Technical Note 130:
General Guidance on Use of Liners in CROHMIQ® FIBC

CROHMIQ® Static Protective FIBC Fabrics provide protection against hazardous electrostatic discharges by safely dissipating charge through low-energy corona. The corona generated by CROHMIQ fabric dissipates charge effectively from its surface and from materials in close proximity to its surface. Liners that are placed inside CROHMIQ FIBC will be protected by the fabric provided the all parts of the liner, including inlet and discharging spouts, remain within the confines of the FIBC. Whereas the information in this Technical Note provides general guidance on the use of liners in CROHMIQ FIBC, we do recommend that all liner/FIBC combinations be tested to determine their safety.

Acceptable types of liner

Liners made from non-conductive materials, e.g. plain HDPE, LDPE, etc. are acceptable. Although liners made with such materials will not dissipate static charge, CROHMIQ fabric will dissipate charge from them provided they remain within the confines of the FIBC.

In many applications "antistatic" or "static dissipative" liners offer increased protection against hazardous discharges. It is not possible to give specific guidance on antistatic liners because of the wide range of performance of all types on the market. As there are no standards defining performance or classification, some liners described as antistatic may in fact be conductive and should not be used (see next section).

Antistatic liners are made from materials with intermediate resistivity, i.e. between ~10⁴ Ω and ~10¹² Ω. Some liners with resistivities towards the top end of this range may be acceptable (i.e. between ~10⁸ Ω and 10¹¹ Ω), whilst others with resistivities towards to lower end of the range are not acceptable. The acceptability of antistatic liners in CROHMIQ FIBC can only be assessed by testing specific liner/FIBC combinations.

Unacceptable types of liner

Conductive liners, i.e. those made from materials with resistivity less than 10⁶ Ω, are not recommended for use with CROHMIQ FIBC. Conductive materials easily produce spark discharges even at low levels of charging. The only way to safely eliminate the risk of hazardous sparks from conductive materials is to securely ground them. CROHMIQ FIBC are designed to operate safely without grounding. So, although there is no risk of hazardous electrostatic discharges from isolated CROHMIQ FIBC, there is a risk of hazardous sparks from isolated conductive liners.
Laminated liners incorporating metallized layers (usually aluminum) may have a surface resistivity much greater than 106 Ω, because of non-conductive layers either side of the metallization. Nevertheless, from an electrostatic perspective such liners are regarded as being conductive because of the very low resistivity of the metallized layer. To eliminate the risk of hazardous sparks from this type of liner, the metallized layer must be connected to ground, and so they are not recommended for use in CROHMIQ FIBC.

Note: laminated aluminum layer liners are often used in food contact applications because they provide an excellent barrier to oxygen and odors. Other designs of laminated liner are available, e.g. polyethylene/nylon/polyethylene, that also have excellent oxygen and odor barrier properties and are acceptable for use in CROHMIQ FIBC.

Means of attachment

The main criterion for an acceptable means of attachment is that it should ensure the entire liner remains within the confines of the FIBC. All common examples in current usage should be acceptable provided they are employed correctly. A good example of liner attachment is where all eight corners of the liner are securely attached to the FIBC. A bad example is where only the top four corners are attached. In this case, the vacuum created when discharging the FIBC draws the liner inwards and downwards so that it ends up protruding out of the discharge spout. In this condition, CROHMIQ fabric may not provide effective static protection.

THIS INFORMATION RELATES ONLY TO THE SPECIFIC MATERIAL DESIGNATED AND MAY NOT BE VALID FOR SUCH MATERIAL USED IN COMBINATION WITH ANY OTHER MATERIALS OR IN ANY PROCESS. SUCH INFORMATION IS, TO THE BEST OF OUR KNOWLEDGE AND BELIEF, ACCURATE AND RELIABLE AS OF THE DATE COMPILED. HOWEVER, NO REPRESENTATION, WARRANTY, OR GUARANTEE IS MADE AS TO ITS ACCURACY, RELIABILITY OR COMPLETENESS. IT IS THE USER'S RESPONSIBILITY TO SATISFY HIMSELF AS TO THE SUITABILITY AND COMPLETENESS OF SUCH INFORMATION FOR HIS OWN PARTICULAR USE. WE DO NOT ACCEPT LIABILITY FOR ANY LOSS OR DAMAGE THAT MAY OCCUR FROM THE USE OF THIS INFORMATION, NOR DO WE OFFER ANY WARRANTY AGAINST PATENT INFRINGEMENT.