In search of new market developments, our company constantly explores the possibilities offered by industries that require massive movement of liquid flows. The technological capacity of Krah pipes allows to handle large diameters with low pressures, which positions the technology against usual competences. In this context, rice planting industry introduce a very suitable market for this type of profiled pipes, which Krah America Latina SA has ventured into in recent years, with great success.
This document includes relevant aspects of use of the Ecoline by Krah Piping and Fittings System in the rice planting industry in Argentine.
The rice planting market
Traditional method for cultivating rice is flooding fields while, or after, setting young seedlings. This simple method requires a sound irrigation planning, but it reduces the growth of less robust weed and pest plants that have no submerged growth state and deters vermin. While flooding is not mandatory for cultivation of rice, all other methods of irrigation require higher effort in weed and pest control during growth periods and a different approach for fertilizing the soil. Rice requires slightly more water to produce than other grains. It´s production uses almost a third of Earth’s fresh water. Water outflows from rice fields through transpiration, evaporation, seepage and percolation. It is estimated that it takes about 2.500 litres (660 US gal) of water need to be supplied to account for all these outflows and produce 1 kg (2 lb 3 oz) of rice.
Rice cultivation requires flooding during plant development. If we consider that 290,000 ha are planted in Argentina and during the entire rice crop cycle approximately 1.0 m3 of water is needed for each m2 of land, each season 2,200 million m3 of water are flowed. The water required in each field is usually pumped from a reservoir or river to a certain height and then distributed through canals by gravity. Throughout production cycle we can define two points in water path where pipes are used: pumping and distribution. Consider the amount of hydraulic capacity needed to mobilize this volume of water at different levels of height and we will have a great business in hand.
What is Rice?
Rice is a monocot belonging to the family Poaceae (grasses). The roots are thin, fibrous and fasciculate. Rice is a seed of grass species Oryza sativa (Asian rice) or, less commonly, Oryza glaberrima (African rice). The name wild rice is usually used for species of genera Zizania and Porteresia, both wild and domesticated, although the term may also be used for primitive or uncultivated varieties of Oryza. As a cereal grain, domesticated rice is the most widely consumed staple food for over half of world’s human population, particularly in Asia and Africa. It is an agricultural commodity with the third-highest worldwide production, after sugarcane and maize. Since sizable portions of sugarcane and maize crops are used for purposes other than human consumption, rice is the most important food crop regarding human nutrition and caloric intake, providing more than one-fifth of worldwide consumed calories by humans. There are many varieties of rice, and culinary preferences tend to vary regionally.
Rice is normally grown as an annual plant, although in tropical areas it can survive as a perennial and can produce a ratoon crop for up to 30 years. Rice cultivation is well-suited to countries and regions with low labour costs and high rainfall, as it is labour-intensive to cultivate and requires ample water. However, rice can be grown practically anywhere, even on a steep hill or mountain area with the use of water-controlling terrace systems. Although its parent species are native to Asia and certain parts of Africa, centuries of trade and exportation have made it commonplace in many cultures worldwide. Production and consumption of rice is estimated to have been responsible for 4% of global greenhouse gas emissions in 2010.
Rice production in the world & Argentina
Rice is second most produced cereal in the world behind maize (1 billion tonnes) and ahead of wheat (713 million tonnes). Many hectares are dedicated to rice cultivation in the world. It is known that 95% of this crop extends between parallels 53º, north latitude, and 35º, south latitude. In 2020, world production of paddy rice was 756.7 million metric tons, led by China and India with a combined 52% of this total. Other major producers were Bangladesh, Indonesia, and Vietnam. The five major producers accounted for 72% of total production, while top fifteen producers accounted for 91% of total world production in 2017. Developing countries account for 95% of total production.
Argentina produces 1.6 million tons per year. In last 10 years production increased by 121%, accompanied by a 16% increase in yields. Argentina currently exports around 640 thousand tons of rice, of which 55% of shipments are concentrated in semi-milled rice, about 30% in husked rice, 12% in broken rice and rest in paddy rice and rice for planting. In the nineties there was a boom in expansion of planted area reaching a record of 290,850 hectares and a production of 1.66 million tons representing 0.22% of world production.
Analysing geographical location of places where planting is recorded, it is observed that Corrientes is the province where farmers declared the largest area planted for rice 2021/2022, representing 48.78%. In second and third place are provinces of Entre Ríos and Santa Fe with 26.44% and 12.33%, respectively. Between three provinces they represent 87.55% of total planted area.
Rice cultivation and materials used
Most rice is grown in flooded fields. The success of production is based on water management for adequate irrigation, which involves construction of walls and use of waterwheels, as well as ensuring that water penetrates more than five centimetres into the soil. For this reason, it is convenient that fields to be flooded are relatively close to lagoons that provide necessary water.
First, property margins and walls for delimitation are built on bottom of the land. Soil is provided from some shallow place of lake, for which a dredge is used until sides reach a height of half a meter above lagoon water level, forming the cerrado. Then the cerrado itself is filled with earth until it reaches neighbouring fields level.In case of rice fields located on flat lands, where fields level and lagoon level are the same, pumps are used to extract water from fields to ditches. To flood fields, it is enough to open the floodgate. In case of land located at higher altitudes, as is more common, fields form terraces. Water passes through pipes driven by pumps that take water and raise it to closed ones that must be flooded. Therefore, as we said previously that throughout production cycle two points are defined in path of water where pipes are used: pumping and distribution; Let’s analyse each one.
There are different variants of pumping. Broadly speaking, and following path that water travels, installation begins with a suction section of little or no length, the pump, a short segment where diameters are adapted and valves and chimneys are placed, and finally a counter-slope discharge line that usually is at least 200 meters long. Nowadays these facilities are made of rolled sheet metal and welded from start to finish. Except for smaller diameter pumps (up to DN600) where in several cases discharge lines are made of solid PVC. Sheet metal installations have several drawbacks. The first and main one is that sheet rusts and even more so in operational context of this type of installation. Carbon steel is in constant contact with water while it is being watered (6 months); The steel pipe is filled with water and the rest of the year it contains water partially since installation is never completely emptied. The second scenario is even more unfavourable because of having humid areas in contact with oxygen. Pipe cannot be buried and must be installed above ground since installation service life is a few years and soil movement are not justified. In addition, if buried, corrosion phenomenon would be aggravated by moisture and galvanic corrosion. Even leaving laying on ground, these corrosion phenomena would appear throughout lower part where soil and pipe come into contact. For this reason, lines are usually placed on tries to keep them separate from ground (remember that the lines have a length of 200 meters on average).
Because pressures are low, pipes are made by rolling 1/8” or 3/16” sheets and welding them. This construction method results in a pipe of a nominal pressure suitable for the project, but with a very poor annular stiffness in large diameters. This lack of stiffness causes two types of very recurrent failures in this type of installations:
• First, in transient vacuum phenomena pipe buckles and collapses leaving installation out of operation.
• Additionally, the pipe constantly undergoes an “oscillating deflection”, with is the deflection and return to its original shape cyclically both in transient phenomena, where amplitude is greater, and in permanent regime where fluid turbulence generates deflections of lower amplitude, but higher frequency. This oscillating deflection fatigues material and longitudinal cracks occur.
It is evident that channels used to transport such a volume of water in such large areas of soil must be piped in some sections so that it can be passed overhead, to be able to pass under embankments, or even so that one channel passes under another. In cases of larger producers, where field surfaces are larger, the need for gravity pipes increases.
Let us consider the case of largest rice producer in Argentina with approximately 60,000 hectares under cultivation. This customer differs from rest of producers by its cultivation system of zero level or controlled slope. Here we are not going to delve into details of this methodology, we will focus on what is relevant in terms of pipes.
The system requires dividing land into rectangular portions of between 20 ha and 25 ha each. Each rectangle has a pipa. It is called pipa to a set of water gate plus pipe segment of 3 m to 9 m; the reason of that is to regulate water level in each portion of land, while pipe makes a crossing so that vehicles and machinery can access said rectangle.
The Ecoline system - A superior alternative
Throughout northeastern region of Argentina, western Uruguay and southern Brazil and Paraguay, this market has great potential for us, where our technology stands out. It is clearly a niche market that is technologically behind when it comes to driving systems.
Obviously when working with polymers the oxidation problem is eradicated, but our differentiation regarding to other suppliers of plastic pipes is the profile design and electrofusion. With working on profiles, we achieve pipes with nominal pressure and accurate stiffness as installation requires, even in some of the executed lines we have designed pipes of different nominal pressures at different line points in order to optimize costs. Additionally, electrofusion reduces significantly working costs since it would be totally impractical to mobilize butt fusion equipment for lengths of this type of installations.
We are the only ones in the region with the ability to offer this combined solution. Corrugated plastic pipes on the market do not withstand the working pressures of this type of installation, while solid profile pipes (HDPE or GRP) should be thicker than that required by working pressure to have a stiffness that can withstand transient phenomena.
This results in a significant impact on costs. Working smart, we can have this market captive to Krah technology.
In pumping section, what interests us is the discharge line; all above has large diameter variations, low radius curves, derivations, etc. that are very complex to do in HDPE. The diameter range of these installations is from DN/ID400 mm to DN/ID1200 mm.In working regime, discharge line works with relatively low pressures, between 1 and 4 kg/cm2; However, transient phenomena in pumping with internal combustion engines are much more recurrent than in other types of facilities due to pumps stops and start-up due to power cuts in electrical installations or lack of diesel, mechanical damage, etc. In these transient phenomena installations experience water hammer (overpressure) as well as phenomena of separation of fluid column (depressions and / or voids).
Case Pumping station – Aguaceros Dam 2
For hydraulic analysis and preparation of the design report, consultant used following basic information:
- Estimated altimetric pipeline profile
- Permanence curve of levels in Aguaceros 2 dam, estimated from water balance considering recharges and extractions for irrigation.
- Brand and model of the pump to be used.
- Information from pipe suppliers, profiled polyethylene pipes from the supplier Krah
The estimated longitudinal profile considered for pumping analysis consisted of a uniform slope ramp from a point at elevation +74.00 m where manifold and protection mechanism against water hammer were installed, to discharge in cylinder head at height +86.0 m, whose beginning is at a point 366 m away. For the dam to be built, water inside reservoir will present variations in water height between +74.0 (full reservoir) and +70.0 m height. Based on an analysis of permanence of levels through water balance of reservoir that considers contributions and extractions, 65% of time was determined during harvests, reservoir will find water at elevation +73.0 m or higher, so this lake level is considered as a reasonable value for dimensioning of pumping in condition of maximum instantaneous flows, that occurs at the beginning of harvest. To avoid negative pressures below cavitation line, 4 air valves were placed along rigid pipe, in progressive 80 m, 170 m, 260 m and 450 m. Based on these results, it is observed that the maximum internal pressure in the pipes is around 24 mca, which occurs in the initial section. Therefore, pipes were required to work above the following nominal pressures:
- Progressive 0 m to 84 m: 2.6 kg/cm2
- Progressive 84 m to 160 m: 2.2 kg/cm2
- Progressive 160 m to 240 m: 1.7 kg/cm2
- Progressive 240 m to 360 m: 1.4 kg/cm2
With respect to balance chimney, it must have a height equal or greater than 16,0 m, to avoid water loss during on-regime operation and greater than 25,0 m to avoid water loss in transient scenarios.Observing results, it is concluded that it is viable to pump target flow working with two IMBIL pumps at 440 RPM, complying with engines indicated power. Operating points closest to target, using DN/ID900 mm pipes, are as follows, all with a nominal rotational speed of 440 RPM:
- 1.55 m3/s flow rate, 900 mm pipe, power 310 kW (412 HP)
- flow rate of 1.65 m3/s, pipe of 1,000 mm, power of 321 kW
- flow rate of 1.70 m3/s for 1,100 mm pipe, power of 325 kW
To DN/ID900 mm pipe, a maximum flow of 1.8 m3/s could be obtained working at 450 RPM and using a power of 340 kW, although we understand that engine would work very close to or above its recommended limit. It was finally determined to use DN/ID1000 mm pipes according to the following detail.
- Required flow: 1.6 / 2.0 m3/s
- Pump: IMBIL 750-860 pump
- Stub-end DN1000
San Lorenzo Line:
- Required flow: 1.6 / 1.8 m3/s
- Pump: Worthington 750 Ingersoll-Dresser Pumps, 30 MNI 33 rotor A
- Electric Motor: WEG 480 HP 1000 rpm
- Stub-end DN1000
To connect with master irrigation channel, use of a culvert composed of two Krah Profil pipes of DN/ID1600 mm internal diameter was determined. Depending on working flow, pipes speed can exceed 1.2 m/s, and therefore there is a possibility of soil erosion at entrance and discharge of pipes, so protection measures were defined to prevent erosion at these points.
Krah America Latina