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 Repair and Web Guide Servicing

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Hydraulic Power Pack Repair and Servicing of Web Guide Controllers

Hydraulic power pack repair returns a worn web guide to steady, accurate correction by replacing the parts that have aged: seals, filters, diaphragms, pipes and oil. Krishna Engineering Works repairs and services web guide controllers and power pack units of Indian and imported makes at its factory in Ahmedabad, Gujarat.

What does the repair service cover?

The service covers web guide controllers and the hydraulic power pack units that drive them, whoever made them. Krishna Engineering Works repairs and services all types of Indian and imported web guiding systems, including E+L web guiding systems, BST web guiding systems and Chinese web aligner units.

Indian and imported hydro-pneumatic web aligner power pack units are repaired by replacing the old parts with new parts in the factory in Ahmedabad. The work is done by the people who build the hydraulic power pack and the hydro-pneumo web aligner as new products, so the same parts and the same knowledge of the loop are applied to the repair.

Spares for KEW hydraulic power packs and hydro-pneumatic web aligner units are kept readily available, which keeps a repair from waiting on parts.

How do I know a power pack needs repair?

A power pack needs attention when the guide becomes slower, weaker or less steady than it was, and cleaning the filters and topping up the oil no longer help. The table lists the symptoms seen on the machine, the usual cause inside the unit, and whether the plant can deal with it or the unit should be sent in.

Symptom on the machine	Usual cause inside the unit	First check at the plant	Send for repair if
Guide follows too slowly	Low pump flow, blocked suction or return filter, thick or cold oil	Clean the oil filter, check oil level and grade	Speed stays low with clean oil and filters
Guide cannot move a full reel	Line pressure has dropped: worn pump or a relief valve that no longer seats	Free the stand slides, check for external leaks	Pressure does not recover
Stand creeps when the line is stopped	Internal leakage past the servo valve or the cylinder seals	Check that the sensor is at the edge	Creep continues with the sensor covered and uncovered
Guide hunts or chatters	Air in the oil, a sticking valve, play in the cylinder mounting	Bleed the cylinder, tighten pins and brackets	Hunting remains with firm mounting and bled oil
Guide corrects in one direction only	Torn diaphragm, blocked air pipe or a stuck valve	Blow through the air pipe, clean the air filter	Air reaches the unit but the valve does not respond
Oil on the floor or on the unit	Hardened seals, a cracked pipe or a loose fitting	Tighten fittings, replace damaged pipe	The leak is at the pump shaft, valve body or cylinder rod
Pump is noisy or the oil foams	Air drawn in on the suction side, low oil level, worn pump	Top up the oil, check the suction connection	Noise remains with correct oil level
Unit runs hot	Relief valve passing oil all the time, wrong oil, blocked filter	Check the oil grade and the filter	Heat remains with correct oil and clean filter

Most of these faults come back to the oil. Dirt wears the fine edges of the valve, water and heat age the oil, and aged oil hardens the seals. Hydraulic fluid in a small tank works hard, which is why oil condition is the first thing looked at when a unit arrives.

What is replaced during a repair?

A repair replaces the parts that wear or age and keeps the parts that do not. The tank, the body castings and the frame of a power pack last a long time. The moving and sealing parts are what decide how the unit behaves.

Seals and gaskets. The seals of the cylinder, the pump shaft and the valve are renewed, since hardened seals cause both external leaks and internal creep.
Filters. The oil filter and the air filter are renewed. A blocked oil filter starves the pump and a blocked air filter weakens the sensor signal.
Diaphragm and sensing parts. On hydro-pneumatic units the diaphragm, the sensor and the adjuster are checked and replaced where they no longer give a clean signal.
Pipes. Air pipes and oil pipes that have hardened, kinked or chafed are replaced.
Valve and pump parts. Worn parts of the servo valve and the pump are replaced with new parts.
Cylinder. The rod and bore are checked for scoring. A cylinder with a damaged rod is replaced, because a scored rod destroys new seals quickly.
Oil. The tank is cleaned and the unit is refilled with clean oil of the correct grade.

KEW units use Servo 32, Enklo 44 or Hydro 37 oil. For a unit of another make, state the oil that has been used in it.

Repair or replace: which is the better choice?

Repair is the better choice when the structure of the unit is sound and the trouble lies in seals, filters, valve parts or pipes. Replacement is the better choice when the unit is too small for the duty it now does, when key castings are damaged, or when it has already been repaired several times for the same fault.

Situation	Repair	Replace
Leaks, creep or slow response after long service	Usually the right choice: new seals, filters and oil restore the unit	Not needed
Unit has been run with dirty or wrong oil	Suitable if the valve and pump can be restored with new parts	Consider if both pump and valve are badly worn
Reel weights or line speeds have grown since the unit was fitted	Restores the original performance only	Better: move to a larger model
Imported unit, original spares slow or costly to obtain	Suitable where the worn parts can be replaced with new parts	Consider a new unit matched to the existing cylinder and sensor positions
Cracked housing, corroded tank or damaged mounting faces	Seldom worth doing	Better
A second guide is being added to the machine	Repair the existing unit	Or change to a double power unit with two servo valves on one reservoir

Where replacement is chosen, the two standard models are the KEW-17 with a 0.5 HP motor and a 17 litre tank, and the KEW-30 with a 1 HP motor and a 30 litre tank. A complete replacement for one guiding position is supplied as a web aligner unit, with sensor, adjuster, filters, pipes and cylinder.

Servicing web guiding systems of imported makes

Imported web guiding systems work on the same loop as Indian ones: a sensor, a controller or valve, an actuator and a guide frame. Krishna Engineering Works services E+L and BST web guiding systems and Chinese web aligner units on that basis, treating each unit as a loop to be made whole again.

When you send an imported unit, send its nameplate details and, if you have them, the manual pages that show the connections. Describe what the guide does on the machine, not only what you think has failed. A unit that hunts on the machine may be perfectly healthy and simply badly placed. The client’s web aligner site covers installation, tuning and troubleshooting on the machine in detail.

How the repair is handled

A repair runs smoothly when the unit arrives complete and with a clear description of the fault. The steps below describe the usual order.

Send the enquiry with the make, model and the symptoms, and photographs of the unit and its nameplate.
Drain the oil, plug the ports and pack the unit so that the sensor, valve and fittings are protected in transit.
Send the power pack together with the sensor, adjuster and cylinder where possible, so the whole loop can be checked together.
The unit is opened and examined at the factory, and the parts that need replacement are identified.
Old parts are replaced with new parts and the unit is reassembled.
The unit is returned for refitting, filling with clean oil, bleeding and setting on the machine.

If only the power pack is sent, a fault in the cylinder or the sensor will remain on the machine. That is the most common reason for a repaired unit seeming to show the old fault again.

Servicing that prevents the next repair

Regular servicing at the plant prevents most repairs. The oil side of a web guide is simple, and a short routine keeps it healthy.

Interval	Task
Every shift	Look for oil on the floor and listen for a change in pump noise
Weekly	Check the oil level, wipe the sensor, check that the air pipe is not kinked
Monthly	Clean the air filter and the oil filter, check the cylinder pins for play
At each planned shutdown	Check the oil for darkening, milkiness or smell, and free the stand slides
When the oil has aged	Drain, clean the tank and refill with the stated grade

The intervals are general practice and should be shortened in hot, dusty or humid areas. Never mix oil grades when topping up, and never refill through a dirty funnel. Most of the dirt found inside power packs was poured in with the oil.

The same routine applies to the frames the cylinder moves. A tracking roller assembly or a reel stand that moves stiffly makes a healthy power pack look weak.

Why send the unit to the manufacturer?

A manufacturer repairs with the parts and the knowledge used to build new units. Krishna Engineering Works has 25 years of experience in machinery for flexible packaging, paper, tyre cord and textile plants, and makes its components in its own factory in Ahmedabad, with inspection from raw material to final assembly.

The company is ISO 9001 certified and has won 3 National Awards and 2 International Awards for quality manufacturing. The same service appears under repairing and servicing on the main brand site.

What to send for a repair enquiry

Send the details below and the repair can be assessed before the unit leaves your plant.

Make and model of the power pack or web guide controller, with a photograph of the nameplate
Type of unit: hydro-pneumatic with air sensor, or electro-hydraulic with photocell sensor
Machine it is fitted to and the guiding position: unwind, mid machine or rewind
The symptoms, and when they began
Oil grade in use and when it was last changed
What has already been tried at the plant
Parts you intend to send: power pack only, or with sensor, adjuster, pipes and cylinder
Whether a replacement unit should be quoted alongside the repair

Send the enquiry through the contact page. The full range of new units is on the hydraulic power pack products page, and the guiding loop as a whole is explained under web guiding system.

Frequently Asked Questions

Which makes of web guiding system does Krishna Engineering Works repair?

Krishna Engineering Works repairs and services all types of Indian and imported web guiding systems. The makes named by the company include E+L web guiding systems, BST web guiding systems and Chinese web aligner units. Indian and imported hydro-pneumatic web aligner power pack units are repaired by replacing old parts with new parts in the factory in Ahmedabad.

Where is the repair work carried out?

The repair work is carried out in the factory of Krishna Engineering Works in Ahmedabad, Gujarat, India. The unit is sent to the factory, opened, fitted with new parts in place of the worn ones and returned. Sending the sensor, adjuster and cylinder with the power pack allows the complete loop to be checked together.

Is it worth repairing an old hydraulic power pack?

It is worth repairing an old power pack when its tank, housing and mounting faces are sound and the faults are leaks, creep or slow response. Those faults come from seals, filters, valve parts and oil, which are all replaceable. Replacement makes more sense when the unit is undersized for present reel weights or has structural damage.

Why does my web guide drift when the machine stops?

A guide that drifts with the line stopped usually has internal leakage. Oil passes the worn edges of the servo valve or the seals of the cylinder, so the cylinder cannot hold its position. Check first that the sensor is correctly at the web edge. If the drift continues, the valve and cylinder seals need to be renewed.

Should I send the cylinder and sensor with the power pack?

Yes, send them where possible. The power pack, the sensor, the adjuster and the cylinder form one loop, and a fault in any of them shows as poor guiding. If only the power pack is repaired, a leaking cylinder seal or a damaged sensor will still be on the machine and the old symptom may remain.

How should a power pack be packed for dispatch to the factory?

Drain the oil, plug every port and cap the air connections so that no dirt enters in transit. Protect the sensor, the valve and the fittings from knocks, and fix the unit so it cannot move inside the case. Attach a note with the make, the model, the machine and a description of the fault.

Repairs Servicing by the Original Machine Builders