The patent pending SPM® EXL wing nut is designed to reduce stresses that have been a cause of legacy wing nut failures, while providing a solution that can be implemented on new and in-use customer assets.
There are two primary sources of wing nut failure: fatigue cracks from cyclical loading and excessive load impact from hammer strikes. Continual side load forces paired with the typical pulsations produced during pumping operations create significant levels of stress on hammer unions. Consequently, fatigue crack formations may develop at the thread root which can propagate axially and lead to an unexpected separation.
The patent pending SPM® EXL wing nut helps address failures at their source and features a full root radius on the internal threads to help minimize stress concentrations. This design feature also provides the additional benefit of added clearance for debris accumulation in the threads, assisting with proper assembly. Thicker lugs that extend forward, paired with a larger outside diameter, reduce cracking by suppressing the propagation path and provide a greater surface area to absorb hammer impact loads. The SPM® EXL wing nut can be retrofitted to existing SPM® product and is compatible with most existing hammer union connections of comparable size and pressure rating.
The SPM® EXL wing nut is engineered to minimize stress concentrations at critical locations. A comprehensive analysis confirmed the design reduced fatigue stress resulting in a 235% increase in cycles prior to failure. This fatigue analysis is based on 1,500 lb. alternating side load.