What is rotary union? Types of rotary union & Components

Rotary unions is a type of rotating couplings that transfer fluids like steam, water, air and oil from stationary source to a rotary equipment of machinery without any leakage. It is also be called as a rotary joint. All rotary union functions are same but it is only different depending on the application of uses. 
Rotary union consist of bearings,seals, retaining rings and o rings but its design and construction varies depending on its application. 

Types of rotary union according to passage and application

According to flow of passage 

Single passage and multi-passage are the types rotary union. 

In a single passage rotary unions heat transfer media goes in one direction. At one end of the union medium enters and exits to other end thus making it one passage into the joint. 

In the multi-passage rotary unions has multiple passage in same directions or different directions. 

According to application 

Hot applications rotary joint which outer body is made with temperature resistance steel and setup with tungsten carbide seals supported by pure graphite bushing that can withstand very high temperatures of fluids.

High speed rotary joint can retain high pressure during rotating at high speed. It is made with stainless steel, carbon steel and aluminium that can provide corrosive resistance.High speed rotary union are most commonly used in extruders, laminators, hydraulics operations and rubber mills. 

Components of rotary joint/joint

Housing is the casing of all components of rotary union. Seals,O-rings,bearings,springs and shafts stay inside the housing. Pipes or hoses are connected to the housing. 

 
Shaft is connected with the rotating cylinder or drum and transfer fluids through rotary union to the drum. Bearings and seals are equipped with the shaft. 

Bearing is the most import part of rotary union. One or more bearings are used in different circumstances and environment. Roller,Non roller and tapered bearings are used to allow housing to rotates. 

Seal is the major important component of the rotary union while in operation. seal acts against the forces which come from the fluid pressure and generates friction to the contact face between the stationary part and rotating nipple. 

Spring forces the seal to contact with the rotating shaft and prevent  from internal leaking and also balance the seal with contact face. (Not available in all rotary unions) 

Applications of rotary union

Rotary unions are most commonly used in automobiles and industrial machinery where needs constants supplies of lubrication for moving components to operate smoothly. It is also used in ships, chemical industries, food industries,cement,textile,packaging and pharmaceuticals industries. 

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