JSS: A Case Study
Implementing New Inspection Procedures
Rick Nichols, BHA Designer with StrataLoc Technology was searching for a way to hold closer tolerance limits on all the thread attributes of their RSC connections. Because all of StrataLoc's high tensile straight ACME threads are currently being measured to ANSI System 22 using Gagemaker's functional roll and pitch diameter gauges, Rick decided to inquire about a similar gauge for tapered threads. He then learned of Gagemaker's Joint Strength System (JSS) for rotary shouldered connection inspections. He immediately ordered what he needed and proceeded to measure all his NC70 connections as a trial. He anticipated that measuring the pitch diameters of the NC70 connections would ensure more interference in the threads prior to shouldering and resist any thread damage from the stress experienced down hole.
He inspected 15 sets of NC70 connections with the JSS and the readings were recorded as found in Table 3. The other connections in the string, a 6 5/8" API Reg. box by 7 5/8" API Reg. pin bit sub, a 7 5/8" API Reg. box crossover (drill bit Sub to BHA) and the NC56 crossover were produced at an outside vendor and measured using only the minimum API required attributes which included ring and plug gauges.
The BHA tool was run down hole for 8 days in a well south of OklahomaCity to a TD of 12,000'. Then, the rental tool was sent back to Houston, TX. A re-inspection was performed incorporating the JSS inspection into their normal inspection process. Because the pitch diameter gauge can also be used on used pipe, these measurements were captured again.
A third party inspection group rejected the 6 5/8 Regular box X 7 5/8 Regular pin bit sub, 7 5/8 Regular box API cross over (drill bit Sub to BHA) and the NC56 cross over to the drill string for excessive thread damage per current API RP7G inspection specifications. The damaged parts were from the set of connections only inspected to minimum API requirements which included ring and plug gauges and not JSS.
They passed the 15 NC70 connections as there was no excessive damage. Only two boxes showed slight galling on second thread from stabbing damage. This was field dressed and ready to go. These results thrilled Nichols and StrataLoc Technology now requires all tapered threaded connectors be measured using the JSS which provides precise measurements for lead, taper, height and most importantly pitch diameter. Since implementing this new inspection in their procedures, StrataLoc has seen an 85% improvement in performance of their connections and has had fewer failures in the field.
To find out more about the JSS, order Gagemaker's 2011 Prevent Rotary Shouldered Connection Failures White Paper now.