1. Pressure regulators (reducing valves)
Dr S. Parthasarathy MD DA DNB PhD FICA , Dip software based statistics
IDRA

2. Morton inhaler to Heidbrink modification(1917)- pressure regulators

4. One stage and two stage regulators
How does it look like ?
One stage and two stage regulators

5. Why it is needed ? To reduce the high pressures of the system
To supply at the same pressure with differing inlet pressures
Otherwise the flowmeters will blow out
Fine adjustments of flow possible
Constant adjusting of the flow meter not necessary

6. Principle
Pr. H × A1 = Pr. Low × A2

9. Flow meter adjustment – needed ??
constant reduced pressure only if the supplied pressure, Pr. H, is constant. If Pr.H decreases, as when the cylinder pressure falls, Pr.L must decrease to preserve the balance of forces.
With this type of pressure regulator, the flow indicator would constantly need to be adjusted to compensate for the pressure drop
That’s why we need S1

10. What does it do (Spring 1)
forces acting to push the diaphragm upward
PrL × A2
Forces acting to push the diaphragm downward
(PrH × A1) + Fs1
FS 1 is large enough and hence Pr.H variation may not affect
FS1 is , then think of cylinder pressure from 2000 to 500 , the total force / will it get affected much ?

12. What is the work of the second spring ?
This acts to force the seat against the opening from the cylinder.
This prevents gas from flowing from Pr. H to Pr.L when the adjusting spring is completely relaxed and the stopcock open.

13. S1 is very larger than S2 to effect any overall change

14. Direct acting and indirect acting

15. Indirect acting
Spring 1 and spring 2

16. What is made of ? Withstand Up to 4300 PSI
For low-pressure regulators, the diaphragms are frequently made of rubber or neoprene, whereas in those for higher pressures the diaphragm is made of metal.
Adjustments to alter the regulated pressure should be made only by service engineers
Withstand Up to 4300 PSI

17. Pressure relief valve Pressure regulators have safety valves
They open usually at a PSI of 70
The outlet pressure is only 55
Sometimes there may not be any regulator for pipeline supplies !! – wall mounted oxygen !!
Secondary pressure regulators
Modern machines with hypoxia guard systems have two regulators for each gas in the machine

18. Go into the parts
Open
Diaphragm

19. Black, yellow and silver – three portions of the diaphragm
Spring 1
Opposite side
Spring 1

20. Spring 2

21. Interchangeability of regulators
Usually labeled and color coded for gases
Special alloy to prevent corrosion
modern regulators are designed to be compatible with all anaesthetic gases.
This is achieved by using materials such as PTFE coatings on the diaphragms together with nitrile (a hard synthetic rubber) valve seats and chrome-plated brass for the regulator body
The so called universal

22. Two stage regulators
The two-stage regulator is often used to power drills and other orthopaedic instruments in the theatre where you need a higher pressure and perhaps an easily adjustable one

23. Pictures from the internet for closed academic purpose only !

24. Pictures from the internet for closed academic purpose only
Adam’s valve and tongs
Pictures from the internet for closed academic purpose only

25. Hazards !!
Damage to the soft seating of valves may occur as a result of the presence of grit or dust, usually from a dirty cylinder
A hissing noise may indicate a leaking or burst diaphragm.
Adams valves sometimes develop a fault that causes continual ‘jumping’ of the flowmeter bobbin, indicating an intermittent change of pressure and flow rate.
usually due to the ‘lazy tongs’ sticking as a result of wear, tear, dirt

26. Oxygen flow meters in ward
They should not be used to supply oxygen to the anaesthetic machine, since the limited flow (typically 8 or 15 L/min) will be inadequate to operate the quick-flush or ventilator.
This is for the cylinder !!

27. Summary Why are they needed Principle S1 and S2
One stage and two stage
Direct and indirect
Hazards