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Hydraulics industry glossary

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Air breather

A device mounted on top of the reservoir tank to prevent the infiltration of contaminants with air being sucked into the tank.

Air-cooled oil cooler

An oil cooler that cools oil using air. It consists of a radiator and fan motor and is generally best suited for environments where cooling water cannot be used.



Bare tube

The bare tube is opposite the fin tube. A tube that has not undergone finning is called a bare tube. Mainly, a bare tube is used when there are identical fluids for the shell side and the tube sides.

Beta () value

The beta value is the same as the filtration ratio.




When dust filtered within the element accumulates to the point where the element becomes ineffective. Clogging is measured using differential pressures throughout the element. For Taisei Kogyo, the element differential pressure for clogging is set at 0.3MPa.

Cooling area

Refers to the surface area of the outer surface of the cooling pipes. It is the area in contact with the shell side fluid.

Collapse resistance

An industrial-strength element used for normal line-filter applications. It has a differential pressure resistance of 0.7MPa.

Cracking pressure

Refers to the minimum pressure at which the element safety relief valve will operate.



Element (Filter element)

A filtering material attached inside the filter used to remove microscopic solids.




A device which prevents the passage of impurities within fluids and gases.

Filter media

Refers to the filtering material for filter elements. Our company provides paper filters, wire mesh filters, and notch wire filters.

Fin tube

A cooling tube that greatly increases the cooling area by using standing, screw thread shaped fins on the exterior surface of the tube. High fin tubes, low fin tubes, and so on are identified according to fin height. At Taisei Kogyo, we specialize in low fin tubes.

Fin tip number

The fin tip number is the number of tips per unit length of the fin tube. The more tips, the larger the cooling area. Normally the number of tips is measured per inch.

Flange connection

Refers to the tie-in section with the equipment piping and flange. Other connections include the threaded type.

Fluid code

A code attached to the front of the filter model and heat exchanger model that indicates the correct fluid classification for the particular model. The seal material and surface finish classification changes depending on the fluid classification (example: Fluid code hFh - FKM represents the seal material and phosphate ester oil as the fluid used).


The removal of particles from fluids using filtering material with pores like those of wire mesh and paper filters.

Filtration accuracy

The filtration ratio uses particle size of 200 and above. Also, each manufacturer may decide captured particle sizes using traditional methods.

Filtration ratio

The filtration ratio is measured according to the multi-pass test method. The target particle size is calculated using (particle number at the filter outlet side) (particle number at the filter inlet side). For example, if the value is 100, there are 100 dust grains at the inlet side and 1 dust grain at the outlet side.

Fouling factor

Depending on the environment, debris will accumulate in the heat exchanger which may result in a gradual decrease in efficiency after prolonged use. In anticipation of this decrease, at the heat exchanger selection stage, the fouling coefficient is taken into account in efficiency calculations and allows for the heat transfer coefficient. Also, the fouling factor may allow for the heat exchanger area and not the heat transfer coefficient. This is called the gmargin area ratioh or gmargin ratio.h



G screw

Parallel pipe threads (JIS B0202).



Heat load

The amount at which the heat exchanger should exchange heat. Normally, the equipment used releases a quantity of heat. The waste heat quantity taken from the released heat becomes the heat exchange quantity.

High pressure element

Able to withstand up to 21MPa of differential pressure. It is used when there is no relief valve in line-filters with 14MPa and above design pressures.

Heat exchanger

The general name for a device that efficiently transfers heat from high temperature objects to low temperature objects.



Impulse test

A test which applies constant pressure to the product to verify the fatigue strength of the product. Generally, our company tests 10,000,000 times because fatigue strength decrease is low when tested more than 10,000,000 times.


A warning device that signals the level of clogging within the filter element. There are 2 main models, the I model (visual type) and E model (electric contact type). For the E model, a built-in micro-switch trips and sends some form of signal to an external location when a set differential pressure is reached.

Initial pressure drop

The pressure loss value of the filter due to element replacement. The procedures for pressure loss value measurements are specified in the JIS B8356.



Low fin tube

A tube where the fin height of the finned tube does not exceed the outside diameter of the unfinned tubing end is called a low fin tube. By some chance, if a defect occurs in the tubing, the advantage of low fin tubes is that tubes can be exchanged one-to-one.



Maximum flow rate

All maximum flow rates are determined by the following main factors.
EShell side: When the flow rate increases, wear on the exterior of the cooling pipes increases and
@the service life of the heat exchanger decreases.
ETube side: When the flow rate increases there is a potential for erosion corrosion of the cooling @pipes.

Maximum working pressure

The maximum pressure in which filters and heat exchangers can operate safely. The piping circuits with pressure fluctuations are set at the peak pressure of the pressure fluctuations and not the setting pressure of the piping circuit.

Manifold type filter

A filter type mounted directly on the manifold block that mainly comes in high pressure types.

Metallic particle abrasion

Metallic particles generated by the sliding action within the equipment.

Mesh (filtration)

The units for wire mesh size mainly are in the number of mesh per inch (this means that if there are 5 meshes, then within one inch there are 5 gaps). The size of the mesh openings will differ depending on the wire diameter of the wire mesh, even for the same number of mesh. The following is the mesh/micron conversion used by our company.

Mesh 40 60 80 100 150 200 250 325 500 1000 1500 2400
Micron 420 250 185 150 105 75 60 50 30 20 10 5
* The above values are from wire mesh used by our company

Minimum flow rate

When the cooling water flow rate on the tube side is low, scale builds up much easier, thus decreasing the service life of the cooling pipes. Also, when the flow rate is low in both the shell side and tube sides, the heat transfer efficiency decreases considerably.

Micron (filtration)

A Micron is a value for the particle sizes, measured in microns, of the filtration target. For our companyfs C paper filter, the value is over 200. For wire mesh, the size of the gap between the wires is in microns.

Multi-pass test method

A test method that measures the filtration efficiency of the element. Refer to the gFilter evaluation testh for details.

Multi-tube heat exchanger

Same as shell and tube type heat exchanger.



Notch wire

The element inside the filter is constructed from notch wire that is made from tightly-coiled stainless steel wire. The element filters via the gaps between the stainless steel wires. The wire is also manufactured in-house and achieves a higher filtration than wire mesh. Notch wire elements can be washed and reused in the same manner as wire mesh elements. The element also has a flat surface which makes cleaning easy.

Number of passes

Refers to the number of loops the fluid in the tube takes (on the tube side) through the fluid in the shell. In a single pass heat exchanger, the fluid comes in through the cooling tubes on one side of the water chamber cover and exits from the other side of the water chamber cover. In pass 2 and higher heat exchangers, the fluid comes in through cooling tubes from one side of the water chamber cover, loops around to the other side of the water chamber cover, and then exits. Generally, single pass heat exchangers can handle large quantities of fluid. Increasing the pass number will decrease the flow rate but increase the efficiency.



Phosphate ester oil

Fluid used in aircrafts, etc. to provide fire resistance. If used, a warning must be attached to the seal material.

Pressure gauge

An instrument used to measure fluid (liquids and gases) pressure.

Pressure switch

A device that detects fluid pressure and makes electrical contact when a certain set pressure has been reached.



Rc screw

Taper pipe threads (JIS B0203).

Relief valve

A valve to let pressure escape to prevent damage to the element when flow within the element is blocked, resulting in a rise in differential pressure. Generally, set at 0.35Mpa.




A part that scrapes off dust attached to the surface of the element of the AK type and CFK type filters.

Shell and tube type heat exchangers

The heat exchanger is comprised mainly of a shell for high temperature fluid flow and cooling tubes for low temperature fluid flow. A highly reliable and popular design among industrial heat exchangers

Smooth spiral serration

A process in which small spiral irregularities are formed on the surface of the flange seal. Our company performs the process using measurements based on ANSI B16.5.



Water-glycol based oil

Used in an array of hydraulic machinery to provide fire resistance. The fluid contains 30-50% water.

Welding spatter

Particles, m- mm in size that spatter when welding.