NH3 Manifolds

Agriculture.com Staff 03/05/2009 @ 9:00am

The manifolds used to divide the flow of anhydrous ammonia (NH3) on application equipment didn't change much until the mid-1990s. They were basically hollow chambers with outlet holes around the perimeter. They were rugged, simple, and cheap. Unfortunately, however, they didn't work particularly well.

Tests conducted at Iowa State University (ISU) showed that some of the outlets on these manifolds released two to four times as much nitrogen as other outlets.

In a nurse tank, anhydrous ammonia is a liquid under pressure. As this liquid NH3 moves through the system and into the manifold, the pressure drops, and some of the liquid converts to gas. Therein lies the problem. It is virtually impossible for hollow-chamber-style manifolds to meter a combination of liquid and gas. Vapor doesn't carry much nitrogen, and, in old-style canister manifolds, it seems to get in the way during the metering process. The vapor blocks the flow of liquid.

You could be applying exactly the intended rate per acre but still be misapplying it because of nonuniform distribution across the width of the applicator.

Port-to-port variation is more of a problem at relatively low rates - like those used for wheat or sidedressing corn - than it is at higher rates.

Over the past 15 years, several companies have developed new and much more sophisticated manifolds that enable you to apply NH3 more uniformly.

Some manufacturers of NH3 applicators install manifolds at the factory. Others leave it up to distributors and dealers to install the manifolds. That makes it easier for farmers and fertilizer dealers to order the manifold that they want and related items such as splitters (see the chart).

Pictured right: NH3 coming into the bottom of the manifold spins a cone-like needle that has grooves on its face. That distributes the nitrogen uniformly through the ports.

The manifolds used to divide the flow of anhydrous ammonia (NH3) on application equipment didn't change much until the mid-1990s. They were basically hollow chambers with outlet holes around the perimeter. They were rugged, simple, and cheap. Unfortunately, however, they didn't work particularly well.

One of the newest manifold designs is the Impellicone Flow Divider manufactured by CDS-John Blue. The initial design came out of research at ISU by Paul Boyd, Mark Hanna, and others.

Continental NH3 Products ushered in the era of precision manifolds when it introduced the Vertical Dam Manifold about 15 years ago. The company continues to make that version. Three years ago, it added a new, more compact, version to the line of Vertical Dam Manifolds.

There are three models of the Squibb-Taylor Equa-Flo. The model shown in the picture below is the Equa-Flo Junior, which has 21 outlets. The Sweet 16 model looks the same, except it has 16 outlets.

For years, pipe tees were used to divide the flow of NH3 when more than one manifold was used on an applicator. But testing has shown that it is important to make sure that the NH3 headed to the manifolds is divided equally.

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