Plastic Pipes
Maintenance and Cleaning
| Types | Maintenance / Cleaning | Cleaning Frequency |
| uPVC to SS 141 : 1976, SS 213 : 1998 for soil, waste and vent applications, SS 272: 1983 for drainlines and sewers. Joints and fittings for use with unplasticized PVC pressure pipes shall comply with SS 174: 1977. | Regular inspection to detect any chockage or water leakage.
Leak location techniques test can be used to detect the location of the leakage. Three methods can be adopted for pipeline cleaning:
|
Minimum 1x/ year for routine, or as soon as when chockage or leakage is discovered |
| Plastic pipes or tubes not specified as above |
Electromechanical
Electromechanical methods of cleaning pipes and tubes involve the use of powered tools to cut or loosen the contaminants within the pipe. The tool is usually attached to a flexible cable or rod, which in turn is driven by a motor attached to the other end.
A variety of tools and drive systems are available, including a vacuum system combined with the cable feed to assist in the extraction of debris from the pipe.
| Types of Tools | Principal use | Example |
| Brush | Removing loose deposit, burnishing | Soot, light scale, rust |
| Surface scraper | Removing medium hard deposit | Scale, fats, detergents, chemical deposit |
| Serrated rotor | Removing hard deposit | Carbon scale, limescale, resin |
| Spear blade | Breaking through soft blockages | Sewage, aggregation of solids |
| Drills | Penetrating hard blockages | Concrete, resin |
| Carbide cutter | Penetrating hard blockages | Concrete, resin |
| Saw blade | Sawing through tangled fibres | Tree roots |
| Hook | Retrieving solid object lodged in pipe | Masonry, tools |
Source: Dickenson, T. Christopher; Valves, Piping & Pipelines Handbook- 3rd edition; Elsevier Advance Technology; Cambridge; 1999. [4]
Electromechanical cleaning methods can be used on pipes in the range 12 to 300 mm diameter over lengths up to 60m from access points to remove debris and blockage arising from wide variety of contaminants. Electromechanical cleaning methods have general applicability in the removal or unwanted materials from pipe and tubes of all types.
Pigging
Pigging is a method of cleaning pipes and pipelines by hydraulically or pneumatically propelling a tightly fitting plug, or ‘pig’ through the pipe. Contaminants are removed from the walls by the passage of the pig, and these are pushed forward and out of the pipe by the combined action of the pig and surplus propellant escaping past it. Pigs may also be used for gauging pipelines and for plugging pipes during pressure testing.
There are many different configurations of pipeline pigs available today, ranging from different cups and materials, short and long, and large or small pigs. Pigging is particularly suitable for long runs of pipework having many bends and few access points, which cannot easily be cleaned by any other methods. It is not suitable for unblocking pipes which are completely closed.
Standard pig materials, temperature limits and recommended use:
| Cup material | Approx. temperature limit ºC | Recommended use |
| Cast polyurethane | -29 to 82 | Natural gas, hydrocarbon, and water |
| Neoprene | -55 to 149 | Crude oil, natural gas, general chemical, hydrocarbons and amonia |
| Hycar | -7 to 138 | Aromatics, LPG, refined products and water |
[4]
| Types of pig | Principal use | Example |
| Foam | Swabbing: removal of thin, soft or liquid films | Sludge or water in air lines: to avoid damaging pipe surfaces |
| Coated foam | Removal of films and heavy sludges | Oily deposits |
| Abrasive foam | Removal of heavy or hard deposit | Rust, slag, hard scale in water, effluent and hydrocarbon lines |
| Cleaning (brush) | Removal of miscellaneous superficial materials | Light rust and scale, precomission cleaning |
| Scrapper | Removal of hard and strongly adhered films or deposits | Corrosion, wax in effluent and hydrocarbon lines |
| Gauging | Proving minimum bore prior to commissioning | |
| Bi-directional | Plugging pipeline during hydrostatic testing |
Source: Dickenson, T. Christopher; Valves, Piping & Pipelines Handbook- 3rd edition; Elsevier Advance Technology; Cambridge; 1999. [4]
High pressure water jetting
With high pressure water jetting techniques, deposits and blockage in pipes are broken up by the action of fine, high velocity jets of water directed on to them suitably shaped nozzles, and the resulting debris is washed out of the pipe by the flow of spent water. Pressure of up to 1400 bar (20,000 lbf/in², or in some cases higher, and a wide range of flow rates are used, depending on the nature of the material to be removed. Water is delivered to the nozzle through flexible, self propelling hoses for cleaning larger pipes.
| Pressure range | Example |
| Up to 275 bar (4000 lbf/in²) | Grease, paraffing wax, crude residues, algae, pulp, asbestos, PVA, food residues, loose masonry, clay, mud, silt |
| 275-550 bar (4000-8000 lbf/in²) | Bolier scale, carbon, potash, asphalt, cement, plaster, mastic, PVC, unbonded paint, rust, oils |
| 550-1380 bar (8000-20,000 lbf/in²) | Polymer, bonded paint, resins, plastics, synthetic rubber, coke, concrete, silicates, mill scale |
Source: Dickenson, T. Christopher; Valves, Piping & Pipelines Handbook- 3rd edition; Elsevier Advance Technology; Cambridge; 1999. [4]
Currently, this method is the only cleaning method used in Singapore. Chemical solution is sometime incorporated for the stuborn blockage.