Types of Liner Used for Sewer Sanitary System

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There are various types of liners used for sewer sanitary system such as cast in place liners, chemically attached liners and mechanically attached liners which are categorized based on attachment technique and type of material used in the liner production. These types of liners used in the construction and/or repair of sanitary sewer system will be discussed in the following sections.

Fig.1: Liner used for sanitary sewer pipe system to prevent it from corrosion

Types of Liner Used for Sewer Sanitary System

Cast in Place Sewer Liners

There are various types of cast in place sewer liners which are commercially available to be used. It can be used for new construction and repairing works. Cast in place liners are attached to sanitary sewer pipes by means of ribs, knobs, and tees which are embedded into concrete or grout. It creates an acid barrier between sewer water and sewer sanitary pipe wall. Cast in place liner permits the movement of hydrostatic pressure and vapor into sewer pipe without compromising its function which is protection sewer pipe from corrosion. Regarding cast in place liner performance, the best performance is when liners are attached to precast pipes in factory. The inside sewer pipe area that recommended to be covered ranges from 300 to 320 degrees. Lesser coverage may lead to pipe deterioration due to sanitary water flow whereas 360 degree coverage could pose health issues. Finally, it is required to be cautious during liner placement and liner welding which used to attach liners to each other.

Chemically Attached Sewer Liners

Chemically attached liners can be used for new construction and repairing works. It is widely used in rehabilitation works since other types of liners are more economical in the case of new construction. There are two major forms of chemically attached liners. Firstly, PVC sheet with protrusions on one side that pushed into previously applied epoxy mastic on concrete sewer pipe surface. The epoxy would encircle protrusions and satisfactory bond would be generated between liner and concrete. Secondly, PVC sheet liner that attached to sewer pipe chemically using polyurethane mastic. There is chemical agent in the PVC sheet that causes chemical fusion between polyurethane mastic and the liner. Moreover, it is important to bear in mind that concrete pipe surface should be prepared in addition to choose suitable primer under mastic polyurethane or concrete polymer which may be used instead of the mastic. These Measures will ensure a good bond between sewer pipe and the liner.

Fig.2: Chemically Attached Lining Pipe

Mechanically Attached Sewer Liners

This type of liner is widely used for new construction and it has been applied for countless repairing tasks. The most common type of materials used to manufacture this liner types are PVC and HDPE. However, it can be produced from nearly all types of materials. The strongest point of mechanically attached liner is its suitability for almost all construction condition. This is because not only does the liner thickness can be changed but also broad ranges of attachment techniques may be employed. The attachment may vary from small expansion type anchors to stainless steel batten strips with epoxy coat. Design conditions can be easily met with mechanically attached liner since its thickness can be increased to accommodate greater loads. Similar to cast in place liner, hydrostatic and vapor forces cannot be accommodated, so it is permitted to move into sewer environment through the liner. It is necessary to pay attention to the liner and sewer pipe interface during installation otherwise hydrostatic relief issue may arise due to chemical reactions. When this liner is designed, all hydraulic conditions should be accounted. Finally, adequate thickness, hoop strength, attachment security need to overcome expected loads otherwise it would suffer from crucial failures. With regard to attachments, materials used for manufacturing, spacing, type, and size of the attachment play critical role in the safety of the liner.