Sec 8 Piping components - new version 2017

Irrigation Piping Components In the irrigation industry, there are many different types of pipe being used to deliver water to the plant material. The materials used to produce pipe in the irrigation industry vary from aluminum, polyvinyl chloride (PVC), polyethylene (PE) or high density polyethylene (HDPE) Once used as a buried pipe it is now almost exclusively seen as an above ground installation. Fittings are mechanical allowing repeated fastening and removal for quick detaching of pipe lengths.Aluminum Once used as a buried pipe it is now almost exclusively seen as an above ground installation. Fittings are mechanical allowing repeated fastening and removal for quick detaching of pipe lengths. Most widely used in agriculture and horticulture applications where removal of crops or disturbance of the ground would damage a permanently installed underground installation. Common in nurseries, orchards and row crop production. This type of pipe has been installed underground in the past but rapid deterioration of the pipe from incompatible minerals and corrosion have made plastic pipes the more favourable for this type of application. Most of the installations will be of an overhead variety and the pipe will be above grade and made to be removable. This system has one of the highest costs for labour because of the manual assembly/disassembly of the system and moving the entire system along the ground. These can be automated for the movement of the wheel move and center pivot systems. . This system has to be moved manually to the next area that needs water. circles are where the wheels of the pivot system travel. Centre pivot system (below)- the irrigation sprinklers have been ‘hung” below the main line to negate the effect of wind as much as possible This system is known as a “wheel move” and most often the moving process is automated The above fittings are mechanical and use a latch system to join the 2 pipes together. The male end of the pipe has the latch. The female end has a larger diameter and a rubber gasket inside to stop the water from leaking out. The outside diameter of the pipe is controlled so that the pipe will always work with the fittings. Some advantages of aluminum systems is that they are Light weightgood strength and rigidity resistant to corrosionlow material costs (high labour costs)fully recyclable Polyvinyl Chloride (PVC) One of the most widely used pipe in the irrigation industry today. Available in different colours – commonly blue or white with purple being used to designate recycled water.Used today in many underground applications including main lines and lateral line pipes. In agriculture applications it can be used as a mainline to “supply” water for the above ground systems. One of the most widely used pipe in the irrigation industry today. Available in different colours – commonly blue or white with purple being used to designate recycled water. PVC pipe usually comes in 20 foot lengths. The size of the pipe is measured using the outside diameter. In Canada we use IPS(iron pipe size) which is the same size OD as iron pipe.Pressure ratings for PVC pipe are designated as either SDR (standard dimension ratio), schedule or class. (See page 10 under pipe strength for clarification of these terms.) The process of attaching the pipe together is called “Solvent Welding”. A primer to soften the pipe is applied and then a glue is applied immediately to seal the joint. This process will firmly “cement” the joints together once the glue has set. The outside diameter of the pipe remains constant as the fittings go over the pipe The other way to join PVC pipe is to use a “gasketed” pipe. Each section of pipe has a “bell end”. This end has a larger diameter than the rest of the pipe. Inside the pipe is another larger diameter section that houses a rubber gasket. The gasket is lubricated and another section of pipe will be inserted into the bell end. These sections once together in the ground have to be stabilized with “thrust blocks” otherwise the pipes could separate. PVC is popular for the following reasons: It is lightweight and easy to installit has less friction loss comparable to other material due to the smooth wallsit comes in a variety of pressure ratings from 100 – 315 psiit is resistant to corrosion This pipe can have a tendency to get fatigued due to continual surges of pressure caused by “water hammer”. In northern climates the winter can damage the pipe by frost heaving which will shatter the pipe. Otherwise this pipe is very flexible and can withstand small movement in the ground. Polyethylene (PE)Most commonly seen in residential and light commercial applications. Usually associated with low pressure systems. Will be seen in trickle systems and greenhouse irrigation systems. Most commonly seen in residential and light commercial applications. Usually associated with low pressure systems. Will be seen in trickle systems and greenhouse irrigation systems. PE pipe is widely used on small irrigation systems and is very flexible and easy to work with. It is very common to buy the pipe in coils. It is inexpensive to buy and is available in many retail outlets. Note that some contractors will specify CSA approved pipe. The pipe itself has low impact strength and has a high amount of expansion and contraction when used above ground. PE pipe has much more forgiveness to ground movement than PVC and can bend around slight corners without the use of fittings. PE pipe is measured using the inside diameter of the pipe. The fittings being used are called “insert fittings” and have barbs on them. Once they are inserted into the pipe a metal clamp will be put around the pipe and squeezed to secure the pipe onto the fitting. Compression fittings are commonly used on low pressure or micro irrigation systems. This is a much thicker version of polyethylene pipe and is quickly becoming the pipe of choice for many higher pressure irrigation systems. It has also made some inroads into the residential market as well.High Density Polyethylene (HDPE) This is a much thicker version of polyethylene pipe and is quickly becoming the pipe of choice for many higher pressure irrigation systems. It has also made some inroads into the residential market as well. HDPE pipe was originally produced for industries that need to carry products in a high pressure environment commonly seen in the oil and gas sector. It has expanded into the irrigation industry and is very useful in environments where there is accelerated soil movement around the pipes. This pipe can withstand the highest amount of abuse of all of the pipe used in irrigation. It has a wide range of pressure ratings from low to high for all types of systems. This pipe differs from the rest in that the pipe and fitting are attached by a method called “heat fusion”. The joints are heated up in a special machine and then pushed together until the pipes cool. The joint is actually stronger than the rest of the pipe. Special training is needed to perform this operation but when done correctly there are very few instances of pipe failure. This makes this pipe a very long lasting installation with little to no maintenance or costs. . Pipe Strength Pipe Strength Standard Dimension Ratio (SDR) The formula for measuring the SDR is : SDR = outside diameter 2” diameter pipe = SDR 20wall thickness 0.1” wall thickness Pipes of common SDR will have a common pressure rating regardless of their size. SDR 26 means the outside diameter of the pipe is 26 times the thickness of the wall. The lower the SDR the higher the pressure rating that it has. Schedule Pipe Schedule refers to the wall thickness of pipe; Sch 40, Sch 80, etc. As the pipe increases in size the pressure ratings decrease. In smaller diameter pipe up to about 1.5 inches, schedule pipe is stronger than SDR but once the diameter increase above 1.5”, SDR pipe is actually stronger than schedule pipe. Schedule pipe is seldom specified for irrigation systems as SDR pipe is more common in the larger systems Pipe Notations Here is an example of some notations that you will come across stamped on a pipe Example: PVC 1120 - SDR 26 Series 160 PVC = polyvinyl chloride 1120 or 1220 hdp = the ability of the pipe to withstand this pressure continuously for long periods of time with a high degree of certainty that the pipe will NOT fail. SDR 26 = Standard Dimension Ratio - all SDR 26 pipe will have the same pressure rating Series 160 = maximum recommended operating pressure - 160 psiTo account for any surge pressures it is common to design at no more than 78% of the maximum recommended operating pressure. Pipe Installation There are two main methods of installing irrigation pipe underground, trenching or using a vibratory plough. Trenching involves cutting a trench through the ground using a specialized piece of digging equipment; a spinning chain of metal teeth cuts the trench. Trenching is commonly used when pipe sizes exceed 2.5 ”. Smaller pipe sizes allow the use of vibratory ploughs. Vibratory ploughs pull the pipe in behind a vibrating ‘bullet’. The vibrating steel shank moves vertically through the ground, shattering any resistance. The pipe is attached behind the bullet and is pulled underground through the newly broken up soil. There are advantages of each type to installation method. Trenching Advantages allows large pipe sizes to be installedallows the trench to be levelled before the pipe is installed (better grading)Gives more room for pipe connections, installing valves, sprinklers, etc. allows control wiring to be installed simultaneously – expansion coils are then possible to installallows for the use of solvent weld or bell and spigot pipe Disadvantages disrupts the site surfacesettling creates problems (easy to see for years after)slower overall processrequires significant clean up Vibratory Plough Advantages Quick to install (pipe installation times drop by 50-70%)minimal disturbance to the sitedisturbed ground knits quickly Disadvantages Requires only solvent of fusion welded pipe to be usedcannot level pipe (unless a laser transit is used to control the plough depth)cannot install expansion coils when pulling in control wirelimited to smaller pipe sizes Water Hammer Also known as surge pressure. Water flowing in a pipe contains energy due to velocity and pressure. Changes in energy resulting from a change in velocity (flow) will produce a change in the resulting pressure. Causes of water hammer may include: Closing or opening a valve too quickly Air pockets in the line Sudden stop or rapid release of air in pipeline Starting and stopping of a pump Alberta Agriculture Edmonton Alberta Adgex 753-4 Nov 1986 Thrust Blocking Thrust blocks are required at piping direction changes and dead ends. Thrust blocks in residential, light commercial installations are typically concrete blocks, poured in concrete or wood. “The size, shape, and type of thrust blocking required depends on the maximum system pressure, pipe size, appurtenance size, type of fitting, line profile and soil type” Principles of Irrigation, Irrigation Association 3rd edition, Fairfax VA March 2015 pg 156 When installing thrust blocks make sure: The thrust block is in contact with the fitting It covers as much of the joint surface as possible It is placed in undisturbed soil https://www.linkedin.com/pulse/do-solvent-welded-pvc-fittings-need-thrust-blocked-larry-workman Resources Ian Morrow – Olds College Dennis McKernan – Life Works Inc