In general, valves, cylinders and pumps have female threaded bosses for the fluid connection, and hoses have female ends with captive nuts. A male-male fitting is chosen to connect the two. Many standardized systems are in use.

Fittings serve several purposes:

-To bridge different standards; O-ring boss to JIC (hydraulic), or pipe threads to face seal, for example.
-To allow proper orientation of components, a 90°, 45°, straight, or swivel fitting is chosen as needed. They are designed to be positioned in the correct orientation and then tightened.
-To incorporate bulkhead hardware.
-A quick disconnect fitting may be added to a machine without modification of hoses or valves

A typical piece of heavy equipment may have thousands of sealed connection points and several different types:

-Pipe fittings, the fitting is screwed in until tight, difficult to orient an angled fitting correctly without over or under tightening.
-O-ring boss, the fitting is screwed into a boss and orientated as needed, an additional nut tightens the fitting, washer and o-ring in place.
-Flare seal, a metal to metal compression seal with a cone and flare mating.
-Face seal, metal flanges with a groove and o-ring are fastened together.
-Beam seal, a costly metal to metal seal used primarily in aircraft.
-Swaged seals, tubes are connected with fittings that are swaged permanently in place. Primarily used in aircraft.

Elastomeric seals (O-ring boss and face seal) are the most common types of seals in heavy equipment and are capable of reliably sealing 6000+ psi (40+ MPa) of fluid pressure.

Hydraulic hose is graded by pressure, temperature, and fluid compatibility. Hoses are used when pipes or tubes can not be used, usually to provide flexibility for machine operation or maintenance. The hose is built up with rubber and steel layers. A rubber interior is surrounded by multiple layers of woven wire and rubber. The exterior is designed for abrasion resistance. The bend radius of hydraulic hose is carefully designed into the machine, since hose failures can be deadly, and violating the hose’s minimum bend radius will cause failure. Hydraulic hoses generally have steel fittings swaged on the ends. The weakest part of the high pressure hose is the connection of the hose to the fitting. Another disadvantage of hoses is the shorter life of rubber which requires periodic replacement, usually at five to seven year intervals.

Hydraulic pipe is used in case standard hydraulic tubes are not available. Generally these are used for low pressure. They can be connected by threaded connections, but usually by welds. Because of the larger diameters the pipe can usually be inspected internally after welding. Black pipe is non-galvanized and suitable for welding.

Hydraulic tubes are seamless steel precision pipes, specially manufactured for hydraulics. The tubes have standard sizes for different pressure ranges, with standard diameters up to 100 mm. The tubes are supplied by manufacturers in lengths of 6 m, cleaned, oiled and plugged. The tubes are interconnected by different types of flanges (especially for the larger sizes and pressures), welding cones/nipples (with o-ring seal), several types of flare connection and by cut-rings. In larger sizes, hydraulic pipes are used. Direct joining of tubes by welding is not acceptable since the interior cannot be inspected.

Filters are an important part of hydraulic systems. Metal particles are continually produced by mechanical components and need to be removed along with other contaminants.

Filters may be positioned in many locations. The filter may be located between the reservoir and the pump intake. Blockage of the filter will cause cavitation and possibly failure of the pump. Sometimes the filter is located between the pump and the control
valves. This arrangement is more expensive, since the filter housing is pressurized, but eliminates cavitation problems and protects the control valve from pump failures. The third common filter location is just before the return line enters the reservoir. This location is relatively insensitive to blockage and does not require a pressurized housing, but contaminants that enter the reservoir from external sources are not filtered until passing through the system at least once.

Also known as tractor fluid, hydraulic fluid is the life of the hydraulic circuit. It is usually petroleum oil with various additives. Some hydraulic machines require fire resistant fluids, depending on their applications.

In addition to transferring energy, hydraulic fluid needs to lubricate components, suspend contaminants and metal filings for transport to the filter, and to function well to several hundred degrees Fahrenheit or Celsius.

Hydraulic pumps supply fluid to the components in the system. Pressure in the system develops in reaction to the load. Hence, a pump rated for 5,000 psi is capable of maintaining flow against a load of 5,000 psi.

Pumps have a power density about ten times greater than an electric motor (by volume). They are powered by an electric motor or an engine, connected through gears, belts, or a flexible elastomeric coupling to reduce vibration.

Common types of hydraulic pumps to hydraulic machinery applications are;

-Gear pump: cheap, durable, simple. Less efficient, because they are constant displacement, and mainly suitable for pressures below 20 MPa (3000 psi).
-Vane pump: cheap and simple, reliable (especially in g-rotor form). Good for higher-flow low-pressure output.
-Axial piston pump: many designed with a variable displacement mechanism, to vary output flow for automatic control of pressure. There are various axial piston pump designs, including swashplate (sometimes referred to as a valveplate pump) and checkball (sometimes referred to as a wobble plate pump). The most common is the swashplate pump. A variable-angle swash plate causes the pistons to reciprocate.
-Radial piston pump A pump that is normally used for very high pressure at small flows.

Piston pumps are more expensive than gear or vane pumps, but provide longer life operating at higher pressure, with difficult fluids and longer continuous duty cycles. Piston pumps make up one half of a hydrostatic transmission.

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The following is a summary of Estimation of Equivalent Length for hydraulic design

1. Estimation of Equivalent Length

When the piping lay-out is not available, the equivalent length (Le) of the piping will be estimated based on the straight length (Ls) as follows:

-Process Area:    3.0 times Ls
-Common Area:    1.5 times Ls
-Offsite Area:    1.3 times Ls

Note that Ls is the sum of xyz coordinate length.
For large size or high pressure piping, it is recommended to estimate the number of elbows,tees and valves and evaluate the equivalent

length, assuming piping lay-out.

2. Pump suction line

When the piping lay-out is not available, the equivalent length of the pump suction line should be assumed as 50m minimum for process pumps and utility pumps.

3. Expansion loop

For a long and hot service such as steam line, expansion loops which will remarkably increase the equivalent length will be provided, and should be taken into consideration.

a. Equivalent Length

The resistance coefficients (K) for valves and fittings are summarized in Table  in terms of equivalent pipe.  The equivalent length may be applicable for laminar flow.

b.Equivalent Length of Valve and Fittings

The following is a summary of input data to be prepared before the hydraulic design

1. Operational Data

-Service for identification
-Fluid name for identification
-Flow rate(s) of liquid and/or vapor
-Temperature
-Pressure
-Physical Properties

a. Liquid service:    Density,viscosity,vapor pressure,critical pressure,spgr@15oC
b. Vapor service:    Density,viscosity,molecular weight,Cp/Cv,Z-factor
c. Two-phase flow:Densities and viscosities for both liquid and vapor, surface tension

2. Construction Data

-Line class
-Elevation at inlet and outlet of piping system
-Distance between source and destination, sum  of XYZ coordinate length
-Instruments, types and quantities
-Valves and fittings, types and quantities, if available
-Control valves
-Pumps, compressors, and blowers

3. Design Requirement

-Marginal head of the pump NPSH available, if any
-Overdesign %: specification of the design flow rate, if any
-Turndown %: specification of the minimum flow rate, if any

4. Output from the Design

-Final Line size
-Pressure Balance
-Equipment Elevation