Covidien Puritan Bennett 700 Series, Service Manual

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Theory of operation
2-10 10070389 Rev. A Puritan Bennett™ 700 Series Ventilator System Service Manual
2.2.1.1 Gas inlet system components
The gas inlet system includes the components described below; these are shown in Figure 2-5.
• The air intake cover holds the air intake filter element in place and protects it from
contact with liquids.
• The air intake filter , mounted just inside the ventilator cabinet, captures airborne particles
as small as 5 mm. The filter is replaced every 1000 hours, or more often as necessary.
• The air intake manifold provides an intake for the mixing manifold. It has an outlet, which
provides a filtered path to atmosphere for the piston/cylinder. It also provides a vent for
the safety valve. An inlet check valve opens to allow room air intake, and closes to
dampen noise during the oxygen mixing process. A relief check valve relieves any excess
pressure in the intake duct.
• The oxygen fitting and hose connect an external oxygen source (wall or cylinder) to the
ventilator. The choice of available oxygen fittings supports use of female DISS (diameter
index system standard), male DISS, NIST (non-interchangeable screw thread),
Air Liquide™*, Australian type, and Dräger™* hose assemblies.
Warning
To ensure adequate oxygen delivery to the patient, use Covidien-supplied oxygen
hoses only. Use of other oxygen hoses could result in inadequate or inappropriate
oxygen pressures or leaks at the oxygen inlet.
• The oxygen solenoid assembly is a field-replaceable unit (FRU). This assembly includes the
high- and low-flow solenoids, and does not include the oxygen regulator pressure
transducer. Calibration data specific to each solenoid assembly is recorded in NVRAM; this
data must be updated when a new assembly is installed.
• The oxygen regulator is a FRU, which is replaced every 15,000 hours. The oxygen regulator
assembly does not include the oxygen regulator pressure transducer.
The oxygen regulator is a self-relieving regulator that maintains a stable output pressure
of 33
±
5 psi (227.46
±
34.48 kPa) throughout the supply pressure range of 40 to 90 psi
(275 to 620 kPa) under no-flow conditions. It is factory-calibrated to obtain 150 L/min
STPD through the high-flow orifice. Performing a Reg altitude calib (Section 4.2.3.2.2) at
high altitudes decreases this pressure to a level appropriate for the altitude at which the
calibration is performed.
A sintered bronze 5-
μ
m filter inside the regulator prevents particles from entering.
A stainless steel screen outlet filter removes particles of 30 (
μ
m) or larger from the
regulated oxygen.
A bleed of up to 3 L/min improves the regulator’s performance and response time at low
flow rates. The regulator’s vent is directed outside the ventilator to prevent a buildup of
oxygen inside the ventilator.
Warning
Due to excessive restriction of the Air Liquide™*, Dräger™*, and Australian hose
assemblies, reduced FIO
2
levels may result when oxygen inlet pressures < 50 psi
(345 kPa) are employed. Make sure oxygen inlet pressure is ≥ 50 psi (345 kPa) when
using these hose assemblies, to maintain correct FIO
2
levels.