Fire Fighting Pump Mechanical Seal

Sep 27, 2024

Mechanical seal is a shaft sealing device that relies on one or several pairs of end faces that slide relative to the shaft and are maintained in contact and matched with auxiliary seals under the action of fluid pressure and the elastic force (or magnetic force) of the compensation mechanism to achieve leakage prevention.
The commonly used mechanical seal structure consists of a stationary ring (stationary ring) 1, a rotating ring (moving ring) 2, an elastic element 3, a spring seat 4, a set screw 5, a rotating ring auxiliary sealing ring 6, and a stationary ring auxiliary sealing ring 8. The anti rotation pin 7 is fixed on the cover 9 to prevent the stationary ring from rotating. Rotating rings and stationary rings can often be referred to as compensating rings or non compensating rings depending on whether they have axial compensation capability.

There are four possible pathways for fluid leakage in mechanical seals: A, B, C, and D.
C. The D leakage channels are the seals between the stationary ring and the cover, and between the cover and the shell, both of which are static seals. B channel is the seal between the rotating ring and the shaft. When the end face is rubbed and worn, it can only move slightly along the axial direction following the compensating ring, and is actually still a relatively static seal. Therefore, these leakage channels are relatively easy to block. The most commonly used static sealing components are rubber O-rings or PTFE V-rings, while rotating rings or static rings used as compensating rings assist in sealing. Sometimes, rubber, PTFE, or metal bellows structures that also serve as elastic components are used.
The A channel is a dynamic seal in which the end faces of the rotating ring and the stationary ring are in contact with each other and slide relative to each other. It is the main seal in the mechanical seal device and the key to determining the performance and service life of the mechanical seal. Therefore, the processing requirements for the sealing end face are very high. At the same time, in order to maintain the necessary lubricating liquid film between the sealing end faces, it is necessary to strictly control the unit area pressure on the end face. If the pressure is too high, it is not easy to form a stable lubricating liquid film, which will accelerate the wear of the end face; Insufficient pressure leads to increased leakage. Therefore, in order to achieve good sealing performance and sufficient lifespan, it is necessary to ensure that the pressure value per unit area of the end face is within the most appropriate range when designing and installing mechanical seals.
Compared with soft packing seals, mechanical seals have the following advantages:
① Reliable sealing: During long-term operation, the sealing state is very stable and the leakage is very small. Roughly speaking, its leakage is generally only 1/100 of that of soft packing seals;
② Long service life can generally reach 1-2 years or longer in oil and water media, and more than half a year in chemical media;
③ The friction power consumption of small mechanical seals is only 10% to 50% of that of soft packing seals
As the name suggests, fire pumps are pumps used in firefighting, which are classified into different types according to their characteristics of full sealing, no leakage, and corrosion resistance. They are widely used in environmental protection, water treatment, firefighting and other departments to pump various liquids. They are ideal pumps for creating leak free, pollution-free and civilized workshops and factories. Fire pumps are mainly divided into vertical fire pumps and horizontal fire pumps. The flow rate of the transported liquid is one of the important performance data for selecting fire pumps, and the flow rate of the transported liquid directly affects the production capacity of the entire device.
The selection of fire pumps should be based on the process flow of the fire pump application project, water supply and drainage requirements, and consider five aspects: liquid delivery volume, device head, liquid properties, pipeline layout, and operating conditions. Used for fire protection systems
There are several types of pumps: fire sprinkler pump, fire hydrant pump, fire stabilizing pump, and fire booster pump, depending on the actual usage. The pump type used is similar to that of the fire protection system, but the head and flow rate are different.
The shaft seal of the water pump has two forms to choose from: mechanical seal and packing seal. Mechanical seal has a better effect and is less prone to water leakage, while packing seal is more prone to water leakage and has a large amount of leakage, affecting the pump room environment.
Generally speaking, manufacturers have both types of products, and consumers can purchase them according to different needs. However, fire pumps are not commonly used and are well sealed with fillers. Even if there is a small amount of leakage during regular inspections, it will not have a significant impact on the pump room. Can be detected and replaced and adjusted in a timely manner. If a mechanical seal water pump is used, it is difficult to detect problems through regular inspections. Once a fire accident occurs and the seal is damaged when starting the pump, it will affect the normal operation of the water pump.