Grooved-end mechanical piping systems reduce the mechanical room footprint, enhance system performance and save time and cost on installation, says Simon Ouellette, Victaulic Engineering Services Supervisor.
The high cost of commercial and industrial building space and its scarcity has led to a growing trend to squeeze the size of mechanical rooms. Ever tighter architectural designs for new builds are putting pressure on consulting engineers and contractors to deliver reliable, cost-effective HVAC solutions that keep the mechanical room footprint to a minimum. Similar demands are being made for mechanical room retrofits within the structural constraints of older buildings. Grooved-end mechanical piping systems address all these issues.
Switching from welded and flanged specifications to the grooved method for mechanical room installations can make a big difference to the success of a project. The lighter weight, smaller size yet higher integral strength of grooved components make them ideal for projects that are tight on space or where mechanical rooms are located on higherlevel floors. Their ease and speed of installation offer savings on total installed costs and they also deliver improved performance and reliability.
Alternative for rubber bellows
In traditional mechanical room set-ups rubber bellows or compensators are placed in the piping system at either side of the pump to reduce noise and vibration and are sometimes used to correct misalignment between welded pipe and equipment, placing the rubber under intense stress in a certain plane. Not only do they take up valuable plant room space, but rubber bellows are considered the weakest point of an installation and the first component that is likely to fail, as general wear and tear, along with exposure to UV light in the mechanical room, causes the rubber to erode.
They also require ongoing maintenance: as bolts gradually slacken and the system starts to weep, the bolts need to be tightened regularly. With a best life expectancy of 10 years, rubber bellows may need to be replaced several times within the life of the system – which involves system downtime plus the cost of a new unit. Failure of the rubber bellows can be sudden and unpredictable, causing serious health and safety risks.
Installing grooved flexible couplings solves these problems. They are designed with an elastomeric gasket contained inside the internal cavity of a ductile iron or stainless steel housing and are secured by two nuts and bolts to create a leak-tight joint. This unique design gives the couplings noise and vibration reducing properties superior to those of traditional devices. The couplings eliminate the need for costly, bulky flanged units and avoid the use of rubber bellows. Their construction enables the gasket to seal against the pipe, while the metal housing provides both space for the resilient elastomeric material to flex, and containment to prevent overstretching. This creates a discontinuity similar to that of a rubber compensator. Additionally, ductile iron and stainless steel both have their own vibration dampening qualities, so the external housing also serves to absorb sound, thereby protecting equipment and enhancing the life time of the system.
Prevention of misalignment
In addition to noise and vibration attenuation, the grooved couplings allow for alignment ease in a pump installation. Flexible couplings also help to accommodate slight deviation that might be caused if pipework has not been prefabricated to exact dimensions – something which is more difficult to achieve with a welded or flanged system. A further advantage is removing the need for tie rods or the type of bracketry required to support pipework on top of and beneath bellows which increases time, labour and material costs.
Lowering labour risk
Whilst material costs are relatively easy to fix, labour costs are more volatile, leaving contractors open to significant labour risk on project costings. In the case of the grooved mechanical system a larger proportion of the total costs is fixed. A grooved mechanical system with a quick and simple joining method and no need for jobsite preparation offers considerable cost-saving opportunities on installation.
Time spent on the jobsite is a critical cost factor, leading contractors to prefabricate as much as possible offsite, especially when there is limited space on site. Working in such a way avoids the risk of loss or damage to components on the jobsite, whilst reduced material handling lowers the potential for accidents.
Ease and speed of installation are key benefits of grooved mechanical room installations, since just two nuts and bolts are needed to form a secure joint. Once installed, the grooved system provides for quality control through visual confirmation of proper installation. Metal-to-metal bolt pad connection indicates that the joint is properly made and avoids time-consuming X-ray tests.
A system that uses grooved pipe-joining technology can be flushed out and cleaned in a fraction of the time needed for a system joined by other methods. The disconnecting of pieces of equipment can be done quickly and simply. A temporary by-pass around a chiller that might take several days on a welded system can be avoided with the grooved system and the task completed in a few hours.
When it comes to cleaning filters and strainers after flushing, access is much quicker and easier through the loosening of two nuts and bolts and the way the filter is positioned in the strainer makes is easy to extract. Modifications to pipework which may be required at any stage during the project can be completed with similar ease. Tasks such as changing out a filter or replacing a pump can be done in minutes rather than hours.
When turbulent water enters a pump chamber and the suction eye of a pump impeller, the degree of turbulence has a direct correlation with lower pump efficiency and greater hydraulic noise within the pump casing. To reduce the effects of turbulence, suction pipes are typically kept as long and straight as possible before the connection onto the pump flange. Yet creating long lengths of pipe does not sit well with modern design trends which aim to keep mechanical rooms simple and compact. Where a bend is connected directly onto the pump suction, the water flow may spin in opposite directions within the eye of the impeller. Pump energy then has to be spent correcting this action before producing the expected performance.
A simple alternative is to fit a suction diffuser that straightens out the spinning fluid created by the change in direction (bend) and enables pipework to be connected closer to the pump at a 90-degree angle. Eliminating long pipe runs, elbows and reducers makes for a smaller mechanical room footprint and optimum pump performance.Designing mechanical rooms with grooved valves achieves similar space savings. Having grooved check valves, eliminates the use of flanged spool pieces on the pump dressings and cuts out the need for flange adapters. This reduces the mechanical room footprint but space saving is not the only advantage: there are cost benefits too. Avoiding an extra spool between valves means the job is completed more quickly so labour costs are reduced.