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How to choose a tank cleaning contractor

A common mistake that many organisations make when selecting a tank cleaning contractor is to assume that tank cleaning is essentially the same as diving, simply because it is often executed by divers. This is simply not true. Potable tank cleaning presents a multitude of risks that must be understood and appropriately managed, that are specific to tank cleaning and lie outside the sphere of normal diving risks. Depending on the situation, these risks can include:

  • Working at height
  • Working on structures with unknown structural integrity
  • Differential pressures
  • Contamination of drinking water supplies
  • Confined space entry
  • Exposure of divers to pathogens
  • Hyperthermia (heat stress)
  • Inability to rescue from height
  • Asset damage from poor drainage practices
  • Poor public perception

A responsible tank cleaning contractor will maintain a management system that addresses the above risks in detail, including detailed procedures, risk registers, safety management plans and work instructions. It is imperative that any equipment entering potable water is dedicated to this purpose and is appropriately tagged to indicate this. Some tank cleaning contractors may offer robotic solutions to tank cleaning or inspection. When evaluating a contractor to provide robotic tank cleaning solutions the following issues should be considered:

  • “Flying” type ROV’s that rely on thrusters to manoeuvre around a tank are unsuitable for potable water tank cleaning due to the large amount of sediment they mobilise into the water column when manoeuvring near the bottom of the tank.
  • Both divers and robots have different strengths, weaknesses and limitations. A professional tank cleaning contractor should be able to provide unbiased advice in this area to determine which solution is most suitable to a client’s applications, and deliver the appropriate service.
  • Non all robots are created equal. Robots used in drinking water applications should be designed and build specifically for this purpose utilising oil free parts or food grade oils only.  Robots should be suited to the scale of the application and be able to efficiently clean at an acceptable rate for the task.  A contractor that offers robotic solutions should offer different sized robotic options for different sized jobs.

Other important considerations include the rate of cleaning and the quality of the accompanying inspection. Tank cleaning times can vary significantly between contractors by in excess of 500%. Cleaning systems, cleaning methods, experience of personnel and supporting systems will all contribute to the overall cleaning times. It is important to consider both the cost per day of the tank cleaning team and the estimated number of days for the job. It is surprising how often the lowest cost solution per day can work out more expensive over an entire job. A responsible contractor will usually offer to provide a fixed price option for the job, or alternately cap the cost of job at a fixed percentage of the original estimate.

To find out more about key considerations when selecting a tank cleaning contractor please contact Fremantle Commercial Diving today.