How to choose between soft-seal and hard-seal valves? YEKE will guide you

When selecting a valve, the question of "soft seal or hard seal?" is a core one that cannot be avoided. The wrong choice can lead to leaks, downtime, and even safety accidents. YEKE believes there's no absolute superiority or inferiority, only a perfect match for the operating conditions. This article will provide a thorough understanding of the differences between the two, supporting your critical decision-making.

What to choose for "Tight Shut-off"?

The answer is: soft-seal valves, which use flexible non-metallic materials such as EPDM, PTFE, and NBR as sealing elements. The elasticity of these materials can perfectly fill the tiny gaps between metal parts, thus achieving bubble-level sealing (zero leakage).

Typical application scenarios:

Municipal water services: Soft seals are widely used in butterfly valves and ball valves in waterworks and sewage treatment plants. These operating conditions require clean media, moderate temperature and pressure, and soft seals precisely meet the core requirement of "tight sealing" at an economical cost.

However, if encountering a high temperature and high pressure environment (such as the steam pipes in a power plant), the disadvantages of soft seals will become apparent, the rubber will age, and the plastic will deform, resulting in loss of sealing performance.

How to choose for harsh service conditions of “ high temperature and high pressure ” ?

When soft seals fail, hard seals come into play. Hard seals typically utilize metal-to-metal sealing, typically with a hard alloy overlay welded onto the valve seat surface, a hardened valve core, and precision grinding to ensure stability under harsh conditions. Their core advantages are resistance to high temperatures, high pressures, and erosion.

Of course, hard sealing technology also has its "has its pros and cons":

The processing technology of hard-sealed valves is complex and the cost is high.

It is difficult to achieve absolute zero leakage at the soft seal level, but its trace leakage rate is in line with the levels allowed by international standards such as API and ISO, meeting industrial safety and environmental protection requirements.

Sealing solutions for special service conditions

Safety-critical operating conditions (toxic, hazardous, flammable, or explosive media): Zero leakage must be the primary goal. In these conditions, as long as temperature and pressure permit, soft-seat valves are the undisputed first choice. Their superior sealing performance effectively prevents even the slightest leakage of hazardous media, providing the highest level of protection for personnel and environmental safety.

For cryogenic conditions (such as LNG), metal seals are preferred. Rubber loses its elasticity and becomes ineffective at cryogenic temperatures. Valve design must also carefully account for the varying thermal shrinkage of materials to ensure effective sealing pressure even in cryogenic conditions.

For highly corrosive environments (such as chemical media), a "soft seal + corrosion-resistant alloy" combination is recommended. For example, a Hastelloy valve body is designed to resist media corrosion, while a PTFE soft seal is incorporated within. This design balances the corrosion resistance of the valve body with the tightness of the seal.

Choosing YEKE means partnering with a knowledgeable and trustworthy expert. We not only provide high-quality soft and hard seal valves, but also provide you with professional operating condition analysis and selection guidance, ensuring you get the best value for your investment.

Contact the YEKE professional team to provide you with one-stop fluid control solutions!