There are two 457MCL compressors in the public works of a petrochemical company. During operation, oil leakage occurred due to bearing temperature. Bearing operating temperature is the most comprehensive working parameter among various factors reflecting bearing quality. It reflects the influence of the thermal effects associated with internal friction, rolling, vibration, collision and other factors under the combined action of bearing load, rotational speed, oil lubrication, abnormal unit operation, and external temperature. It can also be used as an effective means of judging bearing faults (heat build-up, temperature rise).

1. The function of bearing temperature in the unit control system

The large compressor bearing temperature measurement signal is usually connected to the unit protection and alarm system, which acts on the compressor unit to stop or alarm. For example, the thrust bearing is one of the key parts of the steam turbine unit, and the pad temperature of the thrust bearing is the only means to monitor the operating state of the thrust pad, and the temperature signal must be connected to the protection system. When the temperature of the thrust tile reaches 80°C, the system will issue an audible and visual alarm; when the temperature of the thrust tile reaches 95°C, the protection system triggers the stop operation command of the compressor unit to safely stop the compressor.

2. Reasons and consequences of oil leakage due to bearing temperature

2.1 Reasons for oil leakage

The protective structure of platinum thermal resistance is generally composed of PTFE sheath and steel wire braided pins. The platinum thermal resistance is prone to wear under the action of the inside of the body and the scouring of the lubricating oil and the vibration of the body for a long time. And the temperature inside the body is relatively high, in this case the production

The raw lubricating oil oil and gas use the damaged sheath as the outer channel, and finally condense at the terminal head and become droplets. With the accumulation of time, the condensed oil droplets accumulate more and more, and finally the lubricating oil overflows to the surface. in the surrounding environment.

2.2 Consequences of oil spills

(l) There is oil seepage at the terminal of the thermal resistance, which is easy to cause poor contact, aging of the wire core, etc., thus triggering the malfunction of the temperature interlock, causing the compressor to stop running, and causing major losses to production;

(2) The temperature measuring probe and lead wire are immersed in the turbine oil flowing along the rotation direction of the unit for a long time, and are subjected to the radial shear force of the oil flow and the upper and lower shear force of the vibration of the unit. Normal monitoring of bearing temperature cannot be achieved

It is also easy to cause interlocking malfunction;

(3) The leakage of oil and gas pollutes the surrounding environment, and also causes the waste of lubricating oil;

(4) The leaked oil can easily cause unsafe phenomena such as smoke and fire at the high temperature part of the body, threatening the normal operation of the unit, and even lead to forced shutdown in severe cases. Once the bearing temperature is confirmed as its own fault, it can only be carried out during the outage of the compressor unit for maintenance.

Replacement, so its reliability requirements are relatively high.

3. Treatment measures and comparison of effects

 3.1 Treatment measures and effects during production

In view of the particularity of the production period, we have mainly taken the following measures to ensure the safe operation of the unit:

(l) Further seal and reinforce the lead wire at the sealing joint of the lead wire outlet of the casing to prevent the leakage of oil and gas inside the body as much as possible;

(2) Raise the height of the platinum thermal resistance threading pipe to a height higher than the lubricating oil level inside the body, and try to make the condensed droplets fall back to the interior of the body at the middle of the threading pipe without overflowing; Effect: The oil leakage problem still exists and cannot be solved.

3.2 Transformation measures and effects during the first overhaul

In view of the cause of the oil leakage, we mainly took the following measures during the first maintenance:

Peel off the PTFE sheath of the platinum thermal resistance and the integrated dense mesh shielding layer inside the lead at the sealing joint of the lead outlet of the casing, and take sealing and reinforcement measures at the sealing joint.

The effect of this measure:

It achieves the function of preventing oil leakage during the operation of the compressor. But this measure also has some negative effects:

(l) The installation and processing workload is large, and the wire core is easily broken during the process of stripping and tightening the sealing joint, resulting in waste of resources and extension of the construction period;

(2) During the process of use, the wire core is corroded by the oil mist, which makes the wire core aging and brittle, and it is easy to break during the maintenance and disassembly process. In order to ensure the reliability of instrument measurement, it must be replaced every maintenance cycle, resulting in increased costs.

3.3 Transformation measures and effects during the second overhaul

In order to make up for the shortcomings of the first transformation measures, the measures we took are: design and purchase an integrated package temperature measuring element,

That is: from the micro pin-mounted temperature measuring thermal resistance to the lead wire, it is an integrated package structure, and is equipped with a sealing joint with an oil-resistant rubber plug.

The effect of this measure:

After long-term operation inspection of the compressor, this measure can completely solve the oil leakage problem.