cemanet.org€¦ · Web viewREF 70 bolts are not recommended for flat back plastic buckets. Figure 6.34 - Reference 70 Bolt with Large Oval Washer Figure 6.33 - Reference 70 Elevator

CEMA Bucket Elevator Book-Section 6May 5, 2015

PART 3 - FULL DOCUMENT WAS 10MB'sCEMA Bucket Elevator Book, Best Practices in Design

1st Edition-SECTION 6, BucketsBucket Elevator CommitteeChair: Warren Knapp, SCC

Vice-Chair: Kris Gililland, KWS

CHAPTER 6 - PART 3, CONTINUED


AttachmentsElevator bolts are designed for fastening elevator buckets to an elevator belt. Common design features include a large circular head with a flat top surface and a shallow conical bearing surface and an integrally formed square neck under the head.

The large head design significantly reduces the chance of belt pull-through. The conical bearing surface facilitates sinking into the belt and the flat top surface allows for a smooth tangential contact with the surface of the pulley. The square neck helps prevent the bolt from turning during installation.

Elevator bolts are available in imperial and metric sizes, in carbon steel and stainless steel materials. Carbon steel bolts are typically SAE J429 Grade 2 or ISO Grade 5.8 with a zinc plated finish. Stainless steel bolts are typically Grade 302.

There are several styles of elevator bolts available. Style selection criteria include: ease of installation, pulley diameter, pull-through resistance and personal preference.

No. 1 Norway BoltThe name Norway refers not to the country but rather to the type of steel originally specified for the manufacture of these bolts (Figure 6.24). Its proper name is the “flat countersunk head” elevator bolt. Norway bolts are the most common and the least expensive of the standard styles.

Norway bolts are typically installed with a hex nut, spring lock washer and fender washer. It is important to periodically re-tighten these assemblies as they tend to loosen over time. The assemblies loosen due to vibration experienced within the bucket elevator system. Also, over time the elevator belt tends to elongate and become thinner. As this happens, the tension on the spring lock washer diminishes and subsequently so does its effectiveness to hold the hex nut tightly in place.


Fanged BoltThe fanged elevator bolt is characterized by two sharp teeth that are intended to penetrate the carcass of the elevator belt (Figure 6.25). Once the teeth penetrate the belt they keep the bolt from turning. Because the bolt does not turn freely, it is possible to pair the bolt with a lock nut. Although more costly, this assembly is considered more reliable than the Norway system since the lock nut is less likely to come loose as a result of belt elongation and/or system vibration.

A variation of the fanged bolt is the “pointed end” fanged bolt where the tip of the shaft is formed into a point (Figure 6.26). The pointed end of the fanged bolt facilitates insertion through elevator belts with poor holes.

Fanged bolts should not be used with thinner belts as the fangs could potentially damage the belt. Alternatively, a less aggressive turn-resisting bolt style like the Western 3-Prong or Easifit bolt can be employed.

Install fanged bolts with fangs inline across the width of the belt. This results in more uniform tangential contact with the pulley for smoother and more reliable system operation.

Western 3-Prong BoltThe Western 3-Prong elevator bolt is designed with three small prongs underneath a smaller diameter flat head. It is ideal for small

Figure 6.28 - No. 1 Norway Elevator Bolt

Figure 6.29 - Fanged or Sabre-Tooth Elevator Bolt

Figure 6.30 - Pointed Fanged Elevator Bolt

Figure 6.31 - Fanged Bolts Installed with Fangs Inline


bucket elevators with thinner belts and smaller pulleys. It offers some of the same resistance to turning as a fanged bolt but with less belt penetration.

Reference 70 BoltReference 70 elevator bolts are designed with a small concave head and four prongs on the underside to help prevent turning during installation. Their small head design makes them ideal for smaller diameter pulleys and pressed steel buckets with recessed holes. When coupled with a large oval washer, they become ideal for pulleys over 20 inches in diameter. The REF 70 bolt and large oval washer combination offers the greatest belt pull-through resistance available. REF 70 bolts are not recommended for flat back plastic buckets.

Figure 6.32 - Western 3-Prong Elevator Bolt


When using the large oval washer with the REF 70 bolt, the washer should be placed with the widest part horizontally across the belt in order to minimize stress on the system as it passes around the pulley.

No. 3 Reliance BoltNo. 3 Reliance bolts are characterized by a smaller diameter, flat, slotted head and a six pointed radial star beneath the head. The protruding ridges of the star offer some resistance to turning during installation and the slot in the head can accommodate a flat-head screwdriver. This bolt is typically used in applications with smaller diameter pulleys where reduced tangential contact is desired.

Easifit BoltEasifit elevator bolts employ a hexagon tip. A special installation tool (Figure 6.34) locks onto the tip, keeping the bolt from spinning as the lock nut is tightened. Easifit bolts are especially useful for repair jobs where only the elevator buckets and not the belt are being replaced since they eliminate the problem of elongated bolt holes that can no longer hold the square shoulder of standard bolt styles.

Figure 6.33 - Reference 70 Elevator Bolt

Figure 6.34 - Reference 70 Bolt with Large Oval Washer

Figure 6.35 - Reference 70 Bolts Installed with Large Oval Washers

Figure 6.36 - No. 3 Reliance Bolt


Euro Bolt (DIN 15237)The DIN 15237 bolt derives its name from the 1980 Deutsche Institute für Normung (DIN) Standard No. 15237 covering “continuous mechanical handling equipment; seating screws and cupped washers for the attachment of components to belts”. This fastening system is comprised of two components: an elevator bolt with two prongs and a mating domed washer (Figure 6.35).

Popular throughout Europe for the last 30 years, this fastening system is typically specified in metric thread only and intended for the attachment of pressed steel elevator buckets incorporating recessed bolt holes. The recessed area surrounding the bolt hole (Figure 6.36) is intended to accommodate the similarly domed surface under the bolt head. Because of this domed area under the bolt head, these bolts are not recommended for attaching flat back plastic buckets.

Figure 6.37 - Easifit Elevator Bolt Figure 6.38 - Easifit Installation Tools

Figure 6.39 - DIN 15237 Euro Bolt with Domed Washer

Figure 6.40 - Pressed Steel Bucket with Recessed Bolt Holes


InstallationThe head of the elevator bolt should lie against the inside surface of the elevator belt with the nuts and washers on the inside of the elevator bucket (Figure 6.37).

An ideal installation will result in the elevator bolt head fitting snuggly just below the surface of the elevator belt (Figure 6.38). However, never exceed the maximum recommended torque. Contact your CEMA bucket elevator manufacturer for more information.

Materials of Construction

There are a wide variety of materials of construction available today for buckets. Selecting the appropriate material depends on several factors including abrasiveness, weight, particle size, temperature and type of material being elevated. Traditionally, buckets have been made of some form of cast iron, either malleable or ductile iron. Today, most buckets are made of some form of plastic. These buckets are rustproof, shatterproof, spark proof, and self-cleaning. They weigh a third the weight of steel buckets and a fifth of malleable or ductile iron. Keeping in mind, the material of construction of the bucket can have dramatic impact on the cost of the bucket, selecting the best suited, most economical material for the application is crucial. Below is some information on each type of common material of construction used today, along with some common products handled in each type.

Cast IronDuctile, malleable, normal cast iron are two of the oldest materials for making buckets. Cast iron is one of the oldest building materials, dating back to the 5 th century BC. Today, what is more commonly used for bucket manufacturing is ductile iron. Ductile iron was invented in 1943 and is a variation of cast iron and offers a more ductile material than the normally brittle cast iron. The most common uses today for ductile iron are pipe used for water and sewer lines and automotive parts. Ductile iron buckets are produced in a foundry by pouring liquefied ductile iron in a

Figure 6.41 - Elevator Bolt Installation

Figure 6.42 - Bolt Head Sunk into Belt

Figure 6.43 - Cast Iron

Figure 6.44 - Fabricated Steel

Figure 6.45 - Polyethylene


mold, usually made of sand. Ductile iron buckets offer extremely high impact and abrasion resistance for many applications, significantly higher than malleable or cast iron. Common applications include sand, glass cullet, stone, shot blast, rock, concrete, and other abrasive products. Since they are steel, ductile iron buckets are well suited for temperatures up to 600ºF.

Ductile iron buckets are recommended in applications with greater than 1” particle size product and/or temperatures over 300 degrees F.

Fabricated SteelFabricated steel buckets are very versatile because they can be fabricated from a wide range of materials and to any standard bucket styles or any custom styles and sizes. Usually made of steel in thicknesses from 14GA up to 1/2” thk, fabricated buckets utilize a 2 or 3 piece construction with the pieces welded together. High quality buckets will be CNC cut, formed and precision welded to ensure a consistent and economical product. Because of their versatility they are well suited for almost any material handling application at temperatures exceeding 600ºF, depending on the material of construction. Fabricated steel buckets are recommended in applications with greater than 1” particle size product and/or temperatures over 300 degrees F. They are also utilized in instances where a custom size or style bucket is needed and a plastic alternative is not available.

PolyethylenePolyethylene is the most common plastic in the world and can be seen in many different applications from pipes to bottles to wear liners. Due to high demand and production of this plastic, material costs and bucket costs are among the most economical. It is available in a wide range of bucket styles and is fabricated using an injection molding process. Most buckets are fabricated from a high density version of polyethylene called HDPE. HDPE buckets are well suited for handling many applications including various grains, feed products, and mildly abrasive industrial applications. Being an FDA approved product it is also ideal for handling many food products and is a common packaging material for milk, butter and water. HDPE is not ideal for abrasive products or impact loads and has an operational range from -120ºF up to 180ºF.

Figure 6.46 - Nylon

Figure 6.48 - Pressed Seamless Bucket

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Figure 6.47 - ????


NylonNylon was first invented by DuPont in 1935 as a replacement for silk. Initial uses of this durable polymer included tooth brushes, stockings and parachutes. Today, nylon can be found in a variety of products, including brushes, fabric, pipes, carpet, and even musical instruments. It is the most commonly used plastic for industrial elevator bucket applications and is available in a wide range of bucket styles. Nylon buckets are also fabricated using an injection molding process. Nylon is a very tough, impact and abrasion resistant material and is well suited for handling hot, high impact, abrasive, and dense products such as sand, cement, aggregate, clay, coal, limestone, minerals, etc. Nylon is suitable in temperatures from -60ºF up to 300ºF.

UrethanePolyurethane, commonly just referred to as Urethane, was first invented in Germany in 1937, but was later refined by DuPont in the 1950s. This versatile material can be found in a wide range of applications. Utilizing different formulations, urethane can be made into something as soft as foam padding or as hard as a lawnmower wheel. Common uses included a variety of car parts, gasketing, durable elastomeric wheels and tires, performance adhesives, paint coatings, and synthetic fibers, such as Spandex. Being an FDA approved material, it can also be utilized for food handling applications. It is available in a wide range of bucket styles and is fabricated using an injection molding process. Being flexible and very tough, Urethane buckets are well suited for sharp cutting particles and abrasive materials such as roofing granules and glass cullet. Urethane also has excellent release properties, making it well suited for handling wet, sticky, or fatty products. Operational temperatures range from -60ºF to +180ºF.

Pressed Seamless Steel BucketPressed seamless steel buckets are normally deep drawn from carbon steel or stainless steel sheeting of 1 to 4 mm in thickness. Deep drawing is a manufacturing process in which sheet metal is progressively formed into a three-dimensional shape through the mechanical action of a die forming the metal around a punch. The deep drawing process work hardens the metal, resulting in a seamless finished part that is stronger than the base material. Seamless steel buckets are utilized in agricultural and industrial applications, particularly with abrasive, static-generating or high temperature

GRAPHIC NEEDED?????

Figure 6.49 - Nylon


materials. The 1-piece and no-welds construction of stainless steel seamless buckets make them ideal for food-grade applications.

NyrimNyrim is a rubber toughened nylon material invented by DSM NV from The Netherlands in 1981. It is a polyamide-based material combining the strength, stiffness, heat and chemical resistance of polyamide, with the flexibility and toughness of rubber. Its outstanding resistance to abrasion, impact and fatigue, combined with anti-static and anti-stick properties, place it among the top in high-performance thermoplastics. Common uses include rollers, elevator buckets, tanks, crushers and track pads. Operational temperature range is from -40 F to +280 F.⁰ ⁰

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cemanet.org€¦ · Web viewREF 70 bolts are not recommended for flat back plastic buckets. Figure 6.34 - Reference 70 Bolt with Large Oval Washer Figure 6.33 - Reference 70 Elevator