Changsha Zoomlian Pump Co., Ltd. 长沙中联泵业股份有限公司

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    Is there any difference between chemical industrial centrifugal pumps and ordinary multistage pumps when choosing the sealing method?

    Publication Date:

    2025-06-19

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    Our manufacturer's after-sales service personnel have received many cases where customers ignored the importance of the medium during selection, resulting in many problems with centrifugal pumps during use.

    There are also many after-sales cases caused by incorrect sealing method selection for chemical pumps. So how should the sealing method for chemical centrifugal pumps be chosen?

    First, let's understand the three main types of sealing methods:

    1. Classification of sealing methods and applicable scenarios

    (1) Mechanical seal (mainstream choice)

    Requirements:

    Corrosion resistance: The sealing face material must be compatible with the medium (e.g., silicon carbide, alumina ceramics for strong acids; hard alloys for media containing particles).

    Temperature and pressure resistance: For high-temperature conditions (>150℃), metal bellows seals are required; for high pressure, the sealing ring pressure-bearing design must be reinforced.

    Double-end face seal:

    Used for hazardous media (such as chlorine gas, hydrofluoric acid), requires a barrier fluid system (Plan 53/54).

    The barrier fluid pressure must be higher than the pump chamber pressure (usually 0.1~0.2MPa higher).

    Flushing schemes:

    Plan 11: Self-flushing, suitable for clean media.

    Plan 32: External flushing (injecting clean buffer liquid), used for media prone to crystallization or containing particles.

    (2) Packing seal (limited to specific conditions)

    Requirements:

    Material: Use corrosion-resistant packing (such as PTFE, graphite fiber) to avoid failure caused by medium corrosion.

    Cooling and lubrication: External flushing water or lubricant (such as Plan 13) is required to prevent dry friction and overheating.

    Application limitations: Only for non-toxic, non-hazardous media (such as clean water, low-temperature weak alkaline solutions), and allows slight leakage (about 5~10 drops/minute).

    (3) Magnetic seal (leak-free solution)

    [For more information on chemical pump models, parameters, selection, and quotation plans, you can click the image above to learn more]

    Requirements:

    Isolation sleeve material: Must be resistant to medium corrosion (such as Hastelloy, ceramics) and avoid eddy current heating.

    Power limitation: High-power pumps (>100kW) should be chosen cautiously to prevent demagnetization.

    Applicable scenarios: Highly toxic (such as liquid chlorine), strongly carcinogenic (such as aniline), or high-purity media.

    3. Sealing solutions for special conditions

    (1) Easily vaporized media (such as liquid hydrocarbons)

    Requirements:

    Use double-end face seal + pressurized barrier fluid (Plan 53B) to prevent dry friction caused by medium vaporization.

    The sealing chamber is equipped with a throttling sleeve to maintain stable pressure.

    (2) High viscosity media (such as polymer melts)

    Requirements:

    Enlarge the sealing chamber space to avoid medium solidification and blockage.

    Use heating jackets (steam or electric heating) to maintain fluidity.

    (3) Media containing crystals/easily precipitating media

    Requirements:

    Continuous external flushing (Plan 32) or ultrasonic anti-scaling design.

    Avoid using flat sealing faces; instead, use conical or spiral grooves to enhance self-cleaning ability.

    Chemical pumps themselves are a special industry among pump products because the media transported are mostly harmful to humans. Therefore, the selection and sealing of chemical pumps relate to equipment reliability, safety, and service life. Especially when transporting flammable, explosive, or strongly corrosive media, sealing problems can lead to safety accidents, so extra attention is needed when choosing seals.

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    How to choose the appropriate model for a horizontal multistage chemical pump?

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