Unbalanced mechanical seal
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Unbalanced mechanical seal

High-performance unbalanced mechanical seals for centrifugal pumps and rotary equipment. Available as single-spring, multi-spring and cartridge configurations. Common shaft sizes 16–130 mm; suitable for industrial, chemical and wastewater applications where moderate pressure and reliable leakage control are required.

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Product Overview

What is an Unbalanced Mechanical Seal?
An unbalanced mechanical seal is a single sealing element where hydraulic forces on the rotating seal face are not fully counteracted by the seal design: the seal face is partially exposed to process pressure. This design provides a compact, cost-effective solution for many pump services (clean water, service water, oils, low-to-moderate pressure chemical service). Unbalanced seals are typically used where service conditions do not require the reduced face loading of a balanced seal.

Common aliases / keywords (insert naturally on page):
Unbalanced seal, single-spring mechanical seal, unbalanced cartridge seal, unbalanced single seal, process pump mechanical seal.

Key Features

Core features

  • Simple, compact construction — fast replacement and low inventory complexity.

  • Available as component or cartridge — component (single-piece) or pre-assembled cartridge options to simplify installation.

  • Materials flexibility — carbon, silicon carbide, tungsten carbide, stainless steel, and elastomers (NBR, FKM, EPDM) for varied media.

  • Wide shaft-size coverage — common shaft diameter availability spans roughly 16–130 mm (0.625″–5.12″), matching ISO/API pump shaft ranges used in general industry.

Technical Specifications

NOTE: specify exact part-level dimensions on the downloadable datasheet/catalog (link provided below).

  • Seal type: Unbalanced single / multi-spring / cartridge

  • Shaft diameter (typical availability): 16 mm — 130 mm (0.63″ — 5.12″).

  • Maximum recommended pressure (typical service for unbalanced seals): up to ~1.0–1.2 MPaG (150–174 psi) depending on design and face materials; for higher pressures a balanced seal is recommended.

  • Temperature range (dependent on elastomer/face choice): from −40 °C (with appropriate elastomers) up to commonly ~220 °C for selected face/elastomer combinations.

  • Typical shaft finish / tolerance: ground finish per pump OEM recommendations; use OEM cross-reference/dimension chart to confirm.

  • Face materials: Carbon vs Silicon Carbide (SiC), Tungsten Carbide (TC), Ceramic — selected per media abrasiveness and temperature.

Common sizes & selection guide

Typical stock shaft diameters (mm / inches)

Shaft dia (mm) Inch (approx.)
16 0.63
20 0.79
25 0.98 (1″)
32 1.26
40 1.57
50 1.97
63 2.48
80 3.15
100 3.94
120 4.72
130 5.12

These are the most commonly stocked shaft sizes for ISO/ANSI-style seals; custom sizes above 127 mm (5″) are often supplied as engineered solutions per API/ISO guidelines.

Materials & Face Combinations

  • Carbon vs Ceramic / SiC: Good for rotating faces with good run-in and lower abrasion services.

  • SiC vs SiC: High wear and corrosion resistance, suitable for abrasive or high temperature service.

  • TC vs Carbon: For heavy-duty, abrasive services where carbide hardness is needed.

(Choose elastomer: NBR for petroleum, FKM (Viton) for higher temp/chemical resistance, EPDM for hot water/wastewater.)

Reference: typical face/material offerings in standard mechanical seal catalogs.

Applications

Typical IndustriesUnbalanced mechanical seal

  • Water & wastewater treatment

  • Municipal & sewage pumps

  • Chemical process (low-to-moderate pressure streams)

  • HVAC & cooling-water circulation

  • Oil & lubricant handling (with suitable elastomer)

  • Food & beverage (with food-grade material choices and certifications)

Typical Pump Types

  • Centrifugal end-suction pumps

  • ANSI/ISO process pumps

  • Circulation and booster pumps

(For hazardous/high-pressure or high-emission services reference API 682 and consider balanced seals or dual-seal arrangements.)

Performance & Installation Notes

  • Installation: Cartridge designs reduce installation variability—recommended for field service teams to minimize fitting errors.

  • Lubrication / Flush plans: For solids-laden or hot services consider an appropriate flush/plan per API/ISO recommendations.

  • Maintenance: Keep spare face sets, elastomer kits, and O-rings on site; perform run-in per manufacturer instructions.

Advantages of Unbalanced Mechanical Seals

  • Cost-effective for low-to-moderate pressure duties.

  • Simpler design → fewer spare-part variants and easier inventory management.

  • Suitable for many general-purpose pump services (water, wastewater, oils).

  • Cartridge option reduces installation time and risk of misalignment.

Unbalanced vs Balanced vs Alternative Sealing Methods

Characteristic Unbalanced Mechanical Seal Balanced Mechanical Seal Packed Gland / Lip Seal
Best for pressure Low–moderate (≤ ~1.0–1.2 MPa typical) High pressure, pressure-reversal environments (preferred when face loading must be reduced) Low pressure, cost-sensitive; higher leakage vs mechanical seals
Complexity Simple More complex (may require pusher/non-pusher designs) Simple but frequent maintenance
Cost Lower CAPEX Higher CAPEX (justified for reliability under pressure) Low initial cost, higher lifecycle OPEX
Installation Straightforward (cartridge option fastest) More careful alignment usually required Simple but packing adjustment needed
Recommended when General industrial, water, wastewater High pressure, hazardous fluids, API 682 services Low-speed, non-critical, or budget constraints

Downloadable Resources

FAQ

Q1: How do I choose between an unbalanced and a balanced mechanical seal?
A: Choose an unbalanced seal for general-purpose, low-to-moderate pressure pumps (cost-effective). For service with higher pressure, frequent pressure reversals, or hazardous fluids, choose a balanced seal or contact our engineering team for an API 682 assessment.

Q2: What information do you need to quote a replacement unbalanced seal?
A: Provide shaft diameter, pump make/model, existing seal drawing or part number (if available), operating pressure, temperature, fluid media, RPM, and required face/material preferences.

Q3: Can you supply cartridge unbalanced seals for quick retrofit?
A: Yes — cartridge unbalanced seals are available for many ISO/ANSI pumps and greatly shorten installation time; specify pump housing and shaft O.D. to confirm fit.

Q4: What are typical lead times and MOQ?
A: Lead times and MOQs depend on size/material; standard stock sizes (16–100 mm) frequently ship faster; custom sizes or exotic materials require longer lead times. Contact sales for exact ETA.

Q5: Do you provide mechanical seal exchange kits and onsite support?
A: We supply face sets, elastomer kits and full exchange cartridges. Onsite installation support is available through our service network (arrange via sales).

E-E-T-A

To support buyer confidence and satisfy Google’s E-E-T-A expectations, include the following on the published page (example copy — replace specific claims with your verified facts):

  • Experience: “Our rotating-seal division has handled pump sealing projects across water, chemical and oil sectors; engineering teams support seal selection and retrofit programs.”

  • Expertise: “All technical recommendations are validated by our seal engineers using pump OEM cross-reference checks and ISO/API sizing charts.”

  • Authoritativeness: “Products manufactured and tested to industry standards; we supply replacement kits compatible with major OEMs and ISO/ANSI pump lines.”

  • Transparency/Trust: “Complete material declarations, dimensional drawings and QA test reports are provided with each shipment. Field service and spare-part traceability included.”

(When you publish, append verifiable company credentials — years in business, ISO/TS or ISO 9001 certifications, customer case studies, and contactable references to maximize E-E-T-A signals.)

Why choose our Unbalanced Mechanical Seals

  • Stocked common sizes for fast dispatch.

  • Flexible material options (SiC, carbon, TC) to match your process.

  • Cartridge and component versions to suit installation preference and downtime constraints.

  • Technical support for selection, installation and field troubleshooting.

Contact & Ordering

Hengshui Aohong— Mechanical Seals Division

  • Email: sales@aohongglobal.com (for datasheet requests and fast quotes)

  • Phone: +(86) 153 7318 1024 (please replace with your official number)

  • Address: [Insert headquarter / factory address here]

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