Molecular Sieve Switching Valves High Temperature

Valves Supplied

Size:  2”, 3”, 6x4” ANSI 600 Class
Body Material:    WCC Carbon Steel
Internals:  Carbon Steel – Electrolysis Nickel Plated   
Trim:  Metal & Teflon Seated with Kalrez Seals       
Port:  Reduced Port
Connections:  Raised Face Flanged

Service Conditions

Media:  Natural Gas Dryer – Switching Valve   
Manual / Actuated:  Actuated w/ Manual override
Temperature:  550F Max   
Orientation:  Vertical
Pressure:  900-1000psig   
Cycles / Frequency:  Approx. 4X / day

Application/Service Conditions

The targeted valve installation is a molecular sieve dryer valve (also known as: mole sieve switching valve, de-hydration switching valve, gas de-hy switching valve, among others). Brief overview on molecular sieve dryer; A cyclical adsorption desorption system to transfer contaminants – or non-desired gas molecules from one stream to another.  Mole sieve drying systems are utilized in processes where the end user is ultimately trying to purify (remove moisture and contaminates or isolate specific gas strains).

•    Natural Gas Processing - Removes CO2, H20, H2S, RSH, COS, Hg, S, etc.
•    Petrochemical and Specialty Gas Manufacturing – Allows the separation of specific gas molecules (example methane for liquefaction)
•    Regeneration done thermally with high temperature gas flow

Common application: valve cycles 4-6 times each day - year round. Pneumatically actuated. High temperature swings from ambient to 500F (some as high as 620F max). Potential Issues: On occasion, drying material is upset (desiccate) and is blown into valving during operation. This desiccate dust (material is as small as dust and as large as one inch in diameter) is extremely hard and has the tendency to crush in between the more commonly utilized valve design and damages the seating surfaces to the point that a positive seal cannot be achieved to isolate the dryer beds. Customer has to de-pressure entire system to repair in-line and they cannot repair themselves. Other designs require special tools. Multiple customers with this application complain about the accessibility/availability and cost of the certified repair technicians.

The first Hemiwedge valve was shipped to this customer in the first quarter of ‘09 for testing purposes. It was installed immediately to replace a valve they were previously planning to have repaired. The valve performed well. They have now replaced all of the switching valves in their dryer system with Hemiwedge® valves.