Typical Single Fall Block
Manual/Hand Operated Chain Hoists
Manual Chain Hoists are hand operated chain blocks that are widely used throughout the industry, despite the labour involved in usage.
A manual chain hoist can be a preferred option for a number of applications, including where:
- A permanent installation for infrequent use is required
- A temporary installation for erection or maintenance purposes is required
- Precision location of the load is required
- A suitable power supply is not readily available
Hand Chain Blocks
What are the preferred applications?
The hand chain block tends to be more favoured for applications where there are either long intervals between use or frequent changes of use, which calls for particular attention to be paid during the in-service inspections procedures to ensure that no significant damage or deterioration has occurred since last used.
It’s important to note that Manual Chain Hoists are only designed for hoisting and lowering loads, and not for pulling applications. For pulling a lever operated machine is more suitable.
Suspension Level
Where a chain block is suspended from a hook, the suspension level is the level of the suspending hook saddle. In the case of a block combined with a trolley, it is the level of the surface upon which the trolley runs. In other cases, it is similar appropriate levels.
Drawn-Up Dimensions
The Drawn-Up Dimensions is the distance between the suspension level and the bottom hook saddle when the bottom hook is in the fully raised position.
Range of Lift
The Range of Lift is the vertical distance which the bottom hook travels between the extended and highest positions.
Extended Dimension
The Extended Dimension is the distance between the suspension level and the bottom hook saddle when the bottom hook is in the extended position. It equals the sum of the drawn u dimensions and range of lift.
Operating Level
The Operating Level is the level on which the operative stands.
Effort
The effort is the pull on the hand chain required to lift a specified load. The specified load is usually the working load limit of the block.
Method of Attachment
The block may be of ‘suspended’ or ‘built in’ pattern, many manufacturers producing both options. Suspended types have a top hook, shackle, eyebolt or other fitting by which the block is hung and which allows a degree of articulation between the block and the supporting structure. Built in types are usually combined with a purpose made travelling trolley, although a direct connection to the supporting structure may also be possible. The connection between the block and the trolley or structure is usually rigid.
Typical Single Fall Block with Built-In Travelling Trolley
Typical Multiple Fall Block
Number of Falls of Chain
The lower capacity blocks (e.g. 500kg, 1T) lift the load on a single fall of load chain. Higher capacity blocks may either be of similar design but with a larger frame or may utilise a combination of a larger frame and multiple falls of load chain and may even have two or more frames linked by a yoke.
Grade of Components
Some load bearing components such as chains and hooks are graded according to their performance and may vary between makes and models of blocks. The higher the grade, the smaller and lighter the component will be for a given safe working load. According to the conditions of service, some grades may not be suitable for a particular application.
Slack Chain Collection
The majority of hand chain blocks are purchased without provision for storing slack chain, so that when the load hook is in a raised position, the slack chain hangs freely from the block forming a loop. In some applications this can present a hazard, with the risk of the slack chain becoming caught on obstructions or itself becoming a hazard to persons. A condition can also occur where the brake is held open by the weight of the slack chain. Hoist UK offer a ‘chain bag’ which serves as a collecting bag to house the slack chain thereby minimising the risks.
If a 'chain bag' or other chain collection box is to be used, consideration must be made for:
- Chain is a load in itself and the uncontrolled fall of a length of chain could inflict serious injury upon any person in its path, as well as subjecting the block to a high shock load. To avoid this risk a load chain collecting box or ‘chain bag’ should be properly designed for the job.
- Where moisture or condensation is likely the bag should be provided with a suitable drainage hole to prevent the build-up of water.
- It should be of adequate capacity for all of the load chain when the bottom hook is in the highest possible position, i.e. when the block is fully drawn up. If the ‘chain bag’ has an inadequate capacity, the chain will spill over the edge and once this happens ALL of the chain in the bag will be pulled out an accelerating rate.
General Considerations:
LOLER states that ‘hooks and other similar devices provided for lifting should be of a type that reduces the risk of the load becoming displaced from the hook or other devices’. This requirement can be met by the use of hooks with safety catches or by the use of ‘C’ hooks.
When selecting a hand chain block, consideration should also be given to the following:
- The documentation required by legislation including EC Declaration of Conformity, Report of Thorough Examination, as appropriate. If this is not on record refer the chain hoist to a competent person for thorough examination.
- Available headroom.
- Length of load chain and hand chain required.
- Degree of portability required.
- Operating effort available (particularly for larger capacity blocks).