Cylinder Scales Measure Liquid Levels In Cylinders

iconductor industry uses many different liquid gases inseveral liquid levels to warn operators when a tank is
the production of silicon wafers including nitrogen,nearing empty and has to be refilled or replaced.
argon, silicon tetrafluoride, silicon tetrachloride, silane,These electronic scales also allow for other methods
disilane, and dichlorosilane, to name just a few.of monitoring the liquid level. An analog 4 to 20 ma
Gases are stored in their liquid form in high pressureoutput signal is commonly used to communicate with
cylinders which allows a large amount of gas to beother processing equipment. Today, it is becoming
stored at once. For both safety and generalmore and more common to find a digital RS-232
production considerations, it is extremely important tosignal, or a USB interface used with cylinder scales.
be able to monitor the level of liquid remaining in aThese electronic signals can be used to open and
tank. When filling a gas cylinder, monitoring the liquidclose valves. In addition, the digital scale can be
level can prevent the danger of overfilling. Duringconnected via Ethernet to a local access network,
production, monitoring the rate of gas use isallowing monitoring of the cylinder liquid level from
important to ensure that all products are being madeany computer on the network and even opening up
properly. Damage caused to products due tothe possibility of viewing liquid level data from the
excessive or interrupted gas flow can cost ainternet.
company tens of thousands of dollars. In addition, it isDue to the weight of cylinders, it is important for a
very useful to know how much gas is remaining incylinder scale to have a low profile to allow for easy
each cylinder so that the supply does not run out atloading and unloading of the cylinders. Some scale
an inconvenient time.manufacturers, such as Arlyn Scales, produce high
There are two ways of measuring the amount ofquality cylinder scales that are just over 1 inch in
gas remaining in a cylinder. Gas pressure can beheight. They do this by creating a pocket within the
measured by using a pressure transducer. Pressurebody of the scale to fit a load sensor.
transducers are useless when using liquid gas. As longDue to the weight of gas cylinders and the method
as there is liquid in the gas container, the pressure inof loading them onto and off of industrial scales,
the container will remain the same as gas is releasedelectronic cylinder scales are subject to extreme
from the cylinder and more gas evaporates from theshock loads. It is extremely important that the load
liquid form. Only once all of the liquid has beencells used in these scales are built to survive this
depleted will the pressure quickly decline, giving littleshock. Many manufacturers use aluminum load
warning to the operator that the cylinder has to besensors which can easily be damaged by twisting
replaced.forces. Arlyn Scales cylinder scales contain a much
A much more useful method of measuring liquid levelsmore rugged load cell made from a special stainless
in cylinders is by using an electronic cylinder scale, likesteel alloy. These digital scales are manufactured to
one manufactured by Arlyn Scales. When a cylinderhave a capacity appropriate to that of a full tank of
with liquid gas in it is placed on one of these industrialgas, which usually weights around 250 pounds. In
scales and the known weight of the cylinder isaddition to being resistant to shock, this special alloy
subtracted from the given weight, the total amountis also much more resistant to corrosion from
of gas in the cylinder can be determined.chemicals, as compared to others using plated steel,
The remaining liquid level in the cylinder can beallowing these precision scales to last longer and
constantly monitored. A Setpoint Controller allowsremain accurate throughout their lifetimes.
alerts to be programmed into the cylinder scale at