Objectives

The primary objective is to execute a comprehensive mechanical and electrical refurbishment of rotating half-bridge scraper assemblies on five circular clarifiers (Nos. 1, 3, 4, 5, and 6) at the Grabouw Sewerage Works. The project aims to restore optimal operational performance, ensure structural integrity, and extend the service life of critical wastewater treatment infrastructure through targeted component replacement, precision alignment, and compliance-driven installation.

Scope of Work

The contract encompasses end-to-end servicing, including:

• Safe decommissioning, electrical isolation, and structural propping of clarifier bridges to relieve load from center pivots.
• Removal and inspection of worn center pivot bearings, drive/idler wheels, and obsolete slip ring assemblies.
• Supply and installation of new heavy-duty centre slewing bearings, wheel bearings, and an IP65-rated collector ring unit.
• Precision alignment to original equipment manufacturer tolerances to prevent binding or structural stress.
• Complete lubrication overhaul, including flushing old grease and installing new greasing nipples for future maintenance.
• Full electrical rewiring and termination, followed by insulation resistance, continuity, phase rotation, and live rotational commissioning tests.
• Project completion must occur within three weeks of the official order date.

Technical Requirements

All supplied components and installations must meet stringent specifications:

• Centre Bearings: Four-point contact slewing rings manufactured from 42CrMo or 50Mn steel, grease-lubricated with double NBR seals, hardened raceways (240–300 HB), corrosion-resistant coating, and a minimum 20-year design life.
• Wheel Bearings: Spherical roller bearings using SAE 52100 chrome steel, double-lip NBR seals, EP2 lithium complex grease, split plummer block housings, rated for continuous 24/7 outdoor wastewater operation between -20°C and +80°C.
• Collector Ring: Compliant with SANS 10142, housed in 3CR12 or 304/316 stainless steel enclosures, IP65 rated, moisture-proof, and designed for 400V AC 3-phase power with slow-rotation optimization.
• Greasing Fittings: M8×1.00 metric taper threads, stainless steel construction, 18.5 mm length, with integrated ball-point check valves.
• Safety & Compliance: All electrical installations must adhere to SANS 10142 wiring regulations. The service provider acts as the client’s agent under the Occupational Health and Safety Act, maintaining daily safety logs, tool registers, and ensuring all personnel possess required vaccinations and training.

Skills and Qualification Requirements

Bidders must demonstrate:

• Mandatory CIDB ME1 mechanical engineering contractor grading.
• Documented experience servicing mechanical components in the wastewater treatment sector, supported by references from at least two other local municipalities.
• Attendance at the compulsory site inspection meeting.
• Valid Tax Compliance Status PIN certificate and certified B-BBEE documentation (or EME/QSE affidavit) to qualify for preference points.
• Proof of a municipal account or lease agreement if claiming locality-based preference points.
• Ability to complete all mandatory administrative bidding forms and price every line item in the schedule accurately.
• Capacity to manage health and safety compliance, submit work programs for approval, and assume full responsibility for subcontractors and repair quality.

Key Terms and Definitions

SST: Secondary Sedimentation Tank, referring to clarifiers used in wastewater treatment to settle suspended solids before discharge or further processing.

CIDB ME1: The Construction Industry Development Board’s lowest mechanical engineering contractor grading, indicating eligibility for small-scale mechanical projects up to the specified financial threshold.

80/20 Preference Point System: A procurement evaluation model allocating 80% of scoring weight to price competitiveness and 20% to socio-economic goals, specifically B-BBEE status levels and geographic locality of the bidder.

LOTO: Lock Out Tag Out, a standardized safety protocol for isolating energy sources during maintenance to prevent accidental energization and protect personnel.