Life Cycle Cost Estimating
Many specifiers of piping systems limit their economic analysis to
piping material costs only, because they are relatively simple to
estimate. Yet this approach creates some pitfalls when selecting
either an installation of conventional flanged plastic-lined piping
(PLP) or an installation that fully incorporates Resistoflex's
Joint Reduction Technologies (JRT), consisting of
CONQUEST® flangeless
connections and MULTI-AXIS®
precision bent piping. An evaluation that
considers only the cost of pipe, fittings, flanges and connectors may
result in specification of a system with the higher life cycle cost.
Life Cycle Cost Considers All Cost Factors
Life cycle cost (LCC) analysis includes all costs of system ownership
and permits selection of the less expensive system. Costs can be
divided into the following categories:
- Initial acquisition costs
- Initial acquisition labor
- Operating and maintenance costs
- Costs associated with flange leaks
When deciding to utilize JRT, it's often helpful to perform the
evaluation based on the LCC of current practice (i.e., the use of
flanged PLP) and then consider which costs would change if the
system were designed and installed using the various Joint Reduction
Technologies. Different alternatives can be evaluated with the
judicious use of JRT and elimination of many, but not all, flanged
connections resulting in the most economical PLP installation.
Cost Elements to Consider When Evaluating JRT vs. Conventional PLP
- Initial Acquisition Costs
- Pipe, fittings, flanges, venting & locking collars and
CONQUEST®
connectors. These are the items that are purchased from the
supplier of PLP. Pipe can be supplied already flanged, or spooled,
ready for installation. If the pipe will be fabricated on-site, then
a sufficient number of flanges and/or CONQUEST® connectors should be
purchased. Don't overlook venting collars for PTFE (polytetrafluoroethylene)
or PFA (perfluoroalkoxy) lined pipe if flanged pipe ends will be
fabricated on-site. These collars are not needed if the pipe is joined
with a CONQUEST® flangeless connection.
- Nuts, bolts or studs needed to join flanged
connections.
- Flange protectors or spray shields.
Many corporate or government regulations require that flanged
connections be covered or protected so that if a leak occurs, it is
either contained or flows in a controlled, predictable pattern
instead of spraying at the flanged connection.
- Registration of flanged connections in a corporate database.
Often the location of a flanged connection must be noted in records so
that its location, maintenance and inspection can be reported. One
common technique is to attach a bar code label to the flanged
connection, input location and chemical service information into a
database. Registration is essential if the service is covered by the
1990 Clean Air Act Amendments (CAAA) or other similar laws governing
chemical processes. Many companies register all flanged connections
in critical or hazardous services, even if the service isn't
currently included in regulations. This is often done either for
safety reasons or in anticipation of changes in regulations.
Registration usually occurs at the time of installation and is in
additional to the recurrent costs of periodic inspection.
- Items that are less costly when flanged connections are
eliminated because the piping system is lighter in weight and has a
more streamlined profile. These could includes:
- number and type of hangers
- support structure
- diameter or configuration of insulation
- complexity of heat tracing around connections
- Diameter of the piping system and size of pumps.
Don't overlook the improved flow characteristics of JRT, especially of
MULTI-AXIS precision bent piping. The 3-D bends of
MULTI-AXIS create
less pressure drop than the standard 1.5-D bends of conventional
PLP. It may be possible to specify a smaller diameter piping system
and/or smaller pumps if JRT is specified instead of conventional PLP.
- Initial Acquisition Labor
- Design and design review. The cost of specifying,
ordering and receiving materials can be reduced if the piping is
bought as bulk quantities of unflanged, standard length pipe instead
of numerous flanged spools with different custom lengths. Also the
material acquisition costs for some items (like nuts, bolts, studs,
flange protectors and spray shields) are reduced in direct portion
to the number of flanged connections eliminated by the use of JRT.
- Field fabrication of custom length pipe. The process
of PLP custom spool fabrication includes cutting and threading the
pipe, installing and aligning the flange, installing the venting or
locking collar, heating the plastic stub, flaring the plastic face,
cooling and removing the flaring die and installing a protective wooden
cover over the flared face. This process can be time-consuming and
quality difficult to control if performed on-site by personnel who
fabricate PLP on an infrequent basis. Often custom spools are fabricated
at the factory or by nearby stocking distributors who have fully
equipped shops and certified personnel that fabricate PLP routinely.
If conventional PLP is fabricated at the factory or by a distributor,
then the cost will be part of the purchase price quoted by the supplier
of the fabricated pipe. Understandably, flanged and fabricated spools
are more expensive than plain-end PLP.
- Cost of installation. This includes the cost of
installing the piping system and the associated nuts, bolts, studs,
flange protectors and spray shields with conventional PLP or the cost
of fabricating a CONQUEST® connection when the method is used to
create a joint.
- Miscellaneous labor cost savings. Be sure to include
labor cost savings if the use of lighter weight, streamlined JRT
piping permits a reduction in the number of hangers and supports and
if the elimination of flanged connections speeds up the installation
of insulation and heat tracing. Also, the time required for painting
can be reduced when flanged connections are eliminated. If installation
time is reduced, then it's often possible to reduce the time required
for rental or recharge of equipment like man-lifts.
- Start-up costs. This includes the time to hydrotest
the piping system and perform the recommended retorquing of bolts
after 24 hours of operation. When flanged connections are eliminated,
the start-up time can be substantially reduced. This means that the
system is operational sooner and the process is out of commission for
a shorter period of time.
Operating and maintenance costs
- Monitoring and associated paperwork. Government or
corporate regulations may require the periodic monitoring of flanged
connection for leaks and records of that monitoring activity. If a
service is listed in the 1990 CAAA, then the connection must be "sniffed"
for fugitive emissions and detailed records maintained for submittal
to the government. The monitoring frequency ranges from every six
months to biannually, depending upon the service and history of the
site. Even if regulations don't require monitoring, it's still good
chemical plant operations practice to visually inspect flanged
connections periodically for signs of leaks or emissions.
- Periodic retorquing of flange bolts. It's common for
flange bolt torques to be checked and bolts tightened, if needed, on
a periodic basis. Often this is done semi-annually or annually
depending upon the thermal cycling history of the piping. This
retorquing isn't needed when flanged connections are eliminated through
installation of JRT.
- Cleaning costs. Consider the cost difference in
batch-to-batch cleaning of conventional PLP vs. JRT. In some batch
processes this can be a savings, particularly when directional changes
in the piping are created with MULTI-AXIS piping instead of with
conventional flanged elbows, which have a discontinuity or crevice
at the flanged connection.
Costs associated with flanged leaks
- Unused capacity. Consider the likelihood of plant
outages due to flange leaks and the cost of production that is lost
when the plant isn't operating.
- Out-of-spec product. Flange leaks can create a
sudden and unexpected plant outage resulting in the production of
out-of-spec product.
- Safety issues. The "cost" is difficult to estimate
but can be a tangible concern for some chemical services and/or some
piping system locations. This could include direct injury to workers
and passers-by and indirect issues such as evacuation of the process
site and adjacent areas.
- Reporting requirements. Government or corporate
regulations can require lengthy and time-consuming reports and
investigations in the event of flange leaks. The direct and indirect
costs of these reports shouldn't be overlooked.
Example of Life Cycle Cost Estimating Analysis
Consider a piping system that was recently installed with extensive use
of JRT. The system consists of 2-in diameter (50 mm N.B.) PVDF-lined
piping that was installed in an existing, overhead pipe rack to
replace a conventional PLP system that had reached the end of its
useful life of several decades. The conventional system consists of
670 ft (204 m) of piping, ten directional changes for routing the
thermal expansion purposes and two tees installed as "stand-pipes" to
reduce the effect of water hammer. By specifying JRT, all the flange
connections, except for the first and last connections. In JRT, the
system consists of 620 ft of straight-run piping, three pieces of
MULTI-AXIS® precision-bent piping, two
CONQUEST® flangeless tees and
thirty-seven CONQUEST® connections. The system is depicted in the
isometric drawing. Costs are estimated using 1995 data for the upper
midwest and listed is U.S. dollars.
Initial Acquisition Labor Savings
- Design, design review and material acquisition costs.
Since this system represents an initial JRT installation at this
location, the specifiers decided that the design, review and acquisition
of the system would be no different with either design. After the
installation, they report that the project went very "smoothly" and
they can anticipate savings in design, review and acquisition of future
JRT installations.
- Elimination of field fabrication of flanged custom length
pipe. It takes about 1.15 hr to completely cut, thread, flange,
flare and block the two ends of a 2" PVDF-lined spool. There are
thirty-seven spools in the conventional flanged system design, representing
a total fabrication time of 42.55 hours. It takes about 0.6 hours to
cut, align, trim, butt-fusion weld and install a CONQUEST® connection.
There are thirty-seven CONQUEST® connections in the system, with a total
installation time of 22.2 hours.
- Cost of installation It takes about 0.4 hr to install
the nuts, bolts and flange shield of a 2" diameter connection. There
are forty-nine flanged connections in the conventional design, for a
total installation labor of 9.80 hours. The CONQUEST® connections are
installed during the fabrication process outlined above, so there is
no additional installation time since there are no nuts, bolts or
spray shields used.
- Start-up costs. It's assumed that the cost to hydrotest
the system would be identical for conventional piping and for a JRT
system. However, the costs for hydrotesting of the conventional system
would be higher if leaks occurred at the flanged connections and had
to be corrected during the hydrotest. A leak occurring in a CONQUEST®
connection during hydrotest would not be likely. These costs could be
included based on previous experience at the site. However, the cost
of the 24-hr retorqing of the flanged connections is tangible, at
0.2 hr per connection. With forty-nine flanged connections, there's
an additional 9.8 hrs needed to start up the conventional system. The
conventional PLP system takes nearly fifty hours more to fabricate,
install and start-up than the same system that fully incorporates JRT
to eliminate flanged connections. At $50.00 per hour, the seemingly
"less expensive" system is nearly $2500 more expensive to install
and commission.
So, if both the initial acquisition costs and the initial acquisition
labor is considered, the total installed cost of the system that
incorporates CONQUEST® flangeless joints and
MULTI-AXIS® precision-bent
piping is $3,800 less than the same system installed with conventional
flanged plastic-lined piping. This savings increases if the operating
and maintenance costs are also considered.
Operating and maintenance costs
- Annual monitoring and record keeping. It costs about
$75.00 annually to monitor and record the testing of each flanged
connection in a conventional PLP system. With forty-nine flanged
connections, the system will cost an additional $3,675 per year
to maintain.
- Annual retorquing. The cost to retorque each connection
is about $10.00 per year, creating an additional $490 in annual
operating costs not required to maintain a JRT system. In certain
critical services, retorquing is required semi-annually or quarterly.
- Other costs. Leaks and shut-downs can be very
expensive, yet each location will have to evaluate their annual cost
potential based upon system configuration, location, process conditions
and history. These costs should not be overlooked, but are beyond the
scope of this study.
