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California hospitals do major
surgery on steam boiler systems
San Francisco, California.
- San Francisco's St. Luke's Hospital complex is made up of four buildings,
ranging from 90 to 25 years old. Heating the building required 26,000,000
Btuh, a costly need that had been met for half a century by a high-pressure  steam
boiler.
Regulations in the State
of California require a stationary licensed boiler attendant 24 hr a day,
365 days a year on any direct-fired steam system that generates more than
15 lb of high-pressure steam. As of last year, the cost of St. Luke's
boiler attendants in wages and benefits had risen to $350,000 annually.
The State of California does not require a licensed boiler operator with
a thermal fluid heating system that operates within a closed loop at a
very low pressure. Hot oil is pumped through unfired steam generators
to create steam without high pressure.
The hospital saw the need
to change from direct-fired steam generation to a modern thermal
fluid heater. The job called for removing the 12 by 25 ft steam boiler
and installing three 6,000,000 Btuh Fulton thermal fluid heaters, plus
two 10,000,000 Btuh oil-to-unfired steam heat exchangers. The job
took five months to complete; fortunately, the steam header and steam condensate
piping did not have to be replaced. Because the steam is generated
in unfired pressure vessels, the 60 lb of high-pressure steam can be provided
by the new system without a stationary attendant as required by direct-fired
steam boilers.
Honeywell provided micro-based
DDC controls and Model 7,800 Burner Controls for the new system and served
as the general contractor. The changeover to thermal fluid heaters
also enabled the hospital to reassign the licensed boiler operators to
other duties.
The direct-fired steam boiler
was oversized and consumed energy insufficiently every time it recycled.
With the new system, one 6,000,000 Btuh unit stays in constant operation;
the others only come on line when the load makes it necessary. This
has led to a projected annual saving of 18 percent of the hospital's natural
gas bill.
The new thermal fluid heaters
are charged with Paratherm NF Heat Transfer fluid. Mike Andress,
project manager for Honeywell, stated the fluid was doing an excellent
job - no complaints. Since the NF fluid is rated for 600 F and delivers
precise uniform temperature control, it has no trouble providing the 300
F heat required. In addition, the fluid has very high heat transfer
coefficients for improved efficiency. It is also non-toxic, non-fouling,
and non-hazardous. At the end of its use cycle, it can be mixed with
other spent lube oils and sent to a local recycler - another cost saving
tot he hospital.
At St. Joseph's Medical
Center in Stockton, Calif., the change from high-pressure steam boilers
to Fulton thermal fluid heaters and Fulton 9 1/2 hp boilers was made in
1994. While the new system generated enough steam for most hospital
functions, additional steam pressure was required to operate the laundry.
Jerry Cotton, manger of
maintenance at St. Joseph's, stated that the changeover involved installing
three Fulton 9 1/2 hp tubeless steam boilers. These units generate
less than 15 hp and therefore do not necessitate the 24 hr boiler attendant
required by California law. Once the system was up and running, St.
Joseph's laundry discovered one minor problem - the new system could not
generate the 125 psi steam pressure required by the ironer; it was limited
to a maximum of approximately 80 psi. The problem was corrected with
the installation of a supplemental thermal fluid heater. This hot
oil heater operates in a closed loop system and supplies heat to the ironer,
which is within a 2 F temperature range. The unit has been in service
for over two years without problems. Like St. Luke's, St. Joseph's
charges all the thermal fluid heaters with Paratherm NF heat transfer fluid.
A different situation exists
at the Sutter Roseville Hospital in Roseville, Calif. This new facility
is a 340,000 sq ft general hospital with four new thermal fluid heaters.
Dale Holt, the maintenance and operations supervisor, stated that the system
was designed to operate two heat transfer units and use the other two as
backups. The backups are set to take over automatically if the steam
temperature generated by the primary units falls below a certain point.
To generate 280 F steam,
the hospital maintains the heat transfer oil at 450 F. The closed
loop thermal fluid system is used to provide all of the 700 bhp of central
plant steam required for building heat, kitchen, and sterilization.
To protect the hospital from environmental problems, the hot oil heaters
were designed with low emission burners to meet 30 ppm NOx requirements.
The hot oil heaters, expansion/deaerator
tank, hot oil pumps, and unfired steam generators were skid mounted and
pre-piped at the Fulton factory. Piping was disassembled for shipping
but match marked for easy reassembly at the job site. The system
is fired with natural gas, and there is a 20,000 gal oil storage tank that
can take over in case of emergency.
The system has been up
and running since June 21 of this year. Holt stated that in general
the system is running well, and the heat transfer fluid in the system is
performing up to expectations.
The Sutter Rosevill Hospital,
like St. Joseph's Hospital and St. Luke's Hospital, found that a thermal
fluid heating system costs significantly less to operate than a direct-fired
steam boiler system.
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