SubscribeThe requirement for hose rupture protection on mobile plant is enshrined in law in many territories and likely to become so in many others. ISO8643 requires that, in the event of a hose failure while lowering a boom it should not accelerate to more than twice its original speed with the control lever held in the same position.
Additionally the valves introduced to achieve this should not unduly effect the operation of the machine to which they are fitted. (The current 100% maximum increase may be reduced to 75% in the future). If a hose were to fail while a boom is lifting or static the load should be held in position. Integrated Hydraulics have developed a range of hose rupture valves, designated “BoomLoc”, that are designed to meet the stipulations of ISO8643 and can be applied to a plethora of different machines.
The key to Integrated’s success with these units is their use of screw-in cartridge valve technology. The employment of cartridge valves enable Integrated Hydraulics to design new blocks to suit various manufacturers differing configurations confident that, as the valve cartridges and hydraulic circuit remain the same the BoomLoc unit will work as intended. Development time can be considerably reduced as the cartridges used in a given block can be changed or adjusted to obtain the optimum performance.
BoomLoc valves are reliable because they make use of standard off the shelf components that have been field proven, in most cases for many years. All Integrated Hydraulics cartridge valves are manufactured to a high standard with moving parts hardened and precision finished to give a long trouble free service life. Their performance is predictable so set up and development times can be dramatically reduced even when applied to a new system.
In service the valves perform as intended with cartridges having been tested to over 1,000,000 cycles in their development department and having been used for many years in the field. When operating under normal circumstances, i.e. with hoses intact, BoomLoc valves offer high efficiency, as the hydraulic fluid is free to pass through the valve to the cylinder with negligible pressure loss. And by selecting the most appropriate package to match the performance of any given directional valve pressure losses in the return direction can be kept to an absolute minimum. By minimising development time and utilising standard components made in their thousands, Integrated Hydraulics can offer their customers an extremely cost effective package.
BoomLoc valves can provide a very compact solution. The valve should be mounted on the cylinder, either directly onto its port or connected to the port by rigid tube, so space can be quite restricted. Using Integrated Hydraulics Boomloc valves unique design potential to the full, transfer plates, commonly employed to permit the fitting of more bulky valves can often be eliminated. The block can be designed to suit the customer’s installation and can even be done away with if the cartridge valves are incorporated into cylinder end caps thus dramatically reducing the space requirement and the cost of the overall package. Furthermore additional features can be incorporated in the block making the machine more versatile.
Caption – A typical Circuit
To achieve the desired protection without adversely effecting the operation of the machine it requires the accurate balancing of the hose rupture valve and the main directional valve. In order to work effectively the opening of the hose rupture valve should, ideally, lag behind that of the directional valve and the difference in pressure drop should remain constant throughout the operating flow range. To achieve this the hose rupture valve should be matched to the system in which it is employed, a set up that works on one type of machine would not necessarily work on another.
Due to the unique seat and poppet arrangement in the 1CPB series cartridges used in their “BoomLoc” range and the flexibility of the cartridge valve design “BoomLoc” valves can be tailored to suit most directional valves and so provide exceptionally fine control. A level of control that is particularly desired for levelling and grading, which can reduce (if not eliminate) the “washer board” effect frequently found when other valves are used. This fine control also has the benefits of enabling the operator to accurately position loads during craning operations.
Integrated Hydraulics claim reduced installation costs can be realised using their “BoomLoc” valves as they use a simple direct SAE mounting to cylinder. In order to minimise stock requirements Integrated have, where possible designed the cylinder port face to be suitable for both SAE3000 and 6000 flanges. A pilot bleed port is available on most valves simplifying installation further.
Service costs are also minimal, in the unlikely event of a BoomLoc valve being damaged, repair usually just involves the replacement of one or two self-contained cartridges. What is more there is rarely any need to remove the block from the cylinder when changing the cartridges - reducing the risk of the ingress of contaminants and the down time of the machine. Spares inventory is frequently reduced as the same two, standard, off-the shelf cartridges (albeit set differently) are often used on a wide range of machines.
In Operation
Caption - Free Flow to Cylinder
Upon operating the control to raise a boom, pilot pressure from the hydraulic remote control unit operates the appropriate spool in the main directional valve, permitting flow to the cylinder. At the cylinder the flow passes through the Hose Rupture Valve (HRV) check sections with minimal pressure loss and enters the cylinder. (The fluid from the other end of the cylinder flows directly to tank via the main control valve).
Caption - Holding
When the control lever is returned to neutral, the check valves in the HRV close and any return flow is blocked, the load is now locked in position.
Caption - Relieving
Excessive pressure in the boom cylinder, (bottom end circuit), is prevented by an overload relief located in the HRV. Pressure relieved flow being returned to tank via the main control valves port relief.
Caption – Controlled Lowering
With the joystick pushed forward to the boom lower position, pilot pressure from the hydraulic remote control unit operates the appropriate section of the main directional valve, opening flow from the cylinder return line to tank. As the directional valve opens the pilot pressure then opens the main poppet of the HRV, thus allowing oil to flow from the return end of the cylinder to the tank line.
The rate at which the boom descends is dependent on the total load on the operating cylinder, the position of the poppet in the HRV andthe spool in the main directional valve, both the latter are governed by the pressure in the pilot line. So in the event of a total hose failure the HRV will prevent the boom accelerating above twice its original speed. As the flow rate is now dictated by the pressure drop across only the BoomLoc valve. Releasing the control lever will permit the poppet in the BoomLoc HRV to close stopping the boom from further descent.