Hobas Replaces Wood Stave Penstock
Meandering
through the White Mountains, a large wooden penstock served as the main water
supply for a local hydro facility called Jackman Station. It’s fed by the
Franklin Pierce Reservoir, which was created by the hydro's dam and surrounding
earthen dikes. The water elevation in the reservoir is managed according to
spring run-off.
Public
Service of New Hampshire (PSNH), the Granite State's largest electric utility,
serves more than 475,000 homes and businesses. PSNH’s power generation
facilities consist of nine hydroelectric plants, including the Jackman Hydro
station, which was built in 1926. This facility, located in Hillsborough, has
been serving the area for years, but the penstock was approaching the end of its
service life.
Prior to the
recent improvements, 5,000 feet of wood stave penstock extended from the
Franklin Pierce reservoir to a surge tank upstream of the powerhouse. This
7.5-foot diameter penstock was made up of vintage wood stave sections, circa
1926. Repairs were undertaken in 1954 and in the 1970’s, yet the downstream
sections of the wood penstock still leaked badly. This leakage caused icing
problems during winter months and required constant maintenance. In 2003, the
penstock had a significant rupture that impacted abutting properties. To prevent
future failures and ensure reliable operations of the hydro facility, repairs to
the existing penstock were necessary. In a series of contracts, PSNH decided to
replace the remaining wood stave penstock with a new pipeline.
Kleinschmidt,
headquartered in Pittsfield, Maine, specializes in energy and water resource
projects. They were retained to develop a feasibility study and engineer a
replacement pipeline. Kleinschmidt initially evaluated five pipe material
options for the penstock replacement: wood stave, concrete, HDPE plastic, steel
and fiber reinforced polymer (FRP). Factors that led to the final determination
included the structural reliability, corrosion resistance, hydraulic capacity,
ease of installation (pipe weight) and performance history of the pipe material.
Kleinschmidt provided their evaluation and recommendations to PSNH, which chose
the fiberglass pipe option and purchased CCFRPM pipe manufactured by HOBAS PIPE
USA of Houston, Texas.
“The
corrosion resistance and relative stiffness of FRP pipe meant it could be
supported on the existing grade and half buried, rather than placed on saddles
or completely covered in a buried trench. This design flexibility, combined with
a longer projected service life, lead to a competitive total construction cost
for the FRP alternative,” said Keith Martin, a project engineer and
civil/structural engineer with Kleinschmidt’s Pittsfield, Maine,
office.
“The lower frictional resistance of HOBAS
compared to other materials allowed the replacement pipe to be reduced to a
7-foot diameter without additional head loss,” explained Martin.
The pipe was
half buried in the shallow trench of the existing penstock, requiring minimal
excavation costs and low environmental disturbance. Approximately 300 feet of
the new penstock were supported above ground on steel saddles to accommodate the
topography as well as minimizing the impact to the wetlands that the penstock
crossed.
“HOBAS CCFRPM is
manufactured by a unique computer controlled centrifugal casting process. To
achieve the higher axial strength necessary for the aboveground installation,
additional reinforcement is placed in the longitudinal direction during the
manufacturing process,” explained Rene Garcia, Sr. engineering associate with
HOBAS Pipe’s Houston manufacturing facility. The design flexibility is just one
of the benefits provided by this product.
“PSNH bought
the HOBAS pipe directly and CCB, Inc. of Westbrook, Maine (CCB) was contracted
to install it,” said Newell Porter, project manager with CCB. “Prior to this
project, I had heard of HOBAS pipe but had never installed
it.”
The job site posed some challenges as the
pipe was installed in a remote area. “The pipe arrived as scheduled and was
unloaded near the roadside. This phase of
the job was 1,020 feet of 84-inch diameter HOBAS pipe. The individual joints were then carried
to the point of installation with an excavator. We had no truck access to the
installation point. A HOBAS field rep was onsite pretty much from day one. The
first part of the installation was through a curve where 10-foot joint sections
were connected and then deflected to make up the curve,” said
Porter.
The HOBAS FWC coupling joint
utilized on this project is a pressure joint. It is commonly used in direct bury
application and for above ground installations such as penstocks. It is a
structural filament wound sleeve overwrapped and mechanically locked to an
internal full-faced elastomeric membrane. The sealing design includes both lip
and compression elements so the joint is suitable for both non-pressure and
pressure service up to 250 psi. “In our case, we air tested each joint after
assembly with a 10 psi air test. None of the joints leaked. Once the line was in
operation, we were required to visually inspect each and every joint for
a sign of leakage and
there was none,” said Porter.
JML Trucking
and Excavating of Errol, N.H., was the installation sub-contractor for CCB.
Butch Lane echoed the general contractor’s sentiments, “It really is a good
pipe. The joints are really tight. I know that we’ve had people come by and look
at the project, and they are all happy. We were able to put PSNH online two
weeks ahead of schedule and that makes them happy.”
“At the end
of the project, it was found to be approximately seven times cheaper per foot to
utilize the fiberglass pipe option partially backfilling the penstock than to
support it above ground,” summarized Martin. Hydraulic advantages and longevity
of the line will also provide life long savings.
HOBAS pipes
have been utilized in above ground applications in the USA since 1989 and
worldwide for penstock applications for over 20 years.
Advertisement
HOBAS
pipe is manufactured in sizes from 18 inches to 110 inches in pressure and
non-pressure classes. For more information, please contact HOBAS at
800-856-7473, 281-821-2200 or e-mail at info@hobaspipe.com. Facts are also
available at www.hobaspipe.com.
December 19, 2008
Hobas Replaces Wood Stave Penstock
Meandering
through the White Mountains, a large wooden penstock served as the main water
supply for a local hydro facility called Jackman Station. It’s fed by the
Franklin Pierce Reservoir, which was created by the hydro's dam and surrounding
earthen dikes. The water elevation in the reservoir is managed according to
spring run-off.
Public
Service of New Hampshire (PSNH), the Granite State's largest electric utility,
serves more than 475,000 homes and businesses. PSNH’s power generation
facilities consist of nine hydroelectric plants, including the Jackman Hydro
station, which was built in 1926. This facility, located in Hillsborough, has
been serving the area for years, but the penstock was approaching the end of its
service life.
Prior to the
recent improvements, 5,000 feet of wood stave penstock extended from the
Franklin Pierce reservoir to a surge tank upstream of the powerhouse. This
7.5-foot diameter penstock was made up of vintage wood stave sections, circa
1926. Repairs were undertaken in 1954 and in the 1970’s, yet the downstream
sections of the wood penstock still leaked badly. This leakage caused icing
problems during winter months and required constant maintenance. In 2003, the
penstock had a significant rupture that impacted abutting properties. To prevent
future failures and ensure reliable operations of the hydro facility, repairs to
the existing penstock were necessary. In a series of contracts, PSNH decided to
replace the remaining wood stave penstock with a new pipeline.
Kleinschmidt,
headquartered in Pittsfield, Maine, specializes in energy and water resource
projects. They were retained to develop a feasibility study and engineer a
replacement pipeline. Kleinschmidt initially evaluated five pipe material
options for the penstock replacement: wood stave, concrete, HDPE plastic, steel
and fiber reinforced polymer (FRP). Factors that led to the final determination
included the structural reliability, corrosion resistance, hydraulic capacity,
ease of installation (pipe weight) and performance history of the pipe material.
Kleinschmidt provided their evaluation and recommendations to PSNH, which chose
the fiberglass pipe option and purchased CCFRPM pipe manufactured by HOBAS PIPE
USA of Houston, Texas.
“The
corrosion resistance and relative stiffness of FRP pipe meant it could be
supported on the existing grade and half buried, rather than placed on saddles
or completely covered in a buried trench. This design flexibility, combined with
a longer projected service life, lead to a competitive total construction cost
for the FRP alternative,” said Keith Martin, a project engineer and
civil/structural engineer with Kleinschmidt’s Pittsfield, Maine,
office.
“The lower frictional resistance of HOBAS
compared to other materials allowed the replacement pipe to be reduced to a
7-foot diameter without additional head loss,” explained Martin.
The pipe was
half buried in the shallow trench of the existing penstock, requiring minimal
excavation costs and low environmental disturbance. Approximately 300 feet of
the new penstock were supported above ground on steel saddles to accommodate the
topography as well as minimizing the impact to the wetlands that the penstock
crossed.
“HOBAS CCFRPM is
manufactured by a unique computer controlled centrifugal casting process. To
achieve the higher axial strength necessary for the aboveground installation,
additional reinforcement is placed in the longitudinal direction during the
manufacturing process,” explained Rene Garcia, Sr. engineering associate with
HOBAS Pipe’s Houston manufacturing facility. The design flexibility is just one
of the benefits provided by this product.
“PSNH bought
the HOBAS pipe directly and CCB, Inc. of Westbrook, Maine (CCB) was contracted
to install it,” said Newell Porter, project manager with CCB. “Prior to this
project, I had heard of HOBAS pipe but had never installed
it.”
The job site posed some challenges as the
pipe was installed in a remote area. “The pipe arrived as scheduled and was
unloaded near the roadside. This phase of
the job was 1,020 feet of 84-inch diameter HOBAS pipe. The individual joints were then carried
to the point of installation with an excavator. We had no truck access to the
installation point. A HOBAS field rep was onsite pretty much from day one. The
first part of the installation was through a curve where 10-foot joint sections
were connected and then deflected to make up the curve,” said
Porter.
The HOBAS FWC coupling joint
utilized on this project is a pressure joint. It is commonly used in direct bury
application and for above ground installations such as penstocks. It is a
structural filament wound sleeve overwrapped and mechanically locked to an
internal full-faced elastomeric membrane. The sealing design includes both lip
and compression elements so the joint is suitable for both non-pressure and
pressure service up to 250 psi. “In our case, we air tested each joint after
assembly with a 10 psi air test. None of the joints leaked. Once the line was in
operation, we were required to visually inspect each and every joint for
a sign of leakage and
there was none,” said Porter.
JML Trucking
and Excavating of Errol, N.H., was the installation sub-contractor for CCB.
Butch Lane echoed the general contractor’s sentiments, “It really is a good
pipe. The joints are really tight. I know that we’ve had people come by and look
at the project, and they are all happy. We were able to put PSNH online two
weeks ahead of schedule and that makes them happy.”
“At the end
of the project, it was found to be approximately seven times cheaper per foot to
utilize the fiberglass pipe option partially backfilling the penstock than to
support it above ground,” summarized Martin. Hydraulic advantages and longevity
of the line will also provide life long savings.
HOBAS pipes
have been utilized in above ground applications in the USA since 1989 and
worldwide for penstock applications for over 20 years.
HOBAS
pipe is manufactured in sizes from 18 inches to 110 inches in pressure and
non-pressure classes. For more information, please contact HOBAS at
800-856-7473, 281-821-2200 or e-mail at info@hobaspipe.com. Facts are also
available at www.hobaspipe.com.