Weigh ahead

July 15, 2003
Why accuracy and hygienic requirements are more important than ever in checkweighing scales
The checkweighing scale in many weighing applications usually represents a trade off: all-stainless wash down scale with poor readability or a non-wash down scale with a high readability.  Many stainless checkweighing scales are not even 100 percent stainless. Most are constructed with aluminum load cells featuring stainless-steel shrouds and platforms. Higher-resolution models are commonly not stainless at all and offer challenging wash down ratings. More importantly, checkweighing scales in food, chemical, and pharmaceutical companies must comply with new hygienic regulations for cleanliness.  Low resolution vs. high:It is well known that the average resolution of most stainless checkweighing scales in the industry is 10,000 digital steps of readability. Simply put, a 5-lb. scale has a maximum or suggested readability of 0.0005 lbs. Similarly a 35-lb. scale has a maximum readability of 0.005 lbs.  While these resolutions are currently accepted in most stainless checkweighing applications, increasing raw material costs demand higher readabilities. Companies in need of more accurate checkweighing scales can save money without giving up accuracy when weighing heavier materials, thereby increasing their overall profitability in the long run.  Stainless checkweighing scales are available with a weighing range of 30,000 digits standard, with breakthrough improvements in stainless-steel load cell technology.  The 5-lb. scale is no longer limited to a readability of 0.0005 pounds but rather 0.0002 pounds.  This factor alone can allow tighter checkweighing tolerances and help save lost product that normally would not have been detected on lower resolution scales.  The case for stainless Stainless checkweighing scales are utilized because stainless steel allows for easy cleaning and protection against the harshest industrial environments. Various grades of stainless steel can be found in checkweighing scales, all with slightly varying degrees of protection.  The most common type of stainless steel found in these scales is 304 stainless, which provides a high degree of protection from most harsh environments. One important point requiring careful investigation is the parts of the scale that are actually stainless. Is the pan stainless? Is the base constructed from lower-grade steel? What is the construction of the load cell?A quality stainless checkweighing scale needs to be constructed completely of the same high-grade stainless steel. Offering a scale with partially stainless construction will inevitably lead to product failure as a result of the non-stainless weak points.  Harsh environments filled with corrosive cleaners and high-pressure wash down standards require a completely stainless check-weighing scale.  Scale manufacturers have even gone a step further in offering the most protection for static checkweighing scales by incorporating Titanium stainless steel on the entire piece of equipment.  That grade of stainless offers the maximum protection for the harshest environments and will stand up to corrosive material that will deteriorate iunder ordinary 304 stainless.  Another important attribute of stainless checkweighing scales is their ability to be washed down and cleaned with corrosive cleaning agents. Some applications demand the scales to be submerged in cleaning agents to rid scale surfaces of harmful bacteria and other agents. This type of cleaning requires more than the standard IP65 or NEMA 4 "wash-down" rating that traditionally has been the only option in harsh environments. Scales are entering into the market with higher ratings, up to IP 68, that allows for total submersion without negative effects on the scale.Checkweighing scales are often used in closed-process food production and are in constant contact with the end-product.  With the rapid rise of more stringent regulations in these processes, it is important to make sure your check-weighing scales are approved.  New standards such as Hazard Analysis and Critical Control Points (HACCP), and GMP require scales be cleaned completely so there is no chance of residual contaminations remaining afterwards. New design innovations and production processes in scale manufacturing will allow scales to conform to these standards for many years to come. SIDEBAR Weighty issuesWhen seeking the right stainless checkweighing scale for a weighing application, it's important to consider the following key points:                   What capacity to readability ration is required?      "Low-resolution versus high-resolution"                   What type of stainless steel is required?                         "How harsh is the environment?"                   What production standards must one comply with?       "HACCP, FDA, GMP, etc"                   What options are required?                                             "Communication with a computer or printer,  built-in checkweighing lights, product memory, etc." Finding the right scale for a specific application can sometimes go beyond these points and require consultation with a specialist in weighing. Before investing in a scale that might not fully accommodate your needs call your local weighing specialist for more information.

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