Chapter 41 Flashcards
What are the three safety relief valves?
Frangible Metal Disc: ruptures at a specific pressure
Fusible Plug : melts at a specific temperature
Spring-Loaded valve : opens and vents gas at a set high pressure
Color Codes for Medical Gas Cylinders
Oxygen - green
Carbon dioxide - gray
Nitrous oxide- light blue
Cyclopropane - orange
Helium - brown
Carbon dioxide & Oxygen- gray and green
Helium and oxygen - brown and green
Air - yellow
How do you measure a gas filled cylinder?
Gas filled cylinders have a psi of 2200 and the formula to measure their duration is
Duration of flow = Psig x cylinder factor / Flow ( L/min )
What is the cylinder factor for H/K and E cylinders ?
H/K : 3.14
E : 0.28
What are the two organizations that are associated with Gas Cylinder Safety?
(NFPA). National Fire Protection Agency
(CGA). Compressed gas association
How do you measure liquid gas cylinders?
They are measured by how much the cylinder weighs
1 liter of liquid gas weighs 2.5 pounds
It generates a pressure of 860 psig
The formula for liquid gas is
Amount of gas in cylinder = liquid weigh (lb) x 860 / 2.5 lb/ L
Physical Separation
There are two types of methods to separate O2 from air
- Molecular Sieves : composed of inorganic sodium aluminum silicate pellets. The pellets absorb N2 gases and water vapor from the air providing a concentrated mixture of more than 90% of O2 for patient use.
- Oxygen concentrator : devices that are used primarily for supplying low- flow O2 in the home care setting. It sucks in the O2 and water vapor faster than the N2 (nitrogen). This system can produce a O2 mixture of approximately 40%
Fictional Distillation
Is the most common and least expensive method for producing CO2. The steps are listed below
1. Atmospheric air is filtered to remove pollutants, water, and carbon dioxide
2. The purified air is liquified by compression and cooled by rapid expansion
3. O2 and nitrogen are heated slowly in distillation towers
4. N2 with a boiling point of 195 .8 degrees escapes first followed by argon, krypton, and xenon
5. O2 remaining is transferred to specially insulated cryogenic storage cylinders
Cylinder Labeling and Identification
- The letters DOT or ICC followed by the cylinder classification ( 3A or 3AA )
- The normal filling pressure (psig)
- The letter size of the cylinder ( E,G, H, ETC )
- Followed by the cylinder serial number
- The third line provides a mark of ownership followed by the manufactures stamp
- Dates of test ( every 5-10 years )
An * next to the date indicates DOT approval for 10 year testing
An + means that the cylinder is approved for filling to 10% greater than its surface pressure
Saftey test are conducted every 5-10 years
Cylinders are pressurized to 5/3 of their service pressure
Department of Transportation
DOT
DOT type 3A cylinders are made from carbon steel
DOT type 3AA containers are manufactured with a steel alloy tempered for higher strength
They are both made from seamless steel
Safety indexed connector systems
3 systems used to ensure correct gas source
- American Standard Safety System ( ASSS)
- for the large cylinders and their attachments ( Cylinder H/K ) - Pin- Index Safety System (PISS)
- for small cylinders up to and including cylinder E. - Diameter -Index Pressure safety System (DISS)
- for low - pressure gas connectors
2-5 for oxygen
1-5 for air
Flow Meters and the different types
There are three categories of flow meters that are used in respiratory care
Flow meters allow the rate of gas flow to a patient to be set and controlled.
- Flow Restrictor : is the simplest and least expensive of the flow meters. It consists of fixed orifice calibrated to deliver a specific flow at a constant pressure of 50 psig.
- Bourdon gauge : a type of flowmeter that is used combined with a pressure- reducing valves. It also uses a fixed orifice similar to the flow restrictor. IT operates under variable pressure as adjusted with the pressure- reducing valve. Increasing the upstream pressure increases gas flow out of the device unless downstream pressure also increases.
- Thorpe Tube : is always attached to a 50 psig source. It’s used to measure flow. Functions as a variable - orifice at constant pressure flow meter.
- compensated : prevents change in downstream resistance or back pressure from affecting meter accuracy.
- uncompensated : gas from 50 psig source flows into the metro at a rate controlled by a needle valve located before the flow tube.
Cylinder Storage
Again follows the recommendations of the NFPA and CGA
Steps for storage
- Store in racks or chained to the wall.
- Store full and empty cylinders separately
- Keep away from combustible material ( no heat)
- Keep the temperature less than 125 degree Fahrenheit
Keep cap on if not in use
The Proper way to transfer Cylinders
There are five steps on transporting cylinders
1. Use the cylinder cart
2. Keep protective cap in place
3. Protect cylinders from striking other cylinders and other objects
4. Avoid dragging and dropping
5. Always read labels before use and transport
What are the advantages and disadvantages of Flow Restrictors?
Advantages
- low cost , simple, and reliable
- cannot be set to incorrect flow
- can be used in any position ( gravity independent)
Disadvantages
- different versions require different flows
- accuracy varies with changes in source and downstream pressures
- cannot be used with high resistance equipment