Krishna Engineering Works is a hydraulic power pack manufacturer in Ahmedabad, India, building compact power packs that drive web aligners, web guiding systems and tracking roller assemblies on converting, printing, paper and textile machinery. Each unit joins a motor, pump, oil tank, filters and servo valve in one housing, ready to move a guiding cylinder.
What is a hydraulic power pack?
A hydraulic power pack is a self contained unit that turns electrical power into a controlled flow of oil under pressure. An electric motor drives a pump, the pump draws oil from a tank, and valves send that oil to a cylinder that does the work. When the work is done the oil returns to the tank, is filtered and is used again.
The idea rests on Pascal’s law: pressure applied to a confined fluid acts equally in all directions. A small pump can therefore produce a large, steady force at a cylinder some distance away, connected only by two pipes. That is why hydraulics is the usual choice wherever a heavy load has to be moved slowly, smoothly and precisely.
On the machines this site deals with, the load is an unwind stand, a rewind stand or a steering frame, and the job is to keep a moving web on its path. The power pack is the muscle of the guiding loop. A sensor watches the web edge and the power pack moves the cylinder until the edge is back where it belongs.
What is inside a KEW hydraulic power pack?
A KEW power pack contains everything needed between the electrical supply and the cylinder ports. The main parts and their jobs are listed below.
- Electric motor. A three phase motor drives the pump at constant speed.
- Pump. The pump delivers a fixed flow of oil, which sets how fast the cylinder can move.
- Oil tank. The reservoir stores the oil, lets air and dirt separate out and gives up heat through its walls.
- Oil filter and air filter. Filters keep the oil and the sensing air clean, which protects the servo valve.
- Servo valve. The valve meters oil to one side of the cylinder or the other in proportion to the sensor signal.
- Pipes and cylinder. Oil pipes carry the flow to a hydraulic cylinder mounted on the guide.
The complete breakdown, with the function of each part and the faults that follow when one is neglected, is on the hydraulic power pack page.
Hydraulic power pack models: KEW-17 and KEW-30
Two models cover most guiding duties: the KEW-17 for light and medium loads and the KEW-30 for heavier stands and faster correction. The figures below are the published data for the two units.
| Item | KEW-17 | KEW-30 |
| Motor rating (3 phase, 50 Hz) | 0.5 HP | 1 HP |
| Pump flow rate | 3.4 l/min | 5.8 l/min |
| Tank capacity | 17 litres | 30 litres |
| Line pressure | 14 bar | 21 bar |
| Maximum operating force (50.8 mm diameter cylinder) | 260 kg | 389.5 kg |
| Follow-up speed | 30 mm/sec | 40 mm/sec |
| Weight including oil | 40 kg | 60 kg |
Beyond these two, power pack units are available in different models from 0.25 HP to 3 HP. Double and triple power units are also available, with two or three servo valves on the same reservoir, so that one tank serves several guiding points on a machine.
How do flow and pressure become speed and force?
Flow decides speed and pressure decides force. The cylinder moves as fast as the pump can fill it, so a higher flow rate gives a higher follow-up speed. The cylinder pushes as hard as the line pressure allows across its piston area, so a higher pressure or a larger bore gives more force.
The model table shows both effects. The KEW-30 delivers more oil per minute than the KEW-17 and so corrects faster, and it works at a higher line pressure and so pushes harder on the same 50.8 mm cylinder. Choosing a power pack is a matter of matching these two figures to the weight you must move and the speed at which the web wanders. The broader principles are described under hydraulic machinery.
Products built around the power pack
Every product on this site is either the power pack itself or a guiding unit that it drives. The table shows how they relate.
| Product | What it is | When to choose it |
| Hydraulic power pack | Motor, pump, tank, filters and servo valve in one unit | You need the drive unit alone, or a replacement for an existing guide |
| Web aligner unit | Power pack supplied as a kit with sensor, adjuster, filters, pipes and cylinder | You want a complete guide for one position on a machine |
| Hydro-pneumo web aligner | Aligner that senses the web edge with low pressure air | The area is dusty or solvent laden, or the web is clear film |
| Web guiding system | Sensor, power pack, cylinder and guide frame as one loop | You are planning guiding for a whole line |
| Tracking roller assembly | Pivoting frame with idler rollers, moved by the cylinder | The web must be steered in mid machine |
The web aligner unit is supplied complete with a 0.5 HP motor, 5 metre air and oil pipes, sensor, adjuster, air filter, oil filter and a hydraulic cylinder of 6 inch stroke. The hydro-pneumo web aligner page explains air sensing in detail.
For a complete loop, the web guiding system page shows how the power pack is matched to the guide, and the tracking roller assembly page covers the steering frame used between process sections. All of them are summarised in the hydraulic power pack products catalogue.
Which machines use a hydraulic power pack for guiding?
Any machine that unwinds, processes and rewinds a web can use one. On this site the power pack is offered for rotogravure printing, flexo, lamination, coating, slitting rewinding, doctoring rewinding, inspection rewinding, paper, extruder, liner rewinder and other machines.
The position of the guide changes with the machine. A slitter guides the unwind so the knives cut true to the print. A laminator guides two webs so their edges meet at the nip. A printing press guides before the first unit and again at the rewind. The list of power packs by machine links to a page for each one.
The industries served include converting, flexible printing and packaging, paper, lamination, textile, technical textile, tyre cord fabric processing, aluminium foil, steel and sheet metal.
How to choose a hydraulic power pack
Choose the power pack from the load and the correction speed, then check the installation. The steps below give the order that avoids rework.
- Find the weight that the cylinder must move: the full reel plus the moving part of the stand, or the steering frame.
- Estimate the friction of the slides or wheels that carry it, since the cylinder must overcome friction, not lift the weight.
- Decide how fast the guide must follow. A web that wanders quickly, or a line that runs fast, needs a higher follow-up speed.
- Pick the model whose force and speed figures cover both needs with a margin.
- Choose the sensing method: air sensing for dusty or solvent areas and clear films, photocell sensing with the electro-hydro unit where that suits the web.
- Check the pipe run from the power pack to the cylinder and the space for the unit beside the machine.
A deeper comparison of sensor and actuator types is available on the client’s web guide system site.
Repairs, servicing and spare parts
Krishna Engineering Works repairs and services web guide controllers and power pack units of Indian and imported makes. The work includes E+L and BST web guiding systems and Chinese web aligner units, and worn parts are replaced with new parts at the factory in Ahmedabad.
Spares for hydraulic power packs and the hydro-pneumatic web aligner unit are kept readily available. Details of the service are on the repairs and servicing page.
Why buy from Krishna Engineering Works?
Krishna Engineering Works has 25 years of experience as a manufacturer, exporter and supplier of flexible packaging, paper, tyre cord and textile machinery and equipment. The points below matter most to a buyer of power packs and guiding units.
- Own manufacture. Machines and components are made in the company’s own factory in Ahmedabad, using computerised drawing and design.
- Inspection and trial. Parts are inspected from raw material to final assembly, and a continuous trial is taken before dispatch.
- Certified and recognised. The company is ISO 9001 certified and has won 3 National Awards and 2 International Awards for quality manufacturing.
- Volume supply. The company has the capacity to supply 100 to 150 units per month and invites enquiries from machinery manufacturers who buy in bulk.
- Export supply. Hydraulic power packs and web guiding systems are supplied to customers in India and abroad.
The checks behind these points are described on the quality page, and the full machinery range is on the Krishna Engineering Works main site. General background on the technology is published by the National Fluid Power Association.
What to send for a quotation
A power pack is chosen from the data of your machine, so a complete enquiry gets a faster and more accurate answer. Send the following:
- Type of machine and the position to be guided: unwind, mid machine or rewind
- Web material and web width range
- Maximum reel weight and reel diameter at that position
- Line speed
- How the stand or frame is carried: slides, wheels or pivots
- Area conditions: dust, solvents, heat or moisture
- Whether you need the power pack alone, a complete aligner kit or several guides from one tank
- Make and model of any existing unit to be replaced
Send these details through the contact page and a suitable unit will be proposed.
Frequently Asked Questions
What is a hydraulic power pack used for on a converting machine?
On a converting machine a hydraulic power pack is used mainly to drive the web guide. It supplies oil under pressure to a cylinder that shifts the unwind stand, the rewind stand or a steering frame sideways, so the web edge stays in line. The same kind of unit can also power other slow, forceful movements on a machine.
What does the HP rating of a hydraulic power pack tell me?
The HP rating is the size of the electric motor, and it indicates how much hydraulic work the unit can deliver. A larger motor can drive a pump with more flow, a higher pressure or both. For guiding, the more useful figures are the pump flow, which sets correction speed, and the line pressure, which sets cylinder force.
Which oil is used in a KEW hydraulic power pack?
The oil types named for the KEW-17 and KEW-30 power packs are Servo 32, Enklo 44 and Hydro 37. These are light hydraulic oils that flow easily through the servo valve at normal workshop temperatures. Use one grade only, keep it clean, and top up with the same oil that is already in the tank.
Can one power pack run more than one web guide?
Yes. Double and triple power units are available, with two or three servo valves mounted on the same reservoir. Each valve has its own sensor and cylinder, so each guide works independently while sharing one tank. This saves space on machines that guide several webs, such as a laminator with two unwinds.
Does Krishna Engineering Works supply power packs to machine builders?
Yes. Krishna Engineering Works invites enquiries from machinery manufacturers who purchase hydraulic power packs, web aligners and web guiding systems in bulk orders. The company states a capacity to supply 100 to 150 units per month, and spares for the units are kept readily available for builders and end users.
Can an imported web guide power pack be repaired in India?
Yes. Krishna Engineering Works repairs and services Indian and imported web guiding systems, including E+L and BST systems and Chinese web aligner units. Imported hydro-pneumatic web aligner power pack units are repaired at the factory in Ahmedabad by replacing old parts with new ones. Send the make, the model and a description of the fault with your enquiry.
