conveyor equipment manufacturers association...conveyor chain & sprocket section meeting monday,...

THE VOICE OF THE CONVEYOR INDUSTRY OF THE AMERICAS

2019 CEMA ANNUAL MEETING

CONVEYOR CHAIN & SPROCKET SECTION MEETING Monday, April 1, 2019 – 7:30 am

AGENDA

1. Call to order and introductions.

2. Approval of Minutes of September 19, 2018. (attached)

3. Old Businessa) Conveyor Chain, Installation, Maintenance & Best Practices 001-Chordal Action – Final Draft

pending for approval. (Attached)b) Conveyor Chain Sprocket Types and Definitions – Final Draft pending for approval. (Attached)c) Corrosion Resistant Chains: Coated/Plated vs. Stainless, Plastic Chains. Draft due to

November 30, 2018 – Updatesd) Changes to ANSI Standards – Dan Fannin

4. Conveyor Chain and Sprocket Section Membership.

5. Other Business

6. Next Meeting – September 18th, 2019 at Hilton Chicago O’Hare Airport. Chicago, Illinois.

7. Adjourn

Dean Bogner, Chair Bob Callahan, Vice-Chair and Secretary

Conveyor Equipment Manufacturers Association

(modified1)

THE VOICE OF THE CONVEYOR INDUSTRY OF THE AMERICAS

MINUTES OF THE CEMA FALL MEETING CHAIN AND SPROCKET SECTION MEETING

Wednesday, September 19, 2018

1. Call to Order and Roll Call - Dean Bogner called the meeting to order at 7:00 AM.

2. Approval of Minutes from March 12, 2018 Meeting - Minutes were approved.

3. Discussion of Issues. a) Conveyor Chain, Installation, Maintenance & Best Practices 001 – Chordal Action.

− Naylu Garces brought some questions about the Chordal Action. − Dean Bogner will send a copy to Dan Fannin and Tom Perdue to review and

correct it. b) Sprocket Types and Definitions.

− Final draft established for March 2019. c) Corrosion Resistant Chains: Coated/Plated vs. Stainless, Plastic chains.

− Draft due to November 30, 2018.

4. Chain Section Recruitment − Reviewed handout of Chain Section Recruitment and committee members were

asked to send Kimberly MacLaren any updates. − Bob Callahan will send information regarding two companies that he has referred

(Mar-Con Wire Belt & Renold Jeffrey) to Kimberly.

5. Membership Committee Representation − George Basel, US Tsubaki; was elected as our representative to Membership

Committee.

6. Other Business a) CEMA Whitepapers - The section suggested that at the next Engineering conference

that future CEMA Whitepapers should make use of current & past documents that are “refreshed” for future whitepapers. No volunteers at this time.

b) Changes to ANSI Standards – Dan Fannin explained some of the changes occurring regarding this, there will be a meeting in Atlanta, GA in three (3) weeks. However; Dan does not think there will be any changes affecting the conveyor industry.

7. Next Meeting of the Section - March 29th – April 2nd, 2019 at La Quinta, CA

8. Adjournment - Adjourned at 08:05 AM

Respectfully Submitted, Dean Bogner, Chair Bob Callahan, Vice-Chair

Conveyor Equipment Manufacturers Association

Conveyor Chain Installation, Maintenance, & Best Practices - 001

Created by: CEMA Conveyor Chain & Sprocket Section

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Conveyor Chain Installation, Maintenance & Best Practices-001 Rev. April 2019

PROBLEM POSSIBLE CAUSE WHAT TO DORoller Seams Open • Too few teeth on sprockets (as on

a hoist) and loads too highUse sprockets with more teeth. Or replace chain with a high-strength chain having seamless rollers.

• Chain riding too high on sprocket teeth

Reset initial chain tension. Replace chain if worn too much.

Note: Table shows only some of the more common chain problems and possible causes and cures. It is only a generalguide for troubleshooting. The user should always consult the chain manufacturer when a chain fails.

As sprockets are an important part of a successfully operating conveyor that uses chain or positively-driven belts, an addendum has been included with this document which describes an important aspect of chain-sprocket engagement: that of chordal action. Excessive chordal action associated with rotating sprockets is known to cause increased wear on both chain and sprockets. Information contained in this addendum discusses ways

Engineered Class ChainInstallation and Maintenance Guide

Chain Installation:The information below is for guidance only. You MUST always follow the equipment manufacturer’s safety, installation, and maintenance instructions that were provided with the conveyor. Consult your CEMA Conveyor Manufacturer for more details.

Warning: Observe proper lock-out and tag-out procedures when working on or around the conveyor.

The following list of general instructions is provided to assist with the safe and proper installation of Engineered Class Chains:

1. Locations for connecting lengths of chain together should be limited to those links that are intended by

should be left to or authorized by the chain manufacturer.2. All conveyor tensioning devices should be adequately loosened before attempting to install the chain on

a conveyor.3. The drive shaft on the conveyor should be locked in place to prevent unintended rotation prior to the

attempted chain installation.4.

on the conveyor.5. Final connection of the chain to make it endless should preferably be performed at the sprockets. The

sprockets can provide adequate support and also help to align the adjoining chain components. This is not always possible, so any location on the conveyor where the chain is adequately supported may

6. Engineered Class Chains can be large and quite heavy. The following list of tools and equipment is typically recommended for making chain connections. More specialized assembly tools are usually available from the chain manufacturer. Note: it is extremely important that tools and equipment used for chain installation be properly maintained and in good working condition.

a. Hydraulic chain press or hydraulic jackb. Chain vicec. “C” Clampsd. Parallel spacerse. Pliersf. Grinder

owner

Highlight

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Conveyor Chain Installation, Maintenance & Best Practices-001 Rev. April 2019

Addendum: Chordal ActionDuring operation, both belt and chain drives typically experience a vibration known as chordal action or polygonal

As the sprocket rotates, the engagement position of the chain is restricted by the pitch points of the links. These pitch points create a polygon, with the number of vertices equal to the number of sprocket teeth. The resulting

using Equations 1 and 2. During rotation, the instantaneous speed of the chain changes, however, the percent variation will always be constant for a sprocket with a number of teeth N. Figure 2 illustrates the percentage speed variation versus the number of teeth.

Chordal action can be minimized by reducing the speed of the chain or by using a sprocket with more teeth. As the percentage chordal speed variation is solely dependent on the number of sprocket teeth, the percentage can be found using Equation 3.

In addition to the number of teeth, if the shaft center distance is a common multiple of the chain pitch, chordal action is small. But if the shaft center distance is multiple of the chain pitch +0.5 pitch, chordal action increases.

In chain conveyors, compensating sprockets are sometimes used to cancel speed variations resulting from chordal action. The compensating sprocket would be used as the driven sprocket and mounted on the head shaft

When the conveyor sprocket is located at its fastest position due to chordal action, the compensating sprocket would be located at its slowest position. When the conveyor sprocket is located at its slowest position due to chordal action, the compensating sprocket would be located at its fastest position.

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Figure 2: Percentage speed gap for common sprockets

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Conveyor Chain Sprocket Types

& Definitions

Created by: CEMA Conveyor Chain & Sprocket Section

Conveyor Chain Sprocket Types & Definitions Final Draft- March 2019

DISCLAIMER

The information provided herein is advisory only.

These recommendations provided by CEMA are general in nature and are not intended as a substitute for professional advice. Users should seek the advice, supervision and/or consultation of qualified engineers, safety consultants, and other qualified professionals.

Any use of this publication, or any information contained herein, or any other CEMA publication is made with the agreement and understanding that the user and the user’s company assume full responsibility for the designs, safety, specifications, suitability and adequacy of any conveyor system, system component, mechanical or electrical device designed or manufactured using this information.

The user and the user’s company understand and agree that CEMA, its member companies, its officers, agents and employees are not and shall not be liable in any manner under any theory of liability to anyone for reliance on or use of these recommendations. The user and the user’s companies agree to release, hold harmless and indemnify and defend CEMA, its member companies, successors, assigns, officers, agents and employees from any and all claims of liability, costs, fees (including attorney’s fees), or damages arising in any way out of the use of this information.

CEMA and its member companies, successors, assigns, officers, agents and employees make no representations or warranties whatsoever, either expressed or implied, about the information contained herein, including, but not limited to, representations or warranties that the information and recommendations contained herein conform to any federal, state or local laws, regulations, guidelines or ordinances.

Conveyor Equipment Manufacturers Association5672 Strand Ct., Suite 2

Naples, Florida 34110-3314www.cemanet.org

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Conveyor Chain Sprocket Types & Definitions Final Draft March 2019

Conveyor ChainThe CEMA Conveyor Chain & Sprocket Working Group has prepared this document for the purpose of providing a common level of understanding and terminology of the various types of sprockets used for conveying chains and belts found throughout the industry today. The scope of this document includes descriptions and defini-tions of several sprocket types used for the following types of chains: roller chains, forged chains, cast chains, welded steel chains, agricultural chains, steel bushed chains, chain drive belts, and plastic chains. Overall, this compilation is not intended to be exhaustive, but it does cover most of the types of sprockets one would find when working with conveyor chains and belts used in the most typical industry applications.

Standard Roller Chain Sprockets

Standard roller chain sprockets are a series of toothed wheels that are designed to engage with its conjoining roller chain counterpart in effort to transmit power from the driver sprocket to the driven sprocket. They can be made with many different types of hub styles and sizes. A few of the most common hub styles are:

Standard roller chain sprockets can also consist of plain bore styles and finished bore styles. Plain bore styles can be found with a minimum bore diameter in A-Hub, B-Hub, and C-Hub sprockets with the capability to machine the bore size to the maximum bore diameter allowed. Finished bore styles can be found in B- Hub and C-Hub sprockets with various fixed bore sizes with keyways and 2 set screws that are per ANSI regulated standards. The set screws are commonly placed with one right on the keyway and the second set screw at 90 degrees from the keyway.

These sprockets are generally made of steel to ensure strength requirements for transmitting power. Most finished bore sprocket sizes, typically used as the drive sprocket are made of induction hardened teeth that provide wear resistance, while having anywhere between 2– 3 times the service life as compared to non-hardened sprockets made of a mild carbon steel. Standard roller chain sprockets are also available for extended chain pitch sizes. For corrosive environments, carbon steel sprockets can be black oxidized, plated, or stainless steel.

Common sizes of sprockets are readily available which can be used with their chain counterpart such as: 25, 35, 40, 41, 50, 60, 80, 100, 120, 140, 160, 180 standard roller chains in A-, B-, or C-Hub styles, or double pitch (extended pitch chains) in A- or C-Hub styles typically 2040/2042, 2050/2052, 2060/2062, and 2080/2082.

Agricultural Chain SprocketsSprockets used with agricultural, pintle, or detachable chains are typically made from cast or wrought ferrous materials. Wear resistance is frequently designed into the material of the tooth faces. Sprocket bodies are of many configurations. When hubs containing the sprocket mounting bore are employed, they may project from either side or from both sides of the sprocket body (B- and C-Hub styles). Since these sprockets are often used in areas where debris is likely to engage it, root diameters should be decreased and pitch line clearances increased accordingly. Mud reliefs may be incorporated to prevent root diameter build up. ASME B29.300 contains specifications relating to these sprockets.

A-Hub (sprocket plate only) C-Hub (hub projected on both sides of sprocket

plate)

B-Hub (hub projected on one side of sprocket plate

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Forged Chain SprocketsForged chain sprockets are typically of segmental construction consisting of four segments bolted onto a solid or split B- or C-Hub types. The segmental construction facilitates the replacement of worn tooth segments by allowing the hub to remain mounted to the shaft.

Sprocket segments are generally made from carbon steel, case hardened to 450-550 BHN, or AR400-500 steel. They are also available in grade 420 stainless steel for corrosive applications. Sprocket hubs are typically made from mild steel or 304 stainless steel.

The engagement method with drop forged chain is quite different from traditional chains. The spine of the chain links engage between sprocket segments as shown in figure below. As such, it is critical that the channel between segments remain clear for the chain to engage. For this reason, sprocket cleaners are normally incorporated onto the return rail to strip away any product build up within this area.

Sprockets are fabricated and hardened at a slightly lower hardness compared to the chain to minimize wear. Sprocket replacement is recommended when the teeth are worn ¼” below original surface engagement with the chain, as illustrated in the figure below.

Operating the chain on worn sprockets creates an improper pitch diameter, which can result in damage to the chain, circlips, and lead to chain separation. This condition will also shock load the chain and cause “hooking”, resulting in higher stress loads on the chain due to improper sprocket engagement.

Although sprockets are critical to proper conveyor operation, they often get overlooked during routine maintenance. Typically, sprocket tooth segments should be replaced 1 or 2 times throughout the lifecycle of the chain.

Always install new chain with new sprocket segments.

Additional variations of forged chain sprockets are depicted in the figure below.

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Engineered Class Chain SprocketsCast Chain Sprockets

Cast sprockets are generally used with cast chains. They are used in applications that handle abrasive materials such as sand, gravel, ash or cement.

Cast iron chilled rim (C.I.C.R.) sprockets differentiate themselves because of their hardened teeth. The hardened teeth are achieved by adding a steel ring or rim in the sprocket pocket of the mold. The steel then quenches the iron creating a hard surface. The resulting hardness is approximately 350 BHN at 3/16” depth.

The three types of construction that are available for cast sprockets are solid, split and segmental. The solid and split construction are furnished with either a solid center plate or a spoked arm center. Lightening holes are occasionally used in solid center plates to reduce weight and ease the handling process. The spoked arm sprockets are used on larger sprockets to reduce weight as well. Split and segmental sprockets are used when ease of installation is required without disturbing the shaft, bearings or other sprockets.

An additional feature of cast sprockets is the characteristic of chain saver rims. They are often used in sewage treatment applications. The rims are located under the sidebars, and as the chain wraps the sprocket, they allow for the sidebars to rest on them. The chain saver rims help the chain to run at the pitch diameter of the sprocket.

Lastly, hunting tooth designs are available on cast sprockets. Hunting tooth sprockets have an odd number of teeth, with the pitch of the teeth one half that of the chain. This makes the chain barrel advance one half pitch for each sprocket rotation. This action allows the teeth to alternate which teeth come in contact with the chain, thereby doubling the sprocket life.

Cast Iron Sprocket with Spoked Arm Center and Chain Saver Rim

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Welded Steel Chain SprocketsWelded Steel Chain is generally categorized as mill or drag chain. These two chains contain diverse design characteristics and features. Mill chains are typically narrower than drag chains. Therefore, the sprocket requirements for the two are different.

Mill Chain SprocketsFlame cut flame hardened (F.C.F.H.) sprockets are normally operated in conjunction with mill chains. These sprockets are generally manufactured from medium carbon steel. The teeth on carbon steel sprockets are flame hardened. The flame hardening of medium carbon steel results in a hardness of 40 Rc minimum, with an approximate depth of 1/8”. Flame cut flame hardened sprockets can also be manufactured from alloy steels, as well as stainless.

The two types of construction that are available for mill chain sprockets are solid and split. The split sprockets are used when ease of installation is required without disturbing the shaft, bearings or other sprockets. Four basic hub types are available in both solid and split construction.

• Type “A” is a flat plate with no hub extensions on either side.

• Type “B” is a flat plate with a hub extension on one side of the plate.

• Type “C” is a flat plate with hub extensions that project the same amount on both sides of the plate.

• Type “C Offset” is a flat plate with hub extensions that have different length projections on both sides of the plate.

An additional feature available on mill chain sprockets are mud reliefs. Mud reliefs are used to help keep material from building up in the pocket of the sprocket. The relief is normally machined, burnt or ground in the sprocket plate.

Type “B” Type “C”Type “A” Type “C Offset”

Flame Cut Sprocket with Mud Reliefs

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Drag Chain SprocketsDrag chain sprockets are found in applications where wide drag chains are used. These sprockets are manufactured with full width teeth or a double plate design. The benefit of a full width tooth sprocket design is that they allow for a greater contact area. Larger contact area is a benefit because it allows for reduced wear on a sprocket. In the case where material build up is an issue, double plate sprockets are preferred. The double plate allows the extra clearance for material to pass over the drum in the conveyor. Lastly, many drag chains are manufactured with a non-round barrel. The barrel could be a formed, have a two piece welded design or an elliptical shape found in cast chains. These deviations from a round barrel along with chain direction need to be accounted for in the sprocket design.

The two types of construction that are available for drag chain sprockets are solid or split. The teeth are normally flame hardened and in some instances the drum is also. The teeth are welded to a drum, which is typically either a pipe or a piece of rolled steel. The center part of the drum would consist of one center plate or for wider sprockets they could have end plates with hubs.

Drag Sprocket with Full Tooth

Drag Sprocket with Double Plate

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An additional feature of drag chain sprockets is the option of flanges. Flanges are side extensions added to the drum that keep material from falling onto the shaft. This sprocket feature is usually used in conjunction with drag chains that contain wing attachments. It is imperative that the location of the flange does not interfere with the chain articulation.

Elevator Chain SprocketsElevator chain can operate on sprockets or traction wheels. Sprockets and Traction wheels can be found at the head shaft or the tail shaft.

Traction wheels do not have teeth to engage the chain, consequently they rely on friction to drive the chain. Traction wheels are normally made from medium carbon steel, but can also be made from alloy steels as well as stainless. As a general rule of thumb, the weight of the buckets, material and chain on the carrying side vs. the return side must not exceed a ratio of 1.5:1. Due to the nature of traction wheels, they should not be used when materials are oily or have high lubricity. Additionally, they should not be used in conjunction with chains that contain rollers. Traction wheels are designed so that the outside diameter plus the bushing diameter of the chain do not equal the pitch diameter of a toothed sprocket. This allows the chain to engage in a different spot of the traction wheel increasing the wear life of the traction wheel and the chain bushings. Another advantage of a traction wheel is that the chain will slip in the event of an obstruction or an overload.

Drag Sprocket with Full Tooth and Flanged Rim

Traction Wheel

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Flame cut flame hardened (F.C.F.H.) sprockets are generally used in conjunction with elevator chains. These sprockets are normally made from medium carbon steel. The teeth on carbon steel sprockets or the outside diameter on traction wheels are flame hardened. The flame hardening of medium carbon steel results in a hardness of 40 Rc minimum, with an approximate depth of 1/8”. To achieve higher hardness and deeper case depths, sprocket and traction wheel could be carburized and induction hardened. Flame cut flame hardened sprockets can also be made from alloy steels, as well as stainless.

The three types of construction that are available for elevator sprockets are solid, split and segmental. The solid and split construction is furnished with either a solid center plate or a spoked arm center. Spoked arm sprockets are used on larger sprockets to reduce weight. Split and segmental sprockets are used when ease of installation is required without disturbing the shaft, bearings or other sprockets. Lightening holes are sometimes used in solid center plates for reduced weight as well as for handling.

Split ConstructionSolid Construction

Segmental Rim Construction

Matched Sprockets

In double strand elevator chain, sprocket configurations are important for the head and tail shafts. The head sprockets must have teeth that are in line with each other. This is achieved by having the sprockets matched.

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Plastic Chain and Belt SprocketsSprockets that are used to positively drive plastic chains and belts come in many different shapes, sizes, and materials – the variations of which are too numerous to list. The teeth on these sprockets are designed and molded to match the size and shape of the mating surfaces on the chain and belts. These sprockets can be solid or split, and can be molded to have round bores with keyways, square bores, or even hexagonal bores. The width of the teeth vary according to the width of the drive cavity within a particular style of chain or belt. The sprockets can have single or multiple rows of teeth; multiple rows of teeth can be aligned or offset – again depending on the matching design of the particular chain or belt. Split sprockets, though molded in plastic, can include assembly hardware made from stainless steel to hold the sprockets securely assembled. Stainless steel hardware is also sometimes inserted into keyways on round bore sprockets to increase the torque transfer capacity of the sprocket while preventing wallowing of the keyway during service.

Though some sprockets intended for use with plastic chain and belts may be produced in steel of stainless steel, by far most are produced from plastic resin, mostly acetal and nylon, though other resins are also used depending on the application. The plastic materials typically selected for sprockets promote excellent wear resistance while providing a high level of bearing capacity and a high PV rating. The materials for the sprockets can be selected to be substantially different than the materials used for the mating chains or belts in order to minimize component wear due to contact between like materials.

General Technical Note: Chordal ActionDuring operation, both belt and chain drives typically experience a vibration known as chordal action or polygonal effect which occurs as the effective radius of action in the chain and sprocket system changes during each revolution. Chordal action can cause increased wear on the chain and sprocket. The effect can be minimized by using a sprocket with more teeth and virtually eliminated with a sufficiently large sprocket.

As the sprocket rotates, the engagement position of the chain is restricted by the pitch points of the links. These pitch points create a polygon, with the number of vertices equal to the number of sprocket teeth. The resulting polygon defines the maximum and minimum effective radii illustrated in Figure 1. The radii can be calculated using Equations 1 and 2. During rotation, the instantaneous speed of the chain changes, however, the percent variation will always be constant for a sprocket with a number of teeth N. Figure 2 illustrates the percentage speed variation versus the number of teeth.

Figure 1: Defining Effective Radii

Equations 1 & 2: Minimum and maximum effective radii

Figure 2: Percentage speed gap for common sprockets

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Chordal action can be minimized by reducing the speed of the chain or by using a sprocket with more teeth. As the percentage chordal speed variation is solely dependent on the number of sprocket teeth, the percentage can be found using Equation 3.

In addition to the number of teeth, if the shaft center distance is a common multiple of the chain pitch, chordal action is small. But if the shaft center distance is multiple of the chain pitch +0.5 pitch, chordal action increases.

In chain conveyors, compensating sprockets are sometimes used to cancel speed variations resulting from chordal action. The compensating sprocket would be used as the driven sprocket and mounted on the head shaft with the conveyor sprocket. The cancellation is a result of specific timing of the teeth between the sprockets. When the conveyor sprocket is located at its fastest position due to chordal action, the compensating sprocket would be located at its slowest position. When the conveyor sprocket is located at its slowest position due to chordal action, the compensating sprocket would be located at its fastest position.

Equation 3: Speed Differential

conveyor equipment manufacturers association...conveyor chain & sprocket section meeting monday,...

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