Commissioning Procedure Of Steam Turbine

 Commissioning Procedure Of Steam Turbine

  • The systematic process of commissioning is designed to guarantee that the equipment is tested and verified to operate in accordance with the specifications of the design. the systems and subsystems will be examined throughout this procedure to make sure they are prepared to function under all processing circumstances.
  • Before integrating the subsystems into the water system of machinery, pipes, auxiliaries, and controls, each system, which is composed of subsystems, must be examined and verified.
  • The fundamental commissioning procedure verifies that all systems are functioning as intended and that the equipment will function as intended.
  • Prior to integrating these smaller subsystems into the larger system, each component of the subsystems must first be thoroughly examined to ensure that it is ready to function.
  • This procedure might be compared to what we do during a lengthy vehicle ride. before leaving, we could check that the gas tank is full, that the tries have the proper air pressure and good tread, that the spare tire in the trunk is correctly inflated, that the windshield wipers are working properly, that there is water in the wiper reservoir, and perhaps even change the engine oil.
  • Consider each of these components as a subsystem of the automobile's overall system, with the objective of traveling a distance in a car. first, we have to make sure that every subsystem satisfies our needs and the manufacturer's criteria. for example, the tires have 32 PSI Pressure, the oil level is in the hole range, and the windshield wipers potential to create streaks on the windshield during use.
  • Before we can go on the bigger system or take the automobile on a lengthy journey, they must all be in good working order.
  • Now, let's take a closer look at each of the crucial subsystems needed for steam turbine startup or the first solo run.
We will go over the following things in the future detail:
  1. To ensure that the pipe and steam system are clean, use a steam blower.
  2. The steam and process systems in the strainer.
  3. cleaning the lube oil system using lubrication flushing.
  4. The hydraulic governor is checked.

1). Steam blowing:  

  • Before the steam piping is linked to the steam turbine, a steam blast is used to clear the pipe of any foreign objects.
  • Before the piping is connected to the steam turbine's intake, the interior of the pipe will be cleaned of rust, mill scale, and weld slag using the steam-blowing method. the process involved gradually raising the steam's piping temperature to operational levels and letting it drop to room temperature before raising it to functioning levels once again, or as close to them as feasible.
  • Particles will be eliminated during the steam-blowing process by the frequent expansion, contraction, and thermal shock caused by rapidly increasing the pipe temperature and high steam velocity.
  • Before assuming that the pipe is clean, this technique has to be carried out on the steam targets at least three times with positive results.
  • All strainers and other constraints should be removed from the pipeline upstream of the turbine. next, a temporary short pipe is placed, and the outlet end of the pipe is fitted with a polished brass or stainless steel target.
  • The target set in the pipe should point in the direction of a secure area. this target is affected by foreign particles entering the pipe from the inside and will be right in the steam blow path.
  • After every steam blast, these targets have to be examined, and fresh, polished targets have to be put back in for the subsequent steam blast. the procedure is finished when the polished targets show satisfactory impact signals after two consecutive steam blasts. these procedures may take many hours to complete, so they shouldn't be done in any other time period than when the polished targets are accepted.
  • The steam will be blown into the atmosphere directly with no back pressure which will result in very high steam velocity and loud noises. As a result, every employee has to wear additional hearing protection and avoid being near the steam outflow pipe.
  • The writers have seen steam blasts that use a silencer on the exit pipe to stop any projectiles from the piping and lessen noise. the main goal is to steer the steam exit flow in the direction of a safe region and away from equipment.
  • The Degree of damage seen on the polished target surface determines whether the steam-blowing passes or fails the criterion. the polished target's 1/2 area on both ends needs to be disregarded for determining impact damage and pass/fail standards.
  • It is recommended to verify the targets after every thermal cycle and steam blow. The following are some common pass/fail standards listed in API686:
  1. No collisions or elevated pits.
  2. There should be no more than three pits in every 1/8*1/8 square, and no pit may be bigger than 1/32.
  3. In every 1*1 square of the target surface, no more than five elevated hits greater than 1/64 inch are allowed.
  4. Until the approval conditions are satisfied, keep blowing steam again.

2). Strainers:

  • If at all feasible, strainers should be temporarily positioned immediately upstream of the trip valve, upstream of the steam turbine's input flange. any debris or items in the pipework that were not eliminated during the steam-blowing procedure will be further hindered by this.
  • A conical strainer, often called a "Witches Hat", maybe the standard temporary strainer. it should be mentioned that in order to install this temporary strainer, the system must be designed with a short pipe spool that allows for the installation and removal of the temporary strainer without requiring the steam turbines to be moved.
  • These kinds of transient strainers are widely used, and it's quite probable that they'll be included in the suction lines of compressors and pumps.

3). Lubrication:

  • Systems For Lubrication May Differ greatly in terms of size, complexity, and design. the oil sump and ring lubrication seen in the majority of standard-purpose steam turbines, as well as forced-lubricated systems.
  • Being clean is a fundamental need for any lubrication system. We check and validate that the systems are clean and prepared for the next stage of the procedure during the commissioning phase.
  • Depending on the kind of lube oil system being used, the general-purpose steam turbine's lube oil commissioning procedure varies.
  • A constant-level oiler is used in the majority of applications for general-purpose steam turbines with oil sump pumps. forced lubrication systems are probably used in larger turbine systems.
  • In any scenario, one of the first things that has to be done is to find out what kind of preservation the manufacturer has applied to the oil system and make sure that this is compatible with the lubricant that will be used at the location. Since the majority of preservatives are now compatible with the lubrication oil system, there shouldn't be a problem, but if they aren't, you will need to remove all of the preservatives before adding the oil to the system.

4). Oil sump lubrication:

  • First, we verify that the constant-level oiler has set the lube oil level in the lube oil sump system to the proper level.
  • Additionally, we need to make sure that the sump's oil level covers both of the oil rings at the sump's bottom, below the bearing. you must take off the bearing cap in order to examine this, and you must also check the oil level within the bearing housing.
  • Verify that both oil rings are covered by the oil level. the oiler level adjustment inside the oiler has to be altered in order to reset the level if the oil level is not proper.
  • To remove all of the oil, you must drain the sump's oil level once it has been properly adjusted.
  • To ensure that the pipes, level oiler, and oil reservoir system are operating properly and to eliminate any pollution from the system, you will need to conduct this procedure again.
  • This procedure will verify that the sump is being filled by the oil leveler as needed. never reuse the oil when filling; fresh oil is required for each fill. Now turn the oil rings to make sure they turn smoothly and that there are no machine burrs or hang-ups preventing them from turning. replacing the bearing cap when this has been verified. It is important to emphasize that each fill of lubricant has to be fresh and clean.

5). Flushing pressure lubricating system:

  • Similar to the sump-lubricated system, you must find out from the manufacturer what preservation has been done to the system and if it is compatible with the lubricant that will be used on site.
  • Should it not be compatible, you will have to empty the system of all preservation before adding the last oil that will be used for operation.
  • The lubrication oil pipeline system requires the installation of 100-mesh screens in a number of places before the flushing process can begin. There should always be two screens installed: one at the entry of each bearing or at the bearing jumper lines ( the bypass pipe or hose that surrounds the mechanical bearings ), and the other on the lube oil return line to the oil reservoir.
  • These screens should be periodically removed to check if they are clean or contain particles. Before completing the flushing operation, you must have two screen samples showing that the system is clean. 
  • There are probably two external lube oil pumps in a pressure-lubricated system that may be employed to move lube oil across the system. We need to have the lubricating oil moving through the system at least 15 to 20 feet per second during the flushing process quicker and better.
  • Usually, this may be accomplished by running the main and backup lube oil pumps concurrently. According to the author's flushing experiences, flushing the system without the hassle of installing a bigger pump increases oil velocity enough when both lubricating oil pumps are running simultaneously. this allows for a decent amount of time to be spent cleaning the system.
  • To boost the system's velocity during the flushing procedure, a temporary pump must be installed if the system only has one lubricating oil pump.
  • You will also need to cycle the oil system's temperature from the highest to the lowest setting when flushing. to provide more heat, you may use reservoir heaters or oil coolers, but you have to cycle the oil temperature.
Checklist for oil system flushing:
  1. Install jumpers, or bypass hoses or pipes, around each equipment bearing. it is not advisable to force tainted oil containing tiny particles into gears, bearing regions, or any nearby clearing area.
  2. In the lubricant oil system, remove any orifice plates. If the bypass (jumper) around the bearings is downstream of the orifice, be sure to eliminate any potential orifices on the upstream side of the bearings.
  3. At various points along the system's flange connections, install 100-mesh screens. install a screen at each bearing's entry, on the lubricating oil return line to the oil reservoir, and as close as feasible to the bearing jumpers. these screens should be periodically removed to check if they are clean or contain particles. Before completing the procedure, you must have two sets of screen samples showing that the system is clean.
  4. Verify that, while flushing, both lube oil pumps have strainers on the suction with screens that are at least 100-mesh. If not, put in temporary wire mesh strainers in the suction pipe upstream of the pump.
  5. Certain flushing protocols advise taking off the oil filters when flushing. nonetheless, because they will help with the cleanup, I advise leaving them installed. just don't forget to replace the filters after the system has been cleaned.
  6. Run both of the lubricating oil pumps simultaneously.
  7. During the flushing procedure, cycle the lubricant oil temperature many times from highest to lowest.
  8. Verify that all of the orifices are reinstalled and that all of the jumpers on the lubrication oil system have been removed after the system has been cleansed and verified clean. Take off all of the 100-mesh screens and replace the oil filters.
  9. Verify that the auxiliary oil pump's low-pressure automatic start-up is configured appropriately. put the auxiliary set on standby and activate one of the lube oil pumps to restore all of the lube oil systems to normal. turn off the system's working lube oil pump, check the pressure at which the auxiliary pump begins, and record the system's lowest lube oil pressure. when the equipment is not operating, this will be done.

6). Hydraulic Governors:

  • The first step is already finished if the governor was used during the factory acceptance test. the primary concerns are to empty the oil, restock the appropriate amounts, and modify the speed settings as needed. on the other hand, more setup effort and time will be needed if the governor is not used during the factory test.
You must examine the following if the governor is new and wasn't utilized in the factory acceptance test:
  1. Verify that the steam turbine's direction and the drive shaft's rotating direction on the governor housing match. one may configure the governor to spin in either a clockwise or counterclockwise orientation. the governor drive shaft rotation can only be adjusted in one direction; if it is adjusted improperly, it will malfunction. both the nameplate and the top of the governor will have stamps indicating the direction of rotation. Verify that the turbine and governor are pointing in the same direction. If not, a modification to the governor rotation will be necessary.
  2. At the manufacturer, the governor speed is configured at the rated speed. Before starting up for the first time, the speed adjustment screw has to be reset to the lowest speed.
  3. To enable the governor shaft to move to its greatest extent, the connection between the governor and the governor valve has to be modified. if this adjustment is incorrect, there could not be enough governor valve movement to permit both full load and no load operation. this is normally 40 degrees for full travel. verify that the linkage is spring-loaded in the shutdown direction, does not bind, and runs smoothly.
  4. Once there is a load on the steam turbine, the speed droop should be examined and, if necessary, modified. Before performing a droop check, the steam turbine has to be under load. the governor normally has a factory set droop of around 6%, which is suitable for the majority of applications but should be verified.


Post a Comment