Method of Support and Slew Bearing Arrangement

All Seatrax cranes are based on the well-proven kingpost concept. This basic design consists of a stationary or fixed kingpost and a revolving superstructure, which fits over and revolves round the stationary post. The boom, machinery house, operators cabin, hoists and slewing machinery are all fitted to the revolving superstructure...more.

API Specification 2C Kingpost/Pedestal Design and Fatigue Considerations

Since 1983, API Specification 2C requires the use of conservative allowable stresses for kingpost or pedestal design. The intent has is to ensure operating stresses, with respect to safe working load, are such that the API default 25,000 cycle design criteria will be automatically met without further consideration.

API Specification 2C - Allowable Kingpost/Pedestals Stress

To implement this Specification, API kingposts and pedestals have additional factors of increase of 1.33 and 1.5 added to the safe working load (SWL). This factored load is then used in conjunction with AISC allowable stresses. The nominal AISC allowable bending stress for round tubes is 0.66 * Fy. This equates to a factor of safety of 1.5. When the factors of increase are applied, the resulting factor of safety relative to safe working load is approximately (1.33 * 1.5 * 1.5) = 3.0 with respect to yield. The allowable stress is approximately 33% of yield...more.

Patented API 2C Anti-Blocking System

For many years, Seatrax has used its innovative solution to remedy crane operations accidents caused by the unintentional contact between the hook block (or ball) and the boom point, often referred to as two-blocking.

One type of two-blocking, often described as “booming down into the block,” occurs on most cranes because of the location of the hoist drum, which is typically mounted on the revolving superstructure. (See Figure 1). Through this arrangement, the distance between the hoist drum and the boom tip sheaves increases as the boom is lowered, causing the lower block (hook block) to move closer to the upper block (boom tip sheaves)...more.

Anti-Two-Blocking System Comparison

Two-blocking may also occur when crane operators over hoist the hook block (or auxiliary hook), regardless of the position or angle of the boom. Seatrax, through straightforward geometry, easily solves this problem. This simple system takes advantage of the hydraulic motors Seatrax cranes use to power their hoists...more.