Hydraulic System Requirements
Hydraulic systems come in many forms—from those found in the simple hydraulic jack to the more sophisticated systems found in earth moving equipment. The system required to operate most hydraulic tools found in this catalog would require 8 gpm / 30 lpm and be capable of providing system pressure up to 2000 psi / 140 bar. This system is referred to as a Type II, as classified by the Hydraulic Tool Manufacturers Association (HTMA). But there are also 3 other classifications. They are discussed below.
HYDRAULIC TOOL MANUFACTURERS’ ASSOCIATION (HTMA) REQUIREMENTS
Hydraulic tools fall into 4 classifications, Type I, Type II, Type III, and Type RR as set by HTMA. The system requirements for powering these tools are as follows: • Type I 5 gpm ±10% / 19 lpm • Type II 8 gpm ±10% / 30 lpm • Type III 12 gpm ±10% / 45 lpm • Type RR 10 gpm ±10% / 38 lpm
Hydraulic systems should be capable of providing the appropriate operating pressure and flow for the system types noted above when measured across the tool connections. Deviation from the nominal flow rates should be no more than plus or minus 10% at a operating pressure of 2000 psi / 138 bar. This is the pressure that the tools will normally operate at which is not to be confused with the relief pressure.
Hydraulic systems should be capable of limiting the maximum pressure by using either a pressure compensating pump or a relief valve with a nonpressure compensating pump. The system pressure limiting component shall begin to control the maximum pressure at no less than 2150 psi. This is commonly known as the “cracking pressure”. The system pressure limiting component shall limit the maximum pressure to 2250 psi for a Type I, Type II, or Type III tool. The system pressure limiting component shall limit the maximum pressure to 2500 psi for a Type RR tool.
The hydraulic systems should generate no more than 250 psi / 17 bar return pressure (back pressure) at the tool when operating at maximum flow for the tool type. System conditions for this pressure are at maximum hydraulic fluid viscosity of 400 SUS (SSU) at minimum operating temperature.
The hydraulic systems should have sufficient heat rejection capacity to limit maximum oil temperature to 140° F / 60° C at the maximum expected ambient temperature. Recommended minimum cooling capacities to dissipate tool-generated heat are: Type I 3 Horsepower / 2.24 kW Type II 5 Horsepower / 3.73 kW Type III 7 Horsepower / 5.22 kW Type RR 6 Horsepower / 5.22 kW When determining cooling capacity, the intended duty cycle and the system generated heat must both be considered.
Systems should have 25 micron nominal filtration for the hydraulic fluid. Recommended filter element size is at least three times system rated flow to prevent filter bypass under low temperature start-up. FLUID: Hydraulic systems should use hydraulic fluid that has a viscosity of 130-225 SSU / 27-42 cst at l00° F / 38° C. Hydraulic fluids of petroleum base with antiwear properties and high viscosity indexes over 140 will meet recommended hydraulic fluid requirements over a wide range of operating temperatures. They should be demulsifying type to allow water to settle out of the fluid.