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aNH3 Equaply® system

Accurate control of mixed gas and liquid phases is difficult to achieve. Conventional application systems do an excellent job of applying consistent amounts of anhydrous ammonia over a field. But they don’t provide equal flow to each injector knife. Heat exchangers cool the ammonia below its boiling point before entering a flow meter and control valve. With only liquid present, the valve can exert near perfect control. However, when the anhydrous goes through the control valve it loses pressure and boils, creating a mixture of liquid and gas. This mixture is difficult to be split evenly in a manifold. So distribution among the knives is random and variable.

Strip till farmers can see the effects of poor ammonia distribution. Strip till corn rows and anhydrous rows are in the same place. When distribution is unequal some rows get more vapor and less liquid. “Streaking” is then visible across the width of toolbar application. A plugged anhydrous line becomes very visible after the corn plants emerge. Conventional tillage farmers are less likely to see uneven distribution. They usually over-apply so even the rows with less ammonia have an adequate amount. Also, they often apply at a diagonal; application and planting rows don’t coincide.

Features of the aNH3 Equaply® system are:

1. A pump to boost the pressure of anhydrous ammonia coming from the nurse tank. This pump assures constant pressure where NH3 is manifolded to knives. Anhydrous can be applied consistently over a wide variation in tank pressure, even on a very cold day.
2. Orifices in lines to each injection knife. These orifices keep anhydrous ammonia as a liquid until it has been split with equality of flow between the knives.
3. A flow control system to assure that the application of ammonia is constant. Variable rate application is easy.
4. Each knife line leaving the manifold has a pressure gauge to monitor pressure. With equal pressures at all knives there are equal ammonia flows. These gauges can detect plugged lines and plugged orifices.

Description of the aNH3 Equaply® system -

Nurse Tank connection - Our system requires an Acme coupler with high flow globe valve at the nurse tank. A 1¼” anhydrous hose connects to a high flow breakaway at the inlet to the heat exchanger. For high flow rates, the use of dual tanks is necessary, particularly during cold weather. For very high flow rates we recommend that your fertilizer dealer install high flow 1¼” valves on the tank outlets in place of the usual 1” valves. Unlike Exactrix, our system doesn’t need bottom outlet tanks.

Heat Exchanger - The one and only reason for a heat exchanger is to cool the anhydrous below its boiling point. In systems without pumps, vapor makes most flow meters inaccurate. Most pumped systems such as Equaply® vapor lock when a gas phase is present. A heat exchanger condenses the gas phase and allows the pump to operate. Once pressure has been increased by the pump, the anhydrous is much below its boiling point.

Equaply® uses specially ported Hiniker heat exchangers for increase flow. Our larger flow models have two heat exchangers in parallel.

A basket strainer after the exchanger catches solids from the nurse tank. Another strainer after the pump collects particles which could clog an orifice.

A hydrastat protects against over pressurization by solar heating of a standing, charged system.

All heat exchangers are not created equal. The method of providing a coolant stream of anhydrous to the heat exchanger can make or break the equality of distribution to the knives. Equaply® has two different methods of cooling, each with its own advantages. Normally for a corn system we sent the anhydrous for one row to a heat exchanger and then to a knife. This is the only anhydrous going to that knife and is regulated to be equal with the other knives.

For small grain crops with many openers, we send a small, independent stream of anhydrous to cool the exchanger. It is only 1% to 2% of total flow and is completely vaporized. The vapor goes to a large steel tube on one of the openers as an extra amount.

Pump- The pump assembly is perhaps the most important part of our system. We use a Hypro centrifugal pump because it does not have surges like piston pumps. A hydraulic motor drives our pump. A special hydraulic valve turns the pump motor on and off for each row.

Perhaps the most important reason for a pump is equal distribution. The pump keeps anhydrous as a liquid until it can be split at manifolds. To understand what happens with a mixed liquid/gas stream it helps to have transparent pipes. The Red Ball rotameters in our prototypes were those clear pipes. During startups and when there were malfunctions one could see the vapor as it went through the rotameters. When vapor first appeared in the system it would exit in the first rotameter in a bank of four. Increasing amounts of vapor then reached subsequent rotameters. Vapor takes the easiest path. For example, if there is a circular manifold on a toolbar which tilts down to the left on a hillside, vapor will tend to go out of hose barbs which are up and to the right.

For custom applicators, the most important reason for a pump is the ability to apply at full rate when it’s cold. Conventional systems often slow down during late Fall and early Spring.

Flow measurement and control - Equaply® has a Hiniker flow sensor and Hiniker servo valve. Signals from the flow sensor go to a controller which then operates the servo valve. With our system the flow sensor has maximum accuracy because the it sees only liquid. Equaply® can interface to the AgLeader Insight or John Deere Greenstar

Manifolds & Orifices - After the servo valve, we split flow to three manifolds in the larger systems. Each manifold is controlled by an electrically operated valve. Electric valves allow the option of turning off one or two wings at the edge of a field.

The range of rates possible with a given set of orifices is not great as we would like. This is particularly true with large seasonal temperature differences. Nurse tank pressure can easily range from 50 psig to 150 psig. Fortunately the TeeJet® orifices in the Equaply® system are quickly changed. If large rate variations are necessary as with custom application, we can widen the range using Impellione manifolds.

Side dress applications typically skip a row; a 16 row toolbar will have 15 knives. In that instance, we can supply orifices for the two end rows that have 0.5, 1.5 or 2 times the rate of interior rows.

Flow verification - The Equaply® system uses a pressure gauge per row to verify row to row equality of flow. When upstream pressure and downstream pressures are the same with orifices of equal size, flows are the same. Pressure gages connect to downstream from the knife orifices. They are mounted on a gauge tree or panel between the tractor cab and the toolbar. One can tell at a glance if a knife is plugged (high pressure) or an orifice is plugged (low pressure).

ISSUES INVOLVING INJECTION OF ANHYDROUS

There is a lot of uncertainty as to how much anhydrous can be injected with the currently available openers and knives. Application rates go from 30 lb. of N per acre at 4 mph for wheat to 280 lb. of N at 10 mph for corn.

We believe that “mole” knives made by Hi-Pro Mfg. of Watseka, Illinois can incorporate the highest rates. But many farmers can’t use mole knives, either because of the horsepower requirement or because of soil disturbance. Various mid row banders and disk openers can be used, but they are probably not as effective as “mole” knives at the highest rates. Dawn Equipment and Yetter have some new designs which are worth considering. The trick is incorporate as much of the vapor as possible since it tends to blow away. The correct method of tillage at the knife opening is the key. While not all types of tillage are beneficial to incorporation, some are.

There are a myriad of choices available including attachments to seeders and planters. While we can’t quantify the differences, it is generally true that the more aggressive the tool, the more anhydrous it can incorporate. Also, if you are applying when planting, it is necessary to keep the anhydrous away from the seed.

While we don’t give advice on tool selection, we can provide even flow among the injectors on your applicator. You install the injector and we’ll get anhydrous to it, evenly, and at the desired rate.

We are often asked about the effect of placing orifices at the ends of knives. There has been some misunderstanding about what happens at these orifices. Some believe that this orifice location creates a high velocity stream of liquid anhydrous at the exit of the orifice.

Actually, the stream inside the orifice just before the exit is probably all liquid. However, the instant the liquid exits the orifice it becomes a mixture of liquid and gas. The reason for this is that anhydrous boils at the new lower (atmospheric) pressure so that it can cool to its new saturation temperature of -28° F. For example, the temperature of the anhydrous in the nurse tank may be 50° F at a pressure of 75 psig. As anhydrous exits the orifice, it is no longer under 75 psig pressure so it assumes a new equilibrium condition of atmospheric pressure and the resultant temperature of -28° F. The stream of anhydrous exiting the orifice is from 10% to 20% gas, dependent on the temperature in the nurse tank.

Even at small pressure drops, the volume of vapor dwarfs the liquid volume. CLICK HERE TO SEE A DISCUSSION AND GRAPH ABOUT RELATIVE VAPOR AND LIQUID VOLUMES.

There is a lot of discussion as to whether the stream of anhydrous liquid and gas can cut into the ground. This may depend on the soil and soil moisture. It is highly unlikely that the typical rates for anhydrous do much cutting.

One possible problem with bottom mounted orifices is the velocity of the vapor portion of the anhydrous stream exiting a very small orifice. Since velocity increases with decreasing exit hole size, tiny orifices impart a very high velocity. This may be enough to cause the vapor to “bounce” more from the point of impact.

In a 1962 Douglas Johnston patent, assigned to John Blue Company, pressures of over 3000 psig were used to obtain exit fluid velocities above 700 feet per second. The patented device probably did cut a groove and inject anhydrous into the soil at these conditions. However, no current pumped system (including Equaply®) operates at anywhere near this pressure.

One other problem with having orifices at the ends of the injectors is the elimination of a pressure tap to measure flow through individual lines. For gauges to sense flow, the pressure after to orifice must be considerably greater than atmospheric.