established in 1962 in order to support Belgian
electricity companies with research, development, and specialized services.
Today, it is part of ENGIE, a leader in energy. Its research and support extend
to water quality investigations and analysis of air intake filters for 40 gas
turbines and analyses to help improve selection and operation for a U.S. power
plant operator.
This operation would have the niche expertise and remote
monitoring center staffing to support for example gas turbine inlet filter
decisions at gas turbines worldwide.
The EthosEnergy Monitoring & Diagnostics (M&D) center monitors the performance
of all turbine technologies, including:
M&D is offered at three levels:
Operating parameters are assessed in real-time for any anomalies using scanning
and comparison algorithms as well as equipment performance equations. Whenever
an operating parameter is outside of specifications, a real-time alarm is
generated and automatically notifies all relevant parties of the anomaly.
Additionally, the M&D Center personnel compile operating data and send quarterly
reports that document tuning and performance information, data on each tuning
event and, if applicable, ECOMAX performance result.
EthosEnergy has been awarded a seven- year contract for full operations and
maintenance (O&M) services, plus installation of EthosEnergy’s proprietary
ECOMAX® technology, by Rockland Capital in support of Michigan Power,
a 1x1 GE 7EA natural gas-fired combined cycle cogeneration plant in Ludington,
MI. The contract is for full care, custody and control operations, and
maintenance including transition services, plus the installation of
EthosEnergy’s advanced ECOMAX® auto combustion tuning technology.
This is the second facility of Rockland Capital’s to have ECOMAX®
installed in the last twelve months, and third in total.
CenterPoint Energy-Mississippi River Transmission (CNP-MRT)
owns and operates 8200 miles of transmission pipeline that carried 1.6 trillion
cubic feet of gas throughout a nine-state region in one year. Delivering such
large volumes of natural gas through pipelines requires adequate pressure, which
is accomplished by reciprocating engine compressors typically every 40-100
miles. For CNP-MRT, each compressor station includes an average of four
compressor engines, and at least one of the four engines will run at 80 percent
365 days of the year. These engines maintain a pressurized flow—up to 2500
psi—to reduce gas volume up to 600 times and propel it through a pipeline.
This process entails heavy reliance on data from resistance
temperature detectors (RTDs) and thermocouple sensors to control the engine
compressors. Unfortunately, CNP-MRT’s legacy automation system provided little
visibility for remote management of the equipment, so the company embarked on a
pilot project to update its control architecture at one station that moves
natural gas across a three-state region — Missouri, Arkansas and Illinois.
For this pilot project at Horseshoe Lake station, CNP-MRT
tapped Rockwell Automation’s PlantPAx distributed control system (DCS) and its
open-architecture platform to constantly monitor engine operational data, such
as speed and load control visibility.
McIlvaine Company
Northfield, IL 60093-2743
Tel:
847-784-0012; Fax:
847-784-0061
E-mail:
editor@mcilvainecompany.com
Web site:
www.mcilvainecompany.com