GB/T 34875-2017 in English

This standard is equivalent to ISO 21049:2004 and specifies the technical requirements for shaft sealing systems of pumps used in the petroleum, natural gas and chemical industries. The main technical features include:

Seal type selection

The standard defines three basic seal types:

• Type A: Multi-spring sliding type, applicable temperature ≤176℃
• Type B: Rotary bellows type, preferred for low temperature conditions
• Type C: Rotary bellows type, preferred for low temperature conditions
• Type C: Static bellows type, high temperature can reach 400℃

Layout specifications

Three typical layout schemes:

1. Single-end cartridge type (Layout 1)
2. Double seal with buffer (Layout 2)
3. Double seal with isolation fluid (Layout 3)

Material selection points

Chapter 6 of the standard specifies the material requirements under different working conditions in detail:

• O-ring sealing surface roughness: dynamic 0.8μm, static 1.6μm
• Thermal expansion characteristics need to be considered in the design of perfluoroether rubber (FFKM) groove
• A 3mm corrosion allowance needs to be reserved for the pressure shell

Installation and commissioning specifications

Key installation parameters:

• Radial clearance of sealing chamber ≥3mm
• Radial runout of gland positioning surface ≤0.125mm
• Verification of axial displacement compensation capability

Main improvements of this standard compared with the old version:

• Added technical requirements for non-contact seals (NC)
• Improved the calculation method of seal balance coefficient
• Added sealing solutions for high temperature conditions (400℃)
• Strengthened environmental emission requirements (EPA Method 21)

Typical application case: The feed pump of a refinery hydrogenation unit adopts 3CW-FB type seal, continuous operation time exceeds 30,000 hours, and VOC emission concentration is stable below 500ppm.