Which product should I start with if my web wanders at the rewind?

Start with the web aligner unit if one position needs correction and the stand can move sideways. It arrives as a complete kit with power pack, sensor, adjuster, filters, pipes and cylinder. If the stand cannot move, a tracking roller assembly placed before the rewind steers the web instead, driven by the same kind of power pack.

What is the difference between a web aligner unit and a web guiding system?

A web aligner unit is a set of hardware for one guiding position: power pack, sensor, adjuster, pipes and cylinder. A web guiding system is the complete loop, including the frame or stand that the cylinder moves and the choice of guiding position. In practice an aligner unit becomes a guiding system once it is fitted and set up on the machine.

Are spare parts available for KEW power packs and aligners?

Yes. Krishna Engineering Works keeps spares for its hydraulic power packs and hydro-pneumatic web aligner units readily available. When you order, quote the model of the power pack and name the part, such as the sensor, adjuster, air filter, oil filter, pipe or cylinder, so that the correct item is sent the first time.

Can I buy the power pack without the sensor and cylinder?

Yes. The hydraulic power pack is offered as a drive unit on its own, which suits machine builders who fit their own frames and plants that replace an existing unit. Krishna Engineering Works invites bulk enquiries from machinery manufacturers. State the cylinder size and the sensing method you use, so the unit is matched to them.

How do I calculate the force of a hydraulic cylinder?

Multiply the line pressure by the piston area. Pressure in bar times area in square centimetres gives force in kilograms force, to a close approximation. Real cylinders deliver a little less because of seal friction and pressure losses in the pipes and valve, which is why published operating forces sit below the simple calculated value.

What decides the follow-up speed of a power pack?

Follow-up speed is decided by pump flow and cylinder bore. The pump delivers a fixed volume of oil each minute, and the piston can only travel as fast as that volume fills the cylinder. The KEW-17 gives 30 mm/sec at 3.4 l/min and the KEW-30 gives 40 mm/sec at 5.8 l/min on the published cylinder size.

What is the difference between the KEW-17 and the KEW-30?

The KEW-30 is the larger unit in every respect. It has a 1 HP motor against 0.5 HP, a 30 litre tank against 17 litres, a pump flow of 5.8 l/min against 3.4 l/min, and a line pressure of 21 bar against 14 bar. It therefore corrects faster and pushes harder, and it weighs 60 kg with oil against 40 kg.

How often should the oil in a hydraulic power pack be changed?

There is no single interval, because oil life depends on temperature, cleanliness and running hours. As general practice, check the level and colour weekly, and change the oil and filter element when the oil darkens, smells burnt, turns cloudy or after a major repair. A unit that runs cool and clean keeps its oil far longer than one in a hot, dusty corner.

Why does a hydraulic power pack run hot?

A power pack runs hot when more energy is turned into heat than the tank can shed. The usual causes are a low oil level, a unit boxed in without air flow, a pressure setting higher than the load needs, or a worn pump that slips internally. Restore the level, give the tank free air on all sides and check the pressure.

Can the power pack stand away from the cylinder?

Yes, within reason. The web aligner version is supplied with 5 metre oil and air pipes, so the pack can sit beside the machine, clear of the web and the operator. Longer runs add pressure loss and delay, which makes the guide slower and less stable, so keep pipes as short and as straight as the layout allows.

Why is the tank so much larger than the pump flow?

The tank is sized to hold several minutes of pump flow so that the oil rests between passes. During that time air bubbles rise out, dirt settles and heat passes into the tank walls. On the KEW models the tank holds about five times the flow per minute. A tank that is too small sends hot, aerated oil straight back to the pump.

Hydraulic Power Pack for Machines: 15 Machine Types

Hydraulic Power Pack for Machines: Find Your Machine Type

A hydraulic power pack for machines that handle a moving web is the drive of the web guide: it supplies the oil that moves a reel stand or steering frame until the web runs on its line. This page lists the 15 machine types Krishna Engineering Works serves and says where the guide and the power pack sit on each.

How the hydraulic power pack for machines is chosen

The power pack is chosen from three things on the machine: what has to be moved, how fast the web can drift, and what surrounds the sensor. The machine type decides all three, which is why the range is listed by machine.

Question	What it decides	Where to read more
Is a reel stand moved, or a roller frame?	The force needed and so the model	Hydraulic power pack page
How heavy is the largest reel and how is the stand carried?	Margin between push needed and force available	Each machine page below
How fast does the line run and how badly are reels wound?	The follow-up speed needed	Each machine page below
Is the area dusty, hot, humid or exposed to solvent vapour?	Air sensor or photocell sensor, and where the pack stands	Hydro-pneumo web aligner page
How many guides does the machine need?	Single unit, or a double or triple unit on one reservoir	Web guiding system page

The drive itself is described part by part on the hydraulic power pack page. The two standard models are the KEW-17 with a 0.5 HP motor and the KEW-30 with a 1 HP motor.

Printing machines

On a printing machine the guide decides where the print lands across the web. The power pack usually moves the unwind stand, and often the rewind stand as well.

Rotogravure printing machine. Guides sit at the unwind, before the first print unit and at the rewind, and air sensing is the usual choice beside solvent based inks. See the power pack for a rotogravure printing machine.
Flexo machine. Stack flexo presses run thin, extensible films at low tension, so the unwind guide has to correct quickly but gently. See the power pack for a flexo machine.
Flexible printing machine. This page takes flexible packaging printing as a whole and shows how print position across the web depends on edge position. See the power pack for a flexible printing machine.
Offset printing machine. Web offset presses take paper reels at the infeed, where paper dust settles on everything and guides the choice of sensor. See the power pack for an offset printing machine.
Rotary machine. Rotary printing and rotary textile machines guide fabric at the entry, often in wet and humid surroundings. See the power pack for a rotary machine.

Laminating, coating and extrusion machines

On these machines the web must arrive at a nip or a coating head in exactly the right place, often after a long, hot section. A second guide in mid machine is common, using a tracking roller assembly driven by its own servo valve.

Lamination machine. Two webs meet at one nip, so both unwinds are guided and the edges of the two plies are matched. One reservoir can carry both servo valves. See the power pack for a lamination machine.
Coating machine. The web is held under the coating head and guided again after the dryer, and heat near the pack affects the oil. See the power pack for a coating machine.
Extruder machine. Extrusion coating and film lines run without a break, so winder guiding, heat and oil care over long runs are the subjects. See the power pack for an extruder machine.
Plastic processing machine. An overview for film and sheet processing machines: where a guide is needed and which unit suits. See the power pack for a plastic processing machine.

Slitting and rewinding machines

On a slitter or rewinder the guide protects the two things the customer measures: slit width and the straightness of the finished reel. The web aligner is used on slitter rewinder, winding rewinding, doctoring rewinding and rewinder unwinder machines to guide the material.

Slitting rewinding machine. The unwind stand is shifted ahead of the knives, and the load on the cylinder grows with reel weight. See the power pack for a slitting rewinding machine.
Doctoring rewinding machine. Badly wound parent reels are corrected with frequent stops and reversals, so response at low speed matters. See the power pack for a doctoring rewinding machine.
Inspection rewinding machine. Printed webs are rewound into straight edged finished reels, close to the operators who inspect them. See the power pack for an inspection rewinding machine.
Liner rewinder machine. Tyre industry liner fabric comes in heavy, wide rolls with fabric edges that suit air sensing. See the power pack for a liner rewinder machine.

Paper and rubber machines

Heavy reels and harsh surroundings set the choice on these machines. The larger model and robust cylinders are the usual starting point.

Paper machine. Paper converting and paper machine sections handle heavy reels in dusty air, where force and air sensing both count. See the power pack for a paper machine.
Rubber processing machine. Rubber sheet and coated fabric lines run tacky webs under high load. See the power pack for a rubber processing machine.

Which unit goes on the machine?

Every machine page ends in one of the same few units, since the hydraulic loop is the same on all of them. Two complete units are offered for one guiding position.

The hydro-pneumatic unit is the web aligner unit with air sensing, supplied with a 0.5 HP motor, 5 metre air pipe, 5 metre oil pipe, sensor, adjuster, air filter, oil filter and a hydraulic cylinder of 6 inch stroke. Its sensing side is explained on the hydro-pneumo web aligner page.
The electro-hydro web aligner unit uses a photocell sensor for the edge, an AC motor, an electrical panel board to operate the complete unit, a hydraulic cylinder, an adjuster and an oil pipe.

How the units combine into a scheme for a whole machine is set out under web guiding system. Most of the machines listed here belong to the converting trades, and Krishna Engineering Works builds many of them as well, as shown on the main company site.

What to send with a machine enquiry

Name the machine and send the web material and width, the heaviest reel, the line speed, the position to be guided and the conditions around it. Machinery manufacturers who buy units in bulk are invited to enquire, and the company has the capacity to supply 100 to 150 units per month. Use the contact page to send the details, or browse the hydraulic power pack products by type. Existing units can be sent for repairs and servicing.

Frequently Asked Questions

Is the same hydraulic power pack used on every machine type?

The same design of power pack is used on every machine type, but the model and the fittings change. A light steering frame needs little force, while a heavy paper or rubber reel stand needs the larger model. The sensor is chosen for the web and the surroundings, and the cylinder mounting is made to suit the stand or frame.

My machine is not in the list of 15. Can it still be fitted with a power pack?

Yes, in most cases. Any machine that runs a continuous web from a reel can be guided if a stand can be shifted or a steering frame can be placed in the web path. Send the machine type, a sketch of the web path and the web data, and the guiding position and unit can be proposed.

How many web guides does one machine usually need?

Most machines need one guide at the unwind, and many need a second at the rewind or before a critical process. Laminators need a guide on each unwind. Long machines with dryers often add a steering frame in mid machine. Where two or three guides are close together, a double or triple power unit on one reservoir can feed them.

Can a power pack be fitted to a machine from another manufacturer?

Yes. The power pack connects to the machine only through the cylinder, the sensor bracket and the electrical supply to the motor, so it can be fitted to a machine of any make. The stand or frame must be free to move sideways. Send photographs of the stand and its slides with the enquiry.

Products by Machines Manufacturer & Exporter