General information

A ventilation tube is designed to give a certain amount of fresh air to the people working in the mine or tunnel. A properly designed ventilation system has taken in to account the smaller damage that could occur due to the machinery operating in the mine or tunnel. This damage has to be repair when they become to big or to many otherwise there will not be sufficient air in the tunnel for the people working there.

Example: A ventilation tube has a diameter of 1000 mm and a pressure of 3000 Pa.

If there is a 10 cm long damage the leakage will be 0,5 m3 of air per second.

If the damage instead is 30 cm long the leakage will be 5 m3 of air per second, (10 time more).

It is important to continually maintain the ventilation tube and repair as soon as there is damage. The cost of repair is minimal compare to the increase of energy used for the fan to maintain the airflow. A 10% increase of the fan capacity will increase the energy consumption 22%.

Mounting instruction JP Flexible Ducting System 

Mounting of the wire.
Starting position; New galvanized steel wire rope is to be mounted.

At a distance of 30–50 meter from the end of the previously mounted wire rope an Expander bolt is mounted at a “low” point in the tunnel ceiling. Secure the wire rope at each end to the Expander bolt using wire rope clips. Tighten the wire rope using a wire rope tightener.

After the new wire rope is installed, place at a distance of 4-5 meter Expander bolts along the wire rope. Use a 2-3 mm galvanized steel wire between the Expander bolts and the horizontal steel wire rope without changing the horizontal position of the wire rope. NB! Do not force the wire rope upwards trying to get the wire rope through the Expander.

Mounting of the Flexible Ducting

Suspend the Flexible Ducting to the wire rope using the suspension hooks welded to the ducting.

The galvanized steel hooks are delivered seperately (not mounted) to prevent damages that may occur during transport. The hooks are fixed to the ducting very easily and then hooked on the horizontal steel wire (photo). The suspension is constructed in such way, that if there would be an extraordinary strain on the ducting, the suspension patches will break and leave the ducting without damage. Steel hooks and suspension patches are available as spare parts and can easily be reassembled on the ducting.

Connecting of the Flexible Ducting

Flexible ventilation ducting can be connected in different ways.

Steel coupling;

A steel ring is welded in one end of each tube. The tubes are then connected to each other by mounting the tube end without steel ring over the tube with steel ring. Then a steel connecting ring is mounted over the two tubes and tightened.

A connection system with one inner steel ring a lose tube end gives flexibility and different tube length can be connected to each other.

Zip connection;

We use High Quality YKK Zipper.

Zip connection has been used since the beginning of the eighties. Today it is the most common connection. It's is used when having long tubes and for large diameters. Zip connection is often used in TBM projects. The zip is mounted on the tube in both ends and is easily connected to the next tube.

Velcro connection;

The Velcro connection can be used for larger diameter to make handling and connecting easier. The Velcro connection is mounted on the tube in both ends and is easily connected to the next tube. It is strong and will not be damaged and can be used for many years. 

Inspection and maintenance

When a tunnel is driven it will continually be longer and procure in the ventilation tube will increase. Small damage on the ducting due to handling and the operation of equipment will occur. Because of all this it is of importance to regularly inspect the ventilation system.

Things to be inspected and action to be taken;

  • All damage has to be repaired.

  • Dents and un-strait ducting has to be straitened.

  • Defect or damage couplings have to be changed.

  • Defect suspensions have to be changed or repaired.

  • Suspension hanging against a Expander bolt have to be moved.

  • Lose Expander bolts have to be tighted.

  • Slack wire rope has to be tighted.

  • Control of the fan and all other equipment. 

During the inspection the air speed, pressure in the ducting and the energy consumption of the fan should be measured and registered. 

How to repair holes/tears on a mounted Flexible Duct.

Necessary Equipment

  • One hand held hot air welding machine type Leister.

  • One press roller.


Clean the damaged area from dirt oil/grease and cut the area clean if there is lose treads, make sure the duct is under pressure. If the damage is large, decrease the hole using needle and thread. When you sew, use double thread and choose distance between each thread depended on damage. For better results, sew “up and down”. Cut a piece of fabric which covers the hole/tear with min 50mm overlap. Arrange 220V AC to the place where the repair is to be done. Before starting the vulcanization, make some test on a piece of fabric to make sure that correct heat is adjusted on the welding machine.


Place the piece of fabric over the damage so that it overlaps the damage min 50mm. Press the piece of fabric towards the duct using the press roller. Bring the outflow part of the welding machine between the piece of fabric and the duct (photo).

Let the hot air stream melt the surfaces of the piece of fabric and the duct at the same time as the press roller is pressed and moved with short movements over the part of the piece of fabric which the hot air stream just has melted. Try to avoid that the outflow part of the welding machine touches fabric or it will soon be covered with melted PVC.

The result gives optimal durability of a repaired damage and no leakage. When using hot air gun, always have something direct under the area you are repairing! It is very hot, be careful when using it and protect yourself! During welding there will be some welding smoke. Do not inhale this smoke!

JP Repair kit

1 pcs Hand held hot air welding machine type Leister.

1 pcs Press roller.

1 roll Repair fabric 0,2 x 100 m

1 roll Repair fabric 0,6 x 4 m

3 lit PVC-glue

5 pcs Glue brush

2 pcs Glue spatula

1 roll Cleaning

5 pcs Sewing needles

1 pcs Spoole á 100 m thread

20 pcs Suspension hooks

20 pcs suspension patches


Before taking down the Flexible Ventilation Ducting the ducting should be classified.

Class 1: Ducting with no damage.

Class 2: Ducting with damage that has to be repaired.

Class 3: Ducting with large damage that has to be thrown away.

Due to working environment regulation, all ductings that should be used again should be cleaned. This is easiest done before the ducting is taken down.

All pallets have to be clearly marked with quality, dimension, how many tubes and their length and the class.

The ducting is taken down one by one and packed together, sorted after class and placed on pallets that are then classified.


The ducting should always be stored on whole pallets. The ducting could be stored outdoors but should then be covered from dust, heat and the sunlight.

A true breath of fresh air

Jensen Ventilation Flexible Ducting System, we deliver fresh air to all underground operations around the world.