DEADMAN/FILTER DIFFERENTIAL PRESSURE PROTECTION SYSTEM...
A new JIG bulletin has been released regarding Filter Differential Pressure Switches and Protection Systems and Bulletin 58 states that all differential pressure gauges on hydrant dispensers fitted with monitor elements must be fitted with a DP switch that is linked to the deadman and fuelling control system. The switch must be set at 22psi and it must be designed to stop the fuelling operation when a high differential pressure is detected. It must also prevent the operator from easily resetting the system under the aircraft. The system must be installed so that the only way to reactivate the refuelling operation is to use a key or a similar mechanism.
There are a number of deadman systems, and also some dedicated filter Differential Pressure (DP) protection systems available in the market. However, the DP protection systems which have been developed both monitor and correct the DP. The need for automatic DP correction is the subject of much debate, but it is universally accepted that the operator cannot consistently monitor the filter DP during the refuelling operation. In the event of a water slug passing into the filter monitor elements, they will block very quickly, causing a rapid rise in the filter DP, with little or no warning. When this occurs, it is very unlikely that the operator will be close enough to the DP Gauge to take action and shut the system down quickly. Also, after a rise in filter DP the operator can ‘cheat’ the system and reduce the DP, by reducing the system flow rate. This is a very dangerous situation because although the filter DP can be reduced in this manner, the elements themselves will still remain blocked and the risk of element rupture will remain.
Although filter DP switches are available, up until now there has been little consideration given to the system required to use the output from the DP Switch in the optimal manner. Also, new vehicles can be fitted with a system relatively easily, but retro fit to existing vehicles on site is not so easy and if this task is carried out with insufficient consideration, it is possible that the final system may not be completely satisfactory. It is also likely that there will be no standard operating mode, if there is a mix of converted and new vehicles at a location and this will lead to confusion among the operators.
We are pleased to announce that we have developed a system that fully complies with JIG Bulletin 58. It is suitable for fitment to new dispensers during build or for retro-fit to existing hydrant dispensers. The Aljac system is a combined system, so it can either be used as a deadman, or as DP protection (which can be easily retro fitted alongside any existing deadman equipment), or a combined deadman and DP protection system.
For more information about our Deadman/Filter Differential Pressure Protection System, or a quotation, please contact our Sales Team at This email address is being protected from spambots. You need JavaScript enabled to view it. , or call +44 (0) 1932 269869.
