The lantern ring

The lantern ring performs three basie functions:

1. To supply new lubricant to the packing rings, which is normally lost in operation.

2. To supply 'back pressure', which aids in impeding the entrance of abrasive and corrosive material into the stuffing box. Abrasives and corrosives will damage the shaft or sleeve, and disintegrate the packing.

3. To cool the packing and shaft and dissipate the heat generated between these members, which will increase the normal service life of the packing and pump.

Oil, water, grease, or any liquid or substance compatible with the fluid are forced under pressure into the packing through the lantern ring by means of a connection on the stuffing box wall to provide these three functions.

Recommended instructions for packing a pump arc:

1. On installing Teflon packings, place and seat each ring ringer tight. Do not use wrenches or pliers.

2. Bring the gland up to the packing rings and adjust the gland nuts by hand. (No tools yet.)

a. Open the flush line to the packing.

b. Start the pump.

3. Permit the pump and packing to leak generously for about 15 minutes to allow the packings to absorb the pumped fluid, swell, seat and adjust to the stuffing box wall and the shaft.

4. If excessive leakage continues, tighten the gland nuts '/&th of a turn with a wrench. Don't permit the temperature to rise in the packing.

5. Continue adjusting the gland nuts '/.th of a turn every 15 minutes until the leakage is controlled to about 1 drop per second per inch of shaft diameter.

PRECAUTION

Too many gland adjustments will cause the packing to crystallize and burn, which will shorten the packings' useful life and damage the shaft or pump sleeve.

Know and Understand Centrifugal Pumps The packing lubricant

The use of die appropriate lubricant is an important consideration. Generally Graphite, moly grease, and oils are good lubricants depending on the application. Many pumps are set-up to use cold water flushed into the stuffing box as a coolant, and lubrication for the packings.

Graphite is a common lubricant for general service. Molybdenum disulfide (moly grease) is an excellent lubricant because it creates a lubricating film barrier between the shaft and the packings, protecting both. It also works well with high temperatures. Mica is also a good lubricant for very high temperatures. However, it tends to contaminate the pumped liquid with particles. It certainly wouldn't be indicated in a milk pump. Any oil compatible with the pumped liquid is adequate as a general lubricant.

Be aware that the packing is destined to fail the moment it is installed. It has to resist every basic operating tendency of the pump. The packing consumes energy decreasing the pump's efficiency. It generates frictional heat by grabbing and abrading the shaft. The packing itself suffers from abrasion and corrosion originating in the liquid moving through the pump.

Repacking the pump is a difficult and dirty job and falls down to the bottom of the mechanics favorite 'to do' list. Extreme care should be taken to assure a proper installation. It's a job usually put off until the very last moment. Repacking a pump correctly takes a lot of time. Not following the correct repacking and start-up procedures results in short packing life.

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  • Fabiana
    What is the purpose of lantern ring in centrifugal pumps?
    6 years ago

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