Tool JointsDesign Torquing Inspection Schlumberger Anadrill Sugar Land Learning Center - SLC Page 1 Objectives At the end of this presentation you will be able to l List the five criteria that are the requirement for a good tool joint design. l List the five criteria that go into the design of a tool joint. l List 5 common joint types and drillpipe grades. l Describe hole a drill joint makes its seal. l Describe why Bending Strength is important. l Describe the consequences of incorporate torque in a connection. l State where the most stress in a connection is. Schlumberger u Anadrill Sugar Land Learning Center - SLC Page 2 Describe 4 joint failure modes. Demonstrate how to find the correct joint torque from the torque charts in the PowerPulse UOP. Schlumberger u Anadrill Sugar Land Learning Center . Describe (briefly) 5 methods of inspection. List the major steps in torquing a connection.SLC Page 3 . List 5 reasons why tool joints are inspected.Objectives l l l l l l Identify a stress relieved connection. It must provide a hydraulic seal such that drilling fluid may be pumped down the inside. It must be able to resist most reasonable conditions being made up and broken out.Why Have a Connection? To make a continuous length of pipe Provide hydraulic seal Transfer torque from surface to bit Pin Box Schlumberger u Anadrill Sugar Land Learning Center . under high pressure (several thousand PSI) without leakage. It must be able to withstand normal drilling torque and bending from reasonable rotation and doglegs without parting or unscrewing. Page 4 . Finally it must have a reasonable service life. However there are several other critical requirements of the joint used in the drilling environment. like dirt particles in the threads. It must satisfactorily connect two pipes together and not unscrew under the action of normal drilling operations.SLC The primary requirement of a tool joint is to allow the connection of a number of pieces of pipe together to make a continuous string of pipes. that exist in the drilling environment. of the string of pipe. Although this will heavily depend on material type as well as design. It will also allow the Pin to be stabbed into the Box and make up even if there is drilling fluid right to the top of the box. This space can allow for excess thread compound. in bending. Page 5 . The threads do not form a seal in fact they allow for a open channel from the bore to the shoulder seal.Connection Design Considerations l Thread Types (profile) (Grade) l Material l Sealing l Bending l Joint Strength Torque Schlumberger u Anadrill Sugar Land Learning Center . as the the box when made to the recommended torque. foreign matter and thread wear.SLC The connection or tool joint is a tapered threaded jack screw that forces the shoulders together in such a way as to provide a seal at the shoulder face and act a a structural member to make the pin equally as strong . 000 150. Anadrill uses a number of different non-magnetic materials for its tools. Each has various mechanical properties.Thread Types & Material Reg NC IF H-90 FH - Regular Numbered Connections Internal Flush Hughes Full Hole Schlumberger u Anadrill Sugar Land Learning Center .000 75. The most common are the thread types such as 7 5/8” Reg for BHA’ s and 4 1/2” IF for 5” drill pipe. E grade is very common and so is S grade for long reach highly deviated wells. they differ in their taper.000 - Page 6 . Anadrill does not use regular threads for its tools internal connections because the ID of the collars is too great due to the electronic packages that fit inside them. thread profile and teeth per inch.000 105. Grade D55 E 75 X 95 G105 S 135 V 150 Used Symbol D E X G S V U Minimum Yield 55.000 135.SLC There are a number of different types of thread.000 95. Drillpipe is classified by strength as a grade. inconel (a high grade stainless steel) and beryllium copper (BeCu). these include austenitic stainless steel (monel). Identifying a Thread Type Use a Tool Joint ruler Schlumberger u Anadrill Sugar Land Learning Center . Screwing on a known thread protector is not adequate as many protectors are designed to fit several threads and many threads will screw just together but be unable to withstand any load.SLC To identify an unknown tool joint use a Drilco tool joint identifier ruler. Page 7 . some circumferencial scoring is okay. they must be in good condition with no radial scoring or raised defects. Page 8 . this allows dirt or fluid to escape as the connection is screwed together. Since the seal comes from the two faces.SLC Channel Schlumberger u Anadrill The seal keeps the fluid inside the drill pipe which is under very high pressure from leaking out at the connection. The shoulder face of the box and the shoulder of the pin provide this seal. The thread does not provide any sealing in fact it allows a channel all the way round the thread into the center of the collar.Sealing Sealing Face The threads DO NOT provide the hydraulic seal Shoulder is the only seal Box Pin Sugar Land Learning Center . This is called “galling”. Any defect in the faces that may allow fluid to flow from the inside to the outside could lead to a twist off. Notches or surface defects around the tool joint will localize the stress and increase crack initiation and propagation. The Bending Strength Ratio of a joint combination is an indication of the connections compatibility to resist bending. will cause any small defects in the joint to grow resulting in a crack that will eventually cause a twist off.SLC During the life of a collar it will be subjected to continual flexing that will result in fatigue failures. This will result in the most flexing occurring at the joint. So it is important to try to match the flexing of the pin and box so that the bend at the same rate but when combined in a properly torque connection they are not so weak that all of the collar flex is located at the tool joint like a hinge. the body of the drill collar is much stiffer than the joint. Consequently. As the the collar rotates in a deviated well it will be subjected to cyclic stress which. Proper torque is critical for this. Page 9 . if high enough. most drill collar failures occur in the joint.Bending Strength Tension Joint Flexing Compression Schlumberger u Anadrill Sugar Land Learning Center . Unlike drillpipe. Also. the material yield strength. too little torque could result in failure of the connection due to bending stresses. and provides the proper bending strength. When a pin and box are screwed together as more and more torque is applied the metal of the pin and box will elongate or compress by some amount. the correct torque to apply can be calculated.SLC Like any nut and bolt there is a correct torque for a connection. Hence working backward from the joint cross-sectional area.Joint Torque Schlumberger u Anadrill Sugar Land Learning Center . This strain in the metal when the torque is released will clamp the two parts together. See section 2. friction will stop the joint coming apart. the thread design and the friction coefficient. However if too much torque is applied the pin will stretch too much and the box compress too much to the point where the metal will be permanently deformed and there will be no strain in the joint allowing the connection to become loose. Also if too little strain is applied to the joint then there will be too little friction force stopping the connection from unscrewing. The correct amount of strain will be a function of the load area. Hence the connection will back off under use. the linear force and of course the mechanical properties of the material of the tool joint. Page 10 . The connection requires the correct torque so that it does not come loose in use.5 of the PowerPulse UOP for the torque specification for any of Anadrill’ s connection. The linear force will be a function of the thread pitch. the coefficient of friction between the two materials and the applied torque. however. the shoulder supports the bending localizing tension in the last thread of the pin. It is. maximum bending stress occurs in the thread roots of the first engaged thread near the base of the pin. the shoulders can separate so that the pin is not supported by the shoulder. Fatigue cracks develop in these thread roots. Cracks begin from the thread root on the inside of the box because the thread acts as a notch. these threads are exposed to corrosive drilling fluid. Maximum flexing occurs in the box threads just beyond the last engaged thread at the end of the pin.SLC In drill-collar joints there are two areas where stress concentration can occur: Consider a properly made-up joint where the shoulder supports the pin in bending . Additionally these threads are exposed to corrosive drilling mud. resulting in corrosion pitting in the thread root. When joints are not properly made up. Resulting corrosion pits in the thread roots making them points of stress concentration. Furthermore. Also as the pin flexes.Joint Stress Cracking in last thread of Pin Stress in Pin Cracking in last thread of Box Stress in Box Schlumberger u Anadrill Sugar Land Learning Center . restrained by the box threads. Failures begin from the thread root on the inside of the box because the thread acts as a notch. Thus. This is made worse if the joint is under torqued. Page 11 . Maximum flexing occurs in the box threads just beyond the last engaged thread at the end of the pin. Stress Relief Normal Pin Pin with Stress Relief Groove Normal Box Schlumberger u Anadrill Box with Bore Back Box with Stress Relief Groove Sugar Land Learning Center . because bending in the joint occurs in areas of smooth relief surfaces. It is essential that the surfaces of the stress-relief areas be free of tool marks. and replacing them with smooth. located near the base of the pin and in the bottom of the box just beyond the last engaged thread of the pin. Bore diameter is of a size to insure that the last thread root in the box is covered by the threads at the end of the pin. These relief grooves are intended to release stress concentration in the critical bending areas of the pin and box. stencil marks or other notches. They do this by removing unnecessary threads. Page 12 . stress relief grooving increases the amount of material which must be removed when a thread is required to be re-cut. This provides a more flexible joint. which are notches. hence shortening the service life of a collar. The smooth bore continues beyond the end of the pin and then is gradually contoured with large radii to the bore of the collar. However. Another modification of the box threads is the Drilco “bore back”. large radius contours. A machinist can produce a smooth surface in the stress-relief area with this bore-back design more easily than he can with the undercut design of the API stress-relief groove. This design consists of a straight cylindrical bore in the bottom of the box. less likely to crack in fatigue.SLC Stress-relief grooves can be cut in a joint. SLC Page 13 .Joint Inspection Schlumberger Anadrill Sugar Land Learning Center . called galling. or serious tool damage when fluid leaks into our electronics or more severely when flow is established and washing occurs causing failures and the junking of parts.e.SLC If we are to run our tools in a drilling environment we must be certain that our drilling tools i. surface damage can occur. so it is necessary to assess whether they still pass the minimum dimensional specifications for that connection type. collars and connections can withstand the stress and strain they will be subjected to. a certificate of inspection is issued for that joint. This is vital whenever a incident occurs to any Anadrill connection at the wellsite which costs the client money. Whenever a tool is inspected and passes. Any undetected cracks or surface damage that may lead to a crack can ultimately lead to a twist off and lost in hole expense to us and our client. particularly in non-mag connections. As the connections are made up and broken out they wear. Our client often requires a copy of these certificates before they will run any of our equipment in the hole and in some cases they will come and inspect our equipment in our base before we ship it to the wellsite. This causes extra friction in a joint and therefore could lead to under-torquing or if in the surface of a shoulder this could lead to a washout. Also. Page 14 . This is why Anadrill itself does not inspect its own connections but rather a independent “third party”.Why Inspect Connections? l l l l l Guarantee the integrity of our connections Avoid lost in hole Avoid tool damage such as flooding & washouts To assess threads for repair Customer requirements Schlumberger u Anadrill Sugar Land Learning Center . Radiographic method uses X-rays to take a photograph of the area under inspection. Visual inspection is always carried out as part of any third party inspection where OD’ s and ID’ s are measured and the general appearance of the joint is assessed for damage. Page 15 . In Magnetic Particle a powder is put onto the test piece and then a strong magnetic source is applied to the piece. cracks. Clearly this method is dangerous. Visual inspection should be carried out by the engineer at the wellsite prior to making any connection involving Anadrill’ s equipment. depending on the type of test material used. The magnetic field strength is highest in areas of “sharp” geometry i.SLC In Ultrasonic a sound wave is directed into the area under inspection and the return wave is monitored. Any discontinuities or density changes cause changes in the propagation of the wave. however those inside a crack will not be washed off and will show up under ultraviolet light. This may indicate sub-surface damage or cracking. Any suspicious connection should not be used and returned immediately to town for professional inspection. The magnetism is removed and the particles washed off. so can be seen under UV. therefore the particles will migrate to these areas. Liquid penetrant is very similar in principle to magnetic particle in that the test liquid is drawn into a crack by capillary action and is not removed when the excess liquid is washed off.e.Inspection Methods l l l l l Ultrasonic Magnetic Particle Liquid (Dye) Penetrant Radiographic Visual Schlumberger u Anadrill Sugar Land Learning Center . by thread protectors or baskets. It is particularly a problem in wells with Hydrogen Sulfide (H2S). Whenever lifting Anadrill’ s equipment. this is called stress corrosion cracking. Page 16 .SLC The threads and shoulders of a connection can be damaged through miss handling of the collars. insist on a tag line however short the move. All Anadrill tools have a dogleg limit for rotation and sliding. as soon as they are removed from the basket they must have protectors. Even if the tool is sitting on the pipe rack and is not being moved it is vulnerable to damage from collision with other items in transit around the rig site.Failure Modes l l l l Mis-handling Incorrect torque Fatigue Stress corrosion cracking Schlumberger u Anadrill Sugar Land Learning Center . However. washouts or twist offs. Over torquing will plastically deform the box and pin reducing the stress in the connection leading to backoff down hole. All connections at all times must be protected. Under torquing will allow the joint to over flex leading to cracking and twist off if it has not backed off first. exceeding this will cause damage. Non Magnetic material is prone to failure due to a reaction with certain substances and high load. If the load gets out of control it will be damaged when it hits something. This is most likely to occur if the tool has no thread protectors. Making a Connection at the Rigsite Schlumberger Anadrill Sugar Land Learning Center .SLC Page 17 . SLC When picking up the tool always have thread protectors on the tool and have tag lines on the end of the collar if it is not dragged in. Do not rely on makeup to spread a glob of lubricant applied to the pin or box. Then it is made up again with the chain tongs before the rig tongs and high make-up forces are finally applied. In the workshop a layer of Moly-duo-lube (an anti galling dry lubricant) is sprayed onto the threads then KoprKote dope is applied before any connection is made up. All drillers should do this. Pipe dope is a good-quality viscous lubricant containing powdered metallic lead. Page 18 . if it is a slick collar. breaking it out. Make sure that as the collar comes through the vee-door it does not swing freely and its entry to the rig floor is controlled by a rope. Kopr-Kote is preferred for non-magnetic material as non-mag is prone to galling.Applying Dope Schlumberger u Anadrill Sugar Land Learning Center . Then. Every surface must be lubricated in order to avoid galling on make-up. copper or zinc and should be carefully applied to the threads and the shoulders. When putting in the slips make sure that the dyes do not rest on any wiring channel or antenna or anything that looks unable to withstand the compression of the slips. install the dog clamp before unlatching the elevators (all drillers will do it this way). This procedure works the lubricant into the surfaces and avoids galling of threads and shoulders on the initial make-up. Some drillers make a practice of lubricating a new thread. making it up hand tight with the chain tongs. and re-lubricating it. Page 19 .SLC Before stabbing the connections remove any extender protector caps. Particularly with the Anadrill connections involving real-time extenders it is imperative to stab the collars together by hand as centrally as possible. Remember that if there is a motor with a bend below the rotary table. the BOP’ s. turning the rotary table to make connections may damage the bit.Stabbing Schlumberger u Anadrill Sugar Land Learning Center . with a bit. Then start the connection by hand with a chain tong. or the riser so should be avoided. therefore potentially under-torquing the joint. Also the tongs on the box connection should be a minimum 6” from the shoulder to avoid compressing the box as the torque is applied. Page 20 .SLC As with the slips when placing the tongs on our equipment avoid any wiring channel.Tong Placement Schlumberger u Anadrill Sugar Land Learning Center . hole in the collar or anything that would in your judgment be damaged by placing the tongs on them. SLC When you are satisfied with tong placement stand back! And even better stand behind something substantial such as a girder or beam.Ready to Torque Schlumberger u Anadrill Sugar Land Learning Center . Page 21 . since when a tong breaks or a line/chain snaps it is like an explosion and the parts will seriously damage you. the tables in this section can be used to calculate the required torque for all of Anadrill’ s tool connections for tools greater than 6” OD. this will appear on a gauge in the dog house which you must be watching as the Driller applies the pull. The lower of the torque for the pin or box should be used. Anadrill’ s torque are always lower than rig connections because non-magnetic material is “softer” than steel and our ID’ s are usually much greater than standard therefore there is less cross-sectional area with which to spread the load over. these devices will display torque directly. Page 22 . Some more modern rigs have an Iron Roughneck which is a hydraulic device which makes up the connections. therefore you must know the length of the tong from it’ s center to where the force is applied. The Driller will ask you the torque you wish to apply to your connection.line pull.SLC The torque is applied by pulling on the end of the tong arm. Once the torque has been agreed on.5 of the PowerPulse UOP. Assuming the line is at right angles to the tong arm then the torque applied will be the product of the arm length and the tension in the cable or chain .Line Pull Line Pull Gauge Schlumberger u Anadrill Load Cell Sugar Land Learning Center . this can be obtained from section 2. the Driller will pull on the tong and measure the tension in the line with a load cell.