NOV Bowen Casing Spear System Calculator helps to determine the overall load rating and mode of failure for the spear, mandrel, grapple, and casing in each application.
The strengths in the instruction manual are based on the Mandrel tensile strength only and does not consider the entire system together.
We are now able to model the entire system including Mandrel, Grapple, and Casing together. Our calculations were developed based on feedback from the field, various scale lab testing up to failure, and FEA models.
- We consider the catch range for the Grapple as well as API tolerances per API Specification 5CT
- We always take the worst-case scenario as the maximum pull value (Grapple range or max API tolerance) since it results in lowest contact between Grapple and Mandrel Helix
- Ratings are only valid if fish is within catching range of the Grapple.
- Casing ID is calculated based on OD and Weight if those are manual inputs
- For lighter casing weights, the casing contributes more significantly to reducing system ratings than it does for heavier weight casing which can asymptotically approach the publish Mandrel tensile strength in many cases
Calculated values are theoretical yield strengths and are considered accurate to within +/-20%. They assume the worst case scenario based on API tolerance. All strengths assume straight and steady pulling of a fully engaged round fish. Any irregularities in the fish ID/OD, damage to the grapple or mandrel, or jarring can reduce the strength substantially. Ratings are based on Grapple range only. These values are presented without any safety factor. Please contact NOV Engineering if there are any questions.