10 Reasons To Get A Hydrostatic Scale
The Advantages of Hydrostatic.
Scales are as essential to our lives more than we realize. If it is sold then at some point in the production process then it was weighed. When coming to accuracy of weighing, there are several options that are considered. Analog and electronic load cells seem to be the main options, but the one not mentioned as much is hydrostatic scales. This post will go over the 10 reasons why hydrostatic scales should be considered.
What is a hydrostatic load cell?
The Hydrostatic load cell is basically a simple mechanical mechanism which functions according to known Laws of Physics. It consists of a piston, a base, a cylinder and a diaphragm. A thin film of fluid is sandwiched between the base and the diaphragm. The piston presses against the diaphragm. The result is only a small amount of fluid is required (less than one (1) pint of fluid used in a 70 foot truck scale). Each Hydrostatic load cell type is designed with an exact "acting area" - a known value in units of square inches. For example, when a known weight is applied to a Hydrostatic load cell with a known "acting area", the output in PSI is predictable. A 50,000lb weight applied to an "acting area" of 50 square inches will have an output of 1,000 PSI.
Lightning and Power Surges.
Lightning strikes and power surges plague large industrial scales more than realized. When this happens with electronic load cells installed, then there usually will be some downtime when lightning strikes. Hydrostatic load cells are unaffected by electrical surges, power failures, stray voltages or even lightning strikes. Electronic load cells are highly susceptible to these common industrial occurrences and are often damaged requiring replacement. Outdoor tank scales or truck scales often lose all load cells from a lightning strike, even with surge protectors.
corrosion
Hydrostatic load cells are available in grade 304 and 316 stainless, with improved life and performance over the more common aluminum and carbon steel. Most electronic load cells are made of nickel plated tool steel, or at best 17-4PH grade stainless steel, which is far less corrosion resistant that that of 304/316. Many electronic load cell manufacturers avoid stainless steel completely due to performance deterioration. In environments that are washed down, this can be bad for electronic load cells due to the moisture getting into the wiring and boards on top of potential corrosion from the type of steel used.
durability
Durability is essential to separating the good scales from the bad. A scale that is unable to handle the amount of measurements it receives will eventually cost more money than it earns, this also includes downtime for the repairs.Hydrostatic scales are a lot more durable compared to their electronic counterparts. They are able to last for decades without any sort of parts replacement. Whereas mechanical scales require periodic replacements of pivots and bearings. Electronic load cells will have to be replaced numerous times throughout the life of the scale.In harsh environments the hydrostatic scale will definitely be up to the task. Less moving parts with a design to handle the harshness of the environment places hydrostatic above electronic and analog.
Special materials
Hydrostatic load cells can be manufactured out of many special alloys, with no loss of accuracy. They are available in 304 stainless, 316 stainless, titanium, monel, as well as teflon and hastelloy. Electronic cells require a certain hardness, and therefore can only be made with aluminum, steel, or 174PH stainless, which are less corrosive resistant.
Shock loading
Hydrostatic load cells have a natural inherent quality of shock absorption. Electronic load cells have no inherent energy absorbing qualities. In the event of severe shock loading resulting in load cell damage, the hydrostatic load cell can be easily repaired. Due to the simple design nature of hydrostatic load cells, it is very easy to repair them on site. Electronic load cells have to be rebuilt at a repair shop. They are unable to be repaired on site and almost always require a full replacement.
Calibration
In the unlikely event that a hydrostatic load cell ever needs to be replaced, the scale rarely needs to be recalibrated. Hydrostatic load cells with identical acting areas have matched outputs, whereas electronic load cells have variations in millivolt output, requiring the scale to be recalibrated whenever a load cell is replaced.
Temperature
Hydrostatic load cells are available with a 500 degree operating range, from -50 degrees F to 450 degrees F. Electronics operate at less than half this range. The adhesives used in electronic cells deteriorate in high temperatures and become brittle in cold temperatures, causing total failure or inaccurate readings, frequently resulting in load cell replacement.
high capacity
Hydrostatic load cells have been manufactured with capacities exceeding 1 million lbs. There was actually a 12 million pound load cell that has been operating in a testing machine at the National Institute of Standards and Technology since 1968. In addition, high capacity hydrostatic load cells require a minimum expense in mounting hardware, while the hardware for high capacity electronic load cells can cost more than the cell itself and often must be made of specialty hardened steel.
Installation
Hydrostatic load cells are “dead” until activated with fluid. Therefore, the load cell is almost impossible to damage during installation. While electronic load cells frequently require “dummy” load cells during installation, hydrostatic load cells never do. An electronic load cell is “live” from the time it leaves the factory. It can easily be damaged beyond repair by being dropped, when placed under a tank leg, overloaded, left exposed to weathering, etc. Many are replaced before ever being used.
Cost of ownership
With all these advantages listed, it should be easy to see that scales with hydrostatic load cells have the lowest cost of ownership of any scale on the market today. The fact that hydrostatic load cells are a lot less to maintain, it dramatically reduces your overall cost and keeps you from losing money due to downtime for repairs. Any product that can save you money while being of superior quality is always a plus.
closing words
At American Scale we strive to bring you informed and useful content on all things scale systems related, including products from the top scale manufacturers. Be sure to check out our truck scale articles about truck scale foundation or how much do truck scales cost. We even have a guide to warranties. To learn more about bench scales, it would be good to check out our other articles such as “Bench Scale Basics'' and “How Much Does A Bench Scale Cost?”. These articles will help with the basics of bench scale ownership. Also, take a look at our“Common Problems With Bench Scales'', to help prolong the lifespan on your scale.