Thousands of dollars in labor are lost annually by companies continuing to use
old-fashioned methods to align pipes and fittings, such as weld-on lugs, hydraulic bottle jacks, or ratchet cable pullers, to critically align pipe ends. Companies today cannot afford the loss in productivity or to have their product rejected if it fails to meet alignment criteria.
Personnel are sometimes asked to hold a heavy pipe or fitting in place while the welder tack welds the pipe to the fitting. This process presents a risk of back injury to the person holding the pipe or fitting. Also, the valve or fitting is sometimes incorrectly aligned and the tack welds must be removed and rewelded.
The welding distributor must have sources for companies to purchase the proper clamping equipment to align pipes and fittings faster without sacrificing the safety of the welder.
Clamps to Fit the Application
Five different types of alignment clamps are on the market to cover every aspect of pipe and fitting alignment and reforming needs of companies. Whether the workplace is a small tube or large vessel, a clamp is available to fit the customer's requirements. Clamps are available to internally or externally align pipe or shell diameters from 3Ž8 in. to 20 ft (9.5 mm to 6 m). Clamps are available to reform pipes or tubes
with a wall thickness up to Schedule 80 with an out-of-round condition up to 2 in.
Clamping systems are available for all the purposes listed below.
- To align and reform the mating side of the weld joint.
- To align and reform both sides of the weld joint.
- To align and reform pipes, tubes,
elbows, tees, flanges, and other fittings.
- For rounding pipes.
- To hold tubes in position for orbital welding.
- Pneumatic or hydraulic internal alignment clamps to align the interior of pipe or fittings.
- For full-circle welding of the pipe without removal of the clamp.
- To hold pipe ends against a consumable welding insert.
- To hold pipes in place on jack stands.
- For carbon steel, stainless steel, and other specialty alloys.
Types of Clamping
Chain-type clamps align and reform pipe diameters as small as 1 in. (25 mm) and as large as 20 ft (6 m). Chain clamps allow pipe, elbow, tee, flange, and other fittings to be held safely and securely in place during the alignment and welding process. Each style of chain clamp is designed to reform multiple pipe sizes. Most manufacturers of this style clamp have enough clearance under the jackbar to permit the use of a gas metal arc welding gun or gas tungsten arc welding torch. The inside or outside of the pipe can be aligned with these clamps. Accessories such as level and support devices assist the welder in holding and accurately positioning pipe or fittings for welding. Other accessories such as spacing screws will allow the operator to accurately adjust the weld root opening without risk of injury.
Chain clamp is used to align and hold in position 48-in. pipe for welding.
Cage clamps are available for pipe sizes 2 to 60 in. (51 to 1524 mm). These cable or rigid frame clamps are designed for rapidly aligning the outside diameter and come in two basic styles. The "tack type" cage clamp is used to align pipes for tack welding. The "no-tack" type allows the joint to be completely welded without removal of the clamp. These clamps are designed to align only one pipe size per clamp. The clamps are available in hand lever, ratchet, and hydraulic models.
Full-circle steel-type clamps are available for pipe sizes 6 to 72 in. (152 to 1829 mm) and have multiple contact points to handle aligning, reforming, or rounding applications. These clamps are designed to put pressure on the high point of the pipe or shell and bring them into alignment. The welder is able to do a 100% weld and grind without removal of this type of clamp.
Frame-type clamping devices that make three-point contact with the pipe are available for pipe sizes 1 to 14.5 in. (25 to 368 mm). These clamps adjust from one pipe size to another by means of a T-handle located at the top of the clamp. A range of three or four pipe sizes can be covered with one clamp. The clamps can be used to align the inside or outside of carbon steel or stainless steel pipes. These clamps are used for aligning the pipes and not for reforming the pipe wall.
Some small precision clamps, with a pipe range from 3Ž8 to 12 in. (9.5 to 305 mm), have jaws that work independently of each other. They align and securely hold two sections of small diameter steel or stainless steel pipe or tubing for autogenous welding. The radial clearance and distance between the jaws is such that most orbital welding heads will fit between them. Pipes or tubes align with the clamps. The clamps are available in both carbon steel and stainless steel to complete welds on small diameter steel and stainless steel pipes and tubes.
Internal hydraulic and pneumatic alignment clamps are used mainly for pipeline applications and are available for pipe sizes 6 to 60 in. (152 to 1524 mm). These clamps cover a range of one to six pipe sizes, depending upon the make and model. These clamps allow a full circle to be completed without obstruction. An automated welding system used in conjunction with the clamp increases productivity, lowers weld rejects, and reduces operator fatigue.
Pipe clamping devices help speed the aligning process, lowering operator fatigue. These clamping devices eliminate hydraulic jacks, come-a-longs, and weld-on lugs, which can be an extreme safety hazard to all personnel involved in the aligning and reforming process. When proper clamping devices are employed, the operator is able to safely and precisely align and reform the pipe or fittings. Needless cutting and regrinding are not required because the two pipes or fittings are mated correctly the first time.
Prior to operating the equipment, it should be checked for proper operation and any required maintenance. If an air, hydraulic, or electrical power source powers the tool, it should be disconnected from the equipment prior to inspection or maintenance. The tool should never be used if it is not in proper working order.
The maintenance area should be kept as clean as possible to prevent foreign debris, such as sand, grinding dust, or metal shavings, from being introduced into the final assembly as subcomponents are installed. High-temperature grease, such as gun grease, that is not water-soluble should always used to lubricate the compenents of the tool. Lithium grease is not recommended.
Clamps used to align and/or reform pipes and fittings are some of the most misunderstood and misused pieces of equipment. Due to the weights and tensile strengths of pipes, it is extremely important that operators receive adequate training on the reforming and aligning of pipes to fittings, valves, and flanges. Personnel who use makeshift devices or the incorrect clamp for an application cause many accidents.
Know Your Needs
The following points should be considered when selecting a clamp:
- Diameter of the pipe
- Pipe wall thickness
- Tensile strength
- Type of material
- Need for alignment and reforming
- Operator fatigue.
The customer service departments of clamping device manufacturers are always available to assist the welding distributor in selecting the right clamp to fit the customer's application.
Story based on information provided by Mathey Dearman (www.mathey.com), Tulsa, Okla.