In a shaft sinking operation, there are typically two sets of rope attachments that need to be considered: galloway attachments and kibble attachments. Applications may vary, however, a minimum static factor of safety of 10:1 for both types of attachment strings is industry best practice.
The kibble string of attachments typically consists of a “dolly-ball” or “rope-button”, a socket, a swivel, and a Clivvy Hook. The purpose of the dolly ball is to support the crosshead that sits above the sinking bucket. The cross head is designed with a lifting arm that mates with the rope-button and allows the rope button to lift the entire crosshead. When the crosshead lands on top of the Galloway, the kibble line can continue to proceed down through the Galloway all the way to the bench.
Typically, rotation-resistant ropes are used for the Kibble line. A swivel is typically incorporated into the attachment string in order to minimize any unintended rotation of the rope during hoisting cycles. Due to the harsh nature of the shaft sinking environment, it is important that the swivel chosen is robust and maintains a minimum factor of safety of 10:1. Additionally, the swivel should be designed to withstand some radial loading due to the less predictable loading nature of the sinking bucket during mucking cycles (when changing bale). As such, thrust-bearing type swivels are not appropriate for this application.
The Clivvy hook is a simple attachment that must be very robust. A minimum safety factor of 10:1 shall be employed. Materials with a high fracture toughness are desirable. The hook should be oversized in order to make changing bale as ergonomic as possible. Several latch options exist. Latches should be substantially more robust that the ones found on typical crane hooks. Gravity-assisted latches are a good choice, as there are few (or zero) small delicate hardware components. Lastly, the Clivvy hook shall be rated for the expected number of cycles that it will experience over its service life.