SEWER APPURTENANCE
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Sewer appurtenances are the various accessories on the sewage system in order to make the process of construction easy and to have efficient working and maintenance. If sewer system is not properly maintained silt, ashes, grit, fats, oil etc. will chock the sewer lines, therefore, for proper operation and maintenance of sewer system various devices are required.
Appurtenances are as follows: • • • • • • • • •
MANHOLE CATCH BASIN CLEANOUTS OIL AND GREASE TRAP INLETS LAMPHOLES SEWER VENTILATORS STORM WATER RAGULATORS INVERTED SIPHONS
MANHOL E
Drop Manhole
Flushing Manhole
Straightthrough Manhole
Junction Manhole
STORM WATER REGULATOR
Leapin g Weir
Siphon Spillway
Overflo w Weir
MANHOLES •
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A manhole is an opening constructed on the alignment of sewer to facilitate a person access to the sewer for the purpose of inspection, testing, cleaning and removal of obstruction from the sewer line. The main objective of construction of manhole is firstly they permit inspection, cleaning, maintenance of sewer line and the obstructions in the sewage is collected in manholes.
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Secondly it allows the joining of sewers or changing the direction or alignment. If the manhole covers are perforated, they will allow the escape of undesirable gases and thus ventilation will also be achieved.
MANHOLE are classified as :
SHALLOW MANHOLE
NORMAL MANHOLE
DEEP MANHOLE
SHALLOW MANHOLE • It is constructed at the start of branch sewer or at places, which are not subjected to heavy traffic such as domestic areas. • These manholes are provided with light cover at its top and are called INSPECTION CHAIMBER. • These are 0.70m to 0.90m deep. NORMAL MANHOLE • It is about 1.5m deep . • It is constructed either square or rectangular in cross-section. • Such manholes are provided with heavy cover at its top. DEEP MANHOLE • The depth is more than 1.5m. • Steps are provided in such manholes to enable workers to go up to its bottom. • These manholes are also provided with heavy cover at its top.
Components of Manhole A manhole is considered to be made of three parts:
MANHOLE-COVER
ACCESS SHAFT
Manhole cover resting on a heavy frame Access shaft Working chamber
The manhole is provided with cast iron cover and a cast iron frame at its top. Size of rectangular cover is about 0.6mX0.45m and diameter of circular circular cover is 0.5m-0.6m.
The upper portion of a deep manhole is called access shaft.
WORKING CHAMBER The lower portion of a manhole is known as working chamber which provides working space to carry out cleaning and inspection of sewer line.
STRAIGHT THROUGH MANHOLE
DROP MANHOLE
• It is the simplest type of manhole which is constructed on a straight run of sewer with no side junction.
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JUNCTION MANHOLE
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This manhole is built at every junction of two or more sewers. The soffit of the smaller sewer at a junction should be not lower than that of the larger sewer.
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A manhole in which vertical pipe is used is called drop manhole. When a high level branch sewer is connected to low level main sewer so a vertical pipe is used. It is used when branch sewer enters a manhole by
MANHOLE TYPES
FLUSHING MANHOLE •
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It is a tank holding a supply of water or sewage for periodically flushing out a sewer. Where it is not possible to obtain self cleaning velocities due to flatness of gradient specially at the top ends of branch sewers which receive very little flow. This can be done by making grooves at intervals of 45-50m in main drains in which wooden planks are inserted and water allowed to head up and which will rush on with great velocity when planks are removed.
CATCH BASIN •
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A catch basin or a catch pit are small masonry chambers which are constructed below the street inlets to allow flow of water free from silt, grit etc. into sewer lines. The catch basins collect solids from storm water. These solids are to be removed frequently otherwise they will block the passage. •
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The sewer cleanout fitting provides a point of insertion perpendicular to the direction of flow in the main pipe, but it is angled in such a way that anything you insert into the fitting (such as a drain snake) cannot go against the flow of waste water. A cleanout is generally provided at the upper ends of lateral sewers in place of manholes.
CLEANO UTS
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A grease trap is a plumbing device (a type of trap) designed to intercept most greases and solids before they enter a wastewater disposal system. Common wastewater contains small amounts of oils which enter into septic tanks and treatment facilities to form a floating scum layer. This scum layer is very slowly digested and broken down by microorganisms in the anaerobic digestion process. Large amounts of oil from food preparation in restaurants can overwhelm a septic tank or treatment facility, causing release of untreated sewage into the environment. Highviscosity fats and cooking grease solidify when cooled, and can combine with other disposed solids to block drain
OIL AND GREASE TRAP
LAMP HOLES •
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A lamp hole is a small opening or hole constructed in a sewer for the purpose of lowering a lamp inside. The lamp light is then viewed from the upstream as well as downstream manholes. The obstructed light confirms the obstruction in the sewer. If the construction of manhole is difficult, lamp hole may be constructed at its place.
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STORM WATER RAGULATOR
The main object of providing a storm water regulator is to divert the excess storm water to natural stream or river. • The excess sewage will be mainly composed of storm water and it will therefore be not foul in nature. There are three types of storm water regulators: 1. Leaping weir 2. Overflow weir 3. Siphon spillway
LEAPING WEIR The term leaping weir is used to indicate the gap or opening in the invert of a combined sewer. It has no has no moving parts. When the discharge is small, the sewage falls directly into intercepting sewer through the opening. But when discharge exceeds a certain limit, the excess sewage laps jumps across the weir and it is carried to natural stream or river.
OVERFLOW WEIR In this type of arrangement, the excess sewage is allowed to overflow in the channel made in the manhole. When the quantity of sewage exceeds the capacity of combined sewer, it overflows and falls into the channels and it is conveyed to storm water sewer. In order to prevent the escape of floating matter from combined sewer channel, the adjustable plates are sometimes provided.
INVERTED SIPHONS
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An inverted siphon is a sewer section which is constructed lower than the adjacent sewer section and which runs full under gravity with pressure greater than the atmosphere. inverted siphons are used to carry sewage or stormwater under streams, highway cuts, or other depressions in the ground. In an inverted siphon the liquid completely fills the pipe and flows under pressure, as opposed to the open-channel gravity flow that occurs in most sanitary or storm sewers.
It works on the principle of siphon action. It is automatic in functioning and this is the most effective in all other methods. This arrangement has no moving parts and thus low maintenance. However it is likely to be clogged due to narrow passages.
SIPHON
SEWARE VENTILATORS •
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Various gases are produced in the sewer due to decomposition of organic materials of sewage. These gases are foul in nature , cause harm to human health. The gases produced are highly explosive and may cause explosion. Due to these problems ventilation is provided at every 80-100M which will provide fresh air to the workers working in the manhole. It may be of RCC or cast iron 15 to 23cm in diameter with a cowl provided at the top.
Reference • Wikipedia • Google images
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