Verification Method and Practice of Sealing System for Centrifugal Hot Oil Pump

As the core equipment for transporting high-temperature media, the sealing system of centrifugal hot oil pumps directly affects process stability and equipment life. A systematic verification system needs to be established to control the sealing performance throughout the entire process from selection, installation and commissioning to operation and maintenance, in response to the leakage, increased energy consumption, and stability hazards caused by the failure of the hot oil pump seal.

1、 Sealing system verification

1. Adaptability assessment of sealing structure

The sealing of the hot oil pump needs to take into account the characteristics of the high-temperature medium and the operating conditions. Mechanical seals should choose a balanced structure, which reduces the end face pressure by compensating for the floating ring to avoid excessive wear of the sealing surface at high temperatures. The renovation case of a petrochemical enterprise shows that after changing the unbalanced seal to a balanced seal, the seal life is significantly improved. Bellows mechanical seals are suitable for media containing solid particles, and their non axial motion characteristics can prevent particles from entering the sealing surface. After application in a certain coking unit, the leakage rate is significantly reduced.

2. Materials are not afraid of temperature matching

The sealing end material needs to meet the requirements of hot oil working conditions. The combination of tungsten carbide and carbon graphite has good high-temperature properties and is suitable for high-temperature heavy oil media; Impregnated resin graphite is suitable for light oil products, and its self-lubricating properties can reduce the risk of dry friction. The auxiliary sealing ring should be made of fluororubber or perfluoroether material to ensure elasticity at high temperatures. A certain refinery experienced long-term deformation at high temperatures due to improper selection of sealing rings, resulting in seal failure.

3. Collaborative cooling system

Cooling measures are required for the sealing of the hot oil pump. The temperature of the flushing solution should be controlled within the correct range to avoid thermal cracking of the sealing surface due to excessive temperature difference. A certain enterprise adopts a double end face sealing structure and introduces low-temperature cleaning oil through an external flushing system to form a stable liquid film, which not only reduces the end face temperature but also prevents impurities from entering. For high-temperature conditions, rapid cooling facilities can be added by installing cooling water jackets on the outer wall of the sealed chamber to quickly dissipate heat.

2、 Installation and debugging process verification

1. Installation accuracy control

Sealed installation must strictly follow the process specifications. The axial displacement should be controlled within the allowable range to avoid obstruction caused by the floating of the compensation ring; Radial runout needs to be detected by a micrometer, and the coaxiality between the pump shaft and the sealing chamber. A certain chemical plant experienced severe leakage after operation due to improper coaxiality correction during installation, resulting in uneven wear of the sealing surface. After installation, a static pressure test should be conducted to check for any leakage points in the sealed chamber and connection parts.

2. Verification of flushing plan

The flow rate and pressure of the flushing solution need to be matched with the sealing structure. For the PLAN scheme in the API flushing plan, it should be ensured that the flushing pipeline is unobstructed and the filter pressure difference meets the requirements. During the debugging of a certain enterprise, it was found that the flow rate of the flushing liquid was insufficient. After inspection, it was found that the filter was clogged. After cleaning, the stability of the sealed operation was significantly improved. For high-temperature conditions, it is necessary to verify the cooling effect of the flushing liquid, and the temperature distribution of the sealed chamber can be detected by an infrared thermometer.

3. Initial operation monitoring

Monitoring should be increased during the initial operation of the sealing system. Observe the trend of leakage volume changes. Minor leakage in the initial stage is a normal phenomenon. If it continues to increase, the cause needs to be investigated; Monitor the temperature of the sealed chamber, and if it exceeds the value, check whether the cooling system is functioning properly; Record the vibration value, abnormal vibration may indicate poor contact of the sealing surface. A certain thermal power plant found excessive vibration after sealing and operation. After inspection, it was found that the rotor dynamic balance was poor. After recalibration, the problem was solved.

3、 Operation and maintenance verification

1. Application of state monitoring technology

Establish a sealing system status monitoring system. Vibration analysis can identify bearing wear or rotor imbalance; Temperature monitoring can reflect the friction state of the sealing surface; Acoustic emission detection can capture early leakage signals. A certain enterprise detected the wear of the sealing end face in advance through an online monitoring system, and completed the replacement before the leakage occurred to avoid unplanned downtime.

2. Maintenance cycle optimization

Adjust maintenance strategies based on operational data. For a stable operating sealing system, the maintenance cycle can be appropriately extended; If leaks occur frequently, it is necessary to shorten the maintenance interval and analyze the root cause. A certain refining unit adjusted the maintenance cycle from a fixed duration to an operating state by analyzing the sealing failure mode, which not only ensured stability but also reduced maintenance costs.

3. Improvement of spare parts management

Establish a record of the lifespan of sealed spare parts. Record the sealing model, operating time, and failure mode of each replacement, providing a basis for spare parts selection. A certain enterprise discovered that a batch of sealing end faces were prone to thermal cracking, which was traced back to a defect in the material heat treatment process. The problem was promptly resolved by changing the supplier. At the same time, reserve key spare parts to quickly restore production in case of sudden failures.

4、 Key points for implementing systematic verification

Cross departmental collaboration: Sealing verification requires the joint participation of process, operation, and maintenance personnel to determine the implementation of requirements in each link.

Standardized operation: Prepare instructions for sealing installation, commissioning, and maintenance operations, specifying operating steps and acceptance standards.

Continuous improvement: Regularly review the operating data of the sealing system, identify opportunities for improvement, and enhance the sealing performance through technological upgrades.

Through the implementation of a systematic verification system, the centrifugal hot oil pump sealing system can achieve a transition from passive maintenance to active prevention. Enterprises need to establish a suitable validation process based on their own technological characteristics, in order to determine stable production while reducing equipment lifecycle costs.