Rotary Valve

Airlock Rotary Valve Maintenance

Airlock Rotary Rope Packing Shaft Seal Break-In and Maintenance

There are many types of rotary valve shaft seals.  They are frequently misapplied for the product being metered and/or the application.  Here at DoverMEI we pride ourselves on suppling the best Airlock Rotary Feeder and seal arrangement for your application.

This artical focuses on one typical type of seal arrangement, rope packing.  At DoverMEI we prefer a PTFE type rope packing material.  Rope packing works best when properly commissioned and maintained.  If they are not properly commissioned, you will be rebuilding the airlock almost immediately.  Following the simple procedure below will provide you with reliable long term seal.

There are typically 3-4 rings a of rope packing (item 5). The packing is compressed by tightening a follower gland (item 6) which has nuts (item 15) 180 degrees apart.  Always tighten the packing gland evenly.  Uneven tightening can bind the packing gland against the shaft or the housing.  Make sure you follow the manufactures recommend torque.

Packing Break In

  1. Tighten packing glands prior to start-up of new valve. It is a good idea to tighten the packing when you bump the motor to check rotation, early in the commissioning phase.  Always bump motors without material running through the airlock.
  2. Re-tighten the packing as one of the last things before leaving the job site after system commissioning.
  3. Check packing after two days of running.
  4. Check packing one week after initially running product.
  5. If the packing was loose after one week then check twice weekly the following week.
  6. If packing was tight after one week then check it in two weeks.
  7. If packing was tight after two weeks, check it in a month
  8. If packing was tight after one month, check the packing in two months.
  9. Then check packing tightness quarterly.
  10. When your packing gland reaches or nearly reaches the end plate, back it off and add one new ring of packing and tighten.
  11. Your material may require more frequent tightening of the packing.  Following this procedure, you will discover the best interval for your production rate and material.
  12. Leaking packing glands may require tightening or new packing.

***  Visually inspect Rotary Airlock Feeders daily to check for leaks and noise.  ***

*** A quick daily inspection is worth a pound of cure  ***

 

Other Tips

  1. Many Airlocks Rotary Feeders are equipped with air purge kits.  The air used to purge packing should be regulated at 10-15 psi above the max convey pressure. DoverMEI provides individual flow meters balanced at 20-30 SCFH. If no air flow is obtainable, check solenoid, compressed air supply, and electrical circuit.  After years of tightening of the packing, the aeration rings can get plugged with packing material, at this point you will not have air flow.  This is okay as long as the airlock is working properly and not leaking.  Continue to tighten your packing on your regular schedule and continue installing new packing rings as required.  Basically, if it ain’t broke don’t’ fix it.  Stick to your maintenance plan.
  2. At the same interval you tighten your packing also check:
    1.  Chains and Sprockets
    2. Motor temperature
    3. Gear Box lubrication
    4. Check for leaks, spills, noise, and anything out of the norm.
  3. Many gear boxes are shipped as sealed units, and no lubrication is required.  Please verify your type of gear box and recommended lubrication type and change frequency, if applicable.
  4. Check service manual for motor lubrication, recommendations.  Do not over grease motors.

 

DoverMEI offers:

  • Quarterly Preventative Maintenance
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  • Airlock and diverters rebuilds
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