List of Equipments Used for Cleaning Sewers | Waste Management

In addition, the following special equipments and devices are used for cleaning sewers: 1. Portable Pump Set 2. Manila Rope and Cloth Ball 3. Sectional Sewer Rods 4. Sewer Cleaning Bucket Machine 5. Dredger 6. Roding Machine with Flexible Sewer Rods 7. Scraper 8. Hydraulically Propelled Devices.

1. Portable Pump Set:

In cases where sewers are blocked completely and sewage has accumulated in manholes, the collected sewage has to be pumped to tackle the sewer blockage.

2. Manila Rope and Doth Ball:

This is the most common method of cleaning small sewers up to 300 mm diameter. Flexible split bamboo rods or flexible bamboo strips tied together are inserted into the sewer line at the manhole. When the front end of the bamboo rod or strip reaches the next manhole, a thick manila rope with a cloth ball at the end is tied to the rear end of the split bamboo rods or strips.

The split bamboo rods or strips are then pulled by another man in the downstream manhole and pushed through the sewer line. As the rope is pulled, the ball sweeps the sewer line and the accumulated grit is carried to the next manhole where it is removed out by means of buckets. This operation is repeated between the next manholes until the stretch of sewer line is cleaned.

3. Sectional Sewer Rods:

These rods are used for cleaning small sewers. The sewer rods may be of bamboo or teakwood or light metal usually about one metre long at the end of which is a coupling which remains intact in the sewer but can be easily disjointed in the manhole. Sections of the rods are pushed down the sewer.

The front or the advancing end of the sewer rod is generally fitted with a brush, a rubber ring for cleaning or a cutting edge to cut and dislodge the obstructions. These rods are also useful to locate the obstruction from either manhole.

4. Sewer Cleaning Bucket Machine:

The bucket machine consists of two powered winches with cables in between. The winches are centred over two adjacent manholes of the sewer section to be cleaned. The cable is threaded through the sewer line by means of sewer rods or flexible split bamboo rods.

The cable from the drum of each winch is fastened to the barrel on each end of an expansion sewer bucket fitted with closing device, so that the bucket can be pulled in either direction by the machine on the appropriate end. The bucket is pulled into the loosened material in the sewer until the operator feels that it is loaded with debris.

The winch is then thrown out of gear and the opposing winch is put into action. When the reverse pull is started, the bucket automatically closes and the dirt is deposited in a truck of a trailer. This operation is repeated until the line is clear.

Various bucket sizes are available for sewers of 150 mm to 900 mm in size. The machine is also used along with other scraping instruments for loosening sludge banks of detritus or cutting roots and dislodging obstructions.

5. Dredger (Clam-Shell):

A dredger is used to clean large manholes. It consists of a grab bucket on a wire rope which is lowered into the manhole in open condition with the help of a crane and pulley. On reaching the bottom of the manhole the segments are closed, picking up the accumulated silt.

The bucket is then raised above ground level where the bucket opens and the silt is automatically dropped into a truck or a trailer. The disadvantage in this system is that it cannot clean the corners of the catchpits of manholes. Sometimes the deposits at the corners may become so hard that the same may be required to be chiselled out.

6. Roding Machine with Flexible Sewer Rods:

This consists of a machine which rotates a flexible rod to which is attached the cleaning tool such as auger, corkscrew or hedgehog and sand cups. The flexible rod consists of a series of steel rods with screw couplings.

The rod is pulled in and out in quick succession when the tool is engaging the obstruction so as to dislodge or loosen it. When the obstruction is cleared, the rod is pulled out by means of clamps keeping the rod rotating to facilitate quick and easy removal.

7. Scraper:

Scrapers are used for cleaning sewers of diameter larger than 750 mm. The scraper is an assembly of wooden planks of slightly smaller size than the sewer to be cleaned. The scraper chains, attached to a control chain in the manhole into which it is lowered, is connected to a winch in the next downstream manhole by means of chains.

The winch is then revolved to push the debris ahead of the scraper. The heading up of the flow behind the scraper and the water dropping from the top of the scraper assist in pushing it in the forward direction. This ensures that the bottom and the sides of the sewer are cleaned thoroughly. The scraper debris is removed manually.

8. Hydraulically Propelled Devices:

The hydraulically propelled devices take advantage of the force of impounded water to effectively clean sewers.

The hydraulically propelled devices commonly used are-

(i) Flush bags,

(ii) Sewer balls and sewer pills, and

(iii) Sewer scooters.

(i) Flush Bags:

A flush bag or sewer flusher is a most effective tool for cleaning portions of sewers where rods cannot be used. It is a canvas bag or rubber bag equipped with a firehose coupler at one end and a reducer at the other end. The flush bag or flusher is connected to the firehose and placed in the downstream end from the point where a choke is located.

The bag is allowed to fill up until it expands and seals the sewer. The upstream pressure built up due to this damming effect breaks loose the obstructions. However, care must be exercised in using this device as there is a likelihood of sewage flowing back into the house connections or breaking of the pipes or joints due to high pressures that may develop.

(ii) Sewer Balls and Sewer Pills:

Sewer balls are simple elastic pneumatic type rubber balls which can be blown up to varying degrees of inflation. These are manufactured in sizes from 150 mm to 750 mm diameter when fully inflated. When used in cleaning a sewer, the ball is first inflated and then wrapped in a canvas cloth, the edges of which are sewed together.

A trial line, little longer than the distance between the manholes, is attached securely to the covering. The size of the ball and the covering should be such as to fit fairly snugly into the sewer. Immediately the ball is thrust into the sewer, sewage commences to back up in the manhole and continues to rise until such time as its pressure is great enough to force sewage under the ball and moving it downstream through the pipe.

Acting as a compressible floating plug, it affords enough obstruction, so that a continuous high velocity jet spurts under and to some extent around the ball, thereby sluicing all the movable material ahead to the next manhole. If the ball encounters an obstruction which is immovable, the ball merely indents to the necessary degree and moves forward.

The only fixed obstruction which will stop the forward progress of the ball is a root mass or some similar obstruction tightly wedged into the pipe. Bricks, stones, bottles, loose metal parts, broken pieces of pipes, sand, gravel and settled sludge are easily moved ahead. If the ball stops momentarily a pull on the trial line is usually sufficient to set it in motion again.

If the pipe is very dirty, the trial line may be tied to a step in the upper manhole and the progress of the ball is retarded to the required degree as the lower manhole is reached, thus giving time for complete removal of accumulated silt and debris which has piled up ahead of the ball.

Sewer pills are the wooden balls which can also be used for this purpose particularly for cleaning large outfall sewers. When the ball is dropped into the sewer then owing to its buoyant action rolls along the invert of the sewer. The obstruction caused by it to the flow produces a vigorous scouring action along the invert and the sides which has the effect of removing the growths and the deposits from the sewers. The method is economical and hence it can be used at frequent intervals.

(iii) Sewer Scooter:

This is an improved version of the scraper. It consists of two jacks – a controlling rope and the scooter with a tight fitting shield. The scooter attached to the control rope is lowered into the manhole and then introduced into the downstream sewer line. The downstream manhole jack is lowered into place from the road and the upper manhole jack set across the top of the manhole.

When the scooter is introduced into the sewer line, it stops the flow of sewage thus building up a head behind the shield. The resulting pressure causes the scooter to move through the sewer until it accumulates enough debris to stop its movement.

The head is then allowed to build up approximately 1 m before the control rope is pulled, causing the shield to fold back, thus allowing the accumulated sewage to gush into the sewer downstream, flushing the debris ahead to the next manhole from where it is removed.

The control rope is released, clearing the shield against the sewage and causing the scooter to advance again until the debris stops its movement. This process is repeated till the scooter reaches the downstream manhole where it may be removed or allowed to continue through the next section.