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Low Cracking Pressure in Chemical Processing Condensate Lines

Steam condensate is the liquid by-product formed when steam goes from the vapor state to the liquid state; this process occurs in a wide range of applications, across virtually all industries. The chemical processing industry especially relies heavily on steam and steam-related systems. This necessitates vast, complex networks of boilers, evaporators, steam lines, and condensate return lines throughout many of the steps in the chemical production process.

By its nature, steam will condense back to liquid water at some point. This is unavoidable. In most of the modern industrial processes that use steam, the condensate is collected and recycled back into the system. This is a fiscally and environmentally beneficial practice, but its proper implementation is often overlooked, and poorly managed steam condensate in a system can lead to many serious issues.

One of the most common issues is the pooling of steam condensate—a byproduct of all steam processes—inside the equipment. When released from a high-pressure area to a low-pressure area, pooled condensate can flash, or quickly heat back up into steam, resulting in extreme pressure spikes, audible banging noises, valve and steam line failure, corrosion and even full equipment failure.

To address these risks, manufacturers in the chemical processing industry incorporate steam traps and condensate drain systems into their equipment. These applications also use in-line check valves in the condensate system piping to allow flow in only one direction—from low pressure to high pressure—before sealing.

Cracking pressure, or the minimum upstream pressure at which the valve can operate, is a critical aspect of check valve applications. To help manufacturers ensure they use the best components for their processing system, check valves can be custom sized and specified for unique cracking pressures.

SELECTING CONDENSATE LINE CHECK VALVES

DFT chem steam trapA few key considerations to keep in mind when selecting check valves for steam applications include a tight seal, ability to close quickly, reliability and performance.

Sealing Ability
Resilient, reliable seals will provide a long-lasting, leak-tight seal through the use of engineered elastomers; these seals are highly resistant to abrasion and are mainly used for low-pressure environments (up to 500 psig). Metal-to-metal seals are more reliable for piping systems with temperature and pressure changes, and they are able to withstand higher contact forces and pressures (exceeding 500 psig).

Quick Closing
The check valve must be able to close quickly to prevent any reverse flow that can result from steam condensate flashing. Features of a non-slam axial flow check valve include spring-assisted silent closing of the disk to the seat. These check valves can be installed in any orientation (horizontal or vertical) within the piping system.

Quality Parts & Reliability
A quality system depends on quality materials and parts. The correct valve selection not only allows the valves to last longer, but pumps and other related components on the same system will have increased longevity as well, resulting in reduced overall maintenance and costs. Well-functioning check valves also enhance the safety of their applications.

BEST PRACTICES

Employing preventive solutions is the best way to deal with issues resulting from excess steam condensate; designing and implementing a high-quality condensate piping system is paramount. Also, best practices always should be followed: ASME Power Piping Code B31.1, for example, outlines condensate piping system requirements that are widely considered to be the industry standard.

There are other best practices that are often overlooked despite being seemingly intuitive. For example, condensate piping size issues are common; using standard fluid pipe sizing calculations for condensate pipes can result in pipes that are too small. It’s also important to work with gravity, not against it; ensure that pressure flows from low to high, and install pressure gauges to make it easy to diagnose malfunctions and maintain the health of a steam condensate system.

Finally, make sure to design a condensate piping system that flows back to the original boiler. Recycling this fluid allows for significant reductions in both energy and water use and allows for improved process efficiency and product quality.


This email address is being protected from spambots. You need JavaScript enabled to view it. is vice president and general manager for DFT Inc.  

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