Automatic and Remotely Controlled Shutoff for Direct-Flow Liquid Manure Application Systems
Table of Contents
Direct-flow liquid manure application systems are gaining popularity as a time efficient means of transferring and applying liquid materials from the storage tank to the field site. As with any system pumping liquids under pressure, equipment failure can occur from time to time. In many cases, the ability to quickly turn off the pumping system can dramatically reduce the volume of manure that could be released to the natural environment should an equipment failure occur.
This Factsheet outlines the provisions in the Ontario Regulation 267/03, as amended, of the Nutrient Management Act, 2002 (the Regulation) and the Nutrient Management Protocol (the Protocol) that apply to the operation of manure pipelines and dragline manure spreading systems.
A direct-flow liquid manure application system involves a pump and pipeline that move manure from the storage tank or transfer tank to the field on which the manure is being applied. The system usually operates at high pressures, that are 1035 KiloPascals (KPa) or 150 pounds per square inch (psi) or greater, and high flow rates of more than 2,270 litre per minute (lpm) or 500 gallon per minute (gpm).
Pumps are usually powered by a tractor PTO or stationary engine at the manure tank. From the pump, the manure flows into a 10-20 cm (4-8 in.) diameter pipeline (either solid pipe or hose) that delivers it to the field. Once the pipeline reaches the field, the pipe diameter reduces to an 8.25-12.7 cm (3.25-5 in.) soft flex pipe or hard hose that is dragged behind a tractor.
The manure flows into the application header on the back of the tractor, and is either surface broadcast or injected at high flows (but low pressure, to reduce pumping costs).
Figure 1. A direct-flow application unit. (Photo courtesy of Aerway)
Manure can be pumped over very long distances. A larger scale system (with a 300-hp tractor and pump at the storage tank) can pump manure up to 3.2 km (2 m). These long distances make monitoring more difficult and the higher pumping rates can make the consequences of an undetected failure catastrophic.
Section 50 of the Regulation requires a maximum time delay of one minute from the time of detecting a failure to complete shutdown of the pump. One minute may not seem like much time, but at the large flow rates of typical direct-flow systems, a concentrated flow under pressure can have disastrous effects.
Usually during a pipeline failure the discharged liquid will quickly pool and form a flow heading for the closest low spot - possibly a ditch, catch basin or waterway.
If it took 10 minutes to shut down the system, a 6-inch pipeline with a pumping rate of 2273 lpm (500 gpm) could release 22,730 L (5,000 gal.) of manure to the natural environment.
In some cases, the field may be too far away from the site of the permanent storage tank for a pipeline delivery system to be practical or feasible. In this case, the alternate method for delivering liquid manure to the field edge involves highway tanker trucks and a temporary nurse tank/transfer tank in the field. From there, a pump system will supply the dragline application system in the field.
Most farmers cannot justify such a large investment in equipment for their operation, but this system is commonly used by custom applicators applying liquid manure or non-agricultural source materials. Usually the transfer tank/nurse tank contains at least 1.5 truck-volumes [typically 27,000 - 45,000 L (6-10,000 imp gal.) per truck], and is continually replenished as tanker trucks arrive at the field site. Depending on the site, liquid materials are transferred from the highway tanker truck to the nurse tank/transfer tank by pumping, and in some cases by gravity.
Careful siting of the temporary storage tank in relation to wells and waterways is critical to minimize the risk in the event of an equipment failure.
Section 50 of the Regulation is very clear about the requirements for operators of such systems. In all cases, whether one or two people are operating the system, the operator(s) must have full view of the area of land to which the materials are being applied (the drag hose, pumping unit, supply lines, etc.). They must also have the capability to shut down the entire system in less than one minute once a problem has occurred.
Here is a summary of the requirements found in section 50 of the Regulation.
A recommended component for any spreader unit is an on-board, accurate and reliable flow meter. The flow meter is mounted on the application unit before the distribution unit (see Figure 2b) and a display (see Figure 2a) can be mounted in the tractor so the operator can easily monitor the rate while driving down the field. An observant operator will be able to spot even small changes in flow that may indicate potential leaks or other problems in the system, and take appropriate action depending on the situation. The flow meter has the added benefit of increasing the efficiency of the spreading operation by ensuring that the desired application rates are met if the ground speed is adjusted.
Figure 2a. A manure flow meter on toolbar. (Photo courtesy of Nuhn Equipment)
Figure 2b. A digital display unit in the tractor cab. (Photo courtesy of Nuhn Equipment)
At present, there are no other reliable alternatives on the applicator or other locations to detect equipment problems. Manure consistency varies widely as it is being pumped, and the pressure changes that occur would be misleading as to the state of the system and any possible failures. Therefore, relying on a pressure gauge for leak detection is not advisable.
Starting and stopping equipment must consist of a device that slows down the pumping system first at a fairly gradual rate before shutoff valves can be used. The goal is to prevent excess pressure problems from developing in the delivery system, i.e., the water hammer effect caused by sudden opening or closing of valves when the system is under pressure.
An onboard radio controller is recommended to manage a direct-flow system efficiently. The controller sends a digital signal to a receiver (see Figure 3) at the manure pump (this is not a failsafe device) that controls the throttle. The tractor driver operating the application equipment is in complete control at all times.
The simplest system has three buttons on the controller.
#1 will idle the pump down to allow the tractor applicator to turn around at the end of the field, and other maneuvering where low flow is required
#2 will speed the pump up as the tractor initiates spreading again
#3 is a kill button that shuts down the pump at the storage tank (emergency situations)
A failsafe device is also available that continuously sends/receives a signal from the tractor to the pump and back. There is an audible send/receive signal at each end to notify operators that the system is functioning. If for any reason the signal is not received, the pump will automatically shut down.
Figure 3. Receiving unit controlling the pump engine speed. (Photo courtesy of Vanden Bussche Irrigation)
In some cases the failsafe warning signals can create interference. For example, an auto send or receive signal can delay the response of the operator sending a kill or slow pump signal.
Manure Spills from Direct-Flow Systems
Even when equipment is in good working order and used properly, accidents can happen and spills can occur.
Some examples of spills include:
The following "best practices" are recommended:
The Regulation requires you to have a contingency plan for all manure handling operations. The purpose of a contingency plan is to minimize the potential effects from a spill, such as water contamination and fish kills. Accidents can happen, and if a spill does occur you need to know what actions to take. Manure spills can be costly and difficult to clean up.
By having a contingency plan in place and acting on it when required, you're practicing due diligence. You're doing all you can to minimize the environmental effects caused by a spill, and minimizing the potential cleanup costs and liability associated with a spill.
Training and Certification
Section 107 of the Regulation states that a custom applicator of prescribed materials is required to have a business licence by December 31, 2005, and persons who are employed by a custom applicator to apply prescribed materials require a nutrient application technician's licence by December 31, 2006. Farmers spreading manure from their own operations do not require training under the Act. However, anyone spreading manure is advised to take the training when available.
Liability insurance is an important consideration for anyone spreading manure. Typically, farmers have blanket coverage under any farm insurance policy. It used to be that people spreading manure were either farmers or custom operators. Now, this distinction is becoming blurred as larger farms may be moving manure over municipal roads for greater and greater distances.
Anyone spreading manure needs to meet with their insurance broker or agent and clearly indicate what the manure spreading entails, whether it is done on an adjacent property or at much greater distances by pipeline or trucking. Insurance premiums will be adjusted to take account of the risk involved, but coverage will be current and complete.
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