Main hydraulic valve block leaks on wing-fold planters, multifold spray booms or auto-depth tillage tools can be frustrating to diagnose but are normally easy to repair.
Slow leaks can be pinpointed by thoroughly cleaning and drying the area of the leak with contact cleaner or carburetor cleaner. Then you can toss a handful of planter talc on the suspected fitting or valve. If you operate the machine’s hydraulics several times, even the smallest, slowest leak will show up as a small area of discolored talc.
It’s important to use the correct design and type of O-ring during repairs. Types and chemistries of O-rings are not interchangeable. There are two designs and multiple rubber chemistries of O-rings used with agricultural fluid fittings.
Flat-face O-rings are designed for use with O-ring face seal (ORFS) fittings, which have an O-ring groove machined into the flat end of one side of matched fittings.
- Always lubricate a flat-face fitting’s O-ring during installation to prevent galling the O-ring when the fitting is tightened.
- During installation, the nut on a flat-face fitting should initially tighten easily, then rapidly increase and reach final torque in one-quarter to one-half turn. A slow increase to final torque indicates a pinched or out-of-place O-ring.
Standard O-rings are used on straight-thread O-ring fittings, which come with a metal flat washer, hex nut and an O-ring preinstalled on the fitting.
- To install a straight-thread O-ring fitting, back the nut and flat washer away from the O-ring on the fitting.
- Install the male-threaded end of the fitting into the port of the hydraulic component being repaired until the fitting is hand-tight against its washer and O-ring.
- If the fitting is a 45-degree or 90-degree fitting that must be aligned in a specific orientation, rotate the fitting no more than one revolution back from hand-tight to allow alignment.
- Once properly oriented, tighten the fitting’s nut to press the flat washer against the O-ring to both seal the fitting and lock it into alignment.
Standard-style nitrile O-rings are made of acrylonitrile and butadiene and used in hydraulic and fuel systems. They are often marketed as NBR or Buna O-rings.
Standard-style fluorocarbon rubber O-rings, commonly labeled Viton, are often used in the wet systems on crop sprayers. They meet the same pressure and temperature standards as nitrile O-rings, but they are also designed to withstand caustic chemicals.
Colors often indicate the performance standards of O-rings:
- Black can be nitrile or Viton.
- Brown O-rings are Viton.
- Rust-red O-rings are often used in low-pressure air systems on planters and air seeders and are not recommended for use in high-pressure systems.
