How a Modest Inventory Can Provide Important Savings to the User: The steam-jet ejector is a pumping device with no moving parts. It offers a simple and reliable means for producing vacuum, and is expected to provide many years of trouble free operation. An ejector has no moving parts.
The figure shows the main components of a steam-jet ejector. The steam chest is the connection thru which the high pressure motive supply is introduced into the steam nozzle. The steam nozzle is the heart of an ejector. It converts motive pressure to velocity energy which is used to entrain vapors in the suction head. The suction head connects the steam chest to the diffuser, which is made up of an inlet diffuser, throat and outlet diffuser.
Why Wear Occurs: The main problem an ejector is likely to experience during operation is reduced capacity and/or loss of vacuum because of worn parts. The sources of wear are the moving fluids including:
- Motive fluid which enters the nozzle
- Suction fluid which is entrained in the suction head
- Discharge fluid which is a mixture of the motive fluid and the suction fluids
Steam is the fluid of choice for most vacuum applications. Any moisture in the motive steam will eventually affect the performance of the jet. The high velocity wet stream will erode the metal in a process known as wiredrawing. For this reason a steam separator with a trap is always recommended.
Recommended Spare Parts Inventory
- One spare nozzle for every ejector stage size
- One spare diffuser for each of the final two stages
- One complete last stage (Z-stage) ejector (for critical services involving multistage ejectors)
- One complete spare ejector (for critical services when unit is made of a special-purpose material like ceramic, Haveg, Carbon, Teflon or Fiberglass.)