Helium mass spectrum leak detector is applied to the vacuum system of steam turbine unit in power plant

Thermal power plants use the energy of water vapor to convert generators into electricity, and use coal, crude oil or natural gas to burn heat, which is used to heat water to produce high-pressure water vapor. The water vapor then drives a turbine connected to a current generator, which generates electricity and transmits it to a high-voltage wire.

To improve the efficiency of the plant, water vapor is transmitted through a different set of high – and low-pressure turbines. In modern power plants, steam transmission also bypasses the turbine to preheat the steam boiler’s water supply, creating an extremely complex steam piping system. Once the steam passes through the last turbine, it reaches the condenser. Steam condenses into water in a condenser. The condensate will be pumped back into the pipe in the steam generator and then used again to complete the cycle.

Why do power plants need helium leak detection?

The helium mass spectrum leak detector used in the power plant is mainly for the leak detection of the vacuum system inside the steam turbine, as well as the leak detection of the condensing tank, because every link if there is a leak will increase the production cost, so the leak detection of the power plant is very important in the actual production. The leak point is an important reason for the failure of steam turbine vacuum tightness test. The leakage holes of different sizes will cause the vacuum degree to decrease when the unit is running, which will bring adverse effects on the economy and safety of the turbine generator set.

Primul, the decrease of vacuum degree leads to the increase of steam consumption of the unit, reduces the economy of the unit operation, and seriously restricts the load of the unit.

În al doilea rând, the decrease of vacuum degree increases the exhaust pressure and exhaust temperature, which causes abnormal changes in the expansion difference of the low pressure cylinder of the turbine and the deformation of the low pressure cylinder, changes the center of the unit, causes severe vibration of the unit, and may even cause failure and shutdown.

The condenser must contain only steam in order to operate optimally. Any other gases that leak into the steam circuit, such as surrounding air, will greatly reduce the efficiency of the condenser and thus the efficiency of the entire power plant. Power plants empty the condenser during start-up and operation to remove all other gases from it. In order to maintain the vacuum in the system, it is necessary to avoid leakage anywhere in the complex steam circuit. Any leakage will reduce the overall efficiency of the power plant. According to rough statistics, every increase in vacuum pressure of 1 hPa will improve the net efficiency of about 0.04%.

Which parts of the power plant need leak detection?

In the past, we have learned that the leak inspection is mainly for the internal system of the turbine in the power plant. Prin urmare, all vacuum sealing parts in the condensing area of the main turbine and the feedwater turbine of the power plant are mainly tested for leakage. This includes, de exemplu, condensing chambers, turbine housings (welds), vacuum lines, and any areas where leaks are suspected.

Why use helium mass spectrometer leak detector in power plant?

The vacuum system of steam turbine unit is difficult to detect because of its large volume, complex pipeline and invisibility. Especially the air cooling unit, the exhaust pipe diameter is large, the weld is long, the interface is many, the air cooling radiator temperature is high, the volume is huge, the number of tube bundles is large, the fin structure is complex, and the detection is extremely difficult. The leak detection problem of vacuum system of steam turbine unit has been troubling the technical department of power plant for a long time. All kinds of traditional leak detection methods have various defects and can not reach the expected effect. It is particularly important to find a good leak detection method in order to detect and plug the vacuum system during the normal operation of the unit.

Helium mass spectrometry leak detection technology as an advanced leak detection method, it is easy to operate, fast and accurate, sensibilitate ridicată, no damage, can detect the leak in the normal operation of the unit, reduce the economic loss of downtime, and provide a guarantee for the safe economic and stable operation of the unit. Because the power plant system equipment is huge and complex, every link if there is leakage will increase the production cost, so the power plant leak detection is very important in the actual production. Here we focus on the selection of condenser system for leakage detection, so as to achieve a comprehensive leakage detection of the whole system.

Helium mass spectrometry method for leak detection in power plant

Before detection, helium is sprayed near the flange, stem and weld of the steam valve related to the vacuum system that may leak. If there is a leak point at the measured place, helium will be sucked into the vacuum system through the leak point, then discharged through the vacuum pump exhaust port, collected by the probe (suction gun) at the sampling hole, and sent to the helium mass spectrum leak detector for detection. The method is simple and fast, and does not need to touch any equipment in the power plant.