The use of properly designated, installed and maintained backflow prevention devices can avoid the risk of incidents caused by anti-siphon and back pressure.
The backflow continues to pose a major threat to our fresh water supply. Due to the cross-connection between the drinking water system and a suspected source containing used water, industrial fluids, gas, or any other contaminating material, backflow events are difficult to detect unless there are irregularities and potentially serious symptoms. The use of properly designated, installed and maintained backflow prevention devices can avoid the risk of incidents caused by anti-siphon and back pressure.
Specifying the correct reflow solution depends on the application. It is important to be aware of the potential flaws in the existing piping system design. The following are 10 considerations when specifying.
In terms of minimizing system pressure loss, flow performance is important because the available pressure of the entire system needs to be calculated during the design process. If the pressure loss is too great for the system to provide enough pressure for its components, it may mean that a booster pump must be added or a larger diameter pipe must be used, both of which will increase a lot of costs. Although pressure loss is an area of concern in all systems, it is especially important in fire protection systems.
All reflow manufacturers publish pressure/flow curves for their equipment. When comparing flow curves, make sure they all indicate the same situation—because the increase flow curve and the decrease flow curve are usually very different.
The total theoretical demand of the water supply system is calculated by adding up the known maximum demand of all fixtures in the system. The flow characteristics of the return device can directly affect the overall flow performance of the building’s drinking water or fire sprinkler system. When designating, please pay attention to the building flow requirements.
At the highest rate of typical use, you do not want to exceed the rated flow rate, above which you will experience a tremendous increase in wear and tear. For fire fighting systems, the full fire flow rate should not exceed the UL rated flow rate of the valve.
Despite best efforts, normal operation and unavoidable external sources (such as excessive debris in the water) can still cause the backflow preventer to wear. The backflow preventer inevitably needs maintenance, which should be done by a professional plumber.
There are many factors to consider when choosing a backflow preventer: How easy is it to access internal components? Can the parts be repaired separately? Are they available anytime? Can components such as the pressure relief valve or shut-off valve be removed for repair or replacement? The more difficult the repair and the longer it takes, the higher the repair cost.
Application conditions will have a significant impact on the design, installation and budget of the system. Local authorities have jurisdiction over the types of valves used in each type of application. The total length of the valve can usually be found in the technical data sheet provided by the manufacturer, which is essential when replacing an existing application. If space is at a premium, it can also affect new installations.
What type of environment will the device be located in? For example, decompression zone components may not be used in underground tanks or pits because they may be submerged. Also consider what weather the valve will be exposed to and how it will affect the exposed components.
The weighting factor of equipment selection is mainly the labor cost related to handling and installation. In addition, please consider what material it is made of. Composite materials and stainless steel are generally lighter than cast iron or ductile iron. The smaller the better, because it can leave extra space for the much-needed valves in the system and take up less space in the machine room.
Backflow prevention devices are installed in various locations, from large open spaces to small computer rooms. They are designed to allow multiple installation configurations, enabling design engineers to install equipment into the space. Mounting options are horizontal [most common], vertical, “N” type and “Z” type.
Generally speaking, the valve performance is almost unchanged according to its installation configuration; however, you should always read the manufacturer’s technical information and consult the local plumbing code official before making a purchase decision.
The way to test the valve depends on the requirements of the local water department, but the valve itself will affect the difficulty of valve testing and troubleshooting. The tester needs to use the test cock in order to effectively test the function of the equipment. If the valve has sufficient clearance on all sides, this is usually not a problem, but when this is not possible (violating the manufacturer’s recommendations) or when the valve is modified, the wall or existing pipes may make it difficult or impossible to enter Test cock-this will result in re-piping or complete valve replacement.
In addition to testing the valve, one use of the test cock is to flush the valve in an attempt to remove debris that may contaminate the inspection. A larger test cock will allow more flow, thereby increasing your chances of removing debris. In order to test and troubleshoot the valve, it is important that at least the downstream shut-off valve is tightly closed and leak-free. For this reason, high-quality closures are an important part of return components, and the ability to repair them to make the valve testable again is also critical.
When specifying a backflow preventer, there are many shut-off valve options available, including: Ball valves—typically used for 2-inch assemblies. And allows easy opening or closing of ¼ gear; butterfly valve-when a shorter twist is required, it can be slowly closed by gear operation to avoid water hammer (a fire protection system requirement), or electronic control; NRS [non-vertical stem ] Gate valve-ideal when you have no gap above the handwheel and do not need visual indication of position (open/close); OSY [outer stem and yoke] gate valve-the standard configuration of large-diameter fire valves, because The rising valve stem provides a visual indication of position and can be installed with a tamper switch; PIV [Column Indicator Valve]-usually an option for NRS gate valves, these valves are designed to be connected to a column that will indicate visually ” “Open” or “closed” and are usually used in fire protection systems when the valve is not accessible, such as underground or behind a wall.
It is important to understand your local regulations and requirements, because the device may be allowed to be used in an application in one area, but deemed insufficient in the next area. It is recommended to maintain a relationship with your local pipeline inspector and water department so that you can avoid inspection failures or install more expensive equipment when more economical equipment meets the requirements.
There are resources available to provide information, education, product testing and certification, build product evaluation, and code development assistance. These organizations can help: IAPMO-International Association of Plumbing and Machinery Officials (IAPMO) iapmo; USC Cross-Connect Control and Hydraulic Research Foundation, fccchr.usc.edu; and American Society of Sanitary Engineers (ASSE), asse-plumbing.org.
Plumbers, contractors, and engineers have more options to identify, plan and prevent potential backflow threats before they occur, but changing piping specifications and complex piping systems make it difficult to navigate. Specifying the correct backflow preventer is the first step in a safe and reliable water supply.
The Toronto City Council is considering an accelerated climate strategy. https://www.hpacmag.com/green-technology/toronto-city-council-to-think-accelerated-climate-strategy/1004133508/
Quebec’s new residential fuel oil ban regulations. https://www.hpacmag.com/construction/new-residential-fuel-oil-ban-regulation-in-quebec/1004133504/
Manitoba will allocate funds to upgrade the school’s ventilation system. https://www.hpacmag.com/human-resources/manitoba-to-dedicate-funding-towards-upgrading-ventilation-systems-in-schools/1004133501/
Ontario invests to attract young people to careers in the technology industry. https://www.hpacmag.com/construction/ontario-makes-investment-to-attract-young-people-to-skilled-trades-careers/1004133485/
Video: ASHRAE addresses climate change issues at COP26 https://www.canadianconsultingengineer.com/?p=1003413735
Post time: Dec-01-2021
