2. Understand the three types of plumbing systems: HVAC (hydraulic), plumbing (domestic water, sewerage and ventilation) and chemical and special plumbing systems (seawater systems and hazardous chemicals).
Plumbing and plumbing systems exist in many building elements. Many people have seen a P-trap or refrigerant piping under the sink leading to and from a split system. Few people see the main engineering plumbing in the central plant or the chemical cleaning system in the pool equipment room. Each of these applications requires a specific type of piping that meets specifications, physical constraints, codes, and best design practices.
There is no simple plumbing solution that fits all applications. These systems meet all physical and code requirements if specific design criteria are met and the right questions are asked of owners and operators. In addition, they can maintain the proper costs and lead times to create a successful building system.
HVAC ducts contain many different fluids, pressures and temperatures. The duct can be above or below ground level and run through the interior or exterior of the building. These factors must be taken into account when specifying HVAC piping in the project. The term “hydrodynamic cycle” refers to the use of water as a heat transfer medium for cooling and heating. In each application, water is supplied at a given flow rate and temperature. Typical heat transfer in a room is by an air-to-water coil designed to return water at a set temperature. This leads to the fact that a certain amount of heat is transferred or removed from the space. The circulation of cooling and heating water is the main system used for air conditioning large commercial facilities.
For most low-rise building applications, the expected system operating pressure is typically less than 150 pounds per square inch (psig). The hydraulic system (cold and hot water) is a closed circuit system. This means that the pump’s total dynamic head takes into account frictional losses in the piping system, associated coils, valves and accessories. The static height of the system does not affect the performance of the pump, but it does affect the required operating pressure of the system. Coolers, boilers, pumps, piping and accessories are rated for 150 psi operating pressure, which is common for equipment and component manufacturers. Where possible, this pressure rating should be maintained in the system design. Many buildings that are considered low or mid-rise fall into the 150 psi working pressure category.
In high-rise building design, it is becoming increasingly difficult to keep piping systems and equipment below the 150 psi standard. Static line head above about 350 feet (without adding pump pressure to the system) will exceed the standard working pressure rating of these systems (1 psi = 2.31 feet head). The system will likely use a pressure breaker (in the form of a heat exchanger) to isolate the higher pressure requirements of the column from the rest of the connected piping and equipment. This system design will allow the design and installation of standard pressure coolers as well as specifying higher pressure piping and accessories in the cooling tower.
When specifying piping for a large campus project, the designer/engineer must consciously identify the tower and piping specified for the podium, reflecting their individual requirements (or collective requirements if heat exchangers are not used to isolate the pressure zone).
Another component of a closed system is water purification and the removal of any oxygen from the water. Most hydraulic systems are equipped with a water treatment system consisting of various chemicals and inhibitors to keep the water flowing through the pipes at an optimal pH (around 9.0) and microbial levels to combat pipe biofilms and corrosion. Stabilizing the water in the system and removing the air helps extend the life of the piping, associated pumps, coils and valves. Any air trapped in the pipes can cause cavitation in the cooling and heating water pumps and reduce heat transfer in the cooler, boiler or circulation coils.
Copper: Type L, B, K, M or C drawn and hardened tubing in accordance with ASTM B88 and B88M in combination with ASME B16.22 wrought copper fittings and fittings with lead-free solder or solder for underground applications.
Hardened pipe, type L, B, K (generally used only below ground level) or A per ASTM B88 and B88M, with ASME B16.22 wrought copper fittings and fittings connected by lead-free or above ground soldering. This tube also allows the use of sealed fittings.
Type K copper tubing is the thickest tubing available, providing a working pressure of 1534 psi. inch at 100 F for ½ inch. Models L and M have lower working pressures than K but are still well suited for HVAC applications (pressure ranges from 1242 psi at 100F to 12 in. and 435 psi and 395 psi These values ​​are taken from Tables 3a, 3b and 3c of the Copper Tubing Guide published by the Copper Development Assn.
These operating pressures are for straight pipe runs, which are not normally pressure limited runs of the system. Fittings and connections connecting two lengths of pipe are more likely to leak or fail under the operating pressure of some systems. Typical connection types for copper pipes are welding, soldering or pressurized sealing. These types of connections must be made from lead-free materials and rated for the expected pressure in the system.
Each connection type is capable of maintaining a leak-free system when the fitting is properly sealed, but these systems respond differently when the fitting is not fully sealed or swaged. Solder and solder joints are more likely to fail and leak when the system is first filled and tested and the building is not yet occupied. In this case, contractors and inspectors can quickly determine where the joint is leaking and fix the problem before the system is fully operational and passengers and interior trim are damaged. This can also be reproduced with leak-tight fittings if a leak detection ring or assembly is specified. If you don’t press all the way down to identify the problem area, water can leak out of the fitting just like solder or solder. If leak-tight fittings are not specified in the design, they will sometimes remain under pressure during construction testing and may fail only after a period of operation, resulting in more damage to the occupied space and possible injury to occupants, especially if heated hot pipes pass through the pipes. water.
The copper pipe sizing recommendations are based on the requirements of the regulations, manufacturer’s recommendations and best practices. For chilled water applications (water supply temperature typically 42 to 45 F), the recommended speed limit for copper piping systems is 8 feet per second to reduce system noise and reduce the potential for erosion/corrosion. For hot water systems (typically 140 to 180 F for space heating and up to 205 F for domestic hot water production in hybrid systems), the recommended rate limit for copper pipes is much less. The Copper Tubing Manual lists these speeds as 2 to 3 feet per second when the water supply temperature is above 140 F.
Copper pipes usually come in a certain size, up to 12 inches. This limits the use of copper in the main campus utilities, as these building designs often require ducting larger than 12 inches. From the central plant to the associated heat exchangers. Copper tubing is more common in hydraulic systems 3 inches or less in diameter. For sizes over 3 inches, slotted steel tubing is more commonly used. This is due to the difference in cost between steel and copper, the difference in labor for corrugated pipe versus welded or brazed pipe (pressure fittings are not allowed or recommended by the owner or engineer), and the recommended water velocities and temperatures in these inside each of the materials pipeline.
Steel: Black or galvanized steel pipe per ASTM A 53/A 53M with ductile iron (ASME B16.3) or wrought iron (ASTM A 234/A 234M) fittings and ductile iron (ASME B16.39) fittings. Flanges, fittings and class 150 and 300 connections are available with threaded or flanged fittings. The pipe can be welded with filler metal in accordance with AWS D10.12/D10.12M.
Conforms to ASTM A 536 Class 65-45-12 Ductile Iron, ASTM A 47/A 47M Class 32510 Ductile Iron and ASTM A 53/A 53M Class F, E, or S Grade B Assembly Steel, or ASTM A106 , steel grade B. Grooved or lug fittings for attaching grooved end fittings.
As mentioned above, steel pipes are more commonly used for large pipes in hydraulic systems. This type of system allows for various pressure, temperature and size requirements to meet the needs of chilled and heated water systems. Class designations for flanges, fittings, and fittings refer to working pressure of saturated steam in psi. inch of the corresponding item. Class 150 fittings are designed to operate at a working pressure of 150 psi. inch at 366 F, while Class 300 fittings provide a working pressure of 300 psi. at 550 F. Class 150 fittings provide over 300 psi working water pressure. inch at 150 F, and Class 300 fittings provide up to 2,000 psi working water pressure. inch at 150 F. Other brands of fittings are available for specific pipe types. For example, for cast iron pipe flanges and ASME 16.1 flanged fittings, grades 125 or 250 can be used.
Grooved piping and connection systems use cut or formed grooves at the ends of pipes, fittings, valves, etc. to connect between each length of pipe or fittings with a flexible or rigid connection system. These couplings consist of two or more bolted parts and have a washer in the coupling bore. These systems are available in 150 and 300 class flange types and EPDM gasket materials and are capable of operating at fluid temperatures from 230 to 250 F (depending on pipe size). Grooved pipe information is taken from Victaulic manuals and literature.
Schedule 40 and 80 steel pipes are acceptable for HVAC systems. The pipe specification refers to the wall thickness of the pipe, which increases with the specification number. With an increase in the wall thickness of the pipe, the allowable working pressure of the straight pipe also increases. Schedule 40 tubing allows a working pressure of 1694 psi for ½ inch. Pipe, 696 psi inch for 12 inches (-20 to 650 F). Allowable working pressure for Schedule 80 tubing is 3036 psi. inch (½ inch) and 1305 psi. inch (12 inches) (both -20 to 650 F). These values ​​are taken from the Watson McDaniel Engineering Data section.
Plastics: CPVC plastic pipes, socket fittings to Specification 40 and Specification 80 to ASTM F 441/F 441M (ASTM F 438 to Specification 40 and ASTM F 439 to Specification 80) and solvent adhesives (ASTM F493).
PVC plastic pipe, socket fittings per ASTM D 1785 schedule 40 and schedule 80 (ASM D 2466 schedule 40 and ASTM D 2467 schedule 80) and solvent adhesives (ASTM D 2564). Includes primer per ASTM F 656.
Both CPVC and PVC piping are suitable for hydraulic systems below ground level, although even under these conditions care must be taken when installing these piping in a project. Plastic pipes are widely used in sewer and ventilation duct systems, especially in underground environments where bare pipes come into direct contact with the surrounding soil. At the same time, the corrosion resistance of CPVC and PVC pipes is advantageous due to the corrosivity of some soils. Hydraulic piping is usually insulated and covered with a protective PVC sheath that provides a buffer between the metal piping and the surrounding soil. Plastic pipes can be used in smaller chilled water systems where lower pressures are expected. The maximum working pressure for PVC pipe exceeds 150 psi for all pipe sizes up to 8 inches, but this only applies to temperatures of 73 F or below. Any temperature above 73°F will reduce the operating pressure in the piping system to 140°F. The derating factor is 0.22 at this temperature and 1.0 at 73 F. Maximum operating temperature of 140 F is for Schedule 40 and Schedule 80 PVC pipe. CPVC pipe is able to withstand a wider operating temperature range, making it suitable for use up to 200 F (with a derating factor of 0.2), but has the same pressure rating as PVC, allowing it to be used in standard pressure underground refrigeration applications. water systems up to 8 inches. For hot water systems that maintain higher water temperatures up to 180 or 205 F, PVC or CPVC pipes are not recommended. All data is taken from Harvel PVC pipe specifications and CPVC pipe specifications.
Pipes Pipes carry many different liquids, solids, and gases. Both potable and non-potable liquids flow in these systems. Due to the wide variety of fluids carried in a plumbing system, the pipes in question are classified as domestic water pipes or drainage and ventilation pipes.
Domestic water: Soft copper pipe, ASTM B88 types K and L, ASTM B88M types A and B, with wrought copper pressure fittings (ASME B16.22).
Hard Copper Tubing, ASTM B88 Types L and M, ASTM B88M Types B and C, with Cast Copper Weld Fittings (ASME B16.18), Wrought Copper Weld Fittings (ASME B16.22), Bronze Flanges (ASME B16.24) ) and copper fittings (MCS SP-123). The tube also allows the use of sealed fittings.
Copper pipe types and related standards are taken from Section 22 11 16 of the MasterSpec. The design of copper piping for domestic water supply is limited by the requirements of maximum flow rates. They are specified in the pipeline specification as follows:
Section 610.12.1 of the 2012 Uniform Plumbing Code states: The maximum speed in copper and copper alloy pipe and fitting systems must not exceed 8 feet per second in cold water and 5 feet per second in hot water. These values ​​are also repeated in the Copper Tubing Handbook, which uses these values ​​as the recommended maximum speeds for these types of systems.
Type 316 stainless steel piping in accordance with ASTM A403 and similar fittings using welded or knurled couplings for larger domestic water pipes and direct replacement for copper pipes. With the rising price of copper, stainless steel pipes are becoming more common in domestic water systems. Pipe types and related standards are from the Veterans Administration (VA) MasterSpec Section 22 11 00.
A new innovation that will be implemented and enforced in 2014 is the Federal Drinking Water Leadership Act. This is a federal enforcement of current laws in California and Vermont regarding the lead content in waterways of any pipes, valves, or fittings used in domestic water systems. The law states that all wetted surfaces of pipes, fittings and fixtures must be “lead-free”, which means that the maximum lead content “does not exceed a weighted average of 0.25% (lead)”. This requires manufacturers to produce lead-free cast products to comply with new legal requirements. Details are provided by UL in the Guidelines for Lead in Drinking Water Components.
Drainage and ventilation: Sleeveless cast iron sewer pipes and fittings conforming to ASTM A 888 or the Cast Iron Sewer Piping Institute (CISPI) 301. Sovent fittings conforming to ASME B16.45 or ASSE 1043 can be used with a no-stop system.
Cast iron sewer pipes and flanged fittings must comply with ASTM A 74, rubber gaskets (ASTM C 564) and pure lead and oak or hemp fiber sealant (ASTM B29).
Both types of ducting can be used in buildings, but ductless ducting and fittings are most commonly used above ground level in commercial buildings. Cast iron pipes with CISPI Plugless Fittings allow for permanent installation, can be reconfigured or can be accessed by removing band clamps, while retaining the quality of a metal pipe, which reduces rupture noise in the waste stream through the pipe. The downside to cast iron plumbing is that plumbing deteriorates due to the acidic waste found in typical bathroom installations.
ASME A112.3.1 stainless steel pipes and fittings with flared and flared ends can be used for high quality drainage systems in place of cast iron pipes. Stainless steel plumbing is also used for the first section of the plumbing, which connects to a floor sink where the carbonated product drains to reduce corrosion damage.
Solid PVC pipe according to ASTM D 2665 (drainage, diversion and vents) and PVC honeycomb pipe according to ASTM F 891 (Annex 40), flare connections (ASTM D 2665 to ASTM D 3311, drain, waste and vents) suitable for Schedule 40 pipe), adhesive primer (ASTM F 656) and solvent adhesive (ASTM D 2564). PVC pipes can be found above and below ground level in commercial buildings, although they are more commonly listed below ground level due to pipe cracking and special rule requirements.
In the construction jurisdiction of Southern Nevada, the 2009 International Building Code (IBC) Amendment states:
603.1.2.1 Equipment. Combustible pipelines are allowed to be installed in the engine room, enclosed by a two-hour fire-resistant structure and fully protected by automatic sprinklers. Combustible piping may be run from the equipment room to other rooms, provided that the piping is enclosed in an approved special two-hour fire-resistant assembly. When such combustible piping passes through fire walls and/or floors/ceilings, the penetration must be specified for the specific piping material with grades F and T not lower than the required fire resistance for the penetration. Combustible pipes must not penetrate more than one layer.
This requires all combustible piping (plastic or otherwise) present in a Class 1A building as defined by the IBC to be wrapped in a 2 hour structure. The use of PVC pipes in drainage systems has several advantages. Compared to cast iron pipes, PVC is more resistant to corrosion and oxidation caused by bathroom waste and earth. When laid underground, PVC pipes are also resistant to corrosion of the surrounding soil (as shown in the HVAC piping section). PVC piping used in a drainage system is subject to the same limitations as an HVAC hydraulic system, with a maximum operating temperature of 140 F. This temperature is further mandated by the requirements of the Uniform Piping Code and the International Piping Code, which stipulate that any discharge to waste receptors must be below 140 F.
Section 810.1 of the 2012 Uniform Plumbing Code states that steam pipes must not be directly connected to a piping or drain system, and water above 140 F (60 C) must not be discharged directly into a pressurized drain.
Section 803.1 of the 2012 International Plumbing Code states that steam pipes must not be connected to a drainage system or any part of the plumbing system, and water above 140 F (60 C) must not be discharged into any part of the drainage system.
Special piping systems are associated with the transport of non-typical liquids. These fluids can range from piping for marine aquariums to piping for supplying chemicals to swimming pool equipment systems. Aquarium plumbing systems are not common in commercial buildings, but they are installed in some hotels with remote plumbing systems connected to various locations from a central pump room. Stainless steel seems like a suitable piping type for sea water systems due to its ability to inhibit corrosion with other water systems, but salt water can actually corrode and erode stainless steel pipes. For such applications, plastic or copper-nickel CPVC marine pipes meet corrosion requirements; when laying these pipes in a large commercial facility, the flammability of the pipes must be considered. As noted above, the use of combustible piping in Southern Nevada requires an alternative method to be requested to demonstrate intent to comply with the relevant building type code.
The pool piping that supplies purified water for body immersion contains a dilute amount of chemicals (12.5% ​​sodium hypochlorite bleach and hydrochloric acid can be used) to maintain a specific pH and chemical balance as required by the health department. In addition to dilute chemical piping, full chlorine bleach and other chemicals must be transported from bulk material storage areas and special equipment rooms. CPVC pipes are chemical resistant for chlorine bleach supply, but high ferrosilicon pipes can be used as an alternative to chemical pipes when passing through non-combustible building types (eg Type 1A). It is strong but more brittle than standard cast iron pipe and heavier than comparable pipes.
This article discusses just a few of the many possibilities for designing piping systems. They represent most types of installed systems in large commercial buildings, but there will always be exceptions to the rule. The overall master specification is an invaluable resource in determining the piping type for a given system and evaluating the appropriate criteria for each product. Standard specifications will meet the requirements of many projects, but designers and engineers should review them when it comes to high-rise towers, high temperatures, hazardous chemicals, or changes in legislation or jurisdiction. Learn more about plumbing recommendations and restrictions to make informed decisions about the products installed in your project. Our clients trust us as design professionals to provide their buildings with the right size, well balanced and affordable designs where ducts reach their expected life and never experience catastrophic failures.
Matt Dolan is a project engineer at JBA Consulting Engineers. His experience lies in the design of complex HVAC and plumbing systems for a variety of building types such as commercial offices, healthcare facilities and hospitality complexes, including high-rise guest towers and numerous restaurants.
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