NEWS | Aug. 3, 2021

Patriot: Contaminated Hydraulic Fluid Can Cause Faults

Patriot missile firing
Photo by Jason Cutshaw

Dear Editor,
The Patriot system is deployed worldwide and operates in all types of conditions from hot and dry to moist and freezing. Under these conditions, the hydraulic system can become contaminated by either particles or moisture.
The Patriot’s IETM 9-1430-1600-14&P (Mar 19) offers limited troubleshooting procedures for hydraulic fluid flow. Here are some tips to prevent hydraulic fluid contamination from particles:
  • Keep the container lids, spouts and funnels used to transfer fluid clean.
  • Plug valves and hoses when disconnected.
  • Wipe down and clean the end of the hydraulic hose with a lint-free cloth before reconnecting it.
  • Replace grommets or O-rings when replacing the filters.
Whenever there’s a major change in temperature, chemical containers (the 5-gallon cans to 55-gallon drums of hydraulic fluid) “breathe” and can build up moisture over time. Leaving a container open or loosely covered for a short period of time can have the same effect.
The main thing to remember is, if you can’t keep fluid in a temperature-controlled space, only stock what you’ll need. The simplest solution would be a completely-enclosed POL storage connex. Although it offers limited protection, it keeps fluid containers from direct sunlight and heat, especially in theaters of operations where the direct heat of the day rapidly changes to cooler weather at night. The best solution is for units to have access to or procure a storage container that offers A/C or dehumidifying capabilities.

Hydraulic fluid contamination can be the root cause for minor faults that can lead to larger component failures. In the case of the antenna mast group (AMG), a detailed lube order for the AMG that includes annual filter replacements is found on Page 3-1 of TM 11-5985-368-12&P (Oct 83, w/Ch 5, Sep 88).

Some of the filters are identified by part number in the TM, but these NSNs are your best options:
  • Filter element, NSN 4330-01-182-3579 
  • Filter, NSN 2940-01-150-9593
When the hydraulic system isn’t working right, it’s a good practice to inspect the filters first, prior to other diagnostics.
CW3 Robert T Brower
Letterkenny Army Depot, PA
Editor’s note: Thanks for filtering this helpful information to PS, Chief Brower.