Overview of Slips and Elevator Used in Upstream Drilling Industry

This article will explain the overview of slips and elevator which are very important tool on the rig.

Slips

Slips are wedge-shaped gripping devices which are used to suspend the drill string in the hole. They fit around the body of drill pipe and wedge in the taper of the rotary table’s opening. Slips have serrated inserts or dies that will grip the outside diameter of the tubular when it is set on the rotary table. To set the slips, rig crews place them around the pipe and the driller then slowly lowers the pipe until the slips can take up the load. The dies in the slips will firmly hold the pipe. In order to remove the slips, rig crew grasp the slip handles and as the driller picks up the pipe, they lift them out of the rotary table opening and set them aside.

You can watch this video to see how the rig crew set and remove the slips

 

Figure 1 – Slips are set on the rotary table.

 

Figure 2 - Slips are on the rotary table

Figure 2 – Slips are on the rotary table

When using drill collars and other tubulars that do not have an elevator shoulder, a safety clamp (dog collar) is installed above the slips. If the gripping elements on the slips fail, the drill collar would slide down. Before the collars can slide all of the way out of the slips into a well, the safety clamp would hold the collars against the top of the slips.

Figure 3 – A safety clamp is installed.

There are several types of slips and spiders that are normally used in drilling and running a casing operation. A spider, like slips, suspends the pipe in the hole, but a spider does not fit inside the rotary table’s opening. Instead, they rest on top of it. Spiders are used instead of slips when the rotary tables bushing size is not compatible with the tubular being run. Another case for using a spider elevator (Figure 4) is when flush joint casing is run. Because flush joint casings don’t have the collar, the spiders will grip the body of pipe while running in or pulling out of a hole.

Figure 4 – Spider Elevator (500 Ton air-controlled casing spider).

 

Power slips (Figure 5) are powered by a heavy duty high-strength coil spring or by air and they are used instead of manual handing slip by a human. A driller or rig crew can operate the power slips remotely by a remote control.

Figure 5 – Power Slip (Courtesy of NOV)

Elevator

The elevator is used to latch around the top of pipe joints in the drill string. Once latched, the driller can raise and lower pipe in and out of the hole. Rig crews attach the elevator to the hook or Top Drive with two forged high-grade steel rods called links or bails. One end of the link fits into the link ears on the hook or Top Drive. Link locking arms secure the links into the ears. Crew members then attach the elevator to the other end of the links. Most elevators are hinged and rig crews open and close them by operating the latch with two handles on each side.

Figure 6 – Elevator and Bails

A drill pipe elevator has a tapered seat (Figure 7). This taper matches the taper on the tool joint of the length of drill pipe. When properly latched, the tool joint taper rests in the elevator taper and makes a firm and positive grip without damaging the drill pipe.

Figure 7 – Elevator has a tapered profile (Courtesy of NOV).

Some drill strings or drill collar don’t have a shoulder so a lifting sub is screwed into the end of the joint to aid in the lifting of the drill strings. They latch the elevator onto the taper on the lifting sub to raise or lower drill collars into and out of the hole.

Figure 8 - Drill Collar and Lifting Sub

Figure 8 – Drill Collar and Lifting Sub

For a top drive system, the links holding the elevator have an air operated or pneumatic tilt mechanism (Figure 9). The driller activates the tilt mechanism when the pipe is being pulled from the hole. When the top of the drill string reaches the derrick man’s position at the monkey board, the driller can tilt the top of the stand of the pipe toward the derrick man. The derrick man can then unlatch the elevator and set the stand back in the fingerboard.

Figure 9 – Link Tilt

 

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