Oxygen cylinders are used to transport compressed oxygen gas. They are used in hospitals for artificially administering oxygen to patients. A good ambulance is always equipped with an oxygen cylinder to keep patients breathing while being carried to the hospital. Scuba divers and undersea explorers also carry oxygen cylinders with them to assist with normal breathing. Patients who suffer from respiratory disorders like emphysema, asthma and pneumonia are advised to keep an oxygen cylinder handy.
The shell of the oxygen cylinder is made of aluminum or brushed steel. A single sheet of metal is cut to size by a saw on a conveyor belt. The metal sheet is then put through a metal press that rolls it into a cup shape. The mouth of the cup is closed by the press.
Heating the cylinder for added strength is done through two steps. One is the heating process and the other is the process of artificially aging the cylinder. For the heating process, the roll of metal is heated to 1000 degrees Fahrenheit in a solution furnace. All alloying metals are also put in the furnace and later cooled. The metal is then subjected to the second heating process. It is sent through an age oven heated to 350 degrees Fahrenheit. This process helps the alloys to firmly bind with the metal to make the cylinder stronger.
The threads and the sealing surfaces are machined into the cylinder. The solid metal cylinder is placed on a milling machine which is a press that can move in three directions. A hole is milled in the center of the cylinder by the machine. A form tool is then used to make threads, and the form machines the top of the cylinder in the shape of a neck.
The cylinder is placed under hydrostatic testing, where it is subject to heavy pressure to check whether it can withstand extreme pressure of all types. If it expands greater than a specified size within 30 seconds, the cylinder is rejected. The condemned cylinder is again put under a saw and recycled. The cylinder is sent on a conveyor belt in a horizontal position under an automatic sander to make the surface of the cylinder smooth. The cylinder is painted and a cap or valve is attached according to the specifications of the customer.
Air is compressed and sent through a compartment that has a piston. The air expands in the compartment. When the air expands, the compartment increases in volume and the pressure and temperature of air is lowered. Air is liquefied by this process. The compartment is called an expansion engine. The liquid air is then boiled to remove nitrogen. The simple process of boiling is effective because nitrogen has a lower boiling point that oxygen. The liquid air that is now predominantly made up of oxygen is taken through a large insulated tank and put into the waiting oxygen cylinders. The cylinder is fitted with a pressure regulator to gauge the pressure in the tank.