Q&A  Large size conveyor chain

The following is a list of answers for frequently asked questions from our customers. Select questions to view the answers.

Large size conveyor chain

Words 

Q1 What is usage limits for each component of a conveyor chain?
Q2 What are measures to improve wear resistance of flow conveyor chain?
Q3 Why Bearing Roller Conveyor Chains are economical?
Q4 What precautions should be taken under conditions above 400 ℃?
Q5 What are causes and countermeasures for a stick-slip phenomenon on conveyors?
Q6 What should I set the conveyor chain take-up as?
Q7 How should I guide chain?

Chain Accessories

Q8 How long does a conveyor chain lubricator (TCL type) last?
Q9 Can a conveyor chain lubricator (TCL type) also be installed on inclined conveyors?
Answers
Q1 What is usage limits for each component of a conveyor chain?
A1

Generally, life of a conveyor chain is determined by wear of each part. Which parts will reach an end of their service life first depends on an application.
The wear life limit of each part is as follows.

  1. (1) R-roller・F-roller

    Plate has reached its limit when bottom of a plate begins to touch a rail due to wear on contact surface or sliding area with a bush.

    If there is a curve in a rail then there will be less wear allowance for a corresponding S dimension only as shown on the right. Special care is needed compared to flat conveyance.

  2. (2) S-roller

    The limit is when a roller thickness is worn by 60% and a remaining 40% is reached.

  3. (3) Bush

    The limit is when a bush thickness is worn by 60% and a remaining 40% is reached.

  4. (4) Plate
    • Wear will develop from abrasion between plates and roller and plate contact at (A) and (B) below. Chain strength will be insufficient when wear exceeds 1/3 of the plate's normal thickness.
    • If items are conveyed directly on a plate as with flow conveyors, or if they slide on top of steel plates, then chain life will have been reached when plate height is worn by 1/8 as per the figure below.

  5. (5) Chain Wear Elongation

    A chain articulates when it engages a sprocket or along a curved portion of a rail, at which time a chain will elongate due to sliding wear between bush and pin.

    Chain elongation limit is 2% of a standard basic length (pitch × no. of links). Measure as many links as possible (at least four links) as per the figure below. Measure chain using one of the below methods A or B, compare to standard length, and determine chain elongation (%).

    • (A) Center of pin to center of pin
    • (B) End of pin to end of pin

Back to questions
Q2 What are measures to improve wear resistance of flow conveyor chain?
A2

For flow conveyors used for cement transportation, etc., BT specification that has improved wear resistance by devising material and heat treatment of pins, bushes, and rollers is available. However, for a conveyance of highly abrasive fly ash (one of raw materials for cement) and other materials, further wear resistance was required, and in June 2000 we commercialized a flow conveyor chain (FA specification) for fly ash.

This is a special hardening treatment on outer periphery of bushes and rollers to dramatically improve wear resistance.

【Comparison between BT and FA specifications (for fly ash) 】

【Wear comparison 】

■BT Series

■FA Series

Back to questions
Q3 Why Bearing Roller Conveyor Chains are economical?
A3

Comparing prices of General Use and Bearing Roller Conveyor Chain of the same size, bearing roller conveyor chains are higher. However, Bearing Roller Conveyor Chain has the following features. As a result, cost reduction can be achieved in the following areas, and significant benefits can be obtained at the running cost.

【Features of bearing roller 】

Small coefficient of friction

Bearing Roller Conveyor Chain has a cylindrical bearings inserted between bush and roller for rolling contact. Therefore, rolling friction coefficient of a roller is reduced to 1/3 to 1/6 compared to a general use conveyor chain.

As a result, load applied to a chain is also reduced to 1/3 to 1/6.

[Rolling friction coefficient (µ)]

  • General use conveyor chain
    No lubrication µ = 0.13~0.18, With lubrication µ = 0.08~0.12
  • Bearing roller conveyor chain
    µ = 0.03

[Click to enlarge ]

Large load capacity of rollers

Allowable load of bearing roller is about 3 times larger than that of general use conveyor chain (R roller).

For horizontal conveyance or conveyance with a slight gradient, a chain size is often determined by an allowable load of a roller. In combination with the features of 1, a small conveyor chain of 2 sizes can be used.

Easy maintenance, long life

With cylindrical bearings, lubrication interval can be extended 5 to 10 times longer than general sliding bearing type of general use conveyor chains, and maintenance work is reduced.

Moreover, wear life between bush and roller is significantly improved.

Hard to cause stick-slip phenomenon

Fluctuation of rolling friction coefficient of a roller is small, making it less likely to cause stick-slip phenomenon.

※Refer to section "Q5. What is the cause and countermeasure for stick-slip phenomenon of the conveyor?" .

【Cost merit 】

Back to questions
Q4 What precautions should be taken under conditions above 400 ℃?
A4

Generally, followings are problems when using a chain in a high-temperature atmosphere.

  1. (1) Strength reduction due to decrease in hardness
  2. (2) Increased elongation (may cause creep fracture)
  3. (3) Increased wear due to decrease hardness and increased friction coefficient
  4. (4) Poor articulation of a chain due to thermal expansion, deterioration or carbonization of oil when lubrication is applied.

When temperature exceeds 400 ℃, use stainless steel, and after considering the above problems, select and design a chain according to an application. Contact us for use at 400℃ or higher.

Back to questions
Q5 What are causes and countermeasures for a stick-slip phenomenon on conveyors?
A5

Stick-slip, also called “surging,” is a type of self-induced oscillation where a chain repeatedly starts and stops, despite there being continuous drive from a drive source.

Stick-slip generally happens on conveyors over 10m long and with chain speeds less than 15m/min.

The following are the causes.

  1. (1) Fluctuation of coefficient of friction between bush and roller
  2. (2) Insufficient chain rigidity
  3. (3) Insufficient rigidity of drive unit and frame

The countermeasures are as follows.

  1. (1) Increase chain speed.
  2. (2) Divide a conveyor and shorten a machine length.
  3. (3) Use larger size chains, reinforce a frame and guides, and increase rigidity of a conveyor itself.
  4. (4) Reduce coefficient of friction between bush and roller to stabilize it. There are two ways to do this.
    • Change a chain stick-slip specification and lubricate with Tsubaki stick-slipless oil.
    • Use Bearing Roller Conveyor Chain.

(However, if the chain speed is 2m/min or less, consult us. )

Back to questions
Q6 What should I set the conveyor chain take-up as?
A6

Conveyor chain tension (take-up) is preferably provided with a small amount of slack under the drive unit to avoid excessive tension. However, in the following cases, chain slack must be removed by a take-up of a chain.

  1. (1) Perform positioning on a conveyor
  2. (2) Frequent forward and reverse operation
  3. (3) The chain pushes themself at the conveyance side

In general, it is sufficient to adjust the moderate tension by visual and hand feeling, but the values are as shown below as a guideline.

【Calculation method 】
· Chain weight … M (kg/m) X N (No. of starnds )
· Weight of slats or jigs attached to the chain … W (kg/m)
· Weight of conveyed goods … m (kg/m)
· Distance between shafts … C (m)
· Coefficient of friction between chain (or jig) and rail
 (Chain return side (below) )
… µ
· Gravitational acceleration … G ( = 9.80665m/s2)
  • In the case of rotation direction A (normal rotation)
    Take-up force : F ≧ { (M X N + W) X C X µ } X G/1000 X 2 X 1.2~1.5
  • In the case of rotation direction B (reverse rotation)
    Take-up force : F ≧ { (M X N + W + m) X C X µ } X G/1000 X 2 X 1.2~1.5

With reverse rotation, adjust the take-up force for "when rotating in direction B (reverse)."

【Caution 】

  • F above is the target take-up. Adjust while monitoring conveyor operation.
  • Make sure that the working load with the take-up force does not exceed the maximum allowable load of the chain, or not fall below the proper safety factor.
  • Too much chain tension will promote wear and shorten your chain's life.
Back to questions
Q7 How should I guide chain?
A7

An example of how to guide the chain is shown below. Please use it for reference of design and concept.

  1. (1) Bushed Chain and Block Chain

  2. (2) R-roller and S-roller chain

  3. (3) F-roller chain

Back to questions
Q8 How long does a conveyor chain lubricator (TCL type) last?
A8

Automatic lubricator life is determined by two points.

  1. (1) Unit pump

    When unable to properly lubricate due to overuse.

  2. (2) Checker arm. When a checker arm roller wears and a checker arm body begins to interfere with the base chain roller.

    Normally, (2) will reach an end of its life first.

    A replacement checker arm is available, so please replace the parts.

    Continuous operation will drastically hasten checker arm roller wear damage. When required amount of lubrication has been completed, stop lubrication with cock of an oil tank and make sure that a checker arm does not come into contact with the chain as shown on the right.

    Also note that wear progresses remarkably in an atmosphere of highly abrasive dust, etc.

Back to questions
Q9 Can a conveyor chain lubricator (TCL type) also be installed on inclined conveyors?
A9

If installed on an inclined section, oil discharge failure may occur. Install main body of a conveyor chain lubricator on horizontal section.

Back to questions