Hydraulic Fluids and Hydraulic Parts

Viscosity grade and fluid type: follow the machine's specification

Fluids dominate here, with parts and sensors alongside, so the fluid grade is the first decision. Hydraulic oil is chosen by ISO viscosity grade, such as ISO 15, 22, 32 or 46, where a higher number is thicker. Use the grade in the equipment manual: a fluid that is too thin lets pumps leak internally and wear, and one that is too thick responds slowly and starves the pump in the cold. The base matters too. Mineral oil is the default, biodegradable vegetable-based fluids suit environmentally sensitive sites, food-grade fluids suit equipment near food, and dielectric oils are for insulated aerial lift equipment.

Tractor fluids, pressure sensors and thread forms

Tractor hydraulic fluid is graded by SAE number, such as 10W-30 or 5W-20, because many tractors share one sump between hydraulics, transmission and brakes; it is not a general substitute for industrial oil. Pressure sensors and gauges are picked by range and signal: choose a range comfortably above working pressure, and match the output (4-20 mA, 0-10 V or a switch) to your controller. Match the thread form, commonly NPT or BSP, because those threads differ in angle and usually in pitch and do not seal reliably together.

Questions about Hydraulic Fluids and Hydraulic Parts

Can I use tractor hydraulic fluid in any hydraulic system?

Not automatically. Tractor fluids are formulated for tractors, often with additives for wet brakes and gears, and are graded by SAE number. Industrial hydraulic systems usually specify an ISO grade and an anti-wear standard, so follow the equipment manual.

What does ISO 32 or ISO 46 mean on hydraulic oil?

It is the viscosity grade: ISO 32 oil has a viscosity of about 32 centistokes at 40 degrees C and ISO 46 about 46. A higher number is thicker, and the right grade depends on the pump type and operating temperature.

Can I mix different hydraulic oils?

Avoid it. Different bases and additive packages can foam, react or lose their protection, and adding mineral oil to a biodegradable fluid undermines its biodegradability. If you change fluid type, drain and flush as the machine maker advises.