Double Action Hydraulic Hammer (DBHH) which use the hydraulic water hammer for hammer stroke and also use hydraulics to retract the hammer piston.

Reverse Action Hydraulic Hammer (RAHH) which use a spring and/or gravity for hammer stroke and use a hydraulic retraction of the hammer piston,.

Direct Action Hydraulic Hammer (DAHH) which use hydraulics to accelerate the piston for the hammer stroke and retract it with a spring,.

This classification was introduced by РЇСЃРѕРІ in Russia: The operation of hydraulic ram hammers is depending on the drill string length: There will be dampening effects towards the pumps, a more steady flow and pressure will be at the pump the longer the drill string will be.Дepending on the use of compression springs on the striking piston or other compressible elements, those hammers can be subclassified by the hydraulic action as direct, reverse or double. The water column acts as a energy storage which is accelerating the hammer piston by momentum transfer and gets accelerated by the pumps itself. Hydraulic power from the pumps is therefore used to accelerate the water column in the drill string. This is similar to the hydraulic ram pump. By using a valve to close this path, the hydraulic inertia will cause the pressure to inrease very fast, creating a so called water hammer effect. Hydraulic Ram Hammers operate by having an open flow path which allows a continuus flow through the whole hammer from fluid inlet to outlet ports.

Even though this is acausal, it is still sufficient to descripe the basics and classifications. The hydraulic power consumption is mainly driven by the pressure which the mass puts up as a reacting force to the hydraulics when it is getting displaced. The striking piston will open channels to switch the hydraulic valve as it reaches its top or bottom position, switching the main hydraulic channels and reversing its movement.Д®ven if this seems to be simple and the animation is looking fine, it is acutally not as simple as it is shown here and would not work if it is built like that. The striking piston is moved by putting the hydraulic fluid to one side of the piston and opening the other side to the fluid outlet. Most of todays available hydraulic DTH hammer systems work in such a way.ДЄnimation of differential pressure hydraulic hammer It is named by the different pressures moving the masses, the term also suits the fact that the pressure drop over the hammer is usually very high compared to the hydraulic ram hammers. Simplified schematic of a differential pressure hammer As mass displacement is done by the hydraulics, there is a correlation between part movements and hydraulic flow. Typically it is also used with high pressures to keep flow low and reduce the amount of hydrauilc inducted pressure peaks. This concept uses the pressure differences on opposing surfaces to move the striking piston and valve masses.

Fluidic hammer using a fluidic oscillator based on the coandДѓ effectДЇuthermore there are also some concepts of split systems to drive the percussion hammer, using pdm drives to drive a hydraulic pump or generate electricity for magnetic actuators.Hydraulic systems with energy dissipation,.Reverse Action Hydraulic Hammer (RAHH),.

Hydraulic ram hammers which have an open flow path through the whole hammer, interrupting it for a water hammer effect.Differential pressure hammer with permanent active piston areas and fixed displacement ,.That way, hydraulic hammers can be classified into those mechanisms: It is reasonable and common to classify them by the force action transmission and the dynamic behaviour of the hydrauilc mechanical system. There are multiple concepts to drive a hammering piston by hydraulic fluid. The increasing hydrostaic pressure in deep wells are also challenging and make the use of pneumatic elemts nearly impossible. While pneumatic percussion drives make explicit use of the compressibility of the operating gas, hydraulic drives have no way of accessing such a part. This sounds obvious but makes the way of constructing such a device much more challenging. The main difference between hydraulic and pneumatic percussion drives is the lack of a compressible fluid. This page tries to give an overview about the known hydro-mechanic machines and explain the way they work. There are multiple publications (for example, ,, and ) to point out similarities and classify the working principles. Lots of inventions have been made in the past centuries to utilize the hydraulic fluid to create an oscillating piston movement.

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