In response to local authority concerns about the specification of the plastic ‘knot-balls’ used in the play pond’s net, Rick Foster from the manufacturer HuckPlay offered the following pearls of wisdom: “Monkeyworld in Dorset uses a similar specification to the net at Agnes Riley natural play pond with horizontally rigged knotball nets of identical size and spacing (100 mm squares) using identical rope, but covering much larger areas. These nets have been in daily continuous service for almost 9 years on that site rigged in a horizontal situation, with no controlling limitation on child size or even adult size to play on the main equipment. Using the test knowledge and the data from Monkeyworld to carry out FMEA therefore, we estimate there are 25,000 in service on that site alone, making the probability of replacement for a ball in service from any cause of:- (10 / 25000) / (363 x 8 x 9) = 1.53 x 10-8 per hour. This is actually a higher figure than most flight critical individual components in service on modern civil and military aircraft.”

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