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Drilling Operations
Elevators and Slips
Elevators and Slips are the tools that grip the string at the hook and at the rotary. The Category covers drill pipe, casing and tubing elevators, single joint elevators, elevator links, rotary slips, power slips, spiders and slip bowls. Spare inserts, dies and slip segments are included.
Operating principle
An elevator hangs from the top drive or hook on a pair of elevator links and lifts the string. Shoulder-type elevators bear on a tool joint shoulder or a coupling. Slip-type elevators grip the pipe body with wedging slip segments. Rotary slips sit in the master bushing or an insert bowl and wedge against the pipe as weight comes on, holding the string while the elevator is released. Power slips and spiders do the same job with hydraulic or pneumatic actuation.
Configurations
- Side-door and centre-latch elevators for shouldered pipe. Drill pipe elevators come with an 18-degree taper or a square shoulder seat, to match the tool joint.
- Slip-type elevators for casing and pipe without a usable shoulder.
- Single joint elevators for picking up one joint at a time from the catwalk.
- Elevator links in pairs, in lengths that set how far below the top drive the elevator hangs.
- Manual rotary slips, power slips, and spiders for casing.
Key specifications
| Parameter | Why it matters | Typical classes or units |
|---|---|---|
| Rated load | Must match the rest of the load path | short tons or kN |
| Bore or size range | Pipe OD and shoulder profile it fits | in or mm |
| Seat type | Must match tool joint or coupling | 18-degree taper or square shoulder |
| Link length and eye size | Fit to top drive and elevator ears | in or mm |
| Slip size range | Pipe OD per insert set | in or mm |
| Operation | Manual, hydraulic or pneumatic, with feedback | sensor for door closed and slips set |
Standards and certification
API 8C covers elevators, elevator links and spiders that can act as elevators, with their load ratings, and defines a proof load test at manufacture as supplementary requirement SR1. API 7K covers rotary slips, slip bowls and spiders, both manual and powered. API RP 8B covers inspection and repair of 8C items in service. Its Annex A sets wear limits for square shoulder elevator bores on non-upset casing and tubing. API RP 7G covers slip crushing, the limit on how much hanging weight drill pipe can take in the slips.
Failure modes and inspection
- Bore and seat wear beyond OEM or RP 8B limits, which reduces bearing area on the shoulder.
- Cracks at hinge pins, latch lugs and link ears, found by MPI.
- Latch and latch lock wear on centre-latch and side-door elevators.
- Worn slip inserts and dies, which let the pipe slip or crush it.
- Slip bowl taper wear, which changes how the slips set.
- Link eye wear and elongation.
Inspect with MPI on all load-bearing areas, measure bores and seats against the published limits, and function test latches and power slip actuators.
Documentation
- API 8C or 7K nameplate data, rating and product specification level.
- Material and heat treatment certificates from manufacture.
- Proof load test certificate, and a new one after any repair.
- The last MPI report and bore measurements.
- Repair records, done to the OEM's procedures.
Integration and compatibility
The elevator rating must match the links, top drive or hook, and the rest of the load path. Link eyes must fit both the top drive bails and the elevator ears. The elevator seat must suit the tool joint profile you run. Slips must match the insert bowl and master bushing in your rotary tables. Power slips need a matching seat and controls that tie into your floor interlocks.
Refurbishment and recertification
Load-bearing surfaces may only be repaired or rebuilt to the manufacturer's procedures, followed by NDT and a proof load test. Out-of-procedure welding on a bore or shoulder makes the tool scrap. Inserts, dies and slip segments are wear parts and are changed routinely. Unused surplus elevators and slips often come from projects that ordered sizes they never ran, and they arrive with original certificates.
Common makers include NOV, Forum Energy Technologies, Keystone and Weatherford. Match link and elevator ratings to your top drives.
FAQ
Frequently asked questions
What is the difference between a side-door elevator and a slip-type elevator?
A side-door elevator lifts pipe by a shoulder, such as a tool joint or coupling, and opens on one side to take the pipe. A slip-type elevator grips the pipe body with slip segments. Use slip-type elevators for pipe without a usable shoulder, such as integral-joint casing.
What certificates should used elevators come with?
Used elevators should come with API 8C nameplate data, material and heat treatment certificates, a proof load test certificate and a recent MPI report with bore measurements. Without a current NDT record, inspect the elevator before it goes on the hook.
Can I use the same slips for drill pipe and casing?
Not usually, because rotary slips cover a set pipe size range. Casing generally needs larger slips, a different insert bowl or a casing spider. The slips must also match the insert bowl and master bushing in your rotary table.
What is slip crushing on drill pipe?
Slip crushing is the collapse or damage of drill pipe caused by the radial load slips apply when they hold a heavy string. API RP 7G gives a method to check hanging weight against slip length and pipe size. Long slips and good inserts raise the allowable load.
What is the difference between an 18-degree taper and a square shoulder elevator?
An 18-degree taper elevator seats on drill pipe tool joints made with an 18-degree elevator shoulder. A square shoulder elevator seats on tool joints or collars with a flat shoulder. Using the wrong seat type cuts the bearing area and can let the pipe pull through.
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