derrick floor versus kelly bushing supplier

n: a large load-bearing structure, usually of bolted construction. In drilling, the standard derrick has four legs standing at the corners of the substructure and reaching to the crown block. The substructure is an assembly of heavy beams used to elevate the derrick and provide space to install blowout preventers, casingheads, and so forth.

n: all members in the assembly used for rotary drilling from the swivel to the bit, including the kelly, the drill pipe and tool joints, the drill collars, the stabilizers, and various specialty items. Compare drill string.

n: the column, or string, of drill pipe with attached tool joints that transmits fluid and rotational power from the kelly to the drill collars and the bit. Often, the term is loosely applied to include both drill pipe and drill collars.

A pit in the ground to provide additional height between the rig floor and the well head to accommodate the installation of blowout preventers, ratholes, mouseholes, and so forth. It also collects drainage water and other fluids for disposal.†

A small enclosure on the rig floor used as an office for the driller or as a storehouse for small objects. Also, any small building used as an office or for storage.†

A device fitted to the rotary table through which the kelly passes. It is the means by which the torque of the rotary table is transmitted to the kelly and to the drill stem. Also called the drive bushing.†

A portable derrick capable of being erected as a unit, as distinguished from a standard derrick, which cannot be raised to a working position as a unit.†

The derrickman"s working platform. Double board, tribble board, fourable board; a monkey board located at a height in the derrick or mast equal to two, three, or four lengths of pipe respectively.†

Shallow bores under the rig floor, usually lined with pipe, in which joints of drill pipe are temporarily suspended for later connection to the drill string.†

A hole in the rig floor 30 to 35 feet deep, lined with casing that projects above the floor. The kelly is placed in the rathole when hoisting operations are in progress.†

Shallow bores under the rig floor, usually lined with pipe, in which joints of drill pipe are temporarily suspended for later connection to the drill string.†

The hose on a rotary drilling rig that conducts the drilling fluid from the mud pump and standpipe to the swivel and kelly; also called the mud hose or the kelly hose.†

The principal component of a rotary, or rotary machine, used to turn the drill stem and support the drilling assembly. It has a beveled gear arrangement to create the rotational motion and an opening into which bushings are fitted to drive and support the drilling assembly.

Wedge-shaped pieces of metal with teeth or other gripping elements that are used to prevent pipe from slipping down into the hole or to hold pipe in place. Rotary slips fit around the drill pipe and wedge against the master bushing to support the pipe. Power slips are pneumatically or hydraulically actuated devices that allow the crew to dispense with the manual handling of slips when making a connection. Packers and other down hole equipment are secured in position by slips that engage the pipe by action directed at the surface.†

A vertical pipe rising along the side of the derrick or mast. It joins the discharge line leading from the mud pump to the rotary hose and through which mud is pumped going into the hole.†

The top drive rotates the drill string end bit without the use of a kelly and rotary table. The top drive is operated from a control console on the rig floor.†

The BHA is lowered through the drill floor, Kelly through the wellhead and into the conductor pipe. Once the bit is on bottom, a kelly bushing hexagonal or square shaped pipe, known as a kelly is screwed into the uppermost joint of drill pipe. The kelly is inserted into the kelly bushing (KB) and the rig"s rotary drive is engaged. The rotary table turns the KB, which turns the kelly (Figure 1). The drillstring rotates (turning to the right in a clockwise rotation) and drilling begins. The commencement of drilling is termed spudding in, and, like a birthday, is recorded as the well"s spud date.

The bit"s cutting surfaces gradually wear down as they grind away the rock, slowing the rate of penetration (ROP). Eventually, the worn bit must be exchanged for a fresh one. This requires the drilling crew to pull the drillstring, or trip out of the hole. First, the mud is circulated to bring cuttings and gas up to the surface—a process known as circulating bottoms up. Next, the roughnecks disconnect the kelly from the drillstring and latch the uppermost joint of the drillstring to the derrick"s elevators—metal clamps used for lifting pipe. The driller controls the drawworks that hoist the elevators up into the derrick.

The drillstring is pulled out of the hole one stand at a time. On most rigs, a stand consists of three joints of drillpipe connected together—some rigs can pull only two-joint stands; others pull four-joint stands, depending on derrick height. Each stand is unscrewed from the drillstring, then lined up vertically in rows, guided by the derrick operator.

The Secretary"s citation was directed at the kelly bushing and rotary table on petitioner"s oil drilling rig number 23 at Sidney, Montana. The kelly bushing and rotary table, located in the center of the derrick floor, are part of the power system which transmits torque from the rig"s engines to the drilling bit. They rotate at speeds of 45 to 200 rpm during drilling. The kelly bushing rests on the rotary table. The derrick floor covers most of the rotary table, but the kelly bushing and a six to eight inch band of the rotary table at the base of the kelly bushing are exposed.

The Secretary cited petitioner for failing to guard the kelly bushing and exposed portions of the rotary table. Petitioner contested the citation, contending (1) the kelly bushing used by petitioner was not hazardous because it had recessed bolts rather than protruding "j-bolts" found on older models; (2) alternatively, the use of a guard would create an equal or greater hazard; and (3) the Secretary was collaterally estopped from relitigating these issues because they had been decided adversely to the Secretary in similar proceedings brought against other drilling companies.

The administrative law judge"s finding that the unguarded kelly bushing and rotary table constituted a hazard is "supported by substantial evidence on the record considered as a whole ...." 29 U.S.C. § 660(a). See National Steel & Shipbuilding Co. v. OSHRC, 607 F.2d 311, 316 (9th Cir. 1979).

Petitioner concedes old style kelly bushings with protruding "j-bolts" constitute a hazard since the protruding bolts may catch hoses, chains, or other equipment commonly used in the vicinity of the rotating parts. Petitioner contends, however, that the modern design of the kelly bushing used on its rig eliminates this hazard by countersinking the bolts into the bushing housing. The Secretary presented evidence that employees on petitioner"s rig regularly passed within two feet of the rotating parts, that some employees were inexperienced, that there were chains, hoses, and tools on the rig floor, and that the floor was often wet and muddy. The judge concluded that in such circumstances the "relative smoothness" of the modern bushing would not eliminate the demonstrated hazards posed by the "j-bolt" design, and that the danger remained that employees would fall on the rotating surface, that objects would fall onto and be propelled off the rotating surface, and that chains or other objects would wrap around the bushing. The administrative law judge"s conclusion was supported by the testimony of the Secretary"s witnesses and by the occurrence of two accidents on other rigs, reported in Brinkerhoff Signal, Inc., OSHRC No. 79-2589 (1980), in which an employee was killed and another lost both legs when a chain in one instance, and a water hose in another, became entangled in modern kelly bushings of the same manufacturer as that used on petitioner"s rig.

Petitioner"s other objections to the finding that a hazard existed have no merit. Testimony that the safety precautions undertaken by the drilling industry included a standard practice not to permit employees to approach moving parts during drilling was not impressive in light of direct evidence, including photographs, reflecting a contrary practice on petitioner"s rig. The compliance officer"s testimony that a citation might or might not be issued when an unguarded kelly bushing was present did not reflect inconsistency in regulation, but rather, as the officer testified, that surrounding circumstances, including working conditions and safety procedures, would determine whether employees were exposed to a hazard because of the unguarded machinery. The fact that some state regulatory schemes did not require guards, and that the company that manufactured petitioner"s kelly bushing also manufactured a kelly guard but did not require that both be purchased together, were only distantly relevant, if relevant at all. There was sufficient evidence that the exposed portion of the rotary table, as distinguished from the kelly bushing, was also hazardous, since it increased the danger that employees might fall. Finally, there is no merit in petitioner"s claim that the administrative law judge committed reversible error by considering previous uncontested citations against petitioner because the citations had not been admitted into evidence. The record is unclear whether the compliance officer"s testimony regarding the citations was excluded as well as the citations themselves. In any event, the citations were of little relevance in finding a hazard and the judge does not appear to have relied on them. If error occurred, it was harmless. See General Dynamics Corp. v. OSHRC, 599 F.2d 453, 463-64 (1st Cir. 1979).

Petitioner"s failure to seek a variance is sufficient alone to sustain the administrative law judge"s rejection of petitioner"s defense that available machine guards would have created a greater hazard than the unguarded kelly bushing and rotary table. It is desirable to reach the factual merits of the issue, however, in light of the Fifth Circuit"s decision in Fred Wilson Drilling Co. v. Marshall, 624 F.2d 38.

In that case, the administrative law judge concluded "that use of a Kelly bushing guard would pose serious hazards, but concluded that an unguarded bushing, on balance, presented the more unsafe situation." 624 F.2d at 39. On review, the Fifth Circuit Court of Appeals held the ALJ"s finding was not supported by substantial evidence. The court concluded that on the administrative record before it, "given the present state of development, a Kelly bushing like Wilson"s constitutes more of a hazard guarded than unguarded." Id. at 40. The guard considered in the Wilson case was one designed by Kelly Bushing Guard Manufacturing Company. Id.

In contrast, as we have seen, the record in this case contained substantial evidence that the kelly bushing and rotary table in the circumstances of their use on petitioner"s rig posed a serious hazard to petitioner"s employees. The record also discloses exhaustive consideration of the effectiveness and relative safety of guards for kelly bushings and rotary tables with particular emphasis on recent models developed by Varco International Inc., the manufacturer of the kelly bushing used on petitioner"s rig. Petitioner"s witnesses testified to a variety of possible hazards associated with the use of guards for kelly bushings. However, the Secretary"s witness testified to design features of the Varco guard that reduced or eliminated these risks, and reported Varco had received no complaints or reports of accidents involving the Varco guards. The administrative law judge noted that the testimony regarding hazards from guards was based primarily upon guards of older types, particularly Childress"s "clam shell" guard, and that petitioner"s expert witnesses had not seen a kelly bushing guard or had not seen the newer Varco guards or talked with persons who had used them. The judge noted that earlier cases, including Fred Wilson Drilling Co., had not dealt with "developing refinements in kelly bushing guards," particularly the Varco guard, first marketed in 1977.

The administrative law judge"s finding that petitioner had "failed to prove [its] affirmative defense that properly designed guards present a hazard or that a greater hazard results from guarding the rotating rotary table or kelly bushing" is supported by substantial evidence.

Petitioner argues that whether an unguarded kelly bushing and rotary table of the kind involved in this case constitutes a violation of 29 C.F.R. Sec. 1910.212(a) has been decided against the Secretary in several prior cases, and the Secretary is estopped from relitigating the issue.440 U.S. 147, 155, 99 S. Ct. 970, 974, 59 L. Ed. 2d 210 (1979). Petitioner responds that the administrative law judge did not reject collateral estoppel on this ground, but rather on the ground that application of the doctrine would be contrary to public policy, and his decision may be affirmed only on the ground on which it was based. See SEC v. Chenery Corp., 318 U.S. 80, 63 S. Ct. 454, 87 L. Ed. 626 (1943).

The thrust of the judge"s position was that estoppel was inappropriate because in the earlier cases administrative law judges had ruled for and against the Secretary in cases involving various types of kelly bushings and kelly bushing guards and the "equation of employer-employee safety is an ever changing one," involving "new knowledge and developments involving potential safety or hazards." The judge also noted that in this case there was no pattern of harassment of a particular employer as there had been in Continental Can Co. v. Marshall, 603 F.2d 590 (7th Cir. 1979). It is evident from the remainder of the opinion as well as from these remarks that the administrative law judge on the basis of the approach taken in prior cases and in light of rapidly developing knowledge regarded the issue in each case to be whether the particular kelly bushing in the circumstances in which it was used presented a hazard to the employees and, if so, whether the hazard exceeded that of a kelly bushing protected by the guarding devices available at the time.

The judges in this and prior cases focused on such factors as the precise configuration of the kelly bushing and rotary table involved, how clean and free of tools the derrick floor was kept, whether the employer had and enforced safety rules preventing employees from entering the danger zone, whether and how often employees performed functions close to dangerous equipment, the experience of the workforce, and the availability of safe and feasible guards. None of the cases petitioner relies on found modern kelly bushings were not hazardous or that Varco kelly bushing guards posed a greater hazard. In Grey Wolf II, for example, the judge specifically conditioned his finding of no hazard on the employer"s excellent housekeeping and stringent safety rules, and indicated he would have found a violation had the employer used a kelly spinning chain, which could get caught in the kelly bushing, and which was used at petitioner"s rig. The court in Fred Wilson Drilling Co. was aware of no accidents involving modern kelly bushings and concluded, on balance, not that the kelly bushing was not hazardous, but that the kelly guard at issue in that case, which was not a Varco guard, constituted more of a hazard than the unguarded kelly bushing. 624 F.2d at 40.

Derrick (#14) is the support structure for the equipment used to lower and raise the drill string into and out of the wellbore. This consists of the sub-structure (structure below the drill floor level) and the mast.

Drill floor (#21) is the area on the rig where the tools are located to make the connections of the drill pipe, bottom hole assembly, tools and bit. It is considered the main area where work is performed.

Drill pipe (#16) is a joint of hollow tubing used to connect the surface equipment to the bottom hole assembly (BHA) and acts as a conduit for the drilling fluid. In the diagram, these are stood in the derrick vertically, usually to save time while tripping pipe.

Goose-neck (#10) is a thick metal elbow connected to the swivel and standpipe that supports the weight of and provides a downward angle for the kelly hose to hang from.

Kelly drive (#19) is a square, hexagonal or octagonal shaped tubing that is inserted through and is an integral part of the rotary table that moves freely vertically while the rotary table turns it.

Kelly hose (#9) is a flexible, high pressure hose that connects the standpipe to the kelly (or more specifically to the gooseneck on the swivel above the kelly) and allows free vertical movement of the kelly, while facilitating the flow of the drilling fluid through the system and down the drill string.

Racking board (#15) is the catwalk along the side of the derrick (usually about 35 or 40 feet above the "floor"). The monkey board is where the derrick man works while "tripping" pipe.

Setback (#17) is a part of the drill floor (#21) where the stands of drill pipe are stood upright. It is typically made of a metal frame structure with large wooden beams situated within it. The wood helps to protect the end of the drill pipe.

Stand (#16) is a section of 2 or 3 joints of drill pipe connected and stood upright in the derrick. When they are pulled out of the hole, instead of laying down each joint of drill pipe, 2 or 3 joints are left connected and stood in the derrick to save time.

Standpipe (#8) is a thick metal tubing, situated vertically along the derrick, that facilitates the flow of drilling fluid and has attached to it and supports one end of the kelly hose.

Vibrating hose (#6) is a flexible, high pressure hose (similar to the kelly hose) that connects the mud pump to the stand pipe. It is called the vibrating hose because it tends to vibrate and shake (sometimes violently) due to its close proximity to the mud pumps.

Rotating system on drilling rig consists of rotary table and drill stem (kelly,drill string and bit).Rotary table is a mechanical device with square hole  on derrick floor that provides clockwise rotational force to drill string to help drilling a borehole.It contains rotary bushing which is used to turn kelly and kelly bushing.The number of  revolution rotatory table makes in one minute is called rotary speed.

Kelly is a steel bar which is hexagonal or square in shape with hole in the middle for fluid path.It is used for sending rotary motion from rotary table or kelly bushing to drillstring.Kelly’s outside shape matches that of inside of kelly bushing,so that kelly can be fitted and move freely inside kelly bushing.

The complete assembly containing drill pipe,collars and other bottom hole components which makes drill bit turn at bottom of hole are called drill string.Drill bit is attached to the end of drill collars.As drill bit does the grinding or cutting of the rock,bit type is chosen on the basis of rock type and drilling conditions.Common type of bit used are PDC,tri-cone and diamond.Wellbore is drilled by adding joints of drill pipe to the end of kelly.hoisting system is used to pick up the kelly so that it hangs from the derrick above the rotary table.Kelly is unscrewed from previous joint of pipe by used large capacity,self locking wrenches called tongs,Kelly is than screwed into a new joint of pipe stored temporarily in rat hole.The new joint of pipe and kelly are than screwed to the previous pipe and lowered into the hole to resume the drilling.Trip is referred to pulling out of entire drill string ,wiper trip or  short trip is called when part of drill string is pulled out.These trips are performed to verify that drill string can move through potentially troubled section of well bore  drilled recently.

In modern drilling rigs rotary table and  kelly are replaced by top drive,as an mechanical device it helps in drilling a borehole by  providing clockwise torque .Top drive moves up and down on derrick vertically and is placed underneath  the traveling block .The advantage of top drive is ,it allows to drill 60-90ft or “two to three joints of drill pipe”,depending upon rig size.Whereas with kelly and rotary table driller can drill only one joint (around 30ft) at one time.Top drive helps rig save time and be more efficient.With kelly in order to increase additional length of drilling pipe  entire string must be withdrawn but with top drive, draw works directly picks up a another stand from rack to create double  joints.Making lesser and bigger connection saves rig time and reduces the chances of string getting stuck.Top drives are classified on the basis of  their “safe working load” (SWL)  and different types and sizes of motor.Top drives are big technological advancement as compared to kelly,Availability of top drives has increased the drillers ability to drill more extended reach wellbores.

Hosting system are the parts of drilling rig which are used to perform all lifting activities on rig.Lifting activities on rig includes lifting and lowering of drill stem , casing  and other  equipment’s as per need ,in and out of borehole.The hoisting system includes Crown block,Draw Works.drill line and traveling block.Crown block are located at the top of derrick,its an fixed set of pulleys on which drilling line is threaded.Under the crown block an freely moving section of block is attached containing  set of sheaves through which drill line is threaded,this freely moving section of blocks is called traveling block. The multi thread ,twisted wire rope strung between traveling block,crown block and draw-works is called drill line.Drill lines are strung in multiples of 4,6,8,10 or 12 lines.Higher number of drill lines means higher he lifting capacity but lower the running speed.On bigger drilling rigs,while raising and lowering the derrick ,drill lines are capable of handling traveling block loads of over million pounds.To distribute the line stress and wear,drill line needs to be cut and slipped at every ton-miles.In order to determine amount of hole friction and amount of weight to put on bit ,an weight indicator is attached to the drill line.traveling block,crown block and drill line gives the rig ability to lift hundred of thousands of pound and on larger rigs even million pounds.The large winch on which drill line spools is called draw-works,it is one of the most important part of hoisting system used for raising or lowering the traveling block.drill line winds on draw-works drum and gets connected to crown block and traveling block.Draw-works mainly consists of five parts:-1.Drum,2.Motor(s),3.Gear,4.Main brake and 5.Auxiliary brake.The Draw-works is some time directly connected to diesel engine using metal chain belts or it can be run by AC or DC motors.Gear can come is three speed combination.The main brake may be friction brake or a disk brake usually operated manually whereas auxiliary brake is used to absorb released energy  when heavy loads are lowered,they are connected to drum.

The crown block and drill string  are supported by derrick,derrick is pyramidal in shape and provides good strength to weight ratio.They provide the space to stack the pipe that is pulled out of hole.Height of derrick is referred to in multiples of pipe joints such as double derrick for derrick that can stack double pipe  joint,treble derrick for derrick that can stack triple pipe joints.An pipe joint is approximately 30ft.Higher up in the derrick monkey board and pipe fingers are present.

The derrick man stands on monkey board to handle the top end of each stand of pipe during trips,the pipes are put in the fingerboard and tied properly to make sure it does not falls.The derrick substructure is rated by the weight of drill string stacked on it plus weight of casing that can be lifted.The top of derrick substructure is called derrick floor and it is the primary working area of rig.

The deck located on the side of derrick floor  and between pipe racks is called catwalk.Catwalk is the primary location for core processing and wireline logging tool assembly.

Oilfield workers have one of the most dangerous jobs in America. Over one hundred oil and gas extraction workers are killed on the job each year, not including the thousands who suffer career-ending injuries. The Occupational Safety and Health Administration (OSHA) closely regulates gas and oil extraction to minimize dangers on the rig floor. Some regulations mandate falling hazard protections, that is, hard hats, but workers in these designated hardhat areas face serious dangers beyond falling debris.

Roughnecks injured on the rig floor might have claims for damages in addition to compensation available through worker’s compensation. Connect with the experienced Texas oilfield injury attorneys at the Wyatt Law Firm for your free and confidential case review. We’ve recovered $3,900,000 for a client injured in an oilfield explosion and nearly $3,000,000 after a victim died due to industrial negligence. Let us see what we can do for you.

Welcome to the rig floor, where more oilfield accidents happen than any other location on the drilling rig. Roughnecks on the rig floor are some of the most prone to injury, positioned next to the moving drill string, using heavy tongs and fast-moving spinning chains, heaving the slips, and working around the rotary table.

Slipping and falling is probably the most common rig floor accident. Drilling mud and crude oil slicken the metal floors, even coating the rubber tread on work boots. Falling on the rig floor, however, also means possibly falling beneath or between heavy equipment. To prevent falls, staff must keep the rig floor tidy, and companies should take extra measures (adding non-slip mats, etc.).

Manning the tongs on the rig floor is a dangerous part of the job. Roughnecks use hydraulic or pneumatic metal tongs, which act like suspended pairs of giant pliers, to grab and wrench pipe sections while tripping in and out of the well. Roughnecks risk pinching and crushing injuries from tongs, especially on the fingers and hands. They can also be struck by swinging tongs or even falling tongs, which sometimes fail from lost bearings or pins, rusty chains, or corroded cables.

Some rigs still use spinning chains to screw pipe sections together faster, though many rigs phased them out due to high accident rates. The fast-moving chain can easily trap objects such as clothing and fingers as it’s strung around the pipe—causing injury and even amputation. Taut spinning chains can also unravel or break suddenly, whipping floorhands with enough force to break bones and lacerate skin.

The rotary table is a rotating section of the floor (on many rigs) that uses a kelly systemto spin the drill string through rock. It is most dangerous when people or other objects get caught in it. Getting caught between the kelly bushing and rotary mechanism can cause serious crushing injury, and the moving table itself poses a slipping hazard.

What goes up might come down. Roughnecks and floorhands work directly below anything that might fall from the derrick. Unfortunately, a lot of heavy things can fall from the derrick, including tools, pipes, the drill string, the top drive, the crown block, and other rig structuring during mechanical failure or rig collapse. Unpredictable accidents like these claim lives every year.

For example, spinal cord trauma costs injured workers between $1 million and $5 million in lifetime medical expenses, not including their lost wages, reduced earning capacity, and emotional suffering. Hold these negligent corporations fully accountable for your injuries with a dedicated rig floor accident lawyer.

Oil Rig Owners –Most employees on the rig floor do not work directly for the rig owner. Big oil companies and/or their subsidiaries generally own the rig, but contractors run day-to-day operations. The rig owner bears ultimate responsibility for keeping the worksite safe for contractors and employees. This includes clearing the rig floor of debris and slipping hazards, ensuring equipment functions safely, and putting safeguards in place for workers. While big oil companies contract these responsibilities out to others, it does not eliminate their legal obligations.

Drill Site Owners– Sometimes, the same companies own the rig and drill site, but in many cases, oil companies purchase the mineral (oil and gas) rights from property owners. Injured workers might also hold property owners liable for rig floor accidents under Texas premises liability law.

Drill Equipment Manufacturers – The dangers of the rig floor frequently stem from industrial drilling equipment. Manufacturers of these products may bear direct liability for injuries caused by defective, unsafe, or negligently designed products. This might include injuries caused when manufacturers do not provide proper warnings or instructions about certain hazards.

Injured roughnecks generally have multiple legal claims following rig floor accidents, but it’s essential to preserve evidence of transient conditions and defects. If possible, have co-workers take photographs of slipping hazards, broken/dangerous equipment, and safety violations. Claimants should also immediately report accidents, even seemingly minor falls, to safety supervisors. Many back and head injuries worsen in the hours and days following the initial injury. Contacting an oil and gas accident lawyer might also help claimants obtain essential witness testimony and video evidence before big oil companies interfere with the evidence.

Despite claims to the contrary, oil companies and drill site owners generally carry massive personal injury insurance policies. Claiming this coverage, however, requires legal assistance. Most third parties defer claims to workers’ compensation or deny primary liability. Many roughnecks do not pursue these claims after receiving the initial denial. Experienced catastrophic drill site accident lawyers know how to demand insurance settlements after rig floor accidents.

It costs a lot to follow OSHA safety standards on active drill sites. As such, it’s not uncommon for oil companies and contractors to cut corners. Some rig floor accidents occur after catastrophic safety failures that employees previously complained about. These cases—along with major safety failures – may trigger investigations into regulatory violations.

Roughnecks suffering from devastating and often disabling injuries seldom have the income necessary to pay high hourly legal rates. Most families are emotionally and financially struggling to get by following devastating rig floor accidents. As such, compassionate personal injury attorneys accept viable oil and gas cases on a contingency fee basis. This allows claimants to retain dedicated legal counsel with experience fighting big oil without any upfront fees or costs.

An adapter that serves to connect the rotary table to the kelly. The kelly bushing has an inside diameter profile that matches that of the kelly, usually square or hexagonal. It is connected to the rotary table by four large steel pins that fit into mating holes in the rotary table. The rotary motion from the rotary table is transmitted to the bushing through the pins, and then to the kelly itself through the square or hexagonal flat surfaces between the kelly and the kelly bushing. The kelly then turns the entire drillstring because it is screwed into the top of the drillstring itself. Depth measurements are commonly referenced to the KB, such as 8327 ft KB, meaning 8327 feet below the kelly bushing.