Merits of HRD Piston Rock Splitters

Why a Piston Splitter ?

A wedge splitter has been around for many decades. Why do we need another type of rock splitter ?  Any merit with the piston rock splitter over the wedge splitter?

1. A piston rock splitter performs much more rock splitting than a darda.

 A piston rock splitter  has been developed and improved  mainly in Korea since early 1990. Until this piston type rock splitter was available, wedge type splitter called,Darda splitter had been used for removing concrete structures and rocks. As Korean government enforced law of vibration free rock removal in early 1990's to avoid environmental conflicts between the construction company and residents, many construction companies had to find more efficient methods of rock removal.

Non-vibration or vibration free rock removal was absolutely demanded by many construction companies.  However Darda splitters could not meet too many demands.
Some people  tried other rock removal methods such as PCF( penetrating cone fracture) or NONEX or CARDOX.  Some people tried rubber tube expander in pre-drilled holes.
In some places, a larger size wedge splitter was tried . But the resulting performance was as low as disappointed level.

Spatial distance between holes is the decisive factor in performance.

A mechanical rock splitting needs predrilled holes before splitting. The depth and number of hole decides the  total performance of rock drilling jobs. The number of holes is decided by the splitters' breaking force.
In other words, if the splitter's breaking force is weak, the hole distance must be short enough so that the holes should broken.

When a wdge type splitter is used, this hole distance is 20~35cm  while the piston rock splitter has hole distance of 40~50cm. The number of hole is 3~5 time difference.
The depth of hole is also short with wedge type. As a result, the performance of wedge splitter is very low.

   

Comparison of Manual wedge splitter vs piston splitter

Various sizes of piston splitter were introduced for special applications.

Piston rock splitters have been made mainly for manual operation . That does not mean that mechanized sizes are not possible.  Mechanizing was tried various ways. The splitter had to be maneuverable freely. Mechanized splitters were not so easy in operation.Only a  small number of people are using excavator mounted splitters..  Most of the handling has been manual one. So the weight , the length or thickness of the cylinders are limited within manual range.
For an ordinary Korean worker, recommended weight is less than 35kg per each splitter.
HRD-tech builds ordinary size as under 30kgs in weight . The heavier one is hard for any ordinary worker to handle.

Longer cylinder performs more splitting. However the weight, hole diameter limits the size. Design or building must reflect the sturdy durability under harsh pressed condition.
            
Following photo shows one piston cylinder weighing 38kg each.  It is not easy or comfortable to move one piston cylinder around the rock sites..

Cylinders of 185mm diameter

           Following photo shows the popular cylinder size of 95mm diameter with  9 pistons. Each cylinder weighs 36kg.  This size is favored by contractors who wants to remove hard rocks in tunnel work.  It is rather heavy  for ordinary person to handle manually.  Only experienced  strong  workers can handle them .

Cylinder of 95mm diameter with 9 pistons

Model 9509 ( 95mm diameter 9 pistons) , 9507( 95mm diameter 7 pistons) are built with the same size piston rods and cylinder diameters.  Only the number of piston and the length of cylinder differs. The drilled holes for 95mm dismater splitter is 105mm.

Following photo shows the more popular cylinder size of 85mm diameter with 11 pistons ( Model 8511) or 10 pistons( model 8510). 

6  x  8511 splitters connected to a Power pack in a Case

Each piston of 85mm diameter cylinder weighs less than 30kgs. This weight is good for a strong worker. The drill hole size for the 85mm splitter is 95mm.

HRD-tech.com produces 80mm diameter cylinders  too..  Each piston produces expanding stress of  19.9tons(19,900kp/cm2).  Favored sizes are 10pistons ( Model  8010 ). A splitter has expanding forces of 199tons against the wall inside the rock hole of 89~90mm diameter.

Another size manual splitter is 90mm diameter cylinder. Usually it has 8 pistons in a cylinder. 90mm diameter produces splitting force of  24.5tons each.

Understanding Splitting Principles of Splitters.

A wedge splitter makes fracture of holes by use of expanding force of the feathers/shims. A piston splitter makes fracture of holes by use of expanding force of the pistons. By appearance both tools seem to work in same manner.  Each mechanical force pushes the wall of rock in its pre-drilled holes.

If you look at the fracturing manner carefully, you will be able to find that splitting direction is not straight but perpendicular.to the hole direction. See the below photos.

A wedge splitter's force is working perpendicular to hole's direction. 

 When you see the direction of piston splitter's force, you will see that piston's expanding direction is also perpendicular to the hole direction. See below diagram.

A wedge or a piston forces the wall perpendicular to the hole's direction.

Why Piston Splitters Break More Rocks with  Less Expanding Force?

As you see on pictures 3 & 4, a wedge splitter pushes the rock wall with the continuous feather's surface. On the contrary to this ,a piston splitter pushes the rock wall with tops of pistons.  Both tools push the rock wall. But the concinuity and discontinuity makes a big difference in producing the expanding forces.

A continuous force works on the rock wall as a shearing stress or a compressive strength.   A discontinuous piston particularly the bottom piston works on the rock wall as a " tensional force".( See pic.4 )

The bottom piston splits the rock with tensional force as well as compressional force.
Actual pistons' expanding forces compress f.e . with 90% of compression and 10% tensioning!

Darda also supplies a mechanized wedge splitter of 1500tons and 1800tons.  Their recommended spacing is not known. But we  assume that their spacing must be shorter than Yamamoto's device.

With the piston rock splitter, recommended spacing for the manual piston spliter is 40~60cm. For the ultra hard granite rock ,35~40cm  spacing is  experienced . With machine mounted piston splitter can break the same hard rock with far distance of 1000~1200mm .

Depth of  hole is optional. The splitting depth varies depending on splitter's kind and size. With the wedge splitter only shallow holes are broken leaving the bottom or deep part  not broken always.  Piston splitters break the holes almost to  the  deep bottom . A wedge splitter cannot break to the bottom of the hole. It must leave some vacant bottom which is 30~40% of total depth.

In Korea, wedge splitters are used limitedly in very narrow space only.

For the rock demolition, piston splitters are used on any rock fracturing sites.

It is evident that different performance between the wedge splitters and piston splitters changes the demand for the kind of splitters.  We recommend our customers who are serious to remove the rocks either from tunnel work or ground preparation site to use piston splitters .
.
HRD Piston Rock Splitter

Hwacheon eng co ltd has been specialized in manufacturing piston rock splitters  a few dacades since 1990.

The most important quality is from the sturdy power pack.  it has been modified and modified to suit the rough construction environment.
HRD-tech splitters are not copiable by any compay in the world.  Many tried to copy them to fail. Its machining, heat treating  has special knowhow.

We are happy to hear from our customers their compliments. We started export to USA in 2007. This customer has informed us recently that they have been keeping  a couple of machines more than 10 years in leasing business. They could  sell  a few machines through this lease  experience.

Another customer in New York has been promoting our machines  in their  web site
togetherwith darda and piston splitters for different applications.

Now we have customers around the globe.  Russia, India, China, Chile ,Phillippines, Kenya, keeps our splitters.

Send your inquiry any time to my email: cs@hrd-tech.com 

What is a Piston Rock Splitter?

 A Wedge Splitter has been known as A hydraulic Rock Splitter for some time.

There has been quite a time of hydraulic rock splitters of wedge type for concrete wall demolition. Some companies modified the concepts and made bigger size wedge splitters  for excavator mounted use. This type of wedge splitter has been used for demolition of concrete structures or rock mountain demolition all over the world.

There is one country this wedge type is not popular , i.e  Korea. This does not mean that any wedge type splitter is not used at all in Korea.  The wedge splitters are used limitedly in very narrow space  such as shaft sinking of less than 2 meters of diameter . They did use them very widely until 1990's.
                       

A wedge type splitter mounted on excavator cracks the rock with more powers than manual ones.

A Piston Spliter Appeared disregarding Wedge's Splitting Force.

  HRD-tech started manufacturing piston-cylinder type rock splitters since late 1980 with a concept from a Japanese company. In Japan, some rubber tube splitters were used. One importer visited Korean machining company to find out the steel made splitters.
The concept is simple and clear to understand. The hydraulic power from the pressed oil is transmitted to to the piston's bottom , of which top is expanding and adding stress to the holes' wall of rock. Then rock wall  made by pre-drilled hole  is cracked to the frontal side of the piston.

When one rod of 10 pistons  within a rod of 85mm  is pressed by the stress of pressed oil 1,000 kp/cm2 ,the 10 pistons of 46mm diameter provides surface of 166cm2.
This means 166 tons are produced by a cylinder when the powerpack pressure remains
as 1,000kp/cm2. With oil pressure of 1,300 kp/cm2, one cylinder can produce 215 tons of pressing power.

A cylinder  of   85mm diameter with 11 pistons.

Analysed  Splitter in detail

When the piston rod bottom(Q3) is pushed up by the pressed oil, the piston rises with the power. This power pushes the rock wall in the holes. When the surface Q3 is big, the rod's pushing power is big. But if  Q is too big, the cylinder wall is too weak. We must find the safe but powerful size of the piston by trial and error. In case of 85mm cylinder, this rod power was calculated as 16.6 ton when power pack pressure is 1,200 kp/cm2.

When we use 95mm cylinder, the piston size is increased too. The splitting force is increased too. But the cylinder weighs too heavy for manual handling with 9 pistons.  95mm cylinder is now adopting 6~7 pistons system . 95mm cylinder has been used only for the hard rock breaking. Most popular size has been 80mm or 85mm cy;linder with 10 pistons now.

 Splitters have been tried in various sizes

As the need for more sophisticated application arises, customers look for varying  size splitters.  150mm cylinders and 185mm cylinders are those required.  These sizes are used for the drills made by either core drills or DTH hammers.

150mm Cylinder with 8 pistons

                           

185mm Cylinder with  1 piston 

 With piston type cylinders, the drilling time matters. Splitting can be performed very efficiently.  Ordinary manual rock demolition, the small size ( 80, 85, 95mm ) cylinders are used. The drilling time is not too long. One hole drlling in a rock with 1000mm deep takes 30seconds to 45 seconds per each.  And the normal spacing requires 40cm ~50cm distance for efficient splitting.

However there is very hard rock which must be removed. Then larger size drilling is attempted. 165mm holes or 200mm holes are made. Our 150mm splitter or 185mm splitter is used.

Here we find an interesting fact about the splitting force generated by one or multiple piston splitters.  

When we calculate the piston pushing force which is used for breaking rock, the 80mm cylinder produces the least power. 85mm cylinder produces a bit higher power. 95mm produces higher than the previous one. Naturally  150mm produces the more power. 185mm cylinder produces the biggest power.

But the large size cylinder is limited in its number of piston because of manual lifting.

So 185mm cylinder has only one piston. 150mm cylinder has 2 pistons for manual handling.

Refer to the following table which HRD-tech is used ( hand held types only)

Above table shows only the hand-held splitters which are limited by its weight. Hrd-tech  has limited it under 30kgs.
As we can assume, hard rock may require more powerful breaking stress from the splitter.
 This stress is a combination of power pack pressure, splitter's piston size, number of pistons .
 When the number is more, the weight is increased more.

Of course, we can think about the machine held splitters of larger diameter and longer
but heavier splitters. These areas have been our keen interest for the future development.

 Special Characteristics of a Piston Rock Splitter.

You will find that small size cylinder has less piston strength than large cylinders.

 Considering the total splitting force of a cylinder , we find that SR150 has 58.8 tons  and SR 185 has 114 tons while the 80mm or 85mm cylinder has 182 tons and 229 tons.

Does it mean that 85mm cylinder performs the best? No, not at all. As far as the splitting is concerned,  185mm cylinder does the best splitting job. Why?

This question needs to be solved in terms of the splitting force. The  powerful splitting force does not necessarily mean the total maximum power. It does mean individual piston's force and some part from the splitting force.

Let's look at the following diagram.

Shearing Force & the Fracturing Force

When the piston expands, it makes fractures along the line of cylinder length. The rock is split  from top to bottom in parallel to the cylinders' length. But still the cracking or the shearing is not finished.  Left side rock part must be broken by shearing force .

The important force required to remove the left side rock is from shearing force from the splitter.  This shearing force depends on the pistons' strength plus bottom piston's

pushing force to the frontal direction.

If a narrow area is pushed by a piston rod( hydraulic stress) and cracked like the picture above, this will make cracks ( fracturing), which initiates the shearing simultaneously. This shearing action will require backing force supported by the other pistons.

Fig. Sheared Bottom

 Above figure shows that sheared bottom area  calculated . When we use spacing of 50cm between holes, this area will be roughly 7,500 cm2 (= 50 x 150 ).

 Required shearing strength is  15,000 tons.(= 2,000 kp/cm2  x 7,500 cm2 )

  If we assume that 3 cylinders of 85mm dia.  are used at the power pack pressure of 1,200 kp/cm2, total expanding force will be maximum 520 tons.  This  expanding stress is roughly 1/30 of the required shearing strength. ( =520ton/15,000ton)

    Something must be considered other than shearing strength from above calculation.

The writer has been suspicious about this queer phenomenon. The splitting force of 182~229 tons covers the required shearing strength( 15,000tons ) in reality.

 What happened? How does a splitter of 182tons shear the area ( abb4a4 ) which requies  shearing strength of  15,000tos?

The blogger has a hypothesis that  a hydraulic stress from the piston splitter might act on a very narrow point in frontal direction.   This narrow stressed line is stressed  prior to neighboring line and begins to be cracked.  Immediately after this point is yielded, the neighboring lines are continuously yielded eventually resulting to breakage.

The writer has no proof for this hypothesis yet. However the writer has been experiencing this "queer' breakage in daily work sites.

This is the very special characteristic in piston rock splitting in comparison with the wedge splitting. With the wedge splitters, the wedge indeed has very high splitting force. With the small darda, the splitting force is 2~5 times of piston splitters. With the large size mechanized splitters, the wedge splitting force is 10~15 times higher than that of piston splitter.   In actual demolition site, the wedge  cracks the rock very slowly and less efficiently comparing to a piston splitter.

For example, 12 inch darda splitter has splitting force of 385 tons. This cylinder is inserted into 45mm dia hole.  Then it can split the rock( granite of 200MPa CP) with 25~30cm spacing. With the piston splitter of 85mm dia cylinder, you can break the rock with the spacing of 50cm  easily. A  85mm  piston cylinder has splitting force of 199 tons.  This piston splitter breaks the rock much easier than 12 inch wedge splitter of 385 tons force. But it sounds something wrong. A smaller force splitter splits the rock better and faster?  I am talking about the occurring facts daily.

Applications of the piston splitters.

The piston splitter has been applied to many similar demolition sites to wedge has been applied. So far most of piston spliters are used for rock removal for such places;
 ground rock for building foundation,  underground tunnel rocks, rocks on the mountain , rocks near historical building , rock near residential area. shaft sinking, trench making ,
etc.  

Even the manual piston spliter can perform breaking job very efficiently. It works faster than any wedge splitter of similar size. Manual piston spliters have been popular in many places. Our piston rock spliter has been used in N.Y for breaking Manhattan rock since 2007. Recently our piston spliters are used in African continents. India, Chile, Phillippines, Russia, and China has been using our splitters from time to time.

Following video will show you some tips on how to use a piston rock splitter.

------------------------------------------------------------------------------------------------ 

Before cracking

 The following photo shows how a splitter cracks the rock in inserted hole.

After cracking 

Each cylinder produces more than 166
tons of expanding stress.




 

  When more than a cylinder is used
  in a line to push the rock wall inside the drilled holes, it produces enormous
 power. See below.

3 splitters in line  before cracking.
       

 For a full video, visit Https://Youtu.be/1rfZIfRNtcU.

3 splitters in line after cracking

It is usual to use 4 splitters in line for removing the rocks in foundation site of buildings.
Sometimes they add 2 more splitters in order to increase this power and expedite the demolition work.

A conventional rock spliter done with wedge type is not comparable in its power.( see video http:// Youtu.be/-H1dt5osMJs " breaking Bedrock with a mechanical splitter"

 The piston type splitter is now used on many demolition sites.

 For eg, construction field ( see Youtu.be/1rfZIfRNtcU )

This technology summarized as "Drill & Split" is very useful and efficient in any mechanical demolition.

This system must be optimized based on experiences.  . One drill  with 2 splitters  and an excavator etc must be from  experienced professionals.

If you need  see  details, visit web site, www.hrd-tech.com  for further details.

Rock Removal for Tunnel Work with D&S technology

Manual Piston Rock Splitting is Prevailing in many places. You can upgrade this job by mechanical tools

Upper Heading part has been cleared  and lower bench part remains after drilling.

Hard rock , Korean granite , drilling 95mm diameter holes

Splitting cylinder of 85mm diameters are used for splitting with the space of 40cm 

between the holes.  Drilling takes longer time than splitting. 

One drill makes holes of 3 meter long at a time.

A splitting cylinder cracks the holes a meter deep inside the hole.

The splitter is used in 6 holes at a time. they crack the holes one meter deep.

    Some suggestions are made here for a professional contractor;

    1. Draw a drill plan in advance of drilling on the wall with some color paint.

       This paited pattern makes the rock  drill operator work much easier and faster.

    2.  Make use of the 'free face" in the wall.  We always recommend to make free face 

       prior to any other drilling. A free face is the essential  void without which splitting          takes too long time. See details of free face from other blogs in this site.

                                  Drilling for free face : the spacing between hole is very near

                                          You can split the holes easily by directing the breaking force

                                           toward the center hole.

                                          After the breaking 6 surrounding holes, one large void is made.

                                          This void is used as free face for splitting toward this void.

       When you have a free face  in one place, for.eg , one meter below center top              ceiling. you can split the  wall against those free faces.  

       3. Use a light but powerful splitter like SR 9507 ( 95mm diameter with 7 piston                 cylinder). Recommended spacing in the beginning is 500mm between hole                   centers.  Weaker splitters cannot copy good sturdy splitters. Our SR 9507 is                 light as 29 kgs each. Our competitor splitters are very heavy like 37~39kgs,

       4. We recommend to use our special handle for inserting deeper in the same                   holes. You need to ask more details when needed. 

The tunnel  upper heading was through now. This is for building the subway train.

Our splitting machine is seen ( yellow painted case). It has 6 cylinders connected to

a power pack run by an electric motor.

This tunnel was  made by a fleet of equipment< one drill + one piston splitter

and an excavator and  a truck> .  We have some suggestion to the contractor.

Most of the contractors have their own confidence regardless of our opinion

for their easier performance.

We recommend our customers on the hard rock tunneling;

1)  Study how to drill for free surface in the initial drilling.

2) Then begin to make free surface from top part and 

middle parts from top to down.

3) Start the space based on 50cm space with 95 cylinder

or 85 mm cylinder with 40 cm space for hard rock

 like granite.

4) If you use 85mm cylinder for harder rock , the drill space

is closer than 50cm.

       Getting free surface takes more time than normal rock removal 3~4 times.
       Once you get free surface, then the rock removal proceeds faster.
                   

Drilled wall view from a far place

It would be better for the contractor to have a 'Planned Profile' before start drilling. Then you make marked spots on the wall for easier drilling. This kind "planned profile" makes job easy and fast.

Also you will have some suggestions on many things: Can we use mechanical assistance like winch ( balancer) See below balancer photos.

This balancer would make the lifting work much easier than without it. This lift is useful for vertical splitting work sites.

                           

 Edilgrappa is suggesting A balancer tool as above.( See more at edilgrappa.com)

   Following work site is from one of our customers in USA.  He used D& S technology for making ponds in the rocky place.

Boston.USA

                

------------------ Some more photos for your quick understanding------------

Bench Bed Demolition after drilling

Bench Demolition -closer look

More Closer look after Drilling

Starting Cracking by Inserting cylinders into holes

Cracking Rocks through Holes from up to down

Final Scene of Demolition of Granite Rocks with Hydraulic Piston Splitters

As a manufacturer of this piston type rock splitter, we have some suggestions for consultants or contractors

1. Take into consideration of the size of the tunnel!

A larger size tunnel needs different types of tools and equipment.  If the tunnel length is more than 500m, we  suggest to use 3 boom drill instead of 2 boom or one rock drill.        If you are working for  wall face over 50  m2 , we  recommend you the 3 boom rock drill.
Also we may suggest a different type of rock drill than universal type available from a local contractor or rental house.

             (  Different size tunnel requires different mix of exquipments and working turn. )

   Slot drilling is called by Japanese people as ASB method( Anti-Spin-Bore method) This ASb was used for wedge splitters  and early rubber pouch type splitters. 

  For the hydraulic piston rock splitting, we recommend the free face  mentioned in top part.

2. Consider the performance you expect from the rock splitting.

     Selection of rock splitter decides spacing, depth,and splitting direction.
     Please refer to two drill patterns as below:

  Above drill pans are based on different size splitters.  Plan 1  is made  for rock splitter of 90mm diameter.

 The spacing between bore holes is 500mm.  Plan 2 is made for rock splitter of 110mm diameter. The spacing between bore holes is 750mm.

 In consequence of this selection, the work load of drill/split is quite different.  Plan requires 650holes to be drilled. Plan 2 requires  350 holes to be bored.  Whcih one makes the work faster?

Above drill plan is for the tunnel size of 10meter wide, 10meter high.  You can see the boundary line and paralleled free face drills. In the center vertical close drills are made. One line is made horizontally drilled. next holes are slanted for easy free face . 

One evident advantage of piston rcok splitting against the wedge splitting is the fast performance.  I ask our readers to  compare the technology between piston and wedge splitting carefully. Then you will be able to find  many merits of piston splitter over wedge splitter technology.