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Correct Startup Method of Three-Screw Pump 3GR25X4Q in Low Temperature Environment

Correct Startup Method of Three-Screw Pump 3GR25X4Q in Low Temperature Environment

In thermal power plants, the three-screw pump 3GR25X4Q is a key equipment for conveying fuel oil, lubricating oil and hydraulic oil. Its efficient and stable operation ability is directly related to the energy supply efficiency of the entire power plant. However, when the ambient temperature is below 5°C, the startup of the three-screw pump faces many challenges – the viscosity of the lubricating oil increases, the performance of the sealing material decreases, and even cold start failures may occur. How to start the three-screw pump safely and efficiently under such low temperature conditions is a core skill that every operation and maintenance personnel must master.

 

I. The impact of low temperature on the three-screw pump

The working principle of the three-screw pump 3GR25X4Q relies on the meshing movement between the main screw and the driven screw to achieve continuous liquid delivery through the volume change of the sealing chamber. Under normal operating conditions, its compact structure and pulsation-free output make it an ideal choice for high-viscosity media. However, when the ambient temperature drops sharply, the physical properties of the pump body and the lubricating oil will change significantly:

Lube oil three-screw pump 3GR25X4Q

First, the viscosity of the lubricating oil will rise sharply as the temperature drops. Taking 3GR25X4Q as an example, its design working conditions usually require the medium viscosity to be in the range of 2~760mm²/s, but in a low temperature environment, if preheating measures are not taken, the lubricating oil may become too viscous, resulting in increased resistance when the pump starts, and even causing motor overload or screw jamming.

 

Secondly, the sealing system of the 3GR25X4Q three-screw pump (such as mechanical seals or packing seals) may have increased gaps or hardened cracks due to material shrinkage at low temperatures. This will not only affect the sealing performance of the pump, but may also cause medium leakage and increase safety hazards. In addition, the metal parts inside the pump body shrink unevenly at low temperatures, which may cause abnormal matching clearances and further affect the operating efficiency of the pump.

 

II. Preparations before starting

When starting the three-screw pump 3GR25X4Q in a low temperature environment, the first task is to ensure that the temperature of the pump body and the medium is within an acceptable range. The following are several key steps:

 

1. Preheating measures

Preheating the pump body and lubricating oil in advance is the core of low-temperature starting. The pump casing can be heated by steam heating, electric heating belt or hot water circulation to gradually increase the temperature of the pump body to above 5°C. For example, for high-power pumps such as 3GR25X4Q, it is recommended to turn on the heating device at least 2 hours before starting and monitor the temperature change curve of the pump body.

Lube oil three-screw pump 3GR25X4Q

2. Check the sealing system

Low temperature may cause hardening or abnormal clearance of the seal. It is necessary to manually turn the pump shaft to check whether it rotates flexibly and observe whether there is any jamming. If frost or lumps are found on the seal, warm water or special cleaning agents should be used to remove them to avoid forced starting and damage to the seal.

 

3. Preparation of pipelines and filters

Ensure that the suction and discharge pipelines of the 3GR25X4Q pump are not blocked, and check the cleanliness of the filter. In a low temperature environment, the residual medium in the pipeline may condense into lumps, affecting the suction capacity of the pump. If necessary, compressed air or nitrogen can be used to purge the pipeline to ensure smooth flow of the medium.

 

III. Steps to correctly start the three-screw pump

After completing the above preparations, follow the steps below to start the 3GR25X4Q screw pump:

 

1. Pump priming operation

The three-screw pump is a positive displacement pump with high requirements for suction conditions. In low temperature environments, pump priming is particularly critical. The suction port of the pump must be completely immersed in the medium, and the lubricating oil must be injected into the pump cavity by manual oiling or auxiliary pump to ensure that the necessary seal and lubrication are formed when the pump is started.

 

2. Inching test

Before formally starting, perform an inching test to check whether the motor rotation direction is correct. If reversal is found, the power supply must be cut off immediately and the wiring must be adjusted. At the same time, observe whether the running sound of the pump is stable and whether there is abnormal vibration or noise.

 

3. Slowly load pressure

After starting the motor, the discharge valve should be gradually closed to allow the pump to run at low load for about 5 to 10 minutes. After the pump body temperature and medium viscosity stabilize, gradually increase the pressure to the rated value. This process helps to avoid mechanical stress concentration caused by instantaneous high pressure.

 

4. Monitor key parameters

After starting, closely monitor the pump’s inlet and outlet pressure, current, and temperature changes. If the current is abnormally increased or the pressure fluctuates violently, the pump should be stopped immediately for inspection to check for possible blockage, leakage, or seal failure.

 

IV. Precautions for low-temperature startup

Although the above steps can effectively reduce the risk of low-temperature startup, the following details should still be noted:

 

1. Avoid frequent starts and stops

In low-temperature environments, frequent starts and stops of the three-screw pump 3GR25X4Q will aggravate mechanical wear and seal aging. If not necessary, the number of starts should be minimized, and sufficient warm-up time should be left between two starts.

Lube oil three-screw pump 3GR25X4Q

2. Setting of safety valve

Ensure that the setting value of the pump’s safety valve meets the design requirements, and check its action sensitivity regularly during low-temperature startup. If the safety valve is frozen or stuck due to low temperature, it may cause overpressure damage to the pump.

 

3. Recording and feedback

After each low-temperature startup, record the pump’s operating parameters, such as starting current, pressure curve, temperature changes, etc., and compare them with historical data. If abnormal trends are found, the preheating strategy should be adjusted in time or the manufacturer’s technical support should be contacted.

 

V. Long-term maintenance recommendations

Low temperature environment places higher demands on the long-term operation stability of the three-screw pump 3GR25X4Q. It is recommended to take the following measures in daily maintenance:

 

Regularly replace lubricating oil: Low temperature may accelerate the aging of lubricating oil, which needs to be replaced according to the manufacturer’s recommended cycle, and choose a model with better low-temperature fluidity.

 

Seal system inspection: Check the wear of the mechanical seal every quarter, and replace the dynamic ring or static ring if necessary to avoid medium leakage due to seal failure.

Insulation layer maintenance: Add insulation materials to the pump body and pipelines to reduce the impact of ambient temperature fluctuations on the equipment.

 

As one of the core equipment of thermal power plants, the three-screw pump 3GR25X4Q requires refined management of its startup and operation in low-temperature environments. Through scientific preheating, strict inspection procedures and standardized operating procedures, not only can the efficient operation of the pump be ensured, but also its service life can be significantly extended.

 

When looking for high-quality, reliable screw pump, YOYIK is undoubtedly a choice worth considering. The company specializes in providing a variety of power equipment including steam turbine accessories, and has won wide acclaim for its high-quality products and services. For more information or inquiries, please contact the customer service below:
E-mail: sales@yoyik.com
Tel: +86-838-2226655
Whatsapp: +86-13618105229

 

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  • Post time: Jun-20-2025