Determining which working load your block must be able to handle is just as important as choosing the right type of block. The block load is determined by the angle and pulling force from the line. If the force is coming from the direct opposite side of the attachment point of the block, then the load factor will be 200%. So if you have 100 kg of force in the lines and the angle Φ between them is 0° the block load will be 200 kg. If the line force is 150 kg and the angle is 100° then the block load will be 194 kg (150kg * 1,29 = 193,4).
Now, knowing this all you have to do is to make sure you buy a block with a higher safe working load than your calculated block load. The safe working load (SWL) is normally printed directly on the block. It can also be found in the product specification.
If you feel this is way out of your comfort zone, please don’t hesitate to contact your closest Rutgerson dealer. They will be happy to help you out.