ATIO IALOILWE LVARCO

Subject: Upgrade for the TDS-9S & TDS-11S Carriage Package Date: May 10, 2007

Product: TDS-9S and TDS-11S Top Drive Drilling Systems

Affected Assemblies: TDS-9S & TDS-11 S Carriage Packages (Various PIN's)

Objective: Advise Operators of Kit, Carriage Field Upgrade, TDS-9/11SA (PIN 30184530) for improved attachment of the Carriage Assembly to the Top Drive Motor Housing Assembly.

Issue: A Carriage Assembly on a TDS-11 S Top Drive became detached from the Motor Housing Assembly during heavy drilling and fell to the rig floor. No injuries were reported as a result of this incident.

The Carriage Package, which includes both the Left and Right Carriage Assemblies (various PIN's), attaches to the backside of the Top Drive Motor Housing. The Carriage Package aligns the main shaft over well center and reacts the drilling torque into the guide beam. Each Carriage Assembly is attached to the Motor Housing using six 1.0" 8UNC Hex Head Cap Screws (PIN 50016-20-C5D) and Lock Washers (PIN 50916-C). Each Carriage also uses two 3/4" Spiral Pins (PIN 51222-12-16).

During repeated heavy drilling or heavy V-door loading conditions, the cap screws can possibly become loose or shear and cause the Carriage Assembly to detach from the Motor Housing.

NOV previously released product bulletin TDS-03-22 in December of 2003 advising operators of the importance of inspecting and replacing damaged Carriage Assembly attachment hardware.

Solution: To improve the retention of the Carriage Assemblies, NOV has developed the Carriage Field Upgrade Kit, TDS-9111SA (PIN 30184530) for Top Drives with Carriage Packages. The kit includes Grade 8 Drilled Head Cap Screws (PIN 50016-20-C8D) and Hardened Flat Washers (PIN 939390-10) to replace existing hardware on both the Left and Right Carriage Assemblies.

Also included in the kit are four replacement Spiral Pins (PIN 51222-12-16). NOV also recommends the removal of the top coat (yellow) paint from the contact area around the bolt pattern on the Main Body and Carriage Assembly to increase friction.

Warning! NOV continues to recommend a weekly inspection of all fasteners for looseness, damage, and lockwire installation and inspection of all Spiral Pins for looseness. (See Figure 1) This inspection is especially critical following heavy drilling or jarring operation as previously outlined in Product Bulletin 93.1.

© 2007 National Oilwell Varco TDS-07-04 Rev A

Page 1 of 2

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Figure 1 TDS-11 SA Carriage Assembly (Note: Rollers shown, applicable for Slider Assemblies as well)

Failure to follow these recommendations may result in death, bodily injury or property damage.

Contact your local NOV Service Center for price and availability of these upgrades or for any questions regarding this safety alert.

TDS-07-04 Rev A

Page 20f2

© 2007 National Oilwell Varco