Special bolts for stub shafts: safety first in TST dryers and cookers
For highest safety, ASTW offer higher than standard grade bolts from a specialized company in Europe. Every bolt is CNC machined from high grade alloy and have an advanced coating that is said the be the best available in the market.
Note: The bolts must be used with high grade hardened washers.
Check your bolts ! ASTW keep stock.
Check Your Bolts!
The 12 to 20 units M36 and M45 mm bolts for the stub shafts for the largest TST disc dryers and cookers are extremely high loaded components that connect the stub shafts to rotors weighing up to 60 tons.
The bolts are subject to heavy and variating load for every turn of the rotor, sometimes up to 4 million rotations per year.
The bolts operate in the heat from 6 bar steam at 165 deg C and are exposed to corrosion from FFA – Free Fatty Acids contained in the tallow and fat and also from wear and tear of the raw material.
These bolts can wear out from fatigue, wear and corrosion and finally snap one by one until the rotor falls down and cause damage to shafts and bearings which can take weeks and months to repair at high cost.
Recommended Replacement Intervals:
Therefore the bolts should be checked and changed with regular intervals (estimate):
Equipment Type | Interval |
High temp rendering disc cooker | 3 years |
Low temp rendering disc dryer | 4 years |
Fish meal disc dryer | 5 years |
Normal high tensile bolts available in the market are grade 10.9 and 12.9, but they do not have any corrosion resistant coating and can be of variating quality depending on the supplier.
Hardened washers:
The bolts must be used with special hardened washers (hardness 400 HB) as normal washers are too soft and will yield and allow the bolts to come loose.