Buckets for Elevators – Steel or Plastic?

Bucket elevator

Many buyers of buckets for elevators, have concerns about replacing their steel buckets with plastic. The question of whether static electricity generated when using plastic buckets and the subsequent danger of dust explosion is often mentioned. Here are some facts to consider before making up your mind:

As regards Static Electricity:

  • A static conducive belt may be used in an elevator whereby the static is conducted into the pulleys.
  • Elevator buckets do not generate enough static to supersede the conductivity rating of a static conductive belt (usually 300 Mega Ohms).
  • All static electricity that the bucket does generate is discharged through the elevator bolts into the pulleys of the elevator which would always be grounded.
  • As for dust explosion it should be borne in mind that spark caused by static, or “cold spark”, does not have the necessary energy to ignite a dust explosion.  Only a “hot spark”, one caused by scraping metal on metal, has enough energy to start a dust explosion.

 

Steel buckets versus Plastic buckets:

  • Plastic buckets are non-sparking
  • Plastic buckets are non-corrosive
  • Plastic buckets will flex when they encounter an obstacle, allowing the bucket to pass through without damage, they then return to their original shape.  Steel buckets will dent and loose capacity; the deformation of steel buckets also increases the risk of spark by scraping the casing or another metal object placed near the buckets.
  • Fixing or changing a damaged steel bucket requires costly down-time and labor.
  • Using the proper plastic is for the specific application, bucket life should be as good or greater in most applications.  Stainless steel can for instance be replaced with Nylon or Urethane (the most resistant plastics) at a fraction of the cost.
  • Plastic buckets also have important weight savings that can reduce cost by being able to use a lighter elevator belt. It also improves the life of other drive components in the elevator.
  • Polyethylene and Urethane are approved for use in food applications by the FDA in the United States whereas steel buckets are often not.
  • Nylon, polyethylene and polyurethane buckets are usually substantially less expensive than steel to start with.
  • Light weight plastic buckets with a low profile cut can be placed closer together, thus enhancing capacity over and above the previous heavy steel buckets.

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