how to make a vacuum purge

{"cid":"91191228","title":"Titan P60 Automatic Dental Lab Equipment Programmable Vacuum Porcelain Furnace","imgUrl":"https:\/\/img.silkroadsl.com\/nimg\/26\/0a\/3a0a4f63f4d3a69db140a6c5fd2e-200x200-1.jpg","attrs":{"Price":"Negotiable","Brand Name":"AiXin","Model Number":"Titan P60","Minimum Order Quantity":"1piece","Delivery Time":"3-5days","Certification":"CE, ISO, FDA","Place of Origin":"China","Payment Terms":"L\/C, D\/A, D\/P, T\/T, Western Union, MoneyGram, RMB","Supply Ability":"300pcs\/month","Packaging Details":"carton 24kg 35cm\u00d733cm\u00d743cm","Product name":"Titan P60 Porcelain Furnace","Voltage":"220V\/110V 50\/60Hz","Power":"1200W+350W","Heating Rate":"30~40\u2103","Display Method":"Single Window Display","Final Vacuum":"<35mmHG","Application":"Dental lab","Warranty":"1year"}}

{"cid":"91199780","title":"High quality Full Auto Refrigerant Recovery Machine HW-988 AC Machine R134a 900W","imgUrl":"https:\/\/img.silkroadsl.com\/nimg\/57\/50\/871a40424a993113ed5f5dc5b55b-200x200-1.jpg","attrs":{"Price":"800usd-1200usd","Brand Name":"HUAWEI","Model Number":"HW-988","Minimum Order Quantity":"1units","Delivery Time":"one month","Certification":"CE","Place of Origin":"China","Payment Terms":"T\/T, Western Union","Supply Ability":"1000pc\/month","Packaging Details":"carton","Input power":"900W","Import compressor":"1 HP","Recovery ability":"550g\/min","Charge ability":"1000g\/min","Cylinder capacity":"12kg","color":"red or white","Warranty":"1year","Dimension ( L*W*H,mm)":"1180*670*620"}}