Constant y los dos conceptos de libertad

Normally, a fluid leak in the system is detected by watching the flow meter on the driller's panel. If the flow meter indicates a fluid flow when no functions are being performed, or if it continues to run and does not stop after a function is performed, this generally indicates that there is a leak in the system.

Once you have determined that there is a leak, you should begin a check of the system to determine the location of the leak. 'Me first thing to do is to make a thorough visual inspection of the surface equipment. You do this by carefully examining the hydraulic control manifold and accumulators to see if you can find a broken line in the system or a fluid leak at any of the fittings. If no leak is found, next check the jumper hoses and hose reels to see that all connections are tight and that no hoses are damaged. Sometimes a bad connection at a hose reel R13C junction box will result in a leak. Examine the connections carefully to be certain that they have a firm seat.

While at the hose reel, check the hose reel manifold to make certain that all of the valves are in the centre position. Also, make certain that the needle valve to the manifold pressure supply shutoff is tightly closed. If this valve is left open when the RBQ junction box is connected to the reel, it will allow fluid pressure to be forced back through one of the surface regulators and vent into the tank, thus indicating a leak in the system.

If you find this valve in the open position, then close it and check the flow meter to see if the fluid flow has stopped.

If this procedure does not prove successful in locating and stopping the leak, you should then return to the driller's panel to begin an item by item check of the system.

Upon returning to the driller's panel, change the pod selector valve to operate the system on the other pod.

For example, if you are operating on the blue pod, switch over to the yellow pod.

This will tell you whether the leak is in one side, or both sides, of the system and will let you begin to isolate the leak. If the leak stops when you change from the blue to yellow pod, then you know that the leak is located in the blue side of the system.

If the leak doesn't stop when you change control pods, then you know that the leak is either below the control pods or somewhere in the hydraulic control manifold.

Let's take a hypothetical example and say that the flow meter stopped when you changed from the blue to the yellow pod. Ibis tells you that the leak is somewhere in

the blue side of the system. And, since you made a visual inspection of the surface equipment earlier, you now know that the leak is probably subsea. If conditions permit, you should now change back to the blue pod, and try to isolate exactly where the fluid is leaking. Do this by blocking each function item by item, allowing plenty of time for the function to operate. You should watch the flow meter very carefully while blocking each function to see whether or not the leak stops. If the flow meter does stop when a certain function is blocked, then you have isolated the leak, it is somewhere in that specific function.

Since you are not sure exactly where the leak is, you should next lower a TV camera into the stack. Then unblock the leaking function and try to determine the exact location of the leak. The leak will show up in the water as a white mist seeping from the leak area. If the leak is coming from the pod, there is either a bad regulator or SPM valve in the pod. If the leak is bad enough, you can pull the pod and make the necessary repairs.

Always use the schematic drawing to make certain you are working on the correct valve and follow the repair procedures as outlined in the subsea manual.

If the leak is below the pod, and the problem is serious enough, you can either send a diver down to make the necessary repairs or pull the stack and repair the leak on the surface. If the leak is not of a serious nature, you can simply leave that function in the block position until the next time the stack is brought to the surface and then make the necessary repairs.

If the flow meter did not stop when the pod selector was switched, or when all functions were blocked, you should check the master fluid return line to the tank- If there is a fluid flow in this line, then one of the pilot valves or regulators is leaking.

First, check all pilot valves to make sure they are squarely in the block position or fully opened or closed. Sometimes a partially opened valve will allow fluid to leak by the valve.

If the valves are all fully thrown, next disconnect the discharge line from each pilot valve one at a time. If fluid exhausts from one of the valves after the discharge line has been disconnected, then the valve is bad and should be replaced with a new one.

If the discharge lines on the pilot valves do not show and signs or leaks, then disconnect the discharge lines on the regulators in the same manner checking for a fluid discharge. Any fluid exhaust from the fluid return side of a regulator will indicate that the regulator is bad and should be replaced.

Now, let's continue. For this example we will assume the system is operating normally and you push a button to perform a function. The flow meter begins to

measure the fluid but then continues to run and does not stop at the number of gallons that is required to operate that function.

Remember, the key words here are "continues to run". It is important to note that each time a function is operated it will not take exactly the same amount of fluid listed on the fluid capacity chart. It can vary either way of the listed capacity necessary to operate the function.

However, if the flow meter continues to show a fluid flow after the time required for the function to perform, then there is a leak somewhere in that function.

One possible cause is foreign material or trash in the SPM valve seat causing the valve to stay open and bleed fluid through the system. The best way to check for trash is to operate the valve several times to try and wash out the foreign material.

After operating the valve several times, observe the flow meter to see if the leak has stopped.

Next, go to the hydraulic control manifold and check the one inch line in the other jumper hose. This will tell you whether or not the shuttle valve for the function is leaking. If it is leaking, there will be a fluid return to the surface through the other hose. In other words, the fluid will be flowing down through the blue pod, leaking by the functions' shuttle valve, returning to the surface through the hose to the yellow pod. This fluid return will indicate a faulty shuttle valve. The leak can be stopped by blocking that function in the desired position and then leaving it until repairs can be made later.

If these procedures do not stop the leak, the problem is most likely caused by either a broken line, a bad SPM valve or a bad seal in the function. 1he best way to determine which of these is the problem is to lower a TV camera to observe the system in operation. Any fluid leak should be easily seen as a white mist flowing from the leaking area. If the leak is in the pod, the pod can be retrieved to the surface and repaired. If the leak is somewhere on the stack, you send a diver down and make the necessary repairs. Or, pull the stack, pressure test to locate the leak and then repair it on the surface.

Up until this portion we have been concerned with fluid leaks. Now we will look into some possible malfunctions that can occur in the hydraulic fluid system.

The first thing we will consider is a slow reaction time in the operation of a function.

For instance, if we push a button to operate a particular function that we know is supposed to take 22 seconds, but the operation takes 60 seconds, then we know that there is a malfunction somewhere in the system. This problem will most likely by caused by: low accumulator pressure, a bad RBQ connection, or a partially plugged pilot line.

First check the gauges to see if you have the proper operating pressures. If you do no have the required pressures, then check the pumps to make certain they are operating properly, and check the fluid tank to make sure you have fluid in the system.

The next thing to check in looking for the cause of the slow reaction time is the accumulators. Always make certain the shutoff valves between the accumulators and hydraulic control manifold is open. If someone has been working on the unit, they may have forgotten to reopen the valves when they finished.

If all pressures are good and you can find nothing wrong with the accumulators or the hydraulic control manifold, next check all surface hose connections. If the RBQ junction boxes are not tightly seated, they can restrict the flow rate of the fluid through the connection and thus cause the function operate slowly.

If you have checked all connections and the pressure in the system is good, then the final thing to do is to pull the pod and check the pilot lines for sludge which may have settled out of the hydraulic fluid. This can be accomplished by disconnecting each line at the pod one at a time. As each line is disconnected, it should be flushed out by flowing new fluid through it.

Another malfunction you may encounter is no fluid flow meter indication when a function button is pushed. This can be caused by one of the following problems: No accumulator or pilot pressure, the valve on the hydraulic control manifold did not shift, there is a bad SPM valve, or the flow meter is not working properly.

First, let's troubleshoot for no accumulator pressure or pilot pressure. The first thing to do when troubleshooting for this problem is to check all of the pressure gauges that monitor the system. Normally, these will give you an indication of where the problem is located. Also, before leaving the driller's panel, press the 'Test Button" on the panel to make certain that the lights in the function buttons are working properly.

Sometimes these lights bum out and will not indicate the position of a function.

If you have been unable to solve the problem at the driller's panel, you will next have to go to the hydraulic control manifold and begin looking there. The first thing to do is to double check the flow meter on the driller's panel. This is done by operating the function again while monitoring the flow meter on the hydraulic control manifold. It is possible for the impulse unit which sends the flow meter signal to the driller's panel to malfunction. A bad impulse unit might not indicate a flow on the driller's panel when the fluid actually is flowing through the system.

Another way to check for a bad flow meter is the regulator gauge for that function.

You can always tell whether or not a function operates by watching the regulator pressure after you push the button to operate the function. If the pressure falls 300

to 500 psi after the button is pushed and then comes back up after the time required to operate the function, then you will know the function has been performed regardless of flow meter action.

Next, check the air regulator and the electrical supply to make certain that the proper energy is getting to the hydraulic control manifold. Check the fluid level in the tanks and check the pumps and their pressure switches to make certain they are in the proper operating condition. If the fluid in the tanks has run dry, the triplex pump will have to be primed again before you can get the system back into operation.

Also, check all filters to make certain that they are not plugged with trash.

Also, check the nitrogen pre-charge in the accumulator and bottles. Ibis is done by bleeding the fluid from the bottles back into the tank. Then check each bottle separately to make certain that each has the proper nitrogen pre-charge.

Next, we will give you some troubleshooting hints for what to do if the valve on the hydraulic control manifold fails to shift when the button on the driller's panel is pushed.

The first item to check is the air supply to the system. Too little air supply is one of the biggest causes of unsatisfactory operation and valve malfunction. Check the air gauge for excessive pressure drop. If the gauge shows less than 80 psi or an excessive pressure drop during operation, the air supply is not enough to operate the system satisfactorily.

people hang things over the handles and forget to remove them. These items can sometimes prevent the handles from turning.

If you can easily operate the valve manually at the hydraulic control manifold, there are three other areas to check in troubleshooting this problem.

The button on the panel and the electric solenoids and power relays to the valve.

Check the valve itself to make certain that it is not faulty. The best way to do this is to simply replace the entire valve body assembly. If the function then works properly, you will know that the valve needs to be repaired.

If a plugged pilot or main fluid line is preventing a function from being performed, the only way to solve the problem is to disconnect the hose at the pod, and flush the line with clean fluid.

If there is a bad SPM valve preventing a function from operating, the only solution for this problem is to pull the pod and replace the valve. Always be certain that you use

the schematic in the subsea manual to locate the correct SPM valve before making any repairs. It's always better to double check to be sure you are replacing the correct valve than to run the pod back down and then discover that you replaced the wrong valve by mistake.

Operation of the Electrical Portion of the System

THREE POSITION FUNCTION

OPEN PUSH BUTTON

When the open button is pressed on a remote panel, the open solenoid on the HPU will be energized to the open position. Air pressure will then pass through the normally closed solenoid to a 3 position air cylinder connected to the hydraulic panel manipulator valve on the hydraulic manifold. The manipulator valve is then shifted to the OPEN position. Opening hydraulic pressure pressurizes the pressure switch in the open pilot line turning on the open lamp for this function.

When the open button is released, the air solenoid valve will return to its normally closed position simultaneously venting air pressure off the air cylinder. If required, the panel hydraulic valve may be shifted manually with the handle since air pressure is no longer applied to the cylinder.

The lamps on a three position function use a combination of two pressure switches to turn on the proper lamps. When pressure is applied to the Open hydraulic line, the Open pressure switch is activated. Voltage is applied to the Open lamp through the normally open (N.O.) contact of the OPEN pressure switch and the normally closed (N.C.) contact of the CLOSE pressure switch.

CLOSE PUSH BUTTON

When the CLOSE button is pressed the close solenoid will operate. Air pressure will then pass through the normally CLOSED solenoid to the same air cylinder connected to the same hydraulic manipulator valve. The manipulator valve is then shifted to the CLOSE position. Closing hydraulic pressure pressurizes the pressure switch in the close pilot line turning on the close lamp for this function.

When pressure is applied to the CLOSE hydraulic line, pressure is released from the OPEN hydraulic line. This causes the CLOSE pressure switch to activate and the OPEN pressure switch to deactivate. Voltage is now applied to the CLOSE lamp through the normally open (N.O.) contact of the OPEN pressure switch.

BLOCK PUSH BUTTON

When the BLOCK BUTTON is pressed, both the OPEN and the CLOSE solenoids are energized. Air pressure then passes to both sides of the 3 position air cylinder which is connected to the functions manipulator valve. When this occurs, the manipulator valve will go to its center position. Pressure will be released from both pressure switches.

When pressure is removed from both the OPEN and CLOSE hydraulic lines, both pressure switches are de-activated. The block lamp is turned on through the normally closed (N.C.) contacts of both pressure switches.

MEMORY CIRCUIT

As previously discussed, all pressure is removed from a particular function when the hydraulic manipulator valve is moved to the BLOCK position. In order to “remember”

and illuminate the previous position the manipulator valve was in before BLOCK, a memory circuit is used. Each three position circuit has its own individual memory circuit which consists of two (2) relays. The memory in no way interferes with the normal operation of the system. It is intended to assist the operator in knowing the complete status of the stack.

OPEN MEMORY

As discussed in the three position circuit, pressure applied to the OPEN pressure switch will turn the OPEN lamp on. At the same time voltage is applied to the OPEN lamp, it is also applied to the coil of relay K1. When energized K1 closes a set of normally open contacts which are connected between A positive voltage the K1 coil. At the same time the normally open contacts are closed a normally closed set of K1 contacts are opened in the close portion of the circuit. The normally closed contacts are opened to prevent K2 from energizing.

When the hydraulic pressure is removed from the OPEN pressure switch it will