|Disaster Rescue - Australian Emergency Manual (Natural Disaster Organization, 183 p.)|
|CHAPTER SIX - LIFTING EQUIPMENT|
|Hydraulic Rescue Equipment|
6.7 The Components
(a) Pump, single acting - hand operated. In a normal working position flat on the floor with foot on foot plate, the pump can be used in any position except with the oil reservoir pointing downwards, ie. hose connection uppermost. The operating lever has a metal clip to secure it in position so the lever may be used as a carrying handle.
On the right hand side of the pump is located the release valve. This must be tight when the load is being lifted and unscrewed a couple of turns when the time comes for the ram or spreader to be closed. Lowering can be very finely adjusted by the use of this control. Inside the head of the pump there is located a blow-off valve, which is designed to release when the pressure in the system exceeds 68,900 kPa. As the area of ram base is almost 13cm² this means that the ram will lift almost 10 tonnes before the blow-off valve operates.
Thus ram and pump are protected against overloading, but not so when using any toe configuration, the alligator spreader or the wedge spreader.
It is therefore of great importance that the load of 5 tonnes using toes, 1 tonne using the alligator spreader and 750kg on the wedge spreader should not be exceeded.
(b) Ram - This is simply a compact metal cylinder, out of which extends a metal plunger when oil is pumped in under pressure. Using the ram itself on a vertical lift, 10 tonnes is the limit. If, however, the base plate and ram toe, or the plunger toe and ram toe are being used, a load of not more than 5 tonnes should be applied. This is because the load is being lifted on one side of the central axis and a bending movement is set up in the ram. This bending movement will distort the ram piston and may shear off the toe units, before the blow-off valve can operate.
(c) Other rams - Other lifting rams in common use with rescue teams, have varying lifting strokes and capacities.
(d) Hose - 1.8m or 2.0m lengths with a male coupler at one end and a female coupler at the other. Hoses are interchangeable and are pre-charged with oil ready for immediate use. A slight seepage of oil is of no consequence when couplings are being made or broken. Great care should be taken to ensure inner washers are not displaced or lost and that no dust or grit enters the system when coupling up.
(e) The ram toe is a collar which screws on the top of the ram cylinder and has a lifting lug projecting from it. When used in conjunction with the base plate, jacking can commence from an opening of about 50mm high.
(f) The plunger toe screws on to the screwed adaptor and when used with the ram toe, provides a very useful type of spreader.
Experience will dictate which one of these combinations is the correct one for the job.
(g) Wedge spreader - Where clearances for operating the ram are minimal, this wedge can be inserted after enlarging an opening with a wrecking bar or similar tool and then power applied to it with the pump. An initial lift of about 63mm can be achieved, but the weight at the tips of the wedge must not exceed 750kg.
(h) Alligator spreader - This is an enlarged version of the wedge spreader. When fitting to a ram the serrated saddle is removed from the ram and the push rod of the alligator spreader inserted into the hole in the ram plunger.
The alligator spreader is designed for use with the small 10 tonne rams with strokes of 50mm and 80mm. It MUST NOT be used with the high lift (150mm stroke) ram or the spreader will be seriously damaged.
When closed the spreader requires an opening of 32mm, but has a maximum opening of 305mm. The weight on the tips of the jaws must not exceed 1 tonne (or 1.5 tonne with some recent kits).
Some recent kits have included a 1.5 tonne alligator spreader with an integral cylinder. This does not have to be attached to a ram for operations.