Details

In road pavements failed joints can lead to pumping and undermining. On major roads the ensuing repairs have an extremely high cost to the community. In water retaining structures joint failure leads to leakage and in extreme cases could lead to failure of the facilities leak tightness test. In both cases reducing the likelihood of failure by testing the installed sealant makes good economic sense.

Design

Where an air pressure differential exists across a leak, air flow through the leak will cause bubbles to form in a foaming solution on the low pressure side of the leaks surface. This is how we find punctures in bicycle tyres. The principle is applied in many industries to find leaks. In general a foaming solution is applied over the material to be leak tested and then a vacuum is applied over the surface. Air flow through the leak and foaming solution produces bubbles which can be observed through a viewing glass.

Papworths have developed a range of chambers through which a vacuum can be applied to a length of joint sealant. From small hand held boxes for wall joints to large self contained wheeled rigs (photo right) there is a design to meet the needs of most projects.

The chambers can be built with a petrol motor driven vacuum pump or an electric vacuum pump. The vacuum pump and motor can be built onto the wheeled chamber for floor testing or it can be a separate unit for hand held chambers. The width of the chamber is 150mm standard but can be increased appropriately to test joint bandage systems.

Materials

• Chambers - Machined from aluminium billet.
• Valves - Quick opening to release the vacuum
• Pressure gauge - Shows when the unit has been drawn down
• Gaskets - Neoprene rubber
• Motor/Pump - General Electric
• Glass - 6mm toughened

Leakage Testing

• A liquid foaming solution is applied to a section of the joint.
• The chamber is located over the treated joint.
• The vacuum release valve is closed and the vacuum pump valve opened. The pump sucks air through any leaks and the foaming solution and bubbles form.