Casing Equipment

How casing equipment works

A casing running tool (CRT) hangs from the top drive and grips each joint internally or externally with hydraulic or mechanical slips. It makes up the connection with top drive torque, fills the casing and seals so you can rotate and circulate while running. A conventional spread uses a power tong with a backup to make up connections, a spider in the rotary to hold the string, and a side door or slip-type elevator to lift it. A fill-up and circulating tool fills each joint and lets you circulate without a swage.

Float shoes and float collars carry check valves that stop cement flowing back once it is in place. Centralizers hold the casing off the borehole wall so cement surrounds it evenly.

Configurations

• Internal and external gripping CRTs, sized by casing OD range.
• Hydraulic power tongs with torque-turn monitoring, and spiders and elevators by size range and rated load.
• Float equipment with flapper or poppet valves, including auto-fill types that convert to a check valve.
• Bow-spring centralizers, which flex in tight hole, and rigid or solid centralizers, which give firm standoff in gauge hole.

Key specifications

Standards and certification

API Spec 8C covers casing elevators, spiders and casing running tools as hoisting equipment, at PSL 1 or PSL 2. API RP 8B sets their in-service inspection in Categories I to IV, from in-use observation to full disassembly with NDT of critical areas. API Spec 7K covers power tongs and slips. API Spec 10F covers testing of float equipment for flow durability and for pressure at temperature. API Spec 10D covers bow-spring centralizers, including starting and restoring force tests. Rigid centralizers fall outside 10D, so rely on the maker's test data.

Failure modes and inspection

• Cracks in load-bearing parts of CRTs, elevators and spiders, found by magnetic particle inspection under RP 8B Category III or IV.
• Worn slips and dies that mark or crush casing, or slip on chrome and premium connections.
• Seal leaks and wear in hydraulic CRT and tong cylinders.
• Torque sensor drift, which makes premium connection make-up unreliable.
• Ageing elastomers and composite parts in stored float equipment.

A CRT's hoist rating is its own limit. The load it can really carry on a given casing also depends on how the slips grip that pipe and on the torque applied at the same time. Use the maker's combined load chart.

Documentation

• API Spec 8C certificate, rated load and serial number for each lifting tool.
• Last RP 8B inspection category, date and NDT report, and the last load test.
• Die and slip set inventory by casing size.
• Torque calibration certificates for CRTs and tongs.
• For float equipment and centralizers, manufacturing date, Spec 10F or 10D test data and storage records.

Integration with your rig

Check the CRT against your top drive model for thread, link length, hydraulic and electric control connections, and the maximum torque and rotation the top drive can apply. The CRT's control system must work with your drilling control system and torque-turn software. Spiders must suit your rotary table opening or a flush-mounted insert. Elevators must match your bails. For top drive interface details, see Top Drives.

Refurbishment and when to buy what

A CRT or elevator comes back into service through an RP 8B Category IV inspection, replacement of worn parts with OEM spares, new seals and a load test. A used running tool with current inspection, a load test and a full set of dies is a sound buy. Float equipment and centralizers are consumable, so unused stock with Spec 10F or 10D data and recent manufacture makes most sense. Weatherford, NOV and Volant are well-known CRT makers. For the unit that cements the string, see Cementing Units.