Hardbanding Best Practices
Choosing hardbanding wires and recommended procedures for hardbanding applications
New drill pipe costs $55 to $75 USD per foot, so it is important to extend the useful life of pipe as long as possible. Further, replacing damaged pipe causes expensive downtime. The hardbanding of tool joints with a wear resistant weldable alloy has been the answer to keep drill pipe from wearing prematurely. While there are many kinds of hardbanding wires available, some are more durable and cost-effective, giving oil and gas operators an edge over the competition.
"By selecting the right hardbanding wire and applying it correctly, we are seeing 20 percent greater life between hardbanding applications," says Coleman Hogan, operations manager of Rocky Mountain Inspection Services (Greely, Colo.). Founded in 1974, Rocky Mountain Inspection provides a one-stop facility for the reclamation and management of its oil and gas customers' tubular goods from receipt to inspection, refurbishment, periodic maintenance, storage, trucking and inventory control.
The company also provides mobile hardbanding services, which are in very high demand. Hogan recently took the author to a directional drilling operation in Colorado's aptly named Weld County, part of the Denver-Julesberg Basin. The area of the "D-J Basin" in Weld County also includes the Wattenberg Gas Field, which has, according to the American Petroleum Institute (API), produced 2.8 trillion cubic feet of natural gas as of 2008, with an additional 5.2 trillion cubic feet of recoverable gas remaining. According to the Colorado Oil and Gas Conservation Commission, the Wattenberg field has more than 22,000 active wells. In just one month during 2013, the field produced more than 740 million cubic feet of gas and 100,000 barrels of oil … per day.
Recent drilling production comes from hydraulic fracturing at depths of 6,000 to 8,000 ft. Well operators drill down through the Cretaceous sandstone, shale and limestone, then drill laterally another 7,000 to 10,000 ft. Even if each well only required 10,000 feet of pipe, there would still be more than 2.2 million feet of drill pipe … and a whole lot of hardbanding to protect the hundreds of millions of dollars of drill pipe.
A typical well casing in this area starts with a surface casing with a diameter of 8-5/8 or 9-5/8 in. Extending 500 ft. or more, the surface casing prevents ground water contamination. Next comes a 7-in. intermediate casing, which has cement poured between it and the surface casing. The intermediate casing further isolates the surrounding sandstone/shale/limestone formations and groundwater from the natural gas or oil, as well as the fracturing fluid. Lastly comes a 4-1/2 in. production casing (often called the liner), which will ultimately be perforated to disperse the fracturing fluid. The drill pipe operates within the liner.
The friction between the drill pipe and the production casing is most acute at the "heel" or 90-degree turn (which takes 500 to 900 ft. to complete), as well as on the lateral sections of the pipe. When the outer diameter reaches a certain minimum diameter threshold, the contractor removes the pipe from service. So that the contractors don't have to move the pipe off-site for repair, Rocky Mountain Inspection operates portable, mechanized hardbanding units powered by 500-amp diesel-driven welding generators. Basically a welding shack built on a gooseneck trailer and towed by a pickup truck, each system enables a welder and a helper to easily move from well to well and weld in-situ.
When the Rocky Mountain Inspection's rig arrives, worn lengths of drill pipe are loaded on to racks so that the pipe can be staged. Pipe is rolled into position along the racks, where the helper will use a generator-powered grinder to remove contaminants from the pipe prior to welding. When clean, the pipe is preheated to a minimum temperature depending on the pipe diameter. The pipe is then slid into place using two hydraulic jacks equipped with stainless steel ball transfer attachments that lift it so that the helper can then slide the pipe into the open hole of the "welding box." A third jack supports the pipe, while chucks hold and rotate the pipe at a speed of about one revolution each 90 seconds depending on the pipe diameter.
During hardbanding, Rocky Mountain Inspection will apply three, 1-inch wide bands of a casing friendly, wear resistant alloy on the box end (female end) of the pipe and a 1-inch hardband on the pin end (male end). The welder observes the process through a shaded window to ensure quality while manually indexing the wire feeder forward when making multiple bands.After hardbanding, the helper rolls the completed pipe further along the racks and places a cover on it so that the pipe slow cools in a controlled manner (see "best practices" section below).
Selecting a Hardbanding Wire
Some methods of hardbanding involve the use of a solid wire (such as an ER70S-6) complemented by the introduction of carbides and tungsten granules into the weld puddle via a hopper. Hardbands containing tungsten carbide should not be used in cased holes. Others options involve using specially formulated gas-shielded tubular wires. Rocky Mountain Inspection has tested and used several brands of hardbanding wires, finally settling on HB-56 from Stoody, a U.S.-based manufacturer of hardfacing and high alloy joining filler metals.
HB-56 wire is a 1/16 in. tubular wire that results in a martensitic tool steel alloy deposit that can be applied to carbon and low alloy steels. Stoody HB-56 was tested to last twice as long as mild steel deposit in an ASTM G65 wear test of 6,000 revolutions. It is also engineered to resist cracking while maintaining a high hardness. The casing-friendly Stoody HB-56 wire offers a good balance of impact and abrasion resistance. As someone who purchases tens of thousands of pounds of wire annually, here are the attributes Hogan looks for when selecting a wire:
Good friction co-efficient. A measure of the amount of drag between the weld surface and the casing, a very low co-efficient of friction prevents casing wear and reduces friction between the casing and the hardband in the pipe.
Consistent, high matrix hardness.A hardness of 56 – 60 HRC offers the wear resistance required in both open hole and casing applications. "Directional drilling really puts hardbanding to the test, especially as the pipe goes through the heel and into the lateral sections," says Hogan. "By selecting a wire with both a low friction co-efficient and high matrix hardness, we can help our customers keep the pipe in service 20% longer. That's millions of extra cubic feet of gas produced."
Crack-free application.Cracks can cause problems, most notably during re-application, as they could lead to the weld deposit spalling (having the hardbanding deposit fall off in chunks). Spalling is a worst-case scenario in down-hole drilling because if a piece of hardbanding weld metal is being moved with the drilling mud it could potentially damage the pipe and the casing.
"In the past, we were able to reapply hardbanding wire maybe six times before we became concerned and removed the pipe from service," says Hogan. "Now with the Stoody HB-56 wire, we've been able to apply and reapply many more times with little or no cracking or spalling. That gives us longer service life for the pipe. But no matter what wire you use, the key to effective, repeated reapplication is the ability to hardband over the existing deposit without cracking and porosity."
Lower voltage application.Hardbanding wires with low voltage parameters run cooler, thus prevent damage to the plastic pipe lining. Many 1/-16-in. hardbanding wires run as high as 34 volts to achieve a good spray transfer. This much heat requires the use of water cooling within the pipe. Stoody HB-56 wire can be applied optimally at 26 to 30 volts, thus avoiding the need for extra cooling.
Fearnley Procter NS-1äcertification. This accreditation program provides oilfield equipment and service companies with an industry-recognized approval program that supplements the requirements of API standards and demonstrates superior quality management and performance to offshore and onshore operators. Stoody obtained Fearnley Procter NS-1ä certification for HB-56 in 2012.
Operator friendly.Operators prefer a wire that produces less spatter and that lets them weld with a greater contact tip to workpiece distance (about 1 in.-25 mm- or so). This combination helps the contact tip last longer, increasing uptime while also giving the welder better visibility of the wire as it goes into the weld puddle. Operator-friendly wires also go on more cleanly, which reduces the amount of time required for cleaning up spatter or removing brown scale.
Good technical support.Support from the local distributor and from the manufacturer's technicians and engineers can make the difference between a hardbanding operation that's running smoothly and one that's suffering from expensive downtime.
Best practices for Hardbanding
To ensure high quality hardbanding that keeps drilling operations working smoothly, here are basic best practices that are important for every application:
Maintain a Log
The applicator should implement a log that documents the application welding parameters for each order produced and keep records on file for future reference. They may also produce an internal quality control report. Those records should include:
- Name of hardband operator and unit number
- Wire batch (lot/mix) number and description of the applied wire
- Preheat temperature range and periodically measured temperatures
- Actual welding parameters for voltage, amperage, gas flow, rotation speed, oscillation speed, etc., to verify all were adhered to and in compliance
- Inclusive dates of application
- Tool joint description, etc.
- Number of joints/ends hardbanded
- Visual and dimensional inspection
- Pipe/joint serial numbers upon request by customer
All personnel involved in the handbanding process must read and practice the recommendations set forth in the Safety in Welding and Cutting-ANSI Standard Z49.1 procedure. In addition, they should read, understand and comply with all the safety data sheets provided for all the welding consumables (such as Stoody HB-56) they use.
A pre-inspection of the tool joint hardbanding area must be performed and documented prior to hardbanding. The initial inspection should include verifying the tool joint weight, grade, size, and dimensions. The weld surface of all tool joints or hardband areas should be visually inspected to ensure they are clean and free of all foreign matter such as rust, dirt, grease, oil, paint or pipe coating. All tool joints shall be cleaned using a side-grinder and wire wheel brush (use sandblasting or water blasting if further impurities exist).
Proper preheating of the tool joint must be performed regardless of the outer diameter (OD) or ambient temperature of the steel (see Table 1). A soaking preheat shall be performed while preheating tool joints. To determine a soak heat, a technician can remove the tool joint from the heating source and measure the temperature of the desired heating area. The tool can be covered with thermal blankets, insulation or slow cool cans. After allowing the tool to cool for four minutes in still air, the temperature can be measured again. If the temperature drops more than 50°F (25°C), only a surface preheat was complete. Preheating should continue to preheat until the temperature drop is within the above tolerance. Temperature should be checked using an infrared thermometer.
The hardbanded tool joint must be slow cooled. The tool joints need to be wrapped immediately in thermally insulated blankets or canisters, which can remain on the hardband area until the tool joint has cooled down to less than 150°F (65°C). The cooling rate should be controlled between 50°F to 75°F (25°C to 42°C) per hour in still air without exposure to any wind, drafts, or rain. If slow cooling in windy or cold air conditions, the ends of the drill pipe should be closed to prevent draft, or "chimney effect", through the drill pipe.
Interpass temperature is defined as the highest temperature in the weld joint immediately prior to welding, or in the case of multiple pass welds, the highest temperature in the section of base metal 1 in. (25 mm) on either side of the toe of the previously deposited weld metal, immediately before the next pass is started. The maximum temperature of 700°F (370°C) must be carefully controlled, and welding should be stopped if the interpass exceeds 700°F (370°C) within 1 in. (25 mm) on either side of the toe of the weld.
Shielding gas must be supplied to the arc when welding (Stoody HB-56 wire requires a 98% Argon/2% Oxygen or 75% Argon/25% CO2 shielding gas mixture). A regulated flow of shielding gas should be controlled to deliver 30 to 40 CFH to the arc area. Precaution should be taken to protect the gas flow at the nozzle from being blown away from the arc by external airflow, such as fans or wind.
A post weld hardband inspection must be completed after the hardband has been applied on each tool. Visual inspection of the hardband shall include:
- Measuring the outer diameter of the hardbanding to be no greater than 3/16 in. (4.8 mm) and no less than 1/8 in. (3.2 mm)
- Rejecting any pinholes exceeding 1/16 in. (1.6 mm) in depth or 1/16 in. (1.6 mm) in width
- Rejecting cluster porosity having more than 5 holes exceeding 1/32 in. (0.8 mm) in depth or 1/32 in. (0.8 mm) in width in a 10-square-in. (645 cm2) area
- Removing high spots, protrusions or abrupt changes in bead transition by grinding or other suitable methods
- Checking for a relatively flat weld bead profile (no severe concavity or convexity) and proper overlap of approximately .0625 in. to .125 in. (1.6 - 3.2 mm).
- Ensuring tie-ins between the beads have smooth transitions and do not exceed 1/8 in. (3.2 mm) in depth or 1/8 in. (3.2 mm) in width.
- Rejecting cracks that propagate into the parent metal, blow-holes and voids. Micro cracks found by MPI testing are not relevant for rejection unless they extend from the hardband weld deposit into the parent metal.
It is mandatory to know the history of previous hardbanded weld deposits prior to reapplication of any hardbanding. The existing hardband must be worn to 0.062 in. (1.6 mm) of the tool joint OD before reapplication. The reapplication material must be compatible with the residual hardband and reapplied per the original application Welding Procedure Specifications (WPS) supported by the original PQR.
Inspection Prior to Reapplication
The area to be hardbanded must be visually inspected for cracking, voids, existing slag coverage or entrapped slag, spalling, and porosity. Dimensional measurements should be checked over and recorded to verify if reapplication of hardbanding is possible or needed. If a crack is 1/32 in. (0.8 mm) wide or suspected to penetrate the base metal, the hardbanding shall be completely removed or rejected. Spalling of the existing hardbanding shall be cause for rejection and not be considered for reapplication. Porosity of the existing hardbanding greater than 1/8 in. (3.2 mm) in diameter or porosity having more than 5 holes in the 10 square inch area of the hardbanding shall be cause for rejection. The porosity and hardbanding must be removed prior to hardbanding reapplication.
Reapplication of hardbanding should never be applied over non-metallic covering (slag) on or in unless the slag is entrapped less than 1/8 in. (3.2 mm) or there are fewer than 5 holes not exceeding 1/16 in. (1.6 mm) in depth or 1/16 in. (1.6 mm) in width in a 10-square-in. hardbanding area. Voids greater than 3/16-in. in diameter shall be repaired with compatible hardband weld metal or removed.
The applicator can utilize multiple methods to remove rejected hardbanding weld deposits, such as carbon-arc gouging, plasma-arc gouging, grinding with stationary grinding equipment or machining with a composite or ceramic type of tooling on a conventional lathe or CNC equipment. After removal of existing hardbanding, all aspects of preparation, preheating and welding guidelines noted previously should be followed.
Although Hardbanding may appear to be a fairly simple welding or overlay application, the choice of hardbanding wire and the correct application of procedures are critical in ensuring enhanced life and durability of the drill pipe.
Worn drill pipe awaiting inspection, repair and hardbanding re-application in-situ.
Box ends with 3 in. of new hardbanding re-applied over existing hardbanding. A cleaning with a wire brush awaits and then back into service.
Operator-friendly hardbanding wires offer easy clean-up. It doesn't hurt that Rocky Mountain Inspection can offer its customers hardbanding with good appearance, either.
To maximize drill pipe service life, Rocky Mountain Inspection uses Stoody HB-56, a hardbanding wire that can be re-applied numerous times without cracking.
The "welding box" on Rocky Mountain Inspection's portable trailer.
On site with Rocky Mountain Inspection's portable hardbanding team of operation's manager Coleman Hogan (left), welder Chris Scofield (center) and welder's helper Geoff Scofield (right).
Good hardbanding practices include
cleaning the pipe before re-application.
A can placed over the just-hardbanded box end
controls the cooling rate.
A peak inside the welding box while hardbanding.
Worn drill pipe staged for hardbanding in-situ.
Worn drill pipe staged for hardbanding in-situ.