medical gas & steam principles. in 1961, centralsug ab installed the first vacuum waste system...

Medical Gas & Steam Principles

In 1961, Centralsug AB installed the first vacuum waste system in the world at

Sollefteå Hospital. The system is still in operation today with many original parts

from the early 1960s.

Vacuum System

Vacuum System

Is a network of piping systems connecting vacuum producing devices to suitable vacuum inlets where patient suction is neededMedical Gas and Vacuum are governed by their classificationLevel 1Level 2Level 3

Medical Piped Gas and Vacuum Systems

Level 1Systems servicing occupancies where

interruption of the piped medical gas and vacuum system would place patients in imminent danger of morbidity (create unhealthy condition) or mortality (death)

I.A.W. NFPA99--3.3.903.3.90

Medical Piped Gas and VacuumSystems (Continued)

ICU CCU Surgery OB/Delivery Nursing ER


Level 1 Vacuum System System consisting of central vacuum, producing equipment

with pressure and operating controls, shutoff valves, alarm warning systems, gauges, and a network of piping extending to and terminating with suitable station inlets at locations where patient suction could be required

I.NFPA99I.A.W. NFPA99--3.3.903.3.90


Level 2 Systems serving occupancies where interruption of the piped

medical gas and vacuum would place patients at manageable risk of morbidity or mortality Wards Clinics I.A.W. NFPA99--3.3.91

The Level 3 Vacuum System (Continued)

Can be either: A wet system designed to remove all liquids, air-gas, or solids

through the service inlet A dry system designed to trap liquid and solids before the service

inlet and to accommodate air-gas only through the service inlet I.A.W. NFPA99--3.3.933.3.93

Dental Clinic Surgery for scavenger system

Medical Piped Gas and Vacuum Systems

The Level 3 Vacuum System consists of; Two or more vacuum devices/pumps hooked up in

duplex/parallel located in a dedicated mechanical equipment area, adequately ventilated and environmental controls with any required utilities


The Level 3 Vacuum System Must have Pumps that provide sufficient suction to service the

peak calculated demand with the largest single vacuum pump out of service

Must have flexible motor/pump mounts and connecting pipes to control pump and motor vibration

Must have an automatic means to prevent backflow (i.e. check valve) from any on--cycle vacuum pumps through any off—cycle pumps


The Level 3 Vacuum System Must have a shutoff valve or other isolation

means to isolate each vacuum pump from the centrally piped system and other vacuum pumps for maintenance or repair without loss of vacuum in the system

Medical Piped Gas and Vacuum Systems (Continued)

The Level 3 Vacuum System Must have a receiver/vacuum storage tank that

meets the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Section VIII, Unfired Pressure Vessel specification


Vacuum Storage Tank If liquid goes into this tank, then isolation valves and fluid traps will be used in

conjunction with drain valves to allow automatic liquid drainage There will be a separate shutoff valves and connections between the vacuum

pumps and the receiver Will exhaust in a manner and location that will minimize the

hazards of noise and contamination to the facility and its environment Will be: • Located outside• At least 10 ft./3.050 mm from any door, window, air intake, or other

opening in the building• At a level different from air intakes


Where prevailing winds, adjacent buildings, topography, or other influences that would not divert the exhaust into occupied areas or prevent dispersion of the exhaust

The end of the exhaust shall be turned down and screened or otherwise be protected against the entry of vermin, debris, or precipitation, by screening fabricated or composed of a non—corroding material

Medical--Surgical Vacuum SourceExhaust (Continued)

The exhaust line shall be free of dips or loops that might trap moisture. Where low spots are un--avoidable, a drip leg and drain valve shall be installed

Exhaust lines from multiple pumps can be joined if pipe back pressure is minimized in accordance with manufacturers recommendations

Each exhaust line will have an isolation valve installed to allow for servicing of individual pumps

Vacuum System Electrical Controls

Additional pump/s will automatically activate when the operating pump/s is incapable of adequately maintaining the required vacuum

Automatic or manual alternation of pumps shall allow division of operating time

If automatic alternation of pumps is not provided, the facility staff shall arrange a schedule for manual alternation

Vacuum System Electrical Controls(Continued)

Each pump motor shall be provided with electrical components including, but not limited to, the following: Dedicated disconnect switch for each motor Motor starting device Overload protection If transformers are required there will be a separate transformer for

each motor Power circuits arranged in such a manner that the shutting down of

one pump does not interrupt the operation of another pump

Alarms, Indicators, and Gauges

Pump--motor alarm shall activate a local alarm when the backup or lag pump is running due to primary pump becoming inoperable

Vacuum and Pressure alarms and indicators will be adjacent to each other Pressure gauges will indicate the normal operating pressure

at mid-scale (ex. 50 PSI would indicate straight up on a 100PSI gauge)

Vacuum pressure gauge shall have an operating pressure range of 0 ––760 mmHg/0 ––29.9 in Hg, mid—range is 380 mmHg/12 in Hg

Pressure Gauges (Continued)

The area alarm panel contains the following:

• Vacuum gauge• Gas pressure Gauge• Vacuum alarm• Gas pressure alarm

Reason for Hydraulics Almost 100% efficient

Provides instant application of power Fluids will compress only a very small amount at

extremely high pressure Air in the system takes away from efficiency

Lightweight parts Most components made of aluminum alloy Smaller in size compared to other mechanical

systems

HYDRAULIC PRINCIPLES

Lines easily routed can be easily routed around most obstructions Uses "Tee" fittings, elbows, cross fittings, etc

Self lubricating Components operate in a bath of oil Reduces friction and cools components

Safer Hydraulically moved loads are safer than

mechanically moved loads Using hydraulic jacks compared to using mechanical

jacks


Properties of Fluids Effects of temperature

When heated, fluid volume increases When cooled, fluid volume decreases

Practically incompressible Laminar flow

Smooth even flow (smooth movement) Jerking/jarring movements seldom occur


There is no pressure in a moving body of fluid Resistance to fluid flow gives us pressure Increase fluid flow, pressure will decrease Decrease fluid flow, pressure will increase

Viscosity, thickness of fluid Thick fluids have high viscosity Thin fluids have low viscosity Changes in temperature affect viscosity

Temperature increase, increase in volume Temperature decrease, decrease in volume


Hydraulic Laws Pascal's law - states:

A force applied to a confined body of fluid, will result in pressure being applied equally and undiminished in all directions

The pressure is applied equally to all sides of the balloon, so the balloon is round

Bernoulli's law (Bur-new-lees) - states: The pressure of a fluid decreases at points where the

velocity increases Restrictions cause the same amount of fluid to try to get

through the smaller area The fluid must move faster, result is increased velocity


Relating Hydraulic Formula Actuator - converts hydraulic pressure into useful

mechanical force Components of an actuator

Piston - what the fluid moves Rod - what moves the subsystem Cylinder - what the piston is inside of Stroke - how far the piston and rod move

Extension stroke - actuator gets longer Retraction stroke - actuator gets shorter


Force formula - F = A x P Force - the amount of push or pull on an object

The weight of something Measured in lbs

Area - a measurement of surface Piston surface Measured in square inches

Pressure - the amount of force applied to a given area a The result of resistance b Measured in PSI (pounds-per-square inch)


Problem Indications Bubbling/hissing sound

Usually indicates low oil level If oil level is good, the sound indicates that the

system has air trapped in the lines, and requires bleeding: There is usually a screw at the top of the system

used to bleed the air from the system Press lift lever down/activate the pump Loosen screw to allow air out of the line


Tighten screw before releasing the lever/deactivating the pump

Procedure may require repeating to ensure all air is removed from the line

Slow movement - look for some sort of obstruction, such as: Dirty filter Faulty solenoid Faulty check valve Maladjusted speed control


Applications: Tables

OR OB ER

Chairs Dental clinic Ear, nose and throat/ENT clinic

Equipment stands/columns OR ENT clinics


Physical Principles

Principles of Pneumatics is the branch of Physics that studies the properties of gases at rest or in motion Atmospheric Pressure’s most common unit of

measurement is millimeters of mercury (mmHg) At sea level, atmospheric pressure is normally 760

mmHg (14.763 PSI) In Kabul, Afghanistan atmospheric pressure is

normally 579.1mmHg (11.2 PSI)

Physical Principles (Continued)

The Ideal Gas Law explains the relationship of the absolute pressure, temperature and volume of any gas

This relationship is expressed by the equation P x V/T = K• P = Pressure• V = Volume• T = Temperature• K = Constant; different for each gas

Physical Principles (Continued)

If one variable changes; at least one other variable MUST also change to maintain the constant “K” (Example if Pressures doubles while temperature remains constant, then volume must decrease by 50% to maintain the constant “K”)

Gas Physics

States of matter: in our atmosphere there are four states of matter: solids, liquids, gases, and plasma The state of matter of a substance largely

depends on the kinetic activity (motion) that the molecules of that substance poses

The degree of motion is most dependent on the temperature of these molecules

Gas Physics (Continued)

Increase molecular velocity causes molecules to exert more force when they hit something because of their inertia, such as they collide with each other Inertia (force) = mass x velocity With increased force the molecules tend to move

further apart causing an expansion

Gas Physics (Continued)

The movement and temperature increase of the molecules has the ability to change the molecules from solids to liquids, and liquids to gas

Gas Physics – Melting Point

Melting point is defined as the temperature at which transition occurs from a solid to a liquid state At the melting point of a solid the kinetic

activity is high enough for the molecules to break free from their own mass attraction sufficiently to escape and travel at random within the space of their containing vessel

The substance is now considered to be in the liquid state

Gas Physics – Boiling Point Boiling point is defined as that point at

which a transition occurs between a liquid and gaseous state at atmospheric pressure As the temperature of the substance increases,

the molecules of the liquid gain more and more kinetic activity and then travel around more freely and exert more force At atmospheric pressure and at a temperature at

which the molecules can break free from the attraction of the liquid, and begin to convert to a gas, is considered to be its boiling point

Sublimation Sublimation: under certain conditions

molecules can completely by-pass the liquid state As the heat content increases and the molecules

vibrate more vigorously, they may break loose below the melting point and become free gas molecules Solid Carbon Dioxide (dry ice) is the most common

example of this phenomenon

Every substance known to exist has its own melting and boiling point

Gas Pressure Measurement Pressure: is defined as force per unit area.

The force of gas molecules hitting things because of their kinetic activity causes gas pressure

There are various types of apparatus used to measure gas pressure (examples are liquid barometers and gauges)

Barometers: basically form some type of equilibration of forces between the molecular gas pressure force and a mechanical or weight force

Mercury Barometer The mercury barometer: uses the weight

of a column of mercury to equilibrate with the kinetic activity (force) of the molecules hitting the surface of a mercury reservoir A column is completely filled with mercury and

erected with its opened end below the surface in the mercury reservoir

The mercury in the column attempts to return to the reservoir as a result of gravity, but the reservoir is subjected to the force of gas molecules hitting its surface

Mercury Barometers (Continued)

The force of the gas molecules pushes the mercury up the column from the reservoir

When the force of gravity on the weight of mercury in the column equals the gas pressure force, equilibrium exists and the gas pressure can be measured

This pressure is measured by the height of the mercury column (mmHg)

Aneroid Barometers

Aneroid Barometer: equilibrates/balances gas pressure force with mechanical force or the expansion force of an evacuated metal container An increase in the atmospheric gas pressure on

the surface of the metal container tends to compress it

Aneroid Barometers (Continued)

The change in the container’s dimensions is recorded by means of the gearing mechanism which changes an indicators location on a recording dial

Likewise a reduction of gas force surrounding the container allows the metal container to expand toward its normal shape

Bourdon Gauge

Bourdon Gauge is another mechanism that measures pressure It consists of a coil tube and a

gear mechanism on which anindicator is attached

Bourdon Gauge (Continued)

As the gas pressure within the Bourdon tube increases, its force is exerted on the top of the inside of the tube to a larger degree because of the larger surface area

This increasing pressure tends to straighten the tube, causing the indicator to rotate to a new location on a dial as a result of gearing mechanism

Units of Measurement

Atmospheric pressure: is a unit of pressure equal to the pressure of the air at sea level or approximately 14.763 pounds per square inch

The following illustrates units of measurements that are equal in terms of force measured at one atmosphere:

Units of Measurement (Continued) Atmosphere is = 1ATM (atmosphere)

14.763 pounds per square inch (PSI) 29.21 inches of mercury (inHg) 33.93 feet of water (ftH2O) 1034 centimeters of water (cmH2O) 760 millimeters of mercury (mmHg) 101.3 kilopascals (kPa)

Units of Measurement (Continued)

Conversion factors: there may come a time when you will have to convert from one system of measurement to another The following conversion factors provide a

mechanism to convert from one set of values to another

They can be obtained by dividing one value at atmospheric pressure by another (example: 1034 cmH2O / 760 mmHg = 1.36)

Conversion Factors

Two factors used to convert from one pressure to another should be second nature to the Biomedical Equipment Technician

The first is 1.36 cmH2O for each mmHg. That same numerical valve can be used to convert from mmHg to cmH2O or vice versa

Conversion Factors (Continued)

If you need to convert cmH2O to mmHg Divide cmH2O by 1.36 = mmHg

Example: 27.2 cmH2O / 1.36 = 20 mmHg

If the conversion is from mmHg to cmH2O Multiply mmHg by 1.36 = cmH2O

Example 20 mmHg x 1.36 = 27.2 cmH2O

Conversion Factors (Continued) Another numerical conversion value is

70.34 cmH2O per square inch (PSI)

Conversion from one unit of measurement to the other can be accomplished in the same fashion as just described Example: 0.5 PSI x 70.34 = 35.17 cmH2O Example 35.17 cmH2O ÷ 70.34 = 0.5 PSI

Gas Flow Gas Flow: is the movement of a gas

volume from one place to another in relation to time

This motion of gases is not of the individual molecule’s activity, but rather that of the whole group of molecules moving from one location to another

Flow of gas results from a difference in force (pressure) between one area and another

This is commonly referred to as pressure gradient

Gas Flow (Continued) Gas molecules in an area of high pressure

are closer together, exerting greater force on each other, and literally pushing each other to a low pressure area

In considering the flow of gases with the use of respiratory therapy and anesthesia equipment, there are three factors of concern relating to the flow of a given gas: Factor #1: Pressure gradient, the higher the

pressure gradient is, the higher the flow through a set size opening or restriction

Gas Flow (Continued)

Factor #2: The larger the port size is between two different pressures, the higher the gas flow will be

Factor #3: As gas flow meets a restriction, the molecules must travel faster in a forward direction in the same amount of time, resulting in lower lateral pressure

Gas Flow (Continued) An analogy to this would be in example of

four lanes of traffic with each containing cars traveling at 25 mph. If the highway narrowed to one lane, each car would have to travel four times as fast, or 100 mph, for them all to pass through in the same amount of time

This same phenomenon occurs with gases

Pressure and Flow Components

The Venturi: the purpose of the venturi tube is to direct air flow and restore the delivered (lateral) pressure to a high value The advantage of using a venturi is to attempt to

restore the gas pressure after fluid uptake, back toward its original lateral pressure before the restriction of the jet

Pressure and Flow Components(Continued) This is accomplished by a tube that gradually

increases in diameter, this allows the gas to expand, slows down forward velocity, and resumes an increased lateral pressure.

A device of this nature can be used advantageously in devices in which the end pressure from the unit is of ultimate importance, such as dental suction

Pressure and Flow Components (Continued) Pilot Tubing: utilized in respiratory equipment on

an increased basis

The pilot principles is an open-ended tube that is faced in the direction of flow from the jet orifice, so that the end pressure is equal to the total head pressure as a result of air velocity

The pilot tube design objective is the reverse of a venturi

Pressure and Flow Components (Continued)

Its objective is not to restore lateral pressure toward its restrictive valve but rather to maintain a high forward velocity

The advantage of this type of device is that any restrictions or resistance placed downstream from the unit will not alter fluid uptake as significantly as would happen with a venturi

Pressure and Flow Components (Continued) The difference between the Venturi and

the Pilot Tube can be summed up as: The venturi design delivers pressure with flow

jeopardized The pilot tube delivers flow with pressure

jeopardized

Gas Regulation Devices

Reducing Valves: can be defined as a device that reduces a high pressure, to a lower working pressure

Single-stage Reducing Valve: there are two forces that interplay, allowing the reducing valve to work: Spring tension Gas pressure

Single-stage Reducing Valve The two forces oppose each other; a thin

diaphragm is used to separate them

On the bottom of the diaphragm is gas pressure; on the top is a spring

When the two forces of spring tension and gas pressure are in equilibrium, the diaphragm is straight, and the valve at the bottom closes the inlet from the source

Single-stage Reducing Valve (Continued)

As gas pressure drops, the spring tension is the dominant force and pushes the diaphragm downward; asa result the valve opens, allowing gas to flow into the bottom chamber of thereducing valve

Single-stage Reducing Valve (Continued)

Once enough gas has entered the bottom portion to cause a pressure

rise equaling the spring tension, thediaphragm will be straight, and the valve will close

The equipment operator would use the pressure adjustment handle to adjust the working pressure required for the apparatus (normally 50-55 PS


Multi-stage Reducing Valve: is simply two or more single-stage reducing valves in series Gas enters the first stage (high pressure), which is

in essence, a single-stage reducing valve (Course Adjustment)

Multi-stage Reducing Valve

From there gas pressure is again lowered, this time by a second single-stage reducing valve (low pressure) using a spring with less tension (Fine Adjustment)

The last stage reduces the pressure down to working pressure, and the gas can now be delivered to the attached equipment

Multi-stage Reducing Valve (Continued) Safety factors: there must always be a

pressure release for each stage of a reducing valve A higher-pressure spring is used for the pressure-

control spring, it seats a disk or cylindrical pop-off If a malfunction should allow the pressure in the

reducing valve to rise and equal the pop-off tension, the plate simply moves from its seat and allows gas to escape around it to atmosphere

Multi-stage Reducing Valve (Continued)

Once the pressure has been restored to a lower level, the spring reseats the disk, and the reducing valve return to proper function

Normally a pop-off valve is set at least 50% above the usual working pressure

Medical equipment standards are set to a closer tolerance


Flow meters are relatively simple devices that indicate the volume of gas going through it per unit of time, usually liters per minute

Flow meters do not regulate or indicate pressures

Flow meter Applications

Volume can be used to control pressure (example: breathing, volume in the thoracic cavity is increased by lowering the diaphragm) This results in the pressure within the lungs

decreasing below atmospheric pressure outside the lungs

The resulting difference in the pressure causes airflow into the lungs until the pressure equalizes

Flow meter Applications (Continued)

Pressure is used to move diaphragms to occlude passages or move mechanical valves and parts (examples of both found in dental units and sterilizers)

Pneumatic Tools Pneumatic tools are operated by

compressed air or gas which is normally supplied by: Compressors Pressurized tanks

Advantages of pneumatic tools Simple sturdy design Inherent safety of compressed air

More safety advantages: No problem with leakage current Tools can be operated safely and easily

Characteristics of Pneumatic Tools Disadvantage; if air is wet tools will:

Operate sluggishly Rust Become inoperable

Operate within a pressure range of 15 to 90 PSI

Pneumatic tools are typically small and lightweight

Rotating type (example used by drills and saws Air pressure is used to push vanes mounted around

an axle, a motor powered by air Drills, saws and grinders used in the dental clinic and

surgery

Characteristics of Pneumatic Tools (Continued)

Striking principle: is a device that moves a hammer device back and forth to deliver a cutting force (examples: jackhammer/chisel the size of a highlighter, used in dental lab and surgery)

Suction devices use a venturi system to create a vacuum (examples: used in dental and sterilizer equipment)

Steam Principles Steam:

Water that has been turned to an invisible gas vapor by heating water to the boiling point

Steam under pressure will be at a temperature well above 212° F/100 ° C

Vapor: refers to the visible semi-gaseous state of water Although both words vapor and steam

are used interchangeably, vapor is visible - steam is invisible and much hotter

Steam Principles (Continued)

Vapor often carries the connotation of gaseous matter in a state of equilibrium with identical

matter in a liquid and solid state

Vapor Pressure: at any given temperature, for a particular substance, there is a pressure at which the vapor of that substance is in-equilibrium with its liquid or solid forms


Ambient Pressure: when the ambient pressure equals the vapor pressure of any solid, the solid and vapor are in equilibrium

• Below that temperature, vapor will condense to solid; above that temperature, solid will sublime (turn to vapor)• At any given pressure, the sublimation

point of a substance is the temperature at which the vapor pressure of the substance in solid form equals the ambient pressure


Supersaturating

• The term supersaturating or over saturation refers to a solution that contains more of the dissolved material than could be dissolved by the solvent under existing circumstances

• It can also refer to a vapor of a compound that has a higher (partial) pressure than the vapor pressure of that compound (super saturation of the air – precipitation can occur when still air is moved)


Superheating

• Sometimes referred to as boiling delay• Is the phenomenon that a liquid can be

heated to a temperature higher than its boiling point without actually boiling• This can happen because gas bubble

formation at the normal boiling temperature can only occur in the presence of seeds in the form of small particles of gas bubbles

Superheating This can result in the liquid boiling very

suddenly and violently – a very dangerous situation

Superheating is sometimes a concern with microwave ovens, some of which can quickly heat water without physical disturbance

A person agitating a container full of superheated water by attempting to remove it form a microwave will likely be scalded by sudden release of kinetic energy

Boiling Point (Continued) Boiling Point – of a substance is the temperature

at which it can change state from a liquid to a gas at 1ATM A liquid may change to a gas at

temperatures below the boiling point through the process of evaporation

Evaporation is a surface phenomenon, in which only molecules located near the gas/liquid surface may evaporate

Boiling Point (Continued)

Boiling on the other hand is a bulk process, so at the boiling point molecules anywhere in the liquid may be vaporized, resulting in the formation of vapor bubbles

The boiling point corresponds to the temperature at which the vapor pressure of the substance equals the ambient pressure

Boiling Point (Continued) Thus the boiling point is dependent on the

pressure. Usually, boiling points are published with respect to standard pressure (example 14.763 PSI or 760 mmHg or 1 atmosphere)

At higher elevations, where the atmospheric pressure is much lower the boiling point is also lower

The boiling increases with increased ambient pressure up to the critical point, where the gas and liquid properties become identical

Boiling Point (Continued)

The boiling point cannot be increased beyond the critical point

Likewise, the boiling point decreases with decreasing ambient pressure until the triple point (the temperature and pressure at which three phases “gas, liquid, and solid” of that substance may coexist in thermodynamic equilibrium)

The boiling point cannot be reduced below the triple point

Evaporation (Continued) Evaporation: the process whereby atoms or

molecules in a liquid state (or solid state if the substance sublimes) gain sufficient energy to enter the gaseous state

Factors influencing evaporation Concentration of the substance evaporating in the

air If the air already has a high

concentration of the substance evaporating, then the given substance will evaporate more slowly

Evaporation (Continued)

Concentration of other substances in the air If the air is already saturated with other

substances, It can have a lower capacity for the substance evaporating

Temperature of the substance If the substance is hotter, Evaporation will be

faster

Flow Rate of Air

If fresh air is moving over the substance all the time, then the concentration of the substance in the air is less likely to go up with time, thus encouraging faster evaporation

In addition, molecules in motion have more energy than those at rest, and so the stronger the flow of air, the greater the evaporating power of the air molecules

Inter-molecular Force

The stronger the forces keeping the molecules together in the liquid or solid state, the more energy that must be input in order to evaporate them

Steam Volume

Steam Volume – it is pure, invisible gas, which at atmospheric pressure occupies about sixteen hundred times the volume of liquid water (example: 1 pound of water occupies only .2 cubic feet, when that water turns to steam it occupies 27 (cubic feet)

Terms Saturated – filled to capacity; having absorbed all

that can be taken in

Saturated Solution – a solution in equilibrium at a definite temperature

Saturation Point – the point at which the greatest possible amount of a substance has been absorbed

Quality of steam 97 – 98%

97% saturation (3% water droplets in the steam)

Applications of Steam in Hospital

Steam Sterilizers

Cooking in kitchen

Heating Building Water

medical gas & steam principles. in 1961, centralsug ab installed the first vacuum waste system...

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