FAQ's

(Frequently Asked Questions)
Thruster Motors
Rotary Actuators
Linear Actuators
Hydraulic Pumps & HPU's

Intelligent Valve Packs

Control Units & Interface Cards

Pan & Tilts

Pressure Compensators

Position Sensors

Specialty Pumps

 


 

 Thruster Motors

Question: What is the best way to mount a Tecnadyne thruster to an ROV or AUV?

Answer: We recommend the tried and true approach -- fabricate a saddle mount from aluminum, stainless steel or plastic material that will partially encircle the cylindrical portion of the motor housing. Use two screw drive hose clamps (stainless steel) to hold the thruster to the saddle mount. Put electrical heat shrink tubing around the hose clamps -- this will protect the thruster housing. And place a thin pad of hard rubber between the thruster and the saddle mount. For more information this and other recommended mounting methods, please read the Application Note AN603 - Thruster Installation & Mounting

Question: What is the correct operating voltage range?

Answer: We recommend that you regulate the operating voltage to the thrusters so that it is within +/-15% of the rated voltage for that thruster. Remember, of course, that each model of the Tecnadyne thrusters is available at rated voltages from 48vdc to 330vdc (some models are available at rated voltages as low as 24vdc and some are available to 500vdc). For more information on this subject, please read Application Note AN605 - DC Brushless Motor Interface.

Question: What are the recommended power supply requirements?

Answer: Tecnadyne thruster motors are designed to operate from a wide variety of power sources, including regulated DC power supplies, filtered and rectified AC and batteries. There are a couple of important precautions that must be taken - the power source must have some capacitance to help filter the back EMF from the motors and precautions must be taken to isolate the instrument level signals from the main thruster voltage and to prevent current loops. For a detailed explanation, please read Application Note AN605 - DC Brushless Motor Interface and Application Note AN601 - Back EMF and Ground Loops.

Question: We plan to use computer with D/A card to drive the thruster control signals. However, the analog outputs from the D/A card are not isolated from one another and they are common to the computer chassis ground. Will this cause a problem?

Answer: Most likely, this will cause a problem with ground loops and noise - please refer to Application Note AN601 - Back EMF and Ground Loops. Tecnadyne supplies an isolation card specifically intended to address this problem. This card, the ISO-4, is a 4-channel isolation amplifier that isolates four analog control signals (from your D/A card, for example) and also provides isolated 12vdc instrumentation power to four thrusters - it is highly recommended. Tecnadyne also supplies the ISOMOD-4, ISOMOD-6 & ISOMOD-8, which are 4-channel, 6-channel and 8-channel modules that package ISO-4 cards, with a capacitor bank, fuses and overvoltage protection in a 1-atmosphere housing depth rated to 2,000m. The ISOMOD-4, ISOMOD-6 & ISOMOD-8 can also be fitted with Tecnadyne's ANALOG-8 card, which will control up to eight thrusters over an RS-232, RS-422 or RS-485 data link.

Question: What type of maintenance is required for the thrusters?

Answer: Our thrusters are very low maintenance - simply remove the propeller and flush with fresh water after use. It takes about 30 seconds to do this with each thruster.

Question: How do you remove the propeller?

Answer: On most Tecnadyne thrusters, the propellers are held in place with a simple E-clip that can be removed with the fingers or with a screwdriver. On the Model 260 & Model 300 thrusters, the propeller is held in place with a shoulder bolt that requires a 1/8in Allen key (provided with the thrusters) to remove.

Question: Why is the magnetic coupling a benefit?

Answer: Using a magnetic coupling eliminates the rotating propeller shaft and the shaft seal which are the major cause of leaks and failures with traditional thrusters. The propeller shaft seals in use today were all designed for use at or near the surface where the pressure is relatively low - they inevitably fail when subjected to the pressure of typical ROV and AUV operations (100m to 10,000m). The magnetic couplings developed by Tecnadyne not only eliminate this common cause of failure, the larger sizes are able to reliably transmit over 20hp.

Question: What is the life span of the thrusters?

Answer: The thrusters have an MTBF of 20,000 hours. However, it is very important to remember that the propeller bearings are lubricated by the sea water. If the sea water is clean, the bearings will last for 2,000 hours. If the sea water is sandy (when operating on the bottom) the bearing life is severely reduced. It is easy to check for propeller bearing wear, just by rocking the propeller back and forth. And replacing the bearings takes only several minutes and the bearings are really inexpensive.

Question: What is the standard depth rating of the thrusters?

Answer: Most Tecnadyne thrusters have a standard depth rating of 750m. All Tecnadyne thrusters are available with depth ratings to full ocean depth. However, sales of some thrusters with depth ratings greater than 1,000m requires US Department of Commerce approval when these are shipped to some countries. Please consult the Tecnadyne factory for further information.

Question: What is the standard voltage rating of the thrusters?

Answer: The standard voltage rating for most thrusters is 150vdc. For the larger thrusters (Model 2020 and above) the standard voltage rating is 260vdc to 300vdc. But Tecnadyne thrusters are available with voltages ranging from 24vdc to 500vdc (actual voltages available depends on the thruster model - please consult the data sheets).

Question: Do you offer field spares kits?

Answer: Yes, please consult the factory.

Question: What documentation is supplied with the thrusters?

Answer: All documentation is supplied on PC compatible CDRom. The supplied manual includes installation and integration instructions, field repair procedures, illustrated parts breakdown with parts list and schematics. We also include the final test reports for the thrusters.

Question: Can I operate the thrusters out of water?

Answer: No! But if you do need to operate them out of water, do so for only a few seconds to verify that they are operating OK. If operated for too long, the sea water lubricated bearings will overheat.

Question: What type of testing do you do on the thrusters before shipment?

Answer: Every Tecnadyne thruster goes through a rigorous test cycle. First, we test the electrical isolation of all subsea connector pins to the case of the thruster at 500v. Next, we pressure test the thruster in water to a pressure of 1000psi (7mPa). And then, we repeat the electrical isolation test (this will indicate any water leaks). Once we know the thruster is not leaking, it is placed in our water test tank and is operated for a period of 10 minutes to 1 hour at full power (smaller thrusters, such as the Model 260 are operated for 10 minutes and the larger thrusters, such as the Model 2020 and 8020, are operated for a full hour). We consider this test to be a break-in period. Finally, the thruster is operated throughout its normal operation cycle and all the performance data is collected and this is the final acceptance test of the thruster.

Question: Can I do instantaneous reversals from full power forward to full power reverse?

Answer: No!! It is necessary that you system has a time based ramp from zero speed to full speed and from full speed to zero speed in both forward and reverse. If you are controlling the thrusters with hand operated joystick, the time required to move the joystick from one position to another is probably enough for the thrusters. However, if you are driving the thrusters with computer, it is essential that you program a linear ramp into the thruster control algorithm. The reason that this time based ramp is necessary is because the thrusters generate back EMF and the back EMF is much greater when the speed changes very rapidly. For example, if the time ramp from full power forward to full power reverse is 20ms, the back EMF current spikes will be 10-20 times greater than the steady state current (we have actually measured this). If this ramp is increased to 50ms, then the back EMF current spikes will be about 4-8 times the steady state current. And increase the ramp to over 100ms, and the current spikes will be about 2 times the steady state current. Make the ramp as long as you can and contact the factory if you have any questions.

 

Rotary Actuators

Question: What kind of position feedback options are available in Tecnadyne Rotary Actuators?

Answer: We can supply the rotary actuators with a quadrature output signal generated by internal Hall devices with resolutions ranging from 50 pulses per revolution to over 10,000 pulses per revolution -- the pulse count options available for each rotary actuator is determined by the output gear ratio of the actuator and other factors. Please consult the factory for available pulse counts for the rotary actuator model and speed desired.
We can also supply rotary actuators with internal resolvers which must be powered with 50-60 cycle power and which return two analog signals from which true position can be determined. Tecnadyne does not supply the electronics assembly to power and read resolver.

Question: Are your rotary actuators oil filled?

Answer: Yes, all of our rotary actuators are oil filled and pressure compensated using oil filled flexible tubing (Tygon) over the electrical conductors of the subsea cable.

Question: What type of seal do you use on the actuators?

Answer: We generally use a special compound O-ring which we have found to be very reliable when used on a highly polished shaft at low speeds (less than 150rpm). Tecnadyne has developed a proprietary process to polish the shafts and the final inspection of the shafts is under a 100 power microscope.

Question: Do the actuators have any backlash?

Answer: No.

Question: Can the rotary actuators be back driven?

Answer: Yes, in most cases our rotary actuators can be back driven with a torque that is 30-60% of the rated maximum. However, we do install electrical brakes to actuators when it is necessary that the actuator lock and not be back driven by the load. Also, we have a special version of our Model 20 rotary actuator called the Model 20WD, that uses a worm drive gear assembly which cannot be back driven by the load on the shaft.

Question: What is the correct operating voltage range?

Answer: We recommend that you regulate the operating voltage to the rotary actuators so that it is within +/-15% of the rated voltage for that actuator. Remember, of course, that each model of the Tecnadyne actuators is available at rated voltages from 48vdc to 330vdc (some models are available at rated voltages as low as 24vdc and some are available to 500vdc). For more information on this subject, please read Application Note AN605 - DC Brushless Motor Interface.

Question: What are the recommended power supply requirements?

Answer: Tecnadyne actuators are designed to operate from a wide variety of power sources, including regulated DC power supplies, filtered and rectified AC and batteries. There are a couple of important precautions that must be taken - the power source must have some capacitance to help filter the back EMF from the motors and precautions must be taken to isolate the instrument level signals from the main motor voltage and to prevent current loops. For a detailed explanation, please read Application Note AN605 - DC Brushless Motor Interface and Application Note AN601 - Back EMF and Ground Loops.

 

Linear Actuators

Question: Is position feedback available on the Linear Actuators?

Answer: The linear actuators do not have internal absolute position feedback. However, they are available with internal limit switches and a digital pulse train output - using these it is possible to "home" the actuator to one limit or the other and then count pulses to determine position. However, if absolute positioning is required, it is highly recommended that either the Model 194 Rotary Position Sensor or the Model 195 Linear Position Sensor be installed in conjunction with the Linear Actuator.

Question: Are your linear actuators oil filled?

Answer: Yes, our linear actuators are oil filled and all include a pressure compensator (either integral with the actuator housing or as a separate unit) that compensates the internal pressure to the sea water ambient and also compensates for the change of internal volume as the actuator rod extends and retracts.

Question: What type of seal do you use on the linear actuators?

Answer: The linear actuators use O-rings on the rods. The rods are polished using our proprietary process.

Question: Do the actuators have any backlash?

Answer: Yes, there is a very small amount of backlash in the ball screw and nut. If backlash is critical, we can have the ball screw nuts hand fitted to the ball screws to reduce the backlash to almost immeasurable levels.

Question: Can the linear actuators be back driven?

Answer: Yes, in most cases our linear actuators can be back driven with a load that is 30-60% of the rated maximum. However, we do install electrical brakes to actuators when it is necessary that the actuator lock and not be back driven by the load.

Question: What is the correct operating voltage range?

Answer: We recommend that you regulate the operating voltage to the linear actuators so that it is within +/-15% of the rated voltage for that actuator. Remember, of course, that each model of the Tecnadyne actuators is available at rated voltages from 48vdc to 330vdc (some models are available at rated voltages as low as 24vdc and some are available to 500vdc). For more information on this subject, please read Application Note AN605 - DC Brushless Motor Interface.

Question: What are the recommended power supply requirements?

Answer: Tecnadyne actuators are designed to operate from a wide variety of power sources, including regulated DC power supplies, filtered and rectified AC and batteries. There are a couple of important precautions that must be taken - the power source must have some capacitance to help filter the back EMF from the motors and precautions must be taken to isolate the instrument level signals from the main motor voltage and to prevent current loops. For a detailed explanation, please read Application Note AN605 - DC Brushless Motor Interface and Application Note AN601 - Back EMF and Ground Loops.

 

Hydraulic Pumps & HPU's

Question: Are there advantages to using fixed displacement pumps vs. variable displacement pumps?

Answer: Fixed displacement pumps are generally used when the hydraulic flow requirements are continuous and the flow rate is fixed - a constant speed winch, for example. Variable displacement pumps are generally used when the flow demand varies considerably (when used as a supply to a valve package controlling a manipulator or tool suite, for example) - when the flow requirements drop, the pump displacement drops to a level required to maintain system pressure and the electrical power demand drops accordingly. Since all Tecnadyne hydraulic pumps are powered by variable speed DC brushless motors, it is also possible to use a fixed displacement pump as a variable displacement pump - simply vary the motor speed as the hydraulic flow requirements increase and decrease. However, this does require that use the system hydraulic pressure to close the motor speed control loop. If you have any questions, please contact the factory.

Question: You have Hydraulic Pumps and HPU's - what are the differences?

Answer: Tecnadyne supplies its hydraulic pumps in three basic configurations. The first configuration simply mounts the pump to a DC brushless motor - the DC brushless motor is generally in a hard anodized aluminum housing and the pump is coated with a very rugged ceramic epoxy material. We refer to these as Hydraulic Pumps. The second configuration actually places the pump inside a hydraulic tank that includes a pressure compensator (to compensate for changes in hydraulic fluid volume due to leakage and depth changes). We refer to these as HPU's and they have the advantage that the entire hydraulic supply (pump, tank & pressure compensator) is contained within one housing and that the pump is immersed in oil, which provides the best protection from the sea water. The third configuration, also referred to as HPU's, integrates the pump, tank and pressure compensator of the previous configuration with an internal manifold and four 4/3-way solenoid spool valves, pressure transducer, pressure and tank filters and hydraulic accumulator (if required). This third configuration of HPU provides an entirely self contained hydraulic system - simply connect the A & B ports to the end effectors (cylinders, motors, etc.), connect power and RS485 signal and the system can be operated - way cool. But do consult the factory for special configurations to meet your specific system requirements.

Question: What is the correct operating voltage range?

Answer: We recommend that you regulate the operating voltage to the hydraulic pumps so that it is within +/-15% of the rated voltage for that actuator. Remember, of course, that each model of pump is available at rated voltages from 48vdc to 330vdc (some models are available at rated voltages as low as 24vdc and some are available to 500vdc). For more information on this subject, please read Application Note AN605 - DC Brushless Motor Interface.

Question: What are the recommended power supply requirements?

Answer: Tecnadyne hydraulic pumps are designed to operate from a wide variety of power sources, including regulated DC power supplies, filtered and rectified AC and batteries. There are a couple of important precautions that must be taken - the power source must have some capacitance to help filter the back EMF from the motors and precautions must be taken to isolate the instrument level signals from the main motor voltage and to prevent current loops. For a detailed explanation, please read Application Note AN605 - DC Brushless Motor Interface and Application Note AN601 - Back EMF and Ground Loops.

 

Intelligent Valve Packs

Question: Why do you call you valve packs intelligent?

Answer: We call the valve packs intelligent because we embed a controller, called an ECU-4x8, into each valve pack that operates all the valves and reads the pressure transducer and flow sensor (if installed). The ECU-4x8 is controlled via an RS485 bus and is multi-drop (up to sixteen ECU-4x8 can be configured to operate on a single RS485 bus). The Intelligent Valve Packs can be controlled from the surface using Tecnadyne's dedicated software package, SubF/X, using LabView or using software written in Visual Basic (we will supply the protocol).

Question: How many valves and what type of valve can be installed in an Intelligent Valve Pack?

Answer: The standard valve that is installed in the IVP's is a 4/3-way solenoid spool valve - we can install 16 of these in a single valve pack. The valves we use are made by Wandfluh and are available with flow rates from 8lpm to 60lpm. We also can install 4/2-way solenoid spool valves. We have the ability to install four proportional solenoid valves (which we feel are superior to servo valves in most subsea applications) with flow rates from 8lpm to 60lpm. We can also install proportional pressure and proportional flow regulating valves, pressure transducers, flow sensors, externally adjustable pressure relief valves and externally adjustable manual throttle valves. Almost all of the IVP's that we manufacture are custom designed to the customers specifications. So, please do contact the factory with your requirements.

 

Control Units & Interface Cards

Question: I see your ECU-4x8 controller operates on an RS-485 bus - can I operate more than one of these on the same RS485 or does it require multiple buses?

Answer: The ECU-4x8 is multi drop and so each card can be assigned a unique board address. 16 ECU-4x8's can be individually addressed on one RS485 bus.

Question: Can I write my own software to control the ECU-4x8 card?

Answer: Yes, we supply the control protocol for the ECU-4x8 so that you can write your own software. Tecnadyne also supplies software, called SubF/X, to control the ECU-4x8 or you can write a routine in LabView.

Question: Is the ECU-4x8 card pressure tolerant?

Answer: Yes, it has been soak tested for one week at 10,000psi (70mPa) without any problems.

Question: What is your Analog-8 card used for?

Answer: The Analog-8 card operates on an RS232, RS422 or RS485 bus and has 8 channels of +/-5v analog output. It is specifically designed for operating Tecnadyne DC Brushless motors, as used in the thrusters, rotary actuators and linear actuators. The Analog-8 card is very compact, measuring only 80mm x 54mm.

Question: What is the ISO-4 card used for?

Answer: The ISO-4 card is used to convert 4 channels of non-isolated +/-5v analog control signals into 4 fully isolated +/5v analog control signals. It also provides 4 channels of fully isolated +12vdc instrumentation power. This card is specifically designed to operate Tecnadyne thruster motors (but can also be used with rotary and linear actuators) and should be used in systems that have ground loop problems or poor electrical isolation and grounding. Please refer to Application Note AN601 - Back EMF and Ground Loops.

 

Pan & Tilts

Question: I see that you make several Pan & Tilts. Why do you only sell these to OEM's (original equipment manufacturers)?

Answer: We only supply our camera Pan & Tilt units in larger quantities to several OEM's and larger end users (NASA, for example).

 

Pressure Compensators

Question: Why do you use rolling diaphragms, rather than the more common piston and seal, in your pressure compensators?

Answer: The problem with the piston and seal type of pressure compensator is that one side of the piston is exposed to sea water and will eventually wear and leak. We use rolling diaphragms, which are made of neoprene reinforced nylon fabric and have the shape of a top hat. A spring loaded piston fits within the hat and the outer ring of the hat is clamped between the two portions of the outer housing. The piston can move the full length of the outer housing and the top hat shaped diaphragm rolls between the piston and the housing wall. There is no friction, there is no sliding and there is nothing to wear out and leak.

Question: Do you make pressure compensators in larger sizes.

Answer: No, we are using the largest size rolling diaphragm that can be made on the available machinery.

Question: Will you make a custom pressure compensator to suit our specific requirements?

Answer: Of course!

 

Position Sensors

Question: Can Tecnadyne supply Rotary Position Sensors with true position feedback?

Answer: Yes, we have several standard absolute position options and can install most commercially available rotary sensors into the housing for our Rotary Position Sensors. These include the standard potentiometers, encoders with quadrature output and index pulse and resolvers. Please refer to the product data sheet or send a request to This email address is being protected from spambots. You need JavaScript enabled to view it.  with your specific requirements and we will see what we can do.

 
Specialty Pumps

Question: I see that you have several specialty pumps that are all very different in design and application -- why is this?

Answer: All of our specialty pumps were manufactured to answer a customer's specific requirement. We present them on our website because we feel that they may be useful to other customers, either as-is or with modification. And yes, we are always willing to make a specialty pump for a special application.