What are the common failures of chemical pump body?

Chemical pump pump body in chemical production bears the key role of conveying various types of media, its failure may affect the stability of the entire system. The following are common failures of chemical pump pump body, causes and corresponding solutions:

First, the pump body cracked or broken

Failure performance

Visible cracks in the pump body, resulting in media leakage or a decline in structural strength.

Common causes

Media corrosion: conveying strong acid, strong alkali or high concentration of corrosive media (such as sulfuric acid, sodium hydroxide), the pump body material is gradually eroded.

Mechanical stress: long-term overload operation, frequent starting and stopping or vibration caused by material fatigue; installation of the bolt fastening unevenly caused by local stress concentration.

Freeze crack: low temperature environment, the pump body residual medium icing expansion (such as water-based medium is not emptied).

Cavitation impact: the medium in the pump vaporised to form bubbles, the rupture of the pump body to produce high-frequency impact (especially in the transmission of easy to vaporise the medium).

Solution

Material upgrade: according to the characteristics of the medium to choose corrosion-resistant materials (such as stainless steel 316L, fluorine plastic, titanium alloy).

Standardised installation: ensure that the bolts are uniformly stressed to avoid forced alignment of the pipeline; the installation of vibration-damping bracket to reduce vibration.

Anti-freezing measures: Empty the pump body under low temperature environment, or use tracer heat insulation.

Control of cavitation: adjust the inlet pressure (such as increasing the pipe diameter, reduce the installation height), or the choice of anti-vapor corrosion materials (such as high nickel alloy).

Second, the pump body leakage

Failure performance

Pump body and pipe interface, sealing surface or cracks in the media leakage.

Common causes

Seal failure: mechanical seal wear, O-ring aging or installation misalignment; flange sealing surface uneven or impurities.

Loose bolts: long-term vibration leads to relaxation of connecting bolts, sealing specific pressure is insufficient.

Scouring wear: when transporting media containing particles (such as mud, slurry), the pump body flow channel is scoured to form grooves.

Solution

Check the seals: replace the worn mechanical seal or O-ring, clean up impurities on the sealing surface, and grind the flange surface if necessary.

Tighten bolts: Tighten bolts evenly in diagonal order, use anti-loosening rubber or spring gasket.

Wear-resistant treatment: spray wear-resistant coating on the inner wall of the pump body (such as ceramics, tungsten carbide), or choose wear-resistant materials (such as high chromium cast iron).

Third, the pump body vibration abnormality

Failure performance

The pump body vibrates violently during operation, accompanied by abnormal noise.

Common causes

Rotor imbalance: Impeller wear, dirt accumulation or parts falling off lead to dynamic balance damage.

Bearing damage: insufficient lubrication, media intrusion into the bearing cavity or long-term overload resulting in bearing wear.

Pipe resonance: insufficient pipe support or pipe diameter design is unreasonable, and the pump body vibration frequency coupling.

Cavitation vibration: high-frequency vibration triggered by the rupture of bubbles produced by the vaporisation of the medium.

Solution

Rotor dynamic balance: disassemble the impeller for dynamic balance calibration, clean up the dirt or replace the damaged parts.

Bearing maintenance: regularly replace the lubricating oil, check the bearing clearance, if necessary, replace the bearing; add dust seals to prevent media intrusion.

Pipeline optimisation: add brackets to fix the pipeline, adjust the pipe diameter or elbow position to avoid resonance.

Control of cavitation: see ‘pump body cracks’ part of the solution.

Fourth, the pump body overheating

Failure performance

Abnormal increase in the temperature of the pump body, may be accompanied by media vaporisation or material deformation.

Common causes

Idle running: no medium in the pump impeller and pump body friction heat (such as the inlet valve is not open).

Media viscosity is too high: conveying high viscosity media (such as syrup, ink), the impeller churning resistance increases, the energy into heat.

Insufficient cooling: the pump body with cooling chamber is not connected to the cooling water, or cooling waterway blockage.

Solution

Prevent idling: install liquid level sensor or flow switch, automatic shutdown when idling; confirm the status of import and export valves before starting.

Medium treatment: heating medium to reduce viscosity, or choose a large flow, low speed pump type.

Cooling system maintenance: regular cleaning of the cooling waterway to ensure adequate cooling water flow.

V. Pump blockage

Failure performance

Flow drop, pressure fluctuations, the pump body inside the foreign body stuck.

Common causes

Medium crystallisation / solidification: conveying easy to crystallise media (such as ammonium nitrate solution), the temperature reduction leads to crystal precipitation; high melting point media (such as asphalt) cooling solidification.

Impurity deposition: the medium contains solid particles (such as sand, fibre), after long-term operation in the pump body flow channel accumulation.

Solution

Anti-crystallisation design: the pump body with heat insulation, or the choice of no dead space structure to reduce media retention.

Filtration measures: install filters in the inlet pipeline (such as Y-type screen), regular cleaning of impurities; conveying high-viscosity media when the choice of open impeller to reduce clogging.

Flushing system: before shutdown with a clean medium (such as water) to flush the pump body to prevent residual crystallisation of the medium.

Six, the pump body rattling

Failure performance

Running metal friction sound, impact sound or periodic noise.

Common causes

Impeller and pump body friction: impeller wear, deformation or installation clearance is too small, and pump body scraping.

Loose fasteners: the parts in the pump body (such as impeller nut, bushings) are loose and hit the pump body when running.

Cavitation noise: high frequency noise (similar to the ‘crackling’ sound) generated by the rupture of air bubbles.

Solution

Clearance adjustment: Disassemble and check the clearance between the impeller and the pump body, grind the pump body or replace the impeller to ensure compliance with the design requirements.

Tighten parts: Check and tighten internal fasteners, use anti-loosening devices (e.g., lock nuts, stop shims).

Control of cavitation: see the previous section of the relevant measures.

Seven, the pump performance decline (flow / head insufficient)

Failure performance

The actual flow, head is lower than the design value, reduced efficiency.

Common causes

Impeller wear: long-term transport of corrosive or particulate media, resulting in impeller blade thinning, gap.

Pump body runner wear: media scouring to expand the runner, internal leakage increases (such as impeller and pump body clearance is too large).

Air binding phenomenon: residual air in the pump, resulting in the medium can not be properly inhaled.

Solution

Replacement of impeller: Repair welding, surfacing or direct replacement of severely worn impeller, choose wear-resistant / corrosion-resistant materials.

Repair the pump body: Spray repair the worn runner or replace the pump body, and control the clearance within the permissible range.

Exhaust treatment: Exhaust the air in the pump through the exhaust valve before starting, and avoid air leakage in the inlet pipe.