Rig Inspections Calgary, Drilling Contractors Houston & Nisku | Nelsen



In Canada drilling rig inspection intervals and criteria is provided by the CAODC (Canadian Association of Oilwell Drilling Contractors). The CAODC has a range of recommended practices for various different types of oilfield equipment. Completing routing inspections at regular intervals with qualified inspectors is one of the best ways an equipment operator can reduce downtime. Preventive and routine maintenance is an important part of equipment life cycle management.

NTI has extensive experience with field inspections on all types of drilling rig equipment, have completed hundreds of successful CAODC Level IV inspections on masts and substructures.

NTI’s staff are trained on applicable and current standards, both API and CAODC RP’s that are relevant to drilling rig structures and components. Inspectors have also received CWB Level 1 Inspector tickets to improve knowledge about welding and quality control so recommendations on site come with real world expertise.

Overview of Catwalk Inspections:

NTI offers Catwalk Inspection services in accordance with the recently released CAODC RP 12.0 – Inspection of Catwalks. Our experienced Engineering personnel will provide a full inspection report noting repairs and provide certification. They are experienced in both level III and IV inspections and are accredited in Alberta.

Have a look at our  SAMPLE REPORT to show the type of the in-depth inspections we provide to our clients.

Overview of Level IV Rig Inspections:

The CAODC (Canadian Association of Oilwell Drilling Contractors) regulates that drilling rigs are certified by a professional engineer every 1000 working days. This document is intended to provide an overview of inspection criteria, issues, and interpretation based on API RP 4G 4th Edition – Procedures for inspection, maintenance, and repair of drilling and well servicing structures, April 2012.

The main objective of an inspection of a mast or substructure is to find defects in the equipment. Inspection of masts and substructures should be performed by qualified personnel. Repair of masts and substructures should be completed by qualified welders (AWS or CWB) with qualified weld procedures. NDT inspection personnel should hold a minimum of level II qualifications to either CGSB or ASNT standards. Repairs must be approved by an OEM agent or Professional Engineer.

The drilling structure must be disassembled and adequately cleaned for the inspection personnel to perform required visual inspections and NDT of critical areas.

Areas that require inspection:

  • All welds should be visually inspected.
  • Critical welds should be inspected by methods of nondestructive testing (MPI, UT, or XRAY).
  • Guides and Pin Mechanisms.
  • Crown and Raising Line Sheave Groove Wear.
  • Bolted connections – are tight and locknuts and wire are used where applicable.

 Not Included in NTI inspection, but should be inspected by qualified personnel:

  • Hydraulics – including the mast/sub raising/lowering system, BOP handling system, etc.
  • Wireline – including but not limited to bridal lines, tugger lines, etc.
  • Sheaves.
  • Overhead Travelling Equipment – including the blocks, top drives, etc.

Damage can be classified in three categories:

  • Major – damage to members in the primary load path. (Main legs, crown beams, casing beams, etc.)
  • Secondary – damage to members in the secondary load path. (Diagonal bracing, etc.)
  • Minor – damage to ancillary equipment such as ladders and brackets.


Rectangular tubing material is becoming increasingly popular for construction of masts and substructures. Internal corrosion is a concern if the member is not properly seal welded. Damage can also create cracks that water may enter. It is recommended that members be checked for thickness during inspection. API 4G recommends a repair if the wall thickness has corroded more than 10% of its original thickness. External corrosion on members can be repaired by fill and grind methods, or strapping.


Before repairing masts or substructures, proper information is required. What is the member size? What is the material grade? What is the welding procedure required? Has the OEM or equivalent personnel been contacted about the damage/repair? Do not repair a mast or substructure without approval from qualified personnel. Repairs must be approved by an OEM agent or Professional Engineer.

Lifting Eyes

All pad eyes and lifting eyes require machined holes. Pad eyes below the crown should be labeled with a SWL (safe working load). Welds of pad eyes and lifting eyes must be non-destructive tested. Lifting lugs should also be rated.

Inspection Documentation

All inspection documentation should be provided to the equipment owner. The owner should maintain the inspection documentation with the equipment repair history as recommended by API.

Load Ratings

If the load rating of the equipment is unknown, the rating must be determined in accordance with API Specification 4F, latest edition. To identify a load rating as per API 4G, the mast or substructure must first be measured before an analysis can be performed to establish load ratings. Once a load rating is established, upgrades (if required) must be performed on the structure as determined. After completion of upgrades, a final inspection must take place to ensure compliance.

Design Code Changes

API Specification 4F – Specification for Drilling and Well Servicing Structures has recently been updated to API 4F 4th Edition. Equipment designed and manufactured to previous API 4F editions are suitable for service. Provided that major damage or design flaws have not been identified by field use or OEM updates, it is my opinion that equipment manufactured to previous API 4F Editions are still suitable for use in accordance with original load ratings. If major changes or increases are required to load ratings, a qualified engineer should perform an analysis and the structure should be rated to API 4F 4th edition requirements.

Certification (not an API RP 4G requirement)

The term certification is an expression of professional opinion by the engineer based on his best knowledge, information and belief. Liability arising from this opinion is limited to ten (10) times the amount charged to a maximum of $50,000.00.  Unless specifically stated or contracted to determine load rating, a rig inspection and certification is not an endorsement of load rating. A certification from a rig inspection is an opinion that the rig is in good working condition and meets the requirements of API RP 4G within reasonable limits.