Category Archives: Articles

Conversion of conventional hydraulic surface grinder

Category : Articles

As everyone is aware , the surface grinder uses hydraulic system for reciprocation . Apparently it seems a very simple system only with one double piston rod cylinder with reciprocating action and working at a very low pressure . However only the designers and the maintenance team know how complicated the system is ! Whenever there is break down it becomes really tough job for maintenance team since there are no standard valves used in the circuit except may be a relief valve. All other valves like the direction control valve, flow control valve, deceleration valve etc. are specially manufactured and fitted in a single manifold block by the machine manufacturers . Unless the maintenance person has a thorough knowledge of hydraulics it becomes very difficult to even recognize the components and trace the circuit. Most of the flow control, DC valves are fine tuned by the manufacturer so as to avoid any vibrations or jerks during the reversal. Jerk free movement is very crucial to the operation of surface grinder. Hence trouble shooting of this type a circuit becomes a tough task. It’s not only tough but it consumes too much of time. The spare valves are never readily available as these are specially made for the application by the machine manufacturer and the user has no choice but to contact the machine manufacturer.

Avoid this ! Go for a proportional valve system. The pump, motor and accessories remain the same. A standard NG06 or NG10 size simple open loop proportional valve works like a combination of direction control, flow control and deceleration / acceleration control valves. This becomes the most simplified system. A small change in control panel is needed which can generate a signal of +/- 10V. Reversal signal can be generated by a simple limit or proximity switch. This eliminates the need of complicated cams, dogs, throttle valves etc. All the parameters like maximum speed, acceleration / deceleration values can be controlled on a control panel with potentiometer and a small PLC . In addition, if one uses a low pressure variable volume vane pump then there can be a substantial reduction in the power consumed and heat generation.

Conclusion – conversion to proportional valve system 01. Reduces down time 02. Circuit can be understood easily 03. Ready availability of spares since all valves used are manufactured by standard hydraulic companies 04. Results in lower inventory carrying costs
Go for it !

Using Scanwill oil to oil pressure intensifier instead of separate high pressure power packs / pump motors

Category : Articles

It is observed in lot of applications especially in special purpose metal cutting machines that the main hydraulic system works at very low pressure mainly the indexing and machining slides. However in most of these systems the job is clamped with Clampets which are very compact cylinders. These are used mainly to accommodate them in a very small space available on the machine. Since these are compact cylinders, the piston area is also small.

Normally it is observed that the bore sizes available for these clampets is not more than 50 mm. To achieve a force of say 3T one needs this cylinder to operate at 200 bar ! Invariably there is separate clamping power pack or else there is a separate pump motor assembly may be with a radial piston or some other high pressure pump installed on the same low pressure power pack. So you have an additional electric motor, bell housing assembly, suction strainer, separate relief valve etc. To get rid of the hassles one should think of using an Oil to Oil pressure intensifier. The typically most of the valves used in the metal cutting SPMs are CETOP 3 ( NG 06 ) mounting.

There are oil to oil intensifiers available with CETOP 3 stackable mounting ! This is available in the ‘ A’ line of CETOP stack like depicted below. The main advantage is that all the valves used in the circuit work at low pressure which is the main pressure setting of the system relief valve hence less stressed valves and other pipe lines. The only line which works at high pressure is the A line coming out from the intensifier and going to the clamping cylinder . There is no need to use high pressure series tube fittings before the intensifier since the complete power unit works at a low pressure and ONLY the portion from intensifier to cylinder works at high pressure. This also results in the space as well as cost saving during the assembly. Another big advantage is that these intensifiers are available in various ratios like, 1.4 , 2.0, 3.4, 5.0, 7.0, 9.0 . With these available ratios , the maximum pressure the designer can go up to is 500 bar !. Hence the designer has a freedom to choose the ratio based on the maximum available working pressure on the main power pack. These intensifiers have a very simple construction, work on the principal of area ratio and are easy to repair / replace. In addition to these stackable models, line mounted models are also available. The maximum pressure output is as high as 4000 Bar!

The new design of Scanwill intensifiers are also available to be used with rotary joints.
Some of the applications of these compact intensifiers are as follows:

  • High static pressure testing equipments
  • Fork Lift attachments for drum handlers etc.
  • Rock splitters
  • Rescue Tools
  • Chucking
  • Demolition Tools
  • Torquing Tools
  • Rail Road equipments

These intensifiers are manufactured by Scanwill Fluid Power ApS, Denmark and are available in India through Slimline Hydrotek, Pune.

Water Hydraulics – Hydraulic Power Units working on pure TAP WATER !

Category : Articles

a)Water as a Hydraulic Medium

When we speak about clean , fresh and pure fluid power what comes to our mind is WATER ! Prior to the 20th century water was the only working medium used in fluid power motion controls. With the current concerns for environment and economic concerns it’s regaining the importance in fluid power systems. Now a days water is being considered and seen as an alternative to oil because of it’s eco friendliness, ready availability, almost zero storage cost, ease of disposal, fire resistant properties and cost.

b)Users of water hydraulics

The businesses interested in – Reducing the fire hazards , reducing operating / wastage costs, minimizing the product cross contamination and meeting the government norms and regulations.

c)Major advantages of water hydraulics

Cost – Water is available at a fractional cost compared to the conventional working fluid. In addition the transportation, storage and disposable costs are almost zero !

Safety – Completely fire resistant, nontoxic ,and the user is never ever exposed to any dangerous fumes or vapors as is the case with other fluids. Even the additives used as anti-freezing agents possess almost the same properties as the water.

Insurance Costs – The insurance costs considerably come down when the stored quantity of fluids alike hydraulic oil reduces due to usage of more water hydraulic systems.

Availability – Water is readily available normally through a centralized supply in any industrial establishment means it’s available on the tap ! So very little or almost no storage cost.

Disposal Costs – In most of the developed and developing countries the norms of disposal of oil or any other fluid, are becoming more and more stringent due to environmental issues hence the disposal costs of these fluid are very high as compared to water.

Environmental Compliance – The laws continue to hold the companies responsible for the burdens they put on the eco system / environment which results in increased taxes. These are definitely reduced by using water.

Minimized product contamination – In many industries like pharma, food, textile, wood, paper etc. cross contamination of end product by a working fluid is one of the major concerns since the working fluids like oil actually can change the end properties of products produced. However water ingress is not considered as harmful as the oil ingress.

Green Image of a business – Water hydraulics usage projects the good corporate image. It not only projects but also in reality it indicates cost conscious, caring and sensitive environment friendly management.

Now a days most of the components used in oil hydraulics are available in water hydraulics. Viz. Axial Piston pumps and motors, Pressure Control Valves, Pilot Checks, Flow controls, Direction controls – hand lever as well a solenoid operated, manifold blocks, cylinders etc.

These components are manufactured by The Water Hydraulics Co. Ltd. Hull, UK and available ( with complete application engineering support ) in India through Slimline Hydrotek, Pune