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This standard is developed in accordance with the rules given in GB/T 1.1-2009 Directives for standardization—Part 1: Structure and drafting of standards.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. The issuing body of this standard shall not be held responsible for identifying any or all such patent rights.
This standard replaces DL/T 932-2005 Guide of operation and maintenance of the condenser and vacuum system. In addition to a number of editorial changes, the following technical changes have been made with respect to DL/T 932-2005:
——The operation and maintenance requirements of vacuum pump are added;
——The main failure causes of vacuum pump are added;
——The operation and maintenance requirements of dual-backpressure condenser are added.
This standard was proposed by the China Electricity Council (CEC).
This standard is under the jurisdiction of DL/TC 07 Technical Committee on Power Station Steam Turbine of Standardization Administration of Power Industry.
This standard was firstly issued in 2005, and this edition is the first revision.
In the process of implementing this standard, the relevant comments and recommendations, whenever necessary, may be fed back to the Standardization Center of China Electricity Council (No.1, 2nd Lane, Baiguang Road, Beijing, 100761, China).
Guide of operation and maintenance of the condenser and vacuum system
1 Scope
This standard specifies the general principles and requirements for the operation and maintenance of surface water-cooled condensers and vacuum systems of steam turbine-generator units in power plants.
This standard is applicable to water condensing steam turbine-generator units.
2 Normative references
The following referenced documents are indispensable for the application of this standard. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 5248 Electromagnetic (eddy-current) examination of copper and copper alloy seamless tube
GB/T 7735 Steel tubes—The inspection method on eddy current test
GB/T 12969.2 Method of eddy current testing for titanium and titanium alloy tubes
GB/T 20878-2007 Stainless and heat-resisting steels—Designation and chemical composition
DL/T 561 Guide for chemical supervision of water and steam in thermal power plants
DL/T 581 Condenser tube rubber ball cleaning equipment and cooling water debris filter
DL/T 712 Guideline for the selection of condenser and auxiliary cooler tube materials in power plant
DL/T 794 Guideline for chemical cleaning of fossil plant
DL/T 1078 Performance test code on steam surface condensers operation
3 General
3.1 The design, manufacturing and installation organizations shall, in consideration of the implementation of this standard, create favorable conditions for the reliable and economic operation of condenser and vacuum system.
3.2 The following technical data shall be provided to the preparation of operation regulations for power plants:
a) Influence curve of the backpressure of the unit on turbine heat rate;
b) Influence curve of the backpressure of the unit on the power generation;
c) Off-design characteristic curve of condenser;
d) Operation characteristic curve of circulating water pump;
e) Variation curve between pumping equipment performance and cooling water temperature or working steam parameters;
f) Requirements for water quality indicators such as oxygen content in condensed water.
4 Operation and maintenance requirements
4.1 Condenser
4.1.1 The tightness of vacuum system shall be qualified.
4.1.2 The condenser shall be in good clean condition.
4.1.3 The cooling water flow shall meet the design requirements.
4.1.4 The steam pressure of shaft seal shall be normal.
4.1.5 The supercooling degree of condensate shall be qualified.
4.1.6 The heat transfer end difference of condenser shall be within the design range.
4.1.7 The condensate water quality shall be qualified.
4.1.8 The water level of hot well shall be normal.
4.1.9 The condenser pressure shall be measured with an absolute pressure gauge, and the pressure transmission tube for condenser pressure measurement shall be free of ponding.
4.1.10 After the overhaul of the unit is completed, the condenser and vacuum system shall be flooded for leak testing.
4.1.11 All welds on the condenser body shall be tight and leak-free.
4.1.12 The compensator connected with the condenser throat and the LP cylinder shall be tight and leak-free. When the rubber compensator is equipped with a water seal, the water seal shall be intact.
4.1.13 All connecting tube welds connected to the condenser body shall be tight and leak-free.
4.1.14 The steam side drain valve of condenser shall be tight and leak-free.
4.1.15 The cooling tube shall be free of perforation and leakage.
4.1.16 The expansion joint and weld between the cooling tube and the tube sheet of the water chamber shall be tight and leak-free.
4.1.17 The connection between condenser water level gauge and water level transmitter shall be tight and leak-free, so as to ensure normal water level control and water level indication.
4.1.18 The condenser water level switch shall operate reliably.
4.1.19 The condenser water level shall be within the normal working range.
4.1.20 The vacuum interlock protection shall be normal.
4.1.21 Appropriate anti-corrosion measures shall be taken for condenser water chamber and tube sheet.
4.1.22 The quality requirements of circulating cooling water shall meet the relevant requirements in DL/T 561, and the flow rate requirements of cooling tubes shall meet those specified in Annex A.
4.1.23 When the unit will be shut down for more than 3 days, the cooling water in the condenser water chamber and the condensate in the hot well shall be drained in time after the shutdown of the unit.
4.1.24 When the unit will be shut down for more than one month, the condenser shall be dried and maintained in time after the unit is shut down.
4.1.25 For the condenser with half-side cleaning function, the partition seal between each water chamber shall be tight and leak-free.
4.1.26 The pressure difference between high- and low-pressure condensers of dual backpressure condensers shall reach the specified value. The pressure difference between high- and low-pressure condensers is related to condenser heat load, cooling water temperature, cooling water flow and condenser working state. The condenser pressure difference under different boundary conditions and normal operation state of condenser is defined as a specified value, and supervision shall be strengthened during unit operation.
4.2 Circulating cooling water and rubber ball cleaning system
4.2.1 The circulating water pump shall work normally, and the flow and outlet pressure can meet the requirements of various conditions of the unit.
4.2.2 For the closed circulating cooling system, the cooling capacity of the cooling tower shall meet the design requirements.
4.2.3 The operating pressure difference between the primary strainer and the secondary strainer of circulating water shall not be greater than the specified value, and can ensure the water quality requirements.
4.2.4 The water chamber shall be kept clean to improve the heat transfer effect of the cooling tube and prevent sundries from blocking the cooling tube.
4.2.5 For the condenser water chamber with siphon function, a water chamber vacuum pump shall be installed. The water chamber vacuum pump shall operate reliably and extract the gas accumulated in the water chamber in time.
4.2.6 For condenser water chamber without siphon effect, the water chamber shall be fully exhausted during start-up and regularly exhausted during operation.
4.2.7 When the condenser is in normal operation, the inlet valve of circulating water shall be fully opened, and if necessary, the opening of the outlet valve shall be adjusted to meet the operation requirements of the system.
4.2.8 The rubber ball cleaning spring can be put into normally and work effectively, and its technical indexes such as rubber ball quality, ball throwing quantity, cleaning time interval, cleaning duration and ball collection rate shall conform to the relevant clauses in DL/T 581. For power plants with conditions, the cleaning interval and duration of rubber balls shall be determined according to the cleaning coefficient of cooling tubes.
4.2.9 The quality of circulating water shall be monitored and measured regularly, and effective measures shall be taken to ensure the quality of circulating water when necessary.
4.2.10 There is no obvious scaling on the inner surface of condenser cooling tube.
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4.3 Condensate system
4.3.1 The condensate pump shall meet the requirements of flow and head of each load of the unit under frequency conversion operation or power frequency operation, and can operate normally under the condition of low water level of condenser without cavitation and vibration damage.
4.3.2 The strainer at the inlet of condensate pump (if any) shall be timely checked for blockage and cleaned. For the filter with automatic backwashing function, its function shall be ensured and put into operation frequently, so that the differential pressure of the strainer does not exceed the set value.
4.3.3 If the shaft seal of condensate pump adopts mechanical seal, the gap shall be adjusted to meet the requirements to prevent wear and tear, resulting in excessive gap. If packing seal is adopted, the sealing water and cooling water shall be adjusted moderately, and the packing shall avoid being too loose or too tight to avoid air leakage or excessive wear.
4.3.4 The flange, exhaust valve and steam trap on the section from the hot well to the inlet of the condensate pump shall be tight and leak-free.
4.3.5 The valve stem, flange and welds of its pipeline of the condensate recirculation valve shall be tight and leak-free.
4.4 Shaft seal steam system
4.4.1 The design of shaft seal steam system shall be reasonable, and the steam supply and return of shaft seal shall be smooth.
4.4.2 The steam inlet regulating valves of each shaft seal shall operate normally.
4.4.3 The steam supply parameters of shaft seal shall be adjusted in time according to the operating conditions to maintain the operation of shaft seal system under micro-positive pressure.
4.4.4 The fan of shaft seal heater shall work normally.
4.4.5 The water level of shaft seal heater shall be normal.
4.4.6 The height of water seal in drain U-shaped tube of shaft seal heater shall be reasonable.
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4.5 Pumping system
4.5.1 The condenser vacuum breaker valve shall be tight and leak-free.
4.5.2 The vacuum pump and pumping equipment shall work normally.
4.5.3 The air pumping mode of dual backpressure condenser shall be arranged reasonably to avoid the mutual influence of air pumping systems between high and low pressure condensers.
4.5.4 The water level of steam-water separator of vacuum pump shall be normal.
4.5.5 The cooling water flow shall be adjusted to make the cooling water temperature of pumping equipment as close as possible to the design value.
4.5.6 The working fluid temperature of vacuum pump shall be reduced as much as possible.
4.5.7 Adequate cooling water flow and working fluid flow of vacuum pump shall be provided.
4.5.8 The vacuum pump heat exchanger shall be clean and free from dirt and blockage.
4.5.9 When conditions permit, the low-temperature water with lower temperature than circulating water shall be used as cooling water source of vacuum pump.
4.5.10 The water inlet pressure of the water jet air ejector shall be normal.
4.5.11 When the working water temperature of the water jet air ejector is higher than the normal value, the low-temperature cooling water shall be replenished to the water tank of the extractor in time.
4.5.12 Control the water level of the water tank of the water jet air ejector to be normal.
4.5.13 The working steam pressure of steam jet air ejector shall be normal. If reduced, the working steam inlet valve shall be properly opened to restore the rated value, or the working steam shall be switched to a steam source with higher pressure rating.
4.5.14 The drainage of steam jet air ejector shall be normal without cross flow.
4.5.15 The strainer in front of the air ejector nozzle shall be kept clean.
4.5.16 Check that the cooling water temperature, cooling water flow and cleaning coefficient of the intercooler of the multi-stage air ejector shall be normal.
4.6 Heater drainage and exhaust system
4.6.1 The operating water level of low pressure heater shall be normal.
4.6.2 The exhaust of low pressure heater shall work normally.
4.6.3 The emergency drain regulating valve shall work normally without leakage.
4.6.4 The steam turbine body drainage and pipeline drainage entering the condenser shall be closed during normal operation.
4.7 Low pressure (LP) cylinder of steam turbine
4.7.1 The middle surface of LP cylinder shall be flat without deformation, and tight without leakage.
4.7.2 The shaft seal clearance of LP cylinder shall meet the design requirements.
4.7.3 The safety valve of the LP cylinder shall be tight and leak-free.
4.7.4 The welds, valves and connecting flanges on the steam extraction tube of the heater in the negative pressure section shall be tight and leak-free.
4.7.5 The water spray desuperheating system of the LP cylinder shall work normally.
5 Operation monitoring and test
5.1 Operation monitoring parameters
5.1.1 All parameters listed in Table 1 shall be monitored during operation.
5.1.2 When the vacuum tightness index is unqualified, leakage test shall be carried out in time during operation, or the condenser shall be filled with water for leak test during shutdown and maintenance; when the condenser pressure is more than 15% of the design value under the assessment condition, the test for condenser heat transfer characteristic shall be carried out. The test measurement items shall at least include condenser pressure, cooling water inlet temperature, cooling water outlet temperature, condensed water oxygen content, vacuum tightness, circulating cooling water flow, heat load, condenser cleaning coefficient, heat transfer coefficient, etc.
Foreword i
1 Scope
2 Normative references
3 General
4 Operation and maintenance requirements
5 Operation monitoring and test
6 Operation optimization of cold end system
7 Vacuum system failure and its causes
8 Overhaul and maintenance
Annex A (Normative) Water quality requirements for condenser cooling tubes made of different materials
Annex B (Informative) Supervision curve of condenser operation characteristics
Annex C (Informative) Calculation of overall heat transfer coefficient of condenser
