Ensuring no Loopholes: Leak testing for Gloves and Containment Isolators

In the Pharma industry, cleanliness is an endless cycle, with contaminants like wild cards that can appear from anywhere without notice. The current wide-ranging hygiene levels notwithstanding, there is always room for more precise and detailed cleaning; so much so that it seems pretty difficult to achieve a sure-shot 100% contaminant-free environment.

Having said that, there does exist a detailed containment isolators system, designed in the form of enclosures to bring about a clean atmosphere with a very low concentration of airborne particulates, thus playing a key role in achieving a safe environment. In this device, bulk chemicals and other potent pharmaceutical compounds are safely handled and protected from cross-contamination. 

However, this alone doesn’t guarantee an optimum level of protection, if simultaneously, standard integrity testing is not carried out.

With a view to ensuring that the containment system performs effectively and serves the desired purpose, Fabtech undertakes a containment leak test through what we know as the pressure change method. This method ensures the prevention of leakage of products from the external to the internal environment or vice versa or both at the same time.

Given below is a guide to understanding the test, upon which the performance of the containment system largely depends. The test adheres to the procedures laid down in ISO 10648 -2, and the containment systems are classified as Class 1 – Class 4 on hourly leak rates.

Leak Testing for Containment Enclosures by Pressure Change method

Principle

The method consists of measuring the pressure rise per unit time after isolating the containment enclosure at negative pressure. When the containment enclosure is at a positive pressure, an equivalent method can be used.

Apparatus

• Thermometer (with an accuracy better than 0, 1 degree C) – to measure the temperature inside the containment enclosure.

• Thermometer (with an accuracy of 0, 1 degree C) – to measure room temperature.

• Barometer (with an accuracy of 10 Pa)

• Differential pressure gauge (with a scale division of 10 Pa)

Procedure

• The thermometer and barometer are set up close to the containment isolator and the room temperature and barometric pressure are measured.

• The thermometer is suspended in the middle of the enclosure before the final sealing of the opening.
• The temperature and pressure in the isolator are tested and the test room is allowed to stabilise.
• The containment enclosure negative pressure is set up to the required value (i.e. 1 000 Pa below ambient for the acceptance test, and 250 Pa for operational use checking), and the extract valve is then closed.
• Upon stabilisation of pressure and temperature, the containment enclosure is kept isolated by shutting the valves.
• The temperature and negative pressure in the containment enclosure, along with the ambient pressure is measured for an hour at 15-minute intervals.
• The first and last readings are used for evaluation and the intermediate readings are used to control the test conditions.

Precautions

The method is sensitive to changes in the internal temperature and can lead to internal pressure changes. Therefore, it is vital to keep the doors and windows of the test room closed. Heating by the sun, lighting or heating equipment must be avoided. The method should not be used to measure very low leak rates.

Validity Range

The following conditions should be fulfilled during the 1-hour test-

a) Internal enclosure relative pressure variation shall be lower than 30 % of the initial value.

b) Internal temperature variations shall be lower than ± 0, 3 degrees C.

c) Atmospheric pressure variations shall be lower than 100 Pa.

d) The temperature variations of the test room should preferably be lower than 1 degree C.

If these conditions are not entirely satisfied, the test shall be repeated or an alternative method should be used.

However, leak testing doesn’t always end here. As stated at the beginning of this blog, there is always room for achieving greater hygiene levels in the pharma industry. And this holds true in the enclosed contained isolator that involves a glove system for manual operation. Therefore, it goes without saying that glove-leak testing is equally imperative to achieve the overall integrity of the containment system.

Positive-Pressure Glove-Leak Testing

Overview

A sealing cap to cover the glove/gauntlet aperture is to be fitted with two pipe fittings.

One fitting is used to connect a sensitive valve for admitting and releasing the pressurizing gas. The second fitting is used to attach an electronic micromanometer. This method should only be used before decontamination and is not an in-process test. 

Procedure 

• The sealing cap is placed over the glove-port ring, thus forming a space between the cap and the inside surface of the glove. 

• The space is then pressurised to 1 000 Pa and allowed to stabilise. A drop in this pressure will indicate a leak through the glove fabric or securing arrangement. 

• Prior to the commencement of the test, a thorough visual inspection of the glove/gauntlets must be undertaken for any damage.

• All fingers on the glove must extend into the separative device.

• Connect the airline should be connected with the separative device.

• The manometer is then switched on and adjusted to zero by pressing the “zeroing button” while holding the glove-leak tester in free space. Small variations of ± 3 Pa to ± 4 Pa from zero will not adversely affect the result or the sensitivity of the tests.

• The sealing cap of the glove-leak tester is fitted over the outer port ring of the glove to be tested.

• The glove is inflated by operating the valve. The gauge of the manometer then displays the pressure within the glove in pascals. The glove should be inflated between 500 Pa to 1 000 Pa; this may take a number of injections of air to reach the required pressure as the system stabilizes.

• The reading on the manometer is observed. A stable reading will indicate a sound glove. With experience, operators will be able to identify potential problems in a 10 s test period.

• Suspect gloves/gauntlets are re-tested, and a longer test period may be required to confirm results.

Results 

Pass – If the glove/gauntlet is sound, then the reading shown on the manometer will remain static within 2 Pa to 10 Pa, subject to small variations. 

Fail – If the glove/gauntlet is damaged, then the reading shown on the manometer will keep falling (i.e. 500 Pa, 495 Pa, 490 Pa).

The rate of change will be proportional to the level of damage to the integrity of the glove.

Any test showing probable damage should be repeated. Any tests that record a distinct change in pressure should be closely investigated and the fault (e.g. incorrectly positioned cuff ring, damaged glove) either re-tested or the suspect glove/gauntlet changed and a successful test conducted.

In our continued endeavour for ‘solving for our customers’, we firmly believe in tick-marking our accomplishments only when our equipment serves the targeted purpose. The leak tests conducted by us reflect our earnest pursuit to validate our work and ensure that everything matches your needs.