Skip to main content

Air Pressure Regulator Questions

 Since precision pneumatic instruments operate best when their supply air pressure is at a constant pressure, it is necessary to regulate the fluctuating air pressure from the receiver vessel down to a lower, more constant level for the instrument. The device designed to do this is called an air pressure regulator.

Air Pressure Regulator

A cut-away diagram of an air pressure regulator is shown here:


The wedge-shaped plug can move down to open the passageway and allow more of the high-pressure air to enter the chamber below the diaphragm, and can move up to close off the passageway and reduce the flow of incoming air into the diaphragm chamber. The regulation setpoint is adjustable by the position of the threaded rod pressing down on the diaphragm through a spring.

Describe how this air pressure regulator functions. Suppose that the outlet air pressure is below setpoint. How does this mechanism respond to bring the outlet pressure back up to where it is supposed to be?

If the outlet air pressure rises to too high a level, how does the mechanism compensate to reduce it back down to the setpoint level?

Answer:

If the chamber air pressure is too high, the excess pressure will exert more force on the underside of the diaphragm to push it up, thus moving the plug up and closing off the passageway, reducing the air supply flow:

As the outlet air continues to flow out of the regulator, the chamber pressure will eventually drop back down to setpoint, and the passageway will open again.

If the chamber air pressure is too low, the reduced force on the underside of the diaphragm cannot resist the spring force from above, and the plug moves down. This opens up the passageway, allowing more of the supply air to enter the chamber and increase the pressure:

In short, the opposing forces of spring pressure (and atmospheric air pressure) above the diaphragm, versus the chamber pressure below the diaphragm, act to move the plug up or down as needed to maintain the chamber pressure approximately equal to the equivalent pressure of atmospheric air + spring force on the diaphragm.

The threaded rod with an attached turn handle adjusts the compression of the spring above the diaphragm, and changes the pressure regulation setpoint. Screwing the threaded rod in the downward direction will increase the spring force on the top of the diaphragm and likewise increase the equilibrium point between the three forces, increasing the output air pressure regulation setpoint as a consequence.

Screwing the threaded rod in the upward direction will decrease the spring force on the diaphragm’s top, decreasing the equilibrium point between the three forces and decreasing the pressure setpoint.

Questions for you:
1. Suppose the spring inside this regulator were to break. What effect would this have on the regulator’s output pressure, and why?

2. Suppose the vent hole were to plug. What effect would this have on the regulator’s output pressure, and why?


Labels:

Comments

  1. siddhagirimetalMarch 4, 2021 at 1:22 AM

    This information is meaningful and magnificent which you have shared here. I am impressed by the details that you have shared in this post and it reveals how nicely you understand this subject. You can also visit stainless steel threaded rod for more Siddhagiri Metals & Tubes related information. I would like to thanks for sharing this article here.

    ReplyDelete
  2. duplexpipessteelApril 1, 2021 at 3:52 AM

    This comment has been removed by the author.

    ReplyDelete

Post a Comment

Popular posts from this blog

Ferrules and Cross Ferruling

 Ferrules are identification labels provided for every wire terminations in an instrument, equipment, or electrical/instrumentation control panels. These tube-shaped sleeves can be inserted easily on each individual wire in a multi-core cable. In earlier days fixed digits/letters are used as ferrules, but now Instrumentation engineers/technicians prints out desired ferrules by using a ferrule printing machine. Typical Ferrule The numbers/ letters on the ferrules will be given as per the approved electrical hook up or loop diagrams. This helps technicians to easily identify a particular loop/wiring from a series of terminal blocks and to troubleshoot the desired terminal connection. Separate numbers on the ferrules distinguish the positive and negative polarities of wires, thus ensure the polarity protection of the instrument. Cross Ferruling  As a wire is connected on its both ends, it is quite useful to use a cross reference method for wire identification. Unlike normal ferru...
1 comment
Read more

What is a Torbar? – Averaging Pitot Tubes

 The Torbar is employed for flow measurement of liquids, gases, or steam in circular, square, or rectangular section ducts for large flow rates. The Torbar is an insertion type multi-port self-averaging primary sensor for flow measurement. Torbar TORBAR is a set of Pitot tubes mounted on a bar across the pipeline with no moving parts. An averaging Pitot tube is a technology, while TORBAR is a manufacturing brand name. There are several brands available in the market with VERABAR, ANNUBAR, etc. Averaging Pitot Tube Principle Purpose Averaging Pitot tube can be employed when the average velocity of the flow profile, rather than the velocity in a specific point in the cross-section is desired. Averaging Pitot Tubes Principle It measures the differential pressure between the static pressure tap and the tap of full pressure of a stream. Thus such magnitude of differential pressure is directly proportional to the square of the flow rate. Working The TORBAR is designed in such a way that ...
7 comments
Read more

Dissolved Oxygen Analyzer Working Principle

 What is dissolved oxygen ? Dissolved oxygen refers to oxygen dissolved in water. Its concentration is expressed as the amount of oxygen per unit volume and the unit is mg/L. Biologically, oxygen is an essential element for respiration of underwater life and also acts as a chemical oxidizer. The solubility of oxygen in water is affected by water temperature, salinity, barometric pressure, etc. and decreases as water temperature rises. Measurement of dissolved oxygen by the membrane electrode method The membrane electrode method measures a diffusion current or reduction current generated by the concentration of dissolved oxygen or partial pressure of oxygen to obtain the concentration of dissolved oxygen. This method is not affected by the pH value of water being measured, oxidation and reduction substances, color, turbidity, etc. and the measurement method offers good reproducibility. When a sensor is inserted into water, an air layer forms on the membrane (Teflon membrane). The ox...
1 comment
Read more