Support > FAQ
Q: What is the difference between a Dynamic Load Reducer (DLR) and a Passive Heave Compensator (PHC)?
A: A Dynamic Load Reducer is used on an offshore crane to reduce the dynamic loads associated with lifts from moving vessels. It requires no modification to the crane. The DLR does not increase the design strength of the hoisting system structurally. The DLR reduces the required dynamic factor in order to increase the crane’s rated Safe Working Load (SWL). With the DLR, the dynamic load factor for boat lifts can be significantly reduced, allowing a crane’s rated capacity to be increased by 40% or more depending on the sea state and load.
A Passive Heave Compensator, however is used to reduce dynamic forces on the load while keeping load variations in wires within acceptable limits. PHC is typically used in circumstances where the load is situated on the seabed and in seas where movement compensation is necessary.
Q: What is TENSA Gimbal Insert Brush used for?
A: The TENSA Gimbal Insert Bush is designed to support conductors that must be free to rotate at the top. This avoids developing large bending and fatigue stresses at the top of the conductor due to lateral wave or current loading. Typical applications include supporting a production or test conductor that is tensioned with a standard TENSA conductor tensioner unit.
Q: How does TENSA Dynamic Motion System (DMS) provide accurate vessel heave velocity information?
A: Traditionally, the significant wave height (Hsig) has been used as a method of estimated which is inaccurate as it can easily underestimate loads by 50%. Hsig is a statistical sea state parameter and does not necessarily correlate to the motions of the load on a vessel. TENSA DMS gives a graphical output of the load velocity and allows a crane operator to see the vessel heaving in real time. He can then predict when lulls are likely to occur between large wave sets. The DMS system logging capability offers the ability to record the actual conditions during the lift.
Q: Can we use TENSA Dynamic Motion System (DMS) in a similar way we use Helideck Motion System (HMS)?
A: TENSA DMS unit is not a formal CAP437 device but it does offers the information needed.
- “Heave rate” is “heave velocity”
- “Heave amplitude” is “heave magnitude”. This can be displayed for a 15 minute time frame on the graph and we have 3 minute and 60 minute maximums in the data window.
Q: What are the available sizes of TENSA Gripper type conductor clamps?
A: TENSA Gripper type clamps are made in all sizes from 9 5/8″ to 36″. Standard sizes of 13 3/8, 20″ and 30″ can be delivered at short notice.
Q: What is the difference between TENSA standard Gripper clamps and TENSA Type B Gripper clamps?
A: TENSA Type B Gripper clamps provide the additional feature of supporting casing from the secondary tensioning system (STU) or Top Tensioning System which is connecting from the underneath the drill floor.
Q: What is the difference between Active Heave Compensated Pedestal (AHCP) and Passive Compensated Gangways?
A: TENSA AHCP is designed to be used in conjunction with the Uptime 12m and 15m aluminum gangways for offshore crew transfer. The AHCP transforms the passive compensated gangway into a fully active heave compensated system.
Q: What is the difference between a Passive Heave Compensator (PHC) and Active Heave Compensator (AHC)?
A: A passive heave compensation (PHC) system acts as a gas-loaded spring with a predefined stiffness. It works to reduce dynamic forces on the load while keeping load variations in wires within acceptable limits. In general, these systems are reliable, simple and don’t require power to operate, which is a significant advantage during a power failure. PHC is typically used in circumstances where the load is situated on the seabed and in seas where movement compensation is necessary.
Active heave compensation systems differ from these in that the motions of a vessel are measured using a Motion Reference Unit (MRU), which, in real time, actively controls the load’s position. These systems also differ in that they rely on an external power source.
Q: How does Roborigger work?
A: TENSA ROBORIGGER units uses gyroscopic and inertial forces from rotating flywheels to orient the loads. This is similar technology to that used to orient spacecraft. ROBORIGGER can orient the loads when hanging on a single wire with a swivel. It does not need anything attached to it. The unit has sensors which detect the rotation rate and the heading. The sophisticated adaptive control system ensures that the load rotation is controlled within strict parameters and that the unit is able to hold the load at a constant heading when required.
Q: What are the features of Roborigger?
- Ability to rotate and orient load using a wireless remote control
- Remote hook release that requires 2 button press and will not release under load
- Can store 2 desired headings to allow ease of operation when moving many loads
- 12 hour battery life
- Batteries rechargeable in 4 hours
- Optional exchangeable battery module allowing 24×7 operation
- Integrated load cell with load readout on remote handset
- Inbuilt condition monitoring, lift logging and diagnostics
- Optional downward looking video camera
Q: Is Roborigger safe?
- ROBORIGGER is designed as a lifting appliance in accordance with AS4991.
- Every unit is load tested and comes with a test certificate verifying the load test and performance test
- The remote control complies with the Australian Crane Code AS1418 and includes all of the safety features required for crane operation. If control is lost the unit will coast safely to a standstill.
- The unit has flashing orange warning lights to indicate it is in rotate mode under control of its control system. A buzzer sounds when the load is being released. Red lights indicate a fault. Green lights indicate a healthy system.
- The electrical system uses low voltage and does not require licensed electricians. The external battery charger runs on 240V.
Q: What is the capacity of the Roborigger?
A: The capacity of ROBORIGGER is governed by both the lifting capacity and the amount of rotating torque that the unit can apply. Initially the focus will be on the AR3 and AR5 models which are rated for 3 and 5 tonne loads. We have a design for a 10t model which is quite different and can be scaled up to 50t if required. Two or 3 ROBORIGGER units can be attached to a spreader system to double or triple the rotating capacity. ROBORIGGER subsea uses the same control system and battery pack from the surface system but achieves the rotational capacity by using thrusters. The capacity of this system is virtually unlimited.
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