SureFire Ag products employ pressure sensors in various places as a way to give you more information to ensure your application and use is in line with what you need. These sensors do not affect application, but rather, give you the information you need to determine if a change should be made to orifices or metering tubes. It is important for the sensors to provide correct readings; if you ever find the pressure sensor on your SureFire product not working use these steps to troubleshoot:
- Be sure pressure sensor is plugged into the correct pressure sensor connector. Multi-product systems will have more than one pressure sensor connector. Some single-product systems may have connectors for two pressure sensors. Make sure the pins where the harness screws on to the end of the sensor have not been bent.
- Be sure pressure sensor is set up and calibrated in the display. When entering the calibration number it is best to unplug the sensor so it will set the 0-PSI voltage correctly. The SureFire 3-wire sensor which is used on most systems is a 0 to 5 volt, 100 PSI sensor. The calibration for this sensor is 50 mv/PSI. The SureFire Commander II controller uses a 2-wire, 4-20 milliamp sensor. There is no setup calibration to do on these.
Setup > System > Check the box for Pressure Sensor 1 > Calibrate Pressure Sensor > Voltage-based Calibration > 50 mv/PSI.
- There should be a green LED light on the end of the pressure sensor. This may be difficult to see in daylight. The sensor needs 12 v. Check between pins B&C on the pressure connector on harness that connects to the pressure sensor. If there is no voltage here, check the voltage between pins 1 & 2 on the 12-pin connector labeled PUMP.
What is the pressure reading telling me?
On most systems, the pressure sensor is merely an information tool. It has nothing to do with the application control process. The pressure reading lets us know if we should change orifices or metering tubes. It is important to understand what a pressure sensor tells us. The pressure reading is simply an indication of how hard the system has to push to get the product through the system. The pressure will be what it is depending on how hard it has to push to get the amount of liquid you are moving from the pressure sensor to where it leaves the system. The pump will not build pressure beyond what it takes to push the amount of liquid you want through the system. This pressure will depend on the product itself, the volume (gal/min) you are moving and how much restriction there is to that flow. The orifice or metering tube will be the primary restriction, but it is possible that other parts of the system may add to the total pressure. Opening or closing a recirculation valve will not change the pressure that is needed to push the product through the system.
The pressure a system develops will be less (possibly much less) with water than it will be with a fertilizer product. When testing with water, it is common for the normal speed and target rate to not create enough pressure to open all the check valves. Some rows may not flow. The system may surge as check valves alternately open and close. You may need to run a rate that is two or three times as much to get the same pressure that you will have with fertilizer.
What pressure is “too low”?
You need enough pressure to open the check valves. If the pressure is too low, some check valves will open before others, so that some rows may be flowing while others are not. With 4 lb check valves, we like at least 8 PSI. With 10 lb check valves, we like 15-20 PSI.
What pressure is “too high”?
There are a few products that may have flow characteristics that are better at lower rather than higher pressures. With most products that is not a concern.
The plumbing components of a SureFire system are rated at 100 PSI or above. On an electric pump system, the pump capacity decreases as the pressure increases. Our standard Tower pump has an internal 70 PSI bypass. With an electric pump, we like to see pressures from 10 to 30 PSI. If the pump has the capacity to hit the rate at higher pressures, there is not a problem with doing that, but for long-term operation it would be best to switch to a larger orifice or metering tube.
The SureFire PumpRight hydraulic pump has the ability to pump up to 290 PSI. SureFire plumbs these with a 100 PSI pressure relief valve (PRV) so that plumbing components will not be damaged if high pressure develops. Typical operating pressures with hydraulic pumps will be 20-60 PSI, but the pump will work fine at 80-90 PSI if that is needed. If continually running in that high range, consider a larger orifice or metering tube.
Lower pressure will not necessarily reduce the velocity of the output stream at the row. Conversely, higher pressure will not necessarily increase the velocity of the output stream at the row. The velocity of the output stream is determined by the volume of the flow and the size of the opening at the output. Changing the pressure by changing an orifice or metering tube upstream from the outlet will not affect the velocity of the output stream if the flow volume remains the same.
Options if pressure is too high with orifices: Use a bigger orifice. Slow down. If pressure is too low, use a smaller orifice.
- Options if pressure is too high: (The pressure in a metering tube is related to the viscosity of the product. Many products change viscosity as the temperature changes. A product will have a higher viscosity (and therefore higher pressure) on a cold morning than it will on a hot afternoon.)
- Use a larger diameter tube.
- Shorten the tubes that are on now.
- Slow down.
- Options if pressure is too low:
- Switch to a smaller diameter tube.
- Use a longer tube.
LiquiShift and the pressure sensor:
On a SureFire LiquiShift system, the pressure sensor IS a vital component of the operating system. The voltage from the pressure sensor is used to determine which valve or valves are open at any given time. This will change as you have speed and/or rate changes across the field.