The pitch of a roller chain is the most crucial dimension of the chain.
The measurement of the chain pitch is performed by measuring a specific length of the chain to ensure that the chain pitch conforms to the standard.
There are several reasons why verifying the length of a roller chain is important:
1. Sprocket Engagement and Operation
Roller chains are designed to operate optimally within specific systems and sprocket configurations.
Validating the chain length ensures that the chain is correctly sized for the intended application.
If the chain is too long or too short, it may not properly engage with the sprockets, leading to poor performance, increased wear, and potential damage to the chain or other components.
2. Tension Control
Roller chains require proper tension to function properly.
Roller chains that are too long or too short can result in uneven or insufficient tension, which can cause the chain to loosen under high loads, skip teeth or create additional friction, vibration leading to the risk of increasing the energy loss, wear and damage.
3. Life cycle and durability
The length of a roller chain is closely related to its life and durability.
If the roller chain is too short, each roller will experience greater load and stress, making the roller chain more prone to wear and tear or breakage.
On the other hand, if the roller chain is too long, the friction and wear between the rollers will increase, which will also reduce its life.
The correct roller chain length helps to ensure that the roller chain will perform reliably for the expected period of use.
4. System accuracy and positioning
In some applications, roller chains are used to ensure precise positioning of mechanical components.
If the length of the roller chain is not correct, the positioning may be misaligned or inaccurate, which will affect the accuracy and performance of the entire mechanical system
Guidelines for Length Measurement
International standards have established norms for measuring the length of roller chains.
The measurement of chain length should be conducted after pre-tensioning and before lubrication.
The standard measurement lengths are divided into two categories based on the chain type specification as follows:
(1) For chains up to 60/12B (inclusive), the standard measurement length is 610mm (minimum).
(2) For chains from 80/16B and above, the standard measurement length is 1220mm (minimum).
The measurement length tolerance also varies depending on whether the chain has attachments:
(1)Chains without attachments: The length tolerance should be +0.15 -0% of the chain’s nominal length.
(2)Chains with attachments: The length tolerance should be+0.30 -0% of the chain’s nominal length.
Required Load for Length Measurement
Due to the presence of gaps between chain links, when measuring the length of the chain, it is necessary to apply a load at one end to eliminate the clearance in order to accurately measure the chain’s length.
The applied load is typically around one percent of the standard tensile strength of the chain.
Here are a few examples of chain models according to the ISO 606 standard:
|
Model
|
Tensile Strength (min.)
|
Required Load
|
|
40
|
13.9 kN
|
120 N
|
|
50
|
21.8 kN
|
200 N
|
|
60
|
31.3 kN
|
280 N
|
|
80
|
55.6 kN
|
500 N
|
|
08B
|
17.8 kN
|
120 N
|
|
10B
|
22.2 kN
|
200 N
|
|
12B
|
28.9 kN
|
280 N
|
|
16B
|
60 kN
|
500 N
|
The verification of the length of roller chains is essential to ensure the proper functioning of the mechanical system, enhance longevity and durability, and ensure precise positioning.
Only by ensuring that the length of the roller chain meets design requirements can the normal operation and reliability of the mechanical system be guaranteed.
