Applications For High Voltage Leak Detection You Might Not Be Aware Of

Source: Nikka Densok USA, Inc.

By Brian Ball, President, Nikka Densok USA

No matter how carefully a pharmaceutical product container is prepared, it is still unsafe for human use if the container has a pinhole or defective seal. These containers are commonly kept in environments with varying temperatures, which can directly impact the product inside. For example, if the environment is too warm, the solution or product may expand, and if the container is defective, there may be a leak from a pinhole or defective seal. Conversely, if a defective container is stored in too cold of an environment, the solution can shrink back into the container bringing with it such contaminants as bacteria from the exterior of the container, thus contaminating the product.

There are a variety of methods widely used to detect pinholes and defective seals in containers. These include vacuum or pressure decay tests and submerging the entire container into a dye solution under pressure to visually inspect for the presence of dye. Most of these tests are destructive to packaging components and cause the loss of good product. In some cases, more advanced vision systems also can be used to inspect for certain defects in the container.

High Voltage Leak Detection (HVLD), a technology first applied to pharmaceutical manufacturing in the 1970s, is totally free from these shortcomings and has additional advantages for ensuring seal integrity. A couple of the biggest advantages are:

•      HVLD is a non-destructive test method.

•      There is absolutely no secondary contamination to the product.

Also, because of the detection principle (see below Principle of HVLD Inspection), HVLD can detect pinholes not consistently found with other methods of inspection. By using the actual product in the container as a conductive path, HVLD can detect small pinholes in pharma packaging that would not be normally found through other inspection methods. The technology enables a more consistent and efficient way of detecting leaks while also reducing the possibility of false rejection.

Moreover, HVLD is designed for continuous 100% in-line inspection and defective containers are automatically rejected from the production line. There are no special chambers or pumps necessary, so neither cleaning the chamber nor being concerned with the integrity of the chamber seal are issues after a leak is detected. Also, because the high voltage and machine parameters are adjustable, a variety of products and containers can be inspected on the same equipment with minimal changeover time.

Principle Of HVLD Inspection

HVLD is based on the principle of using a high voltage spark-test system, and it is capable of handling any product as long as:

•      the container is made of electrically insulated material

•      the product contains an electrically conductive solution.

The high voltage being applied is seeking the least resistive path to the product. The increase in the current volume through the product determines whether the container is good or defective.

V =  High voltage source

R =  Electric resistance of product

C1 =  Volume of static electricity between the inspection electrode and the product

C2 =  Volume of static electricity between the ground electrode and the product

I1 =  Electric current which is produced when the container is sealed

I2 =  Electric current which is produced when the container seal is defective

High frequency high voltage (V) is applied to a specific area of the hermetically sealed container made of a nonconductive material. The high voltage is generated in the control section then boosted via the high-voltage transformer and applied to the inspection electrode. If the container should have a leak at the seal area, a discharge current will flow through the pinhole or defective seal into the container. A signal is sent to the inspection circuit through the detection electrode. Detecting the change in this current volume enables the presence of a defect to be recognized.

•   Fig. 1 is the electrical equivalent circuit of Fig. 2 and Fig. 3. In Fig. 2, the electrical circuit describes a good container while Fig. 3 describes the circuit of a defective container. It should be noted that C1 andC2 work as electrostatic capacitors whereby making the container and the cap liner an insulator while R is the specific resistance of the contents of the container.

•   With a constant voltage being applied to the container, a defective container will have a larger electric current volume (I2) than a container with no leak present (I1). The difference of the electric current volume determines whether the seal is defective:

Applications For High Voltage Leak Detection

All liquid filled, non-metallic containers, including glass vials, glass ampoules, BFS containers, prefilled syringes, IV bags and other types of flexible packaging are applicable for HVLD technologies.

HVLD Helping Vaccine Drug Manufacturers Avoid Risks With Primary Packaging Defects

Defects in primary packaging can create several problems including end user safety, recalls, and wasteful loss of valuable product. HVLD is an FDA-approved method of inspection and ensures manufacturers find these defects early in the process to avoid costly issues down the line. Inline HVLD equipment can find the defective container and reject it off the manufacturing line without impacting manufacturing output.

The future implications of USP 1207 are driving many of the current testing strategies in the global pharmaceutical industry. Ultimately, the location of the end user dictates the regulations (e.g., FDA, European Medicines Agency [EMA], Pharmaceuticals & Medical Devices Agency [PMDA Japan], and China Food & Drug Administration [CFDA]). Often, large pharma companies are required to follow many different regional requirements to meet global demand.

Suggestions For Pharma Manufacturers Unsure Of What Leak Testing Method To Use

Pharmaceutical manufacturing teams should first research the principles of each method to understand how it applies to their specific product and how it impacts the overall manufacturing environment. Product feasibility testing is often the next step in this process, and these results typically guide you in the right direction to the best technology to suit your needs.