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 by Industry: Guiding Units for 15 Sectors

A hydraulic power pack by industry is the same unit asked to do different work: light, fast correction on packaging film, heavy and steady force on paper reels and metal coil, tolerance of lint and dust on textiles. This page groups the 15 industries served by Krishna Engineering Works into five families and links to the page for each.

How to choose a hydraulic power pack by industry

Start from what the industry does to the unit, not from the name of the industry. Four things change from sector to sector: the weight to be moved, the speed of the line, the nature of the web edge and the air around the machine. The table shows how the five families differ.

Industry family	Load on the cylinder	Web edge	Surroundings
Packaging and converting	Light to medium reels	Clean, often clear or printed film	Solvent vapour near presses and coaters
Paper	Heavy reels	Opaque, firm	Paper dust
Textile and technical textile	Medium, wide webs	Soft, sometimes open or curling	Lint, moisture, heat
Tyre cord	Heavy, wide fabric rolls	Corded fabric edge	Heat and dip chemicals
Metals and laminates	Heavy coils and stiff sheets	Hard, sharp	Oil mist, abrasive dust

The weight decides the force and so the pressure and the cylinder. The line speed decides the flow. The edge and the surroundings decide the sensing method. How those figures are worked out is shown on the hydraulic power pack page.

Packaging and converting

Packaging and converting lines run thin webs fast, so they need quick, gentle correction more than brute force. Converters print, coat, laminate and slit reels of film, paper and foil, and every one of those steps depends on the edge being in the right place.

Converting industry

In the converting industry the power pack guides the unwind of slitters, rewinders and coaters. Reels arrive with stepped or wandering edges, and the guide presents them straight to the knives or the coating head.

Lamination industry

In the lamination industry two or three webs meet at one nip and must match edge to edge. Each unwind needs its own guide, which is the usual duty of double and triple hydraulic power units with a servo valve for each guide on one reservoir.

Flexible printing and packaging industry

In the flexible printing and packaging industry the print must sit at a fixed distance from the web edge. Guides work at the unwind and the rewind of the press, often beside solvent based inks, where air sensing has an advantage.

Paper

Paper asks for force and for tolerance of dust. Reels are heavy, so the stand needs a firm push to move and a rigid hold between corrections, and the air around the machine carries fibre that settles on everything.

Paper industry

In the paper industry the power pack guides unwinds and rewinds on converting and finishing machines. The larger model of the range covers the heavier stands, and an air sensor keeps its own ports clear by blowing dust away from the sensing gap.

Textile and technical textile

Textile webs are wide, soft and often damp or hot, and their edges are less definite than the edge of a film. The guide has to read a selvedge that may curl, fray or let air through, and the unit must live with lint.

Textile industry

In the textile industry fabric is guided at the entry to processing machines and at batching. Fabric guiding with dedicated cloth guiders is covered on the client’s cloth guider site.

Technical textile industry

In the technical textile industry coated and laminated fabrics are heavier and stiffer than apparel cloth. The force needed rises with roll weight, and open constructions favour sensing with a photocell.

Jute industry

In the jute industry the cloth is coarse and sheds fibre. Filters need closer attention here than in most plants, on both the air side and the oil side.

Fibre industry

In the fibre industry webs and non woven sheets are light and open. State the weight and openness of the material in the enquiry, because they decide how the edge can be sensed.

Carpet industry

In the carpet industry the web is thick, wide and heavy for its length. Guiding at backing and coating lines calls for high force and a robust cylinder mounting.

Tarpaulins industry

In the tarpaulins industry woven fabric is coated and laminated at wide widths. The guide keeps the fabric central under the coating so that the margins stay even on both sides.

Tyre cord

Tyre cord fabric is among the heaviest and widest webs that are guided, and it runs through hot, wet process stages. Force and reliability matter more here than fine response.

Tyre cord fabric processing industry

In the tyre cord fabric processing industry the fabric is guided at let off, between process zones and at wind up, and liner fabric is guided on rewinders. The machinery of this sector is presented on the client’s tyre cord machinery site.

Metals and laminates

Metal strip and rigid laminates are stiff, heavy and hard edged. A strip cannot be steered sharply like a film, so guiding is done by shifting the coil or by gentle steering over long spans, and the hydraulic side must supply steady force.

Aluminium foil industry

In the aluminium foil industry thin foil is rewound, slit and laminated. It tears easily at the edge, so smooth, proportional correction matters, and the opaque web suits either sensing method.

Steel industry

In the steel industry strip is guided at uncoilers and recoilers. The coil weight sets the force, and the cylinder and its mountings must be chosen for it.

Sheet metal industry

In the sheet metal industry coil is fed to slitting and cut to length lines. A straight entry keeps the slit strips to width and reduces edge trim.

Plywood and laminates industry

In the plywood and laminates industry paper and film are impregnated and pressed onto boards. The guide works on the paper web at the treater and on the laminating line.

Units behind every industry page

The same small set of units serves all 15 industries. The oil side is always a hydraulic power pack, and what changes is the sensing and the frame it moves.

The hydro-pneumo web aligner senses with low pressure air, which suits clear film and dusty paper.
The electro-hydro web aligner senses with a photocell and an electrical panel, which suits opaque and open webs.
The web aligner spare parts page covers the sensors, filters, pipes and cylinders that keep either unit in service.

If you know the machine better than the sector, use the products by machines list. The whole range is on the product catalogue page.

What to send with an enquiry

Name the industry, then give the data of the machine. Send the machine type, the position to be guided, the web material and width, the heaviest reel or coil, the line speed and the conditions around the machine. Use the contact page to send it.

Frequently Asked Questions

Is a different hydraulic power pack made for each industry?

No. The same family of power packs serves every industry listed here. What changes is the selection: the model for the force and speed needed, the cylinder for the load, and the sensing method for the web and the surroundings. The industry is a useful guide to those choices, but the machine data decides them.

Which industries need the most force from the power pack?

Paper, tyre cord, carpet and metal strip need the most force, because the reels, rolls and coils are heavy and the stand must be pushed against real friction. Packaging film needs far less force but faster response. State the heaviest reel or coil and how the stand is carried, so that the force can be calculated.

How does the industry affect the choice of sensor?

The industry tells you what the edge and the air are like. Clear film, dusty paper and solvent areas favour an air sensor, which ignores transparency and blows its own ports clean. Open, porous and textured webs favour a photocell, because an air jet leaks through them. Describe the web in the enquiry.

My industry is not in the list. Can the unit still be used?

Very likely. A guiding power pack works on any continuous web or strip that runs between rollers and has an edge that can be sensed. The 15 industries listed are those named on this site, and the units are also used in related sectors. Send the material, width, weight and speed, and the application can be assessed.

Products by Industry Manufacturer & Exporter