The fall/spring application of the fertilizer Anhydrous Ammonia, also known as NH3, is always a hectic time for those in the agricultural industry. The race to get the precious fertilizer in the ground is fast-paced and everyone is running like gangbusters. Every season fall/spring we field phone calls that stem from concern due to the reliability and service of ammonia hoses.
This post should clear up many questions and will provide some valuable education to you and your team. Below you will find a listing of common questions we run across throughout a season. As always, we are happy to help share our wealth of technical knowledge and experience.
Common Anhydrous (NH3) Hose Questions
Residue on NH3 Hose Exteriors
Question: At times a residue forms rings or cones all over the cover of my anhydrous ammonia hose. This residue resembles or looks like white spots.
What causes this residue to appear and what is it?
Answer: Anhydrous ammonia hoses are designed to allow a small amount of gas through the wall of the hose. This is known as pinpricking and it is a safety requirement. This allows trace amounts of NH3, to permeate through the tube. The pinpricks allow minute amounts of anhydrous ammonia to easily escape into the atmosphere through the hose cover. There is such a trace amount of anhydrous ammonia being released that it is not harmful.
A hose that has been improperly pricked will cause the cover to blister and eventually blow out - this is the same for a hose that has not been pricked at all. A hose blows out when NH3 becomes trapped between the layers in the hose, heats up, and vaporizes - thus causing rapid expansion and bursting through the hose cover.
The single drawback to pin pricking is the residue that is left on the hose and the resulting appearance that the hose is somehow defective, after use. Remember, as the anhydrous ammonia escapes through the pinpricks it comes in contact with the atmosphere and forms the white residue that many operators commonly see throughout the season. The color and consistency of the residue are affected by the amount of dust and relative humidity present in the atmosphere.
This residue does not indicate a defective hose and in no way should be viewed as a problem or unsafe situation for operators. Furthermore, it is a reminder of this built-in safety feature of the anhydrous ammonia hose and that it is, in fact, working as intended.
NH3 Hose Basketing
Question: My stainless steel braided anhydrous ammonia hose has ballooned out behind the coupling.
Why is this happening?
Answer: The symptom described above is referred to as "basketing". Basketing is the result of the thermal expansion of trapped anhydrous ammonia in the hose. By design, the hose is intended to expand in a controlled fashion when this over-pressurization occurs. Most commonly, a user will see basketing form behind the coupling - this intended consequence is meant to keep the NH3 hose from a catastrophic blowout.
Thermal expansion generally occurs when anhydrous ammonia remains or leaks out of a shut-in hose assembly and is allowed to heat up or "cook" in the sun. Extremely high pressures occur, internally, as the black hose is exposed to sunlight for extended periods.
It is highly recommended that all hose assemblies be emptied before storage and downstream valves are checked for compliance and acceptable operation regularly. Furthermore, hydrostatic relief valves should also be checked for correct operation and compliance pressures depending on state and local fire marshal requirements.
Anhydrous Ammonia Expected Service Life
Question: What is the expected service life of an anhydrous ammonia hose?
Answer: Factory-assembled NH3 hose assemblies come in three variations that each have a different service life. Each type is labeled with a removal date. Here is the life span for the different ammonia hose assemblies that we carry at Dultmeier:
Goodall New Hose Expected Service Life - When Coupled by Authorized Goodall Locations:
N1446 - Super Long Life - 10 Year
N2595 - Rifleman - 8 Year
Park New Hose Assemblies Expected Service Life - When Coupled by Authorized Parker Locations:
7262 Green Stripe - 6 Year
Maintenance and Care of Anhydrous Ammonia Hose
Recommended Anhydrous Ammonia hose maintenance and care instructions:
New Hose
- Ensure you have the correct hose. All Anhydrous Ammonia (NH3) hose will be strip branded, stating that the hose is for Anhydrous Ammonia, the working pressure, the name of the manufacturer, and the month and year the hose was made.
- Make sure the couplings are properly put on. After the hose is charged with anhydrous ammonia, check that the couplings are secure and that they have not moved.
- Ensure that the new hose is free from cuts, gouges, and imperfections. Perform a visual check of each hose in service. Run your hand down the length of the anhydrous ammonia hose, checking for soft spots.
- Never secure the coupling in a vise when attaching valves.
- Goodall highly recommends that all relief valves be replaced at the same time a new hose is installed.
- If any of the above imperfections are found to be existent, remove the hose from service immediately.
Used Hose
An anhydrous ammonia hose that is currently in service or has been carried over from the previous year:
- Applicators should remove anhydrous ammonia hoses from the nurse tank(s) before winter and store in a cool, dry place. Keep away from direct heat and any motors that are operating. The best place to store an anhydrous ammonia hose is to hang the hose in a vertical position from the shoulder of the coupling. By doing this one relieves stress on the hose. The hose will be out of the way so as not to be damaged by individuals walking on it, trucks driving over it, or anything being piled on top of it. Furthermore, the storage of anhydrous ammonia hoses indoors prevents damaging UV rays from the sun ruining the hose.
- NH3 hoses should be checked in the spring in the same manner as a new hose is inspected - this way the user ensures that an Anhydrous Ammonia hose is, in fact, an Anhydrous Ammonia hose.
- Each hose should be checked at least daily, if not each time the hose is used, to ensure proper function. Make sure to check for movement of couplings, cuts, gouges, or cracks in the cover. Check for any soft spots - this is done by running your hand down the entire length of the hose.
- Should any of the above imperfections in an anhydrous ammonia hose be found, immediately remove the hose from service.
Always remember - visual and manual inspections SHOULD BE DONE DAILY.
Don't hesitate to contact us should you have any questions. Be safe out there...
