Main Feature
looks to minimising any pipe damage.
Guidance on working practice is also given such as reducing the flow in the pipe prior to jetting to limit the outflow of the pipe downstream during cleaning and setting a dirt trap to collect larger detritus so as not to pass any blockage problems material downstream of the current blockage that may cause further problems either in the pipe or at the treatment plant. This is very brief overview of just some aspects of a well-respected document within the industry, so please do not take this as all it offers! It is very comprehensive and will guide operators well in the industry as it works today.
What does not appear to get presented in the guide is how the configuration works as a whole. Whilst the recommended pressures are the pump pressures this does not take account of losses between pump and nozzle or the effect of the water jet once free of the nozzle.
Some industry participants when questioned highlighted the fact that training of operatives does tend to be Health & Safety centric with training concentrating on how to the use the equipment so that neither the operator, anyone else on or near the work site or the general public gets hurt.
What many think is missing from the training side is the imparting of knowledge of how the nozzle end works and what is needed to get the jets to clean effectively. For example one commentator suggested that few (if any at the domestic end of the jetting scale) understand the ‘engineering’ or ‘science’ behind the cleaning action and where the losses are greatest and so where cleaning may easily become ineffective.
Given that the cleaning nozzle at first lays on the pipe invert until pressured up and that once under pressure it rises into the pipe but not to a central position, does the operator understand that once clear of the jet the greater distance of the nozzle from the target wall the greater the losses in impact force of that jet on the pipe wall and that over that distance the pressure/force of the water declines very rapidly? Probably not to the degree required for effective cleaning in some circumstances.
Does the operator understand that a worn nozzle can cause a pressure reduction or that the wrong nozzle can also have an adverse effect on the cleaning process, does the operator understand that overworking the length of clean can cause a pressure drop in the hose that makes even a good nozzle ineffective once too far into the pipe? Again probably not.
Some think this is very much the case and that more needs to be done to enhance the engineering understanding of the operators at site to ensure that the right choices are made before work starts and also that the right selection of hoses and nozzles are
Jetchem Sprint trailer
made available without recourse to a visit back to base. Without this knowledge and the right equipment time on site can rise, costs can rise with more fuel use and water supplies may be compromised or insufficient if the wrong equipment is used.
Anecdotal evidence also shows that in some cases some operators have not got available a range of nozzles and use the same one no matter what the situation, pipe type or cause of the blockage. This cannot be good for the operator who may have to work twice as hard for twice as long to achieve ay form of complete clean. This cannot be good for the contracting company because fewer jobs are completed successfully in any one day by any one operator and it cannot be good for the client (water company or domestic) who either has to pay for additional time on site (many of the domestic operations charge by the hour) or have to wait for the contractor to turn up late or have to find another more readily available service.
EDUCATION THE KEY TO THE FUTURE
According to various discussions and feedback to questions for this article, pipelines currently are and have been designed generally with an overcapacity of around 20%, in the main this is apparently to allow for fouling and they are as far as possible designed with a degree of self-cleaning built-in! If this is the case then it has to be asked - if most pipes are designed overcapacity and to be self- cleansing how come jetting contractors are always so busy?
Is it bad pipe construction/pipe jointing that allows blockages to develop, bad waste management that allows ‘stuff’ into pipes that should not be there which causes blockages? Or is there a case that even if the pipes are designed to be self- cleansing to a greater or lesser degree they do still need some degree of maintenance over time with regular (if wider-spaced in time) inspection and cleaning than they get now? Such a programme of cleaning might ensure that they continue to operate efficiently and not just sit and wait until a blockage gets to the stage where it needs the call-out. The cost argument might also be that whilst regular cleaning is not deemed economic, are the costs of emergency call- outs such that in the fullness of time the client actually ends out paying more to the emergency contractor than it would cost to have completed regular cleaning in the first place?
The other question that does not seem to be asked by those within the industry is one which may be politically toxic and that is whilst ongoing maintenance is
12 drain TRADER | February 2016 |
www.draintraderltd.com
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80
