SEA are constantly striving to bring new safe gate systems to the market; to that end the company has made the Position-Gate. This device will enable Mini Tank and Half Tank systems to accurately “feel” where the piston rod is, while the gate is travelling open or closed.
By sensing the exact position of the piston rod, the Position-Gate knows where the gate leaf is in it’s travel, how fast it is moving and precisely when it will encounter a physical stop. Therefore, the Position-Gate can be used as an auto learn device and a stop and reverse safety device. It can also operate below the 50mm threshold, where traditional current sensing devices and encoder systems do not work effectively.
SEA UK Position-Gate Force Test Results.
At SEA UK we periodically tests our product range to ensure the highest standards of reliability are maintained. While testing the Position-Gate we carried out a series of Force Tests to confirm the Position Gate worked as intended.
The Gate.
These tests were performed using our repaired motor test gate; if you sign up to one of our free training courses, you will be working with this gate. Our test gate is 2.5m long, weighing approximately 280kgs when fully loaded. To better simulate site conditions, the gate has standard eyelet hinges, with weight added to the front of the gate leaf to increase momentum and loading on the motor. The motor is connected to a central beam which is unsupported by vertical bars. This is an intentional design to simulate common flexing found in many site situations. The operator used is a Half Tank 100, 270mm piston stroke, 230V AC motor. The control system is a Gate 2 DG, 230V control panel.
Testing 2.5m Gate Leaf, Weighing 280kg.
When force testing a gate system, measurements must be taken at the bottom, middle and top of the gate leaf; as well as at different distances away from the close stop position. The diagram below shows where these tests are made and provides a useful numbering system to match up with the results later.
Test Position 8
The first test is typically carried out in position 8, the gates centre, at 500mm from the close stop position. At this point the gate leaf has entered slowdown and is moving at roughly half speed; our gate has no safety edges or other forms of cushioning to absorb the impact.
| Point of Measure | Description of tests | Fd [N] -Measure – Limit | Td [s] – Measure – Limit | Fs [N] – Measure – Limit | Fe [N] – Measure – Limit | Result |
| 8 | Height: at the center of door, or 2500mm above the floor, when the height of door is >5000 mm. Gap: 500mm from main closing edge and the opposing edge. | 119/400 | 0.00/0.75 | 24/150 | 0/25 | PASS |
The results above show a PASS has been achieved, but more information can be seen from the force graph produced by Microtronics Blue Force software. The initial impact is detected very quickly and the gate starts to reverse. The excess weight added to the gate leaf and the lack of central vertical supports on our test gate creates a wobble, this can be seen by the waves in the graph. As the gate moves away from the tester the waves diminish, before falling to 0 as the gate fully clears the tester. The gate is moving away from the obstructions within approximately 2.0 seconds.
This PASS is possible because the Position-Gate knows the precise position of the piston rod. The control panel knows that the gate is within the gate slowdown phase (the 500mm danger area) and is expecting lower momentum with pushing forces adjusted below the 150N threshold. It can therefore accept a longer reverse time allowing for wind slowdown at lower forces.
Test Position 10
Test are not often performed at 1m distance because the motors are moving at full speed. Many systems especially current sensing versions, struggle to pass at this distance due to site conditions and motor reaction times.
Before carrying out the force test SEA engineers perform a separate test to simulate site conditions and the effects of wind on the gate. With default pressures used on the Half Tank our engineers added a 90N (9kg) resistance to the gate. As expected the motor continued to open and close with this added resistance.
Next, with the same pressures, the resistance removed and the gate travelling at full speed again, our engineers carry out the Force Test. A clear PASS is recorded and it would even be possible to increase motor pressures for the Half Tank operator to cope with increased wind loadings if necessary.
| Point of Measure | Description of tests | Fd [N] – Measure – Limit | Td [s] – Measure – Limit | Fs [N] – Measure – Limit | Fe [N] – Measure – Limit | Result |
| 10 | Height: at the center of door, or at 1000 mm above the floor. Gap: 1000 mm from main closing edge and the opposing edge. | 372/1400 | 0.59/0.75 | 12/150 | 6/25 | PASS |
As we can see form the table above and graph below the Position-Gate allows the system to pass the test. Once again, a small bounce is recorded due to the style and construction of the gate, as well as the added weight at the end of the gate leaf.
Test Position 1
More tests are carried out at positions 1 and 2. Here again there is a small wobble due to the excess weight, our testers have added to the gate but importantly the Position-Gate has slowed the motor down ready for the gate to meet the physical stop. This means the initial impact is just above the 25N Fe mark.
| Point of Measure | Description of tests | Fd [N] – Measure – Limit | Td [s] – Measure – Limit | Fs [N] – Measure – Limit | Fe [N] – Measure – Limit | Result |
| 1 | Height: at 50 mm from bottom edge of the door. Gap: 50mm from main closing edge and the opposing edge. | 51/400 | 0.00/0.75 | 18/150 | 0/25 | PASS |
Many encoder and current sensing systems must switch off at distances around 50mm or risk recording a false positive, but the Position-Gate continues to operate up to the physical stop position. This can render other systems ineffective at protecting the small closing gaps at the end of a gates travel. The Position-Gate measures the position of the motor ram switch off distance, which can be accurately and electronically adjusted; resulting in a passed force test.
Our engineers report that when the motors are set up to use low pressure, the impact force of the closing gate is below 25N (not registering on the Force Tester). This would not be recommended on site as it would cause reliability issues. It does however, underline the fine control which can be achieved with the Position-Gate system and reliable hydraulic operators.
Position-Gate Qualities
When considering gate safety products, it is important to understand the relative qualities of each product. The Position-Gate may not be the perfect solution for every site. For example, a very long gate leaf reduces the effectiveness of the system. A close boarded gate can act like a sail; the motor pressures may need to be increased to provide reliability, resulting in the FS Max being above 150N. Furthermore, certain areas of a gate such as the hinge area and curb crushes could still be dangerous and need protecting.
Summary
The Position-Gate is a powerful new tool for SEA hydraulic electric gate systems and will lead to improved safety on many sites. It can pass force tests at all locations allowing the adjustment of the motor power to suit site conditions. However, it should be used in conjunction with a proper risk assessment and other safety devices such as Safety Edges, Photocells, and Hinge Guards.
