Grooved Pipe Joining Technology Explained
Many of the benefits of the grooved coupling are inherent in the physical design of the product, which is why it is important to understand the grooved concept and the features of the product.
A grooved pipe joint is comprised of four elements: the grooved pipe, the gasket, the coupling housing, and the nuts and bolts. The groove is made by cold forming or machining a groove into the pipe ends. A gasket encompassed by the coupling housing forms a seal on the two pipe ends, and the key sections of the coupling housing engage the grooves. The bolts and nuts are tightened with a socket wrench or impact wrench. In the installed state, the coupling housing encases the gasket and engages the grooves around the circumference of the pipe to create a leak-tight seal in a self-restrained pipe joint. There are two basic coupling styles that can be used on grooved pipe: flexible and rigid.
• Flexible couplings allow a limited amount of linear and angular movement.
• Rigid couplings do not allow movement at the joint.
There are a number of benefits to choosing grooved mechanical piping where applicable.
1. Faster Pipe Joining — Standard grooved couplings install up to five times faster than welded joints and up to three times faster than flanged joints.
Recent product enhancements by grooved coupling manufacturers have significantly increased installation times. Some couplings offer proprietary installation-ready joining technology that install in less than half the time of standard grooved couplings. Unlike standard couplings, installation-ready couplings are installed without the need to disassemble the coupling. No loose bolts and nuts translate to less material handling on site.
Unlike welding, brazing, or soldering, grooved mechanical pipe joints do not require a flame or fire watch, and as a result, assembling and disassembling of a pipe joint is much faster and easier. Pipe fitters install grooved mechanical pipe joints properly and accurately with minimal training and no additional safety measures.
2. Ease and Speed of Maintenance — The design of grooved systems allows for easier routine and scheduled maintenance because the grooved coupling provides a union at every joint, which permits easier access to the system compared to other joining methods.
Removing a coupling is easy; the worker loosens the nuts and bolts and removes the coupling housings and gasket. Once maintenance is complete, the coupling can be reassembled on the grooved end of a pipe, valve, fitting or accessory.
Because maintenance does not require torches, grooved systems do not have to be completely drained and dried to perform the maintenance, resulting in minimal system downtime.
3. Greater Design Flexibility — A grooved system not only offers a union at every joint which simplifies system access, but a grooved system offers 360 degrees of rotational movement during installation, reducing field mate-up issues by making it easier to perform adjustments on site.
4. Reliability — The design of grooved couplings, which are secure and leak-tight, make them more reliable than other forms of pipe joining, such as flanges, which require more accurate alignment and specific bolt tightening patterns, increasing the risk of leaks. Couplings require no maintenance and are designed to last the life of the piping system. Welded joints, on the other hand, have to be X-rayed to ensure proper installation. Grooved mechanical piping systems can be pressurized and depressurized repeatedly for years without ever fatiguing the elastomer gasket.
5. Economical — Labor time is the largest cost variable in the field, and grooved systems offer a reduction in total installed costs because they reduce labor time. It is estimated that jobs utilizing welded joints demand up to 45 percent more man-hours on average compared to no-flame piping solutions. The ease and speed at which grooved mechanical piping systems are installed allows contractors to positively impact the bottom line and meet stringent project schedules.
6. Accommodation of Piping System Movement — Thermal transients may impose deflection on a piping system as the pipe grows when heated and contracts when cooled, resulting in stress on the piping system and equipment. Flexible grooved couplings minimize this stress by allowing limited deflection capabilities to accommodate this movement in system offsets or for use in expansion loops. As an added benefit, flexible couplings allow angular flexibility to accommodate piping misalignment and rotational movement for use in seismic swing joints.
7. Reduction of Noise and Vibration — Mechanical room equipment frequently creates noise and vibration which needs to be isolated from the piping system. Flexible mechanical systems allow the pipe to move within the grooved coupling and the elastomeric gasket dampens vibration, thereby localizing the vibrations generated by equipment and reducing the amount of noise transmitted down the pipeline. The design of the mechanical joint performs this function without wearing out the gasket.
8. Safer Jobsites — The safety advantages that grooved systems provide over welding are numerous. They require no volatile tanks or open torches. There are no lead lines to trip over, nor any need for fire watch personnel. And because there is no welding, soldering, or brazing involved, there is no resulting exposure to hazardous fumes or the potential health issues with which they have been linked, such as lung cancer, urinary tract cancer, heart disease and Parkinson’s disease.
9. Sustainability — Grooved piping technology’s inherent qualities naturally make it environmentally friendly. It significantly reduces or eliminates waste, emissions, and noise pollution on the job site. Weld and x-ray machines are not required which reduces the draw on burdened power resources. The indoor and outdoor air quality is preserved because the joining method does not release fumes or particulate matter.
Publication date: 11/07/2011