To minimize operational costs in today’s unstable economy, a lab or facility manager with a new ICP/Mass Spec system must cost-effectively use cryogenic liquid argon dewars to supply gaseous argon.
In terms of specific critical gases requirements, one attractive option is the application of Lng vehicle cylinder, commonly called dewars, to offer gaseous argon to ICP and ICP/Mass Specs. Argon’s unit cost per cubic foot/gaseous liter is quite a bit lower when sent to your facility in cryogenic liquid form in dewars. However, as these containers store the gas within a cryogenic form until it is dispensed as a gas, there are two issues that can decrease the cost-effectiveness of utilizing this mode of supply.
Ever since the argon is held in self-pressurizing containers with relief valves and also the cryogenic liquid is boiling inside, reserve containers waiting for the primary container to empty on a system will, after a while, build internal pressure before the relief valve setting is reached and after that start to vent excess gas at a rate of 2 to 3 percent daily. This is the NER or Normal Evaporation Rate, referenced in the business as the “use it or lose it” phenomenon. Around this rate, in case the reserve cylinder of argon contains 4,500 cubic feet of gas, it equals losing 135 cubic feet daily it sits in reserve. It wouldn’t take long to enjoy up whatever savings resulted from your lower unit cost.
Since most of the gas is cryogenic form, the strain in the container is not going to indicate if the unit is full, half full or empty. The small liquid level indicators on top of the dewars are difficult to read and not very accurate. Since most gas distribution systems rely solely on pressure to change from primary to reserve cylinders, false low-pressure readings can cause lab personnel to get rid of containers with up to 25 percent in the contents still inside.
Solution: CONCOA’s Intelligent Gas Distribution System IntelliSwitch II continuously monitors your reserve container’s pressure, using programmed software logic to find out in case a container is truly empty or contains residual product. IntelliSwitch II 538 Series is definitely the latest within the collection of computer-controlled gas distribution switchover systems using very accurate transducers to keep track of both primary and reserve inlet pressures. Proprietary software logic uses this information to drastically reduce evaporation loss by switching for the reserve dewar to offer the gas to the instrument before the relief valve opens, drawing down pressure from the container to a programmed point, and then going back to the main dewar. This “economizer function” can virtually eliminate losses from the reserve Cryogenic ISO Tank Container.
Additionally, when primary dewar pressure drops underneath the point where the system switches towards the reserve, IntelliSwitch II fails to immediately conclude that the container is empty. It waits a programmable length of time even though supplying the system in the reserve, watches pressure reading around the primary. In the event the pressure rises 46dexkpky the switchover point in that point period, your computer concludes residual liquid was left inside the container and switches back to it to provide the instrument. It does this repeatedly until the dewar fails to create pressure higher than the programmable switchover point, where time it switches for the reserve, and sounds a security alarm to indicate the primary is now truly empty. This “look-back feature” lessens the residual discarded when using dewars to less than 2 to 3 percent.
By eliminating evaporation loss and reducing the residual left in empty containers, CONCOA’s IntelliSwitch II optimizes the price savings of making use of CNG Trailer to provide gas to ICP or ICP/Mass Specs.