Because there are many types of hydraulic pumps in injection molding equipment at present, the same type of pump is affected by power, speed, pressure, flow rate, metal material and other factors, making the selection of hydraulic oil more complicated. Generally speaking, HL oil can be used for low pressure pumps, and HM oil should be selected for medium and high pressure pumps.

The lubrication (anti-wear) effect of hydraulic oil on the three major pump classes is the order of vane pump > plunger pump > gear pump. The hydraulic system of the main oil pump should choose HM oil regardless of its pressure, because the contact and movement form between the blade and the stator of the vane pump is very easy to wear, and the steel to steel friction pair material is most suitable for using high-zinc HM anti-wear hydraulic oil.

HM oil and HL oil are available for low pressure plunger pumps, and zinc-containing HM oil is used for high pressure plunger pumps. However, when the plunger pump has bronze and silver plated parts, the high zinc anti-wear agent will cause corrosion wear, and the ash-free or low zinc anti-wear hydraulic oil is used for this plunger pump.

For gear pumps, HH, HL, HM oil can be used, but high-performance gear pumps should use HM oil. For combination systems such as vane pumps and other pump combinations, vane pumps should be the main choice, when the other pump is a plunger pump, the selected oil should also be accepted by the plunger pump.

Generally, HL oil can be preferred for axial piston pumps, but not for vane pumps, and high-zinc HM oil is suitable for all types of vane pumps. Ash-free HM oil is suitable for axial piston pumps with copper and silver components, as well as medium and low pressure vane pumps, but not for high pressure vane pumps. Low zinc HM oil is suitable for a wide range of medium and high pressure vane pumps, as well as for plunger pumps with copper and copper components.

Reasonable selection of hydraulic oil is only the starting point for the normal operation of hydraulic equipment. During the operation of the system, the performance changes of hydraulic oil should be detected in time to ensure proper maintenance in time, so as to extend the service life of hydraulic oil and the system and components, and avoid system failure or even accidents caused by the working medium.

The service life of hydraulic oil (that is, the oil change period) is greatly different due to the selection of hydraulic oil, the working environment and the different operating conditions of the system, and there are great differences. The selected oil is reasonable, the oil is of good quality, and the hydraulic system and hydraulic oil are well maintained and managed, so the oil change period can be greatly extended.