Turnkey Solutions – Case Study

Refurbishment of ø20m fixed half bridge column mounted primary

settlement tank scrapers

Introduction

• Scottish Water urgently needed to replace two scrapers that had fallen into disrepair at a sewage treatment works near Glasgow.

• A main contract was awarded to GMJV who sourced tenders from the marketplace for the refurbishment of the scrapers.

• As a result Xm Services became involved in the tendering process and was eventually awarded a contract to undertake the refurbishment.

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Poorly performing primary settlement tank scraper

Primary settlement tank scraper with collapsed scum skimming device

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The root cause of poor performance in primary treatment process was the use of peripheral rollers and scum board to support scum skimming arrangement.

The peripheral rollers derailed from the scum board generating excessive forces at the point where the scum skimmer arrangement was fixed to the centrally located diffuser drum causing it to collapse.

Detailed Design

• In order to improve the robustness of the scraper the scum skimming arrangement was designed so that it is supported by the rotating scraper arm

Manufacture of Scrapers

Xm Services worked closely with both its suppliers and GMJV throughout the manufacturing phase:

• Conducting regular project schedule reviews and updates to monitor and control the manufacturing process

• Perform factory acceptance tests to ensure conformance with:– design documentation– WIMES 2.01 data sheets– EC standards

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Manufacture of Scrapers

Scraper Refurbishment

Decommissioning, removal and disposal of existing scrapers:• Preparation of site risk assessments, method statements and lift

plan for inclusion within the contract H&S file• Site supervision and induction of all personnel• Provision of confined space qualified personnel to work inside

the settlement tank• Provision of qualified first aider• Conducting daily toolbox talks• Daily issuing and closure of permits to work• Cranage and execution of contract lift• Scrap disposal

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Scraper Refurbishment

Installation and commissioning new scrapers:• Unloading, unpacking and storage of equipment• Assembly• Installation• No load site acceptance tests• Full load commissioning tests• Customer acceptance and handover

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