Regulating Gas Pressure and Flow Bulk O2 Systems

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Regulating Gas Pressure and FlowBulk O2 Systems
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Introduction

• Regulator is a device that controls both pressure
  and flow
• Reducing valve is a device used when gas pressure
  alone is controlled from a high to a lower
  pressure
• Flowmeter is a device that adjusts the flow of a
  gas, usually after the gas pressure is already
  controlled

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Regulators

• Preset
• Adjustable (Bourdon)
• Multi-stage

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Preset Regulators

• Body of regulator is divided into a gas pressure
  chamber and an ambient pressure chamber by a
  flexible diaphragm
• attached to the diaphragm is a spring which keeps
  pressure at 50 psi
• outflow of gas is controlled by a flowmeter

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Adjustable Regulators(Bourdon)

• Is identified by the threaded hand control on its
  face, which is attached to the end of the spring
  and allows dispacement of the diaphragm
• The valve is closed until the hand screw advances
  the whole mechanism and opens it to allow gas
  flow (this valve can be opened to permit a wide
  range of flows)
• In a preset reg., press. is always 50 psi, but in
  adjust. can be anything up to 100 psi

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Multi-stage Regulators

• Accomplishes pressure reduction in two or three
  steps instead of one
• Is indicated where minimal fluctuations in
  pressure and flow are critical factors(for
  routine hospital use, see single stage)
• Number of stages in the reducing valve can be
  determined by noting the number of vents present
  (one for each press. chamber)

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Flowmetering Devices

• Allows one to see gas movements by a flow
  indicator and to record its rate of movement by a
  scale
• Receives gas at 50 psi and measures the gas
  leaving the device in L/M
• Classified as - Mechanical (cylinder and
  wall O2)
• - Electronic (ventilators)
• Mechanical flowmeters classified as -Thorpe
  tube -Bourdon

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Thorpe Tube Flowmeter

• Variable orifice device
• p. 59, McPherson
• To work properly the flowmeter must be in an
  upright position
• Should be pressure compensated, which all of the
  newer ones are
• Pressure compensation means the meter has been
  designed to anticipate changes in backpressure,
  and is calibrated to 50 psi

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Bourdon Flowmeter

• Is actually a pressure gauge calibrated in
  L/M p. 58, McPherson
• Measures the pressure of gas flowing from the
  pressure chamber of an adjustable reducing valve
  and is calibrated to indicate flow volumes of gas
  at different pressures
• Problem is if an obstruction or restriction past
  the gas outlet exists, may see flow reading when
  flow is diminished or absent

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Bulk OxygenIntroduction

• Consists of any system capable of accomodating
  more than 12,000 cubic feet of the gas ready for
  use or more than 25,000 cubic feet including
  unconnected reserves
• 2 basic types of bulk O2 - Gas manifold
  systems - Liquid bulk systems

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Gas Manifold System

• Large-sized standard cylinders are banked
  together, usually pressurized at 2200 psig
• The cylinders are tied together by a manifold,
  which converts the cylinders into one continuous
  supply
• System contains pressure-reduction valving and
  flow control
• Also contains alarm systems that warn of
  malfunction or depletion
• Can be used as backup to liquid bulk system

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Liquid Bulk System

• O2 has a critical temp. of -181.1F and boiling
  point of -297.3F
• To prevent the liquid from reverting to gas, the
  liquid must be kept below -297F during
  transportation and storage. Accomplished keeping
  in a special container under pressure not gt250
  psig
• If O2 is kept below its boiling point, it can be
  exposed to atm. press. for short periods of time,
  without immed. vaporization

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Liquid Bulk System (contd)

• At its boiling point, 1cubic foot of liquid O2
  is equivalent to 860 cubic feet of gaseous O2 at
  ambient temp. and press.
• Liquid O2 is converted to usable gas by a heating
  unit called a vaporizer
• These systems insure an unlimited gas supply no
  matter what the peak demand load
• Refilled by service tank trucks
• Press. of 50 psi enters hospital

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Hospital O2 Piping System

• p. 644, Egan
• Must be designed specifically for oxygen service
  and made of copper, brass, or bronze
• Must maintain a dynamic delivery press. of 50 psi
• Piping plan includes
• - main supply line - risers - branch lines
• - zones - station outlet pipe

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Piping System (contd)

• Valves in piping plan include - main supply
  valve - riser valve - zone valve -
  station outlets