www . refrigerationandaircon . co . za RACA Journal I September 2023 39
Support
GRANT LAIDLAW
Grant Laidlaw is currently the owner of the Air Conditioning and Refrigeration Academy ( ACRA ) in Edenvale . He holds a Bachelor of Business Administration and an associate degree in educational administration . He has a National Technical Diploma and completed an apprenticeship with Transnet . He has dual-trades status : refrigeration and electrical . He has been involved with SAIRAC for over two decades and served on the Johannesburg committee as chairman and was also president between 2015 and 2018 . Currently he is the SAIRAC national treasurer .
WELCOME TO THE
SOLUTIONS PAGE
By Grant Laidlaw
Many people ask for assistance in the understanding of theoretical and practical aspects of the industry . I will endeavour to enlighten . We are going back to basics as I have questions coming in that indicate that the basic understanding and skills necessary to work in our industry are simply not in place .
“ Hello Mr Grant . Can you please give me some help ? We work with PVC conduit in our installations . We would like some advice on using , joining and bending . Thank you for all the good advice , Sam .
Thank you for your question , Sam . The following represents good practice when working with PVC conduit . PVC conduit with a wide range of accessories is available , allowing for fast and simple installations . PVC conduit is used in the same way as metal conduit but should be protected from mechanical damage and high temperatures . PVC is resistant to most acids , alkalides and oils , does not attract rodents and can be buried in concrete , lime and plaster without harmful effects . The material is light and therefore easy to transport . Cutting is quick and simple using a PVC tube cutter . Bending : Sam , circular conduit not exceeding 25 mm in diameter can be bent cold using the correct size bending spring .
Unlike refrigerant tubing , where the spring bender is used on the outside surface of the tube , the PVC conduit spring is inserted into the tube . The springs have an eye on one end to which a cord could be attached if necessary . This will help remove the spring if the spring gets stuck in the conduit . The tapered end is for easy insertion into the conduit .
Conduit internal bending spring
With the spring inserted into the tube , the bend can be made by hand or by using a hickey . Approximately twice the angle required should be bent and then the conduit allowed to return to the correct angle .
Thus , for a 90 ° bend it should first be bent through 180 ° and allowed to return to 90 °. Do not force the tube to return with the spring inserted . Removal of the spring can be made easy by gently twisting in an anti-clockwise direction .
Sam , when using PVC conduit , the following points should be remembered :
• Saddle the conduit as soon as possible after bending .
• Care should be taken when using glue so as not to apply too much . Excessive glue may form a restriction .
• Insufficient glue will not make a watertight joint .
• PVC expands at a rate of approximately five times more than steel . Where necessary , expansion joints can be used . Up to 6mm per 4m length expansion can be experienced .
• For every 8m of straight run , an expansion joint should be used to prevent the tube from bending out of place on your nice straight run . Use silicon grease in the one side of the joint to facilitate movement and maintain a seal .
“ With the spring inserted into the tube , the bend can be made by hand or by using a hickey . Approximately twice the angle required should be bent and then the conduit allowed to return to the correct angle .”
www . refrigerationandaircon . co . za RACA Journal I September 2023 39