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.
