Additional Considerations - Ultra High Pressure Water Jetting (UHP) The term 'Ultra High Pressure' Jetting, or U.H.P. Throughout this Code the term UHP applies to all Jetting carried out at pressures above 1700 barg. (see Section 2 of this Code) The growing availability and use of UHP Water Jetting Equipment, especially for surface preperation, means that many more operators will be required to work with pressures in excess of 1700 barg than has previously been the case. Additional training and experience It is therefore very important to stress the need for adequate additional training. Inexperienced Operators should also always be deployed with fully experienced Team Leaders in order to avoid the risk of injury. Differences between UHP and conventional High Pressure Jetting There are a number of differences between conventional High Pressure and Ultra High Pressure Water Jetting. The most important of these are listed below. Water flow in UHP systems is generally lower than in conventional HP systems and the nozzle reaction force is not as high, even though the energy released is much greater. Jetting Guns can therefore feel easier to control but this should not be allowed to generate complacency regarding the perceived decrease in risk. The Jet Velocity of a 2500 barg UHP system is in excess of 2,400 Kilometres per hour Energy Comparisons The energy available from a conventional 100 horsepower (or 76 kilowatt) unit working at 350 barg is approximately: 6 kilowatts per square millimetre. The energy available from a similar power unit working at 2500 barg is approximately: 117 kilowatts per square millimetre. The UHP unit therefore has an output of energy approximately: 18 times greater than the 'Conventional ' unit. Risk Assessments must take this factor into account. The Risk Assessment should also consider whether the entire task, or parts of it, can be automated or whether robotic processes can be utilised. Personal Protective Equipment Special PPE is available including boots with improved metatarsal protection. Clothing with enhanced penetration resistance and/or sectional rigid body protection should also be considered. It is important to note that whilst these items offer some improved protection, especially when using multi orifice rotary nozzles, they offer less protection against water jets from single orifice nozzles. Water Quality The filtration of water is critical for the reliable operation of UHP systems and the manufacturers instructions must be carefully followed. Additional Mechanical Considerations The pressure involved in UHP systems require the use of gland fittings ('autoclaves') or equivalent fittings for fluid connectors and hose couplings. Special care must be taken to protect these and to ensure that no dirt enters the system during coupling / uncoupling operations. Hose restraints should be used to reduce the risk of whiplash injury. When in use they must be fitted according to the manufacturers instructions.