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Defects
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Probable causes for the defect
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Design for Maintainability (DfM) Guidelines
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Excessive vibration
 Insufficient vibration damping causing wear-out of parts
 Dented pump impeller |
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Design
- Ensure that pumps are properly sized to meet the required pressure. Head loss, frictional loss and loss at bends should also be considered.
- Sewage pumps should be able to handle long and fibrous material. If required, pre-treatment (e.g. crushing) is provided.
- Specify variable speed drives (VSD) that are able to handle both maximum and variable demand.
- Ensure that the pump is mounted on an isolation bed (e.g. 150mm insulated padding) and that no site adjustment in height or position should be done.
Construction
- Conform to the installation of pumps as per manufacturer’s instructions. Ensure proper construction of isolation beds and installation/mounting of equipment.
- Special attention should be given for tightness of joints, and alignment of bearings and pipes.
- Conduct testing and commissioning of the auto and manual interchange of duty and standby pumps.
Maintenance
- Lubricate pump parts with oil or grease as per manufacturer’s instructions.
- Conduct routine check, clean motor starter and all heavy current contacts, and replace worn parts.
- Visually check for any damage or missing parts (screw, nuts, strainer, etc.).
- Ensure that after installation, pump is tested with power on mode for any unusual vibration, noise, leakage or burnt smell.
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| Water not enough hot / takes long time to appear |
- Wrong design results in excessive ‘dead leg (the pipe length of cold water allowed to run off before hot water appears at tap spout)
- The primary and / or secondary circuit is not insulated to prevent heat loss or insulation damaged with time.
- Short circuiting in the piping of the primary and secondary circuit. Combustible insulation of the primary and secondary circuit of the hot water cylinder melts after some time.
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| Corrosion
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- Piping material not corrosion resistant or galvanic corrosion. Timely action (e.g. paint is helpful).
- Protective coating lost /damaged during installation–improperly done.
- Hard water reaches a temperature > 60ºC forms scales.
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PUB – Requirements for discharge of trade effluent into the public sewers
References
- SS 636 — Code of practice for water services
- SS 375 — Suitability of non-metallic products for use in contact with water intended for human consumption with regard to their effect on the quality of the water
- PUB — Code of practice on sewerage and sanitary works
- SS 608 — Code of practice for gas installation
- BS EN 806 — Specifications for installations inside buildings conveying water for human onsumption
- BS 8554 — Code of practice for the sampling and monitoring of hot and cold water services in buildings
- BS 8558 — Guide to the design, installation, testing and maintenance of services supplying water for domestic use within buildings and their curtilages
- ISO/DIS 24510 — Activities relating to drinking water and wastewater services — Guidelines for the assessment and for the improvement of the service to users.