Connecting Pressure, Flow and Your Overall Efficiency | by Nicole Alvarez

This piece was written for and published by Senninger Irrigation, and reprinted with permission.

Our team has traveled all over the USA and across the globe and noticed two strange things when it comes to pressure regulation: some growers will tell you that pressure regulation is the best way to save water and energy, while others will claim pressure regulation is nothing but a waste of time and money unless you have sloped fields.

We’ve been highlighting the importance of pressure regulation for years but regulation has never been as important as it is now with drought conditions in numerous areas and diminishing aquifer levels. That’s why we’ve created a quick pressure regulation FAQ list to help explain not just how a regulator works, but why they’re needed and how you can tell if yours is working.

How does a pressure regulator work? 

The basic function of a pressure regulator is to limit excessive and varying inlet pressures to a constant outlet pressure. This is done to maintain the desired performance of a sprinkling device.

Pressure regulators accomplish this by automatically modulating their area of opening. By changing the area of opening as upstream pressures fluctuate, pressure loss through the regulator changes proportionally. This allows them to maintain the downstream pressure at a relative constant.

Why do I need pressure regulators?

No matter what type of irrigation machine you have, correct pressure is essential for optimum distribution uniformity and proper flow through emitters. Crops need the right amount of water at the right time and pressure regulators ensure this need is met.

Sprinklers are made to operate within a specific range of flows and pressures. They’ll maintain their application pattern and adequate droplet size as long as they can operate under normal conditions. If these conditions are altered, their application pattern will be affected and you could easily run into uniformity issues, over or under watering, and irregular crop growth.

What causes pressure deviations?

Every irrigation machine will experience some sort of pressure fluctuation. The most common reasons for pressure fluctuations include:

• Elevation changes in a field 
• Pressure loss through pipe fittings 
• End guns cycling on and off 
• Cycling of various irrigation zones and valves 

Do I need a pressure regulator with flat land?

Yes! Your system pressure can change due to the various causes listed above and more. Elevation is just one of the many things that cause pressure fluctuations.

No matter what degree of elevation you have, controlling flow and pressure is essential for machines operating at lower pressures. For example, if a system operating at 30 psi (2.07 bar) experiences a 10 percent flow variation, that will result in a 6 PSI (0.41 bar) pressure variation. That flow variation can adversely impact sprinkler performance and ultimately yields.

How does pressure affect my flow rate?

The operating pressure of an irrigation machine always affects the flow rate. Higher pressures increase flow along any pipe. As that flow increases, water velocity increases as well. This results in pressure decreasing downstream due to friction loss. When water is rushing through a pipe at high velocities, the interior walls of the pipe create friction against it, which causes pressure loss.

How long does a pressure regulator last?

Senninger pressure regulators are built using high-impact engineering grade thermoplastics and are 100 percent water-tested at our facilities. However, like sprinklers, they do not last forever. Irrigators are encouraged to check their pressure regulators at least every three years. Factors that can shorten a pressure regulator’s lifespan include:

• Unflushed chemicals in the pipeline 
• Suspended abrasive materials in the water 
• Long operating hours 

How can I tell if a pressure regulator is bad?

Issues such as dry spots near the head, overwatering in a doughnut shaped pattern, uneven crop growth and streaking in the field and misting are all common signs of pressure regulator malfunctions. Using yield maps and even aerial imaging may prove helpful in identifying issues.

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Senninger® Irrigation A Valley® Irrigation Authorized Provider Founded in 1963, Senninger Irrigation, Inc. is one of the world’s leading manufacturers of agricultural irrigation products. These include sprinklers, spray nozzles and pressure regulators. Senninger products are made in the United States and sold worldwide through qualified dealers. Products can be found in farms, nurseries, greenhouses, open fields, as well as mining operations. Senninger is dedicated to low pressure, high performance irrigation solutions.  This post was written by Nicole Alvarez, the technical writer for Senninger.

End-of-Season Checklist | by Nicole Alvarez

This piece was written for and published by Senninger Irrigation, and reprinted with permission.

This year’s irrigation season is ending for many farmers across the western hemisphere. Several are already working in their combines and reaping the fruits of their labor.

It’s tempting to forget about pivots and just focus on getting crops out of the field and into a bin during harvest. Yet this is one of the best times to evaluate sprinkler packages to make sure your pivots are in top shape and ready for another growing season. This check helps prevent unwanted surprises and helps ensure crops will be irrigated according to schedule. 

We suggest you take a look at this end-of-season checklist for a quick overview of the things you should take care of:

1. Get Your Sprinkler Package Chart
Find a copy of the sprinkler package chart. This contains the location of all sprinklers and pressure regulators along the center pivot. It will also include detailed information for each sprinkler’s nozzle size or flow rate. You’ll need it a little later when you’re walking along your pivot verifying sprinkler location and noting potential issues.

2. Flush Your System
Check the main pipe running from the well to the pivot itself for any potential leaks. Next, remove the sand trap on your pivot and flush the entire system for several minutes. (Make sure the system is not under pressure when you remove the sand trap!) This will flush out any debris or foreign materials that may plug the sprinkler heads or pressure regulators.

Sprinklers on the first few spans are particularly prone to plugging due to their smaller nozzles size so we recommend a good system flush at least once a year.

3. Check System Pressures
Using a pressure gauge, verify your pressure at the pump, pivot point, and at the end of the pivot. Make sure you operate the center pivot  at the design pressure.

Pressure should be at least 5 PSI above the pressure regulator rating. If you have a 10 PSI pressure regulator, your pressure gauge should read a minimum of 15 PSI. Compare the numbers to the design pressure in your sprinkler package chart to make sure everything matches.

Note: It’s best to check pressure with the pivot parked in the same location!

4. Check System Flows 
Sometimes farmers discover that the nozzles along each span do not correspond with what the printout indicates. This is why it’s important to keep your chart on hand

Check the system flow rates by comparing each sprinkler to the corresponding outlet on the chart. Each sprinkler’s nozzle and flow rate should match the number on the sprinkler package chart. If the nozzles are wrong, you may be over or under watering.

If you have a flow meter, verify that it’s taking the correct measurements. Solving issues like a flow meter not receiving a signal or unstable flow rates might require a little detective work on your part using your flow meter installation and troubleshooting guide.

5. Evaluate Sprinkler’s Wetted Patterns
Visually inspect all sprinklers for potential damage, lost parts, and for consistency and uniformity in their distribution patterns. Assure that sprinkler overlap is sufficient.

Disassemble any sprinklers with poor distribution patterns or overlap and check for plugging or defective parts. Sprinklers can wear out and will stop rotating – or rotate out of control. Check sprinkler deflector pads to ensure they do not have a build-up of materials that could affect the distribution pattern or flow rate. You might also notice kinked or damaged drop hoses that need fixing.

Sprinkler issues can result in extra water being applied is some areas and insufficient water being applied in others. This affects water application uniformity and can reduce yields.

According to the University of Nebraska-Lincoln, depending on the location of the problem along the pivot pipeline, the economic impact of a single sprinkler problem can be significant in the amount of yield reduction it causes. This is especially true for sprinklers on the outer 30 percent of the center pivot.

If You Notice Something’s Off….
Hopefully, you won’t notice any runoff or a lack of uniformity while inspecting your sprinklers, but if you do:

• Go back to your sprinkler package chart and check the nozzle sizes and placement of sprinklers that are showing problems – they may be incorrectly installed.
• Consider evaluating your tillage practices to enhance infiltration and decrease runoff.
• Evaluate your system and consider whether a new sprinkler package would be beneficial. Select a sprinkler device that irrigates with low application intensity over a large diameter, and creates relatively large droplets that can combat wind-drift and evaporation.
• If you want to renozzle your system, check with your local power company for possible incentives when you switch to lower pressure systems.

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Senninger® Irrigation A Valley® Irrigation Authorized Provider Founded in 1963, Senninger Irrigation, Inc. is one of the world’s leading manufacturers of agricultural irrigation products. These include sprinklers, spray nozzles and pressure regulators. Senninger products are made in the United States and sold worldwide through qualified dealers. Products can be found in farms, nurseries, greenhouses, open fields, as well as mining operations. Senninger is dedicated to low pressure, high performance irrigation solutions.  This post was written by Nicole Alvarez, the technical writer for Senninger.