Oilfield Rubber Hose

MECHANICAL HAZARDS-1_ RUBBER PROCESSING These vary considerably with the press type and the operating procedure used. At most presses there are trapping hazards between: the moving moulds/platens, either under power and by gravity fall;  the moving platens and the press frame/press tables;  mould loading and stripping devices. The following diagrams shows the main danger areas on a frame construction down-stroking compression press and how fixed and interlock guards can be used to minimise the risk.

Transfer moulding This is a variation on compression moulding and involves loading a pre-formed blank of rubber in a cavity connected to the mould cavity by a runner. The blank is compressed when the mould closes and is forced under pressure into the mould cavity. The safety considerations are the same as for compression moulding. Injection moulding This produces precision mouldings. The rubber is pre-heated and a rotating screw forces it into the mould cavity under pressure. Vertical injection moulding machines are more common than the horizontal type generally used in plastics processing. Injection moulding machines can have a manual mode where the operator removes the moulded item at the end of each cycle. More common are semi-automatic or fully automatic machines where conveyor or pick and place robots remove the moulded product. Injection moulding machines tend to operate at faster speeds and on shorter cycle times than compression/transfer moulding, which effectively inc

Moulding Introduction All vulcanising methods can cause burns. Insulate hot machine surfaces to prevent accidental contact where possible. Otherwise, warning signs and protective clothing (for lower arms as well as hands) are likely to be required. Compression moulding Compression moulding is the most common moulding technique used in the rubber industry. It involves pressing uncured rubber between heated moulds so that the rubber compound first fills the mould cavity before curing to produce the finished article. The presses are usually hydraulically or pneumatically powered and the moulds can be heated electrically, by steam, or by oil. Compression moulding presses are generally vertical (the moving platen is raised or lowered in the vertical plane). The bottom platen can be up stroking or the top platen down stroking. Moulds may be fixed to both the platens, part fixed to a platen, or totally free to be drawn out of the press and loaded and unloaded on a press table. These lo

Feeding ingredients and collecting compound The principal dangers and safeguards on a Banbury type internal mixer are: The rotors, via the feed opening (contact with rotors or falling in on larger machines) These risks can be guarded against by feed tables or conveyors placed in front of the feed opening, with additional fixed side guards, where necessary. Safe reach distances should meet the requirements of Table 4 of BS EN ISO 13857: Safety of machinery. Safety distances to prevent hazard zones being reached by upper and lower limbs. The floating weight trap with the fixed bridge casting from either the feed opening or the rear inspection door. There should be sufficient clearance between the bridge and the fixed bridge casting to prevent a finger-trapping hazard. Prevent access by using the same safeguards as for the rotors. The floating weight and the lower edge of the front hopper door at the feed opening. The trap at the bottom of the weight is more dangerous. Operators ar

Compounding - powder handling, mixing and milling Introduction Compounding involves the measuring and mixing together of raw rubber, process oils, carbon black, bulk fillers, and rubber chemicals in pre-determined proportions, termed formulations. A rubber compounder can typically use between 100 and 200 different ingredients to mix a range of formulations. The finished mixture is known as compound and is the material that is processed into rubber articles by moulding, extrusion, calendering etc. Carbon black storage handling area, bulk bag emptying. Note specialist HEPA vacuum for clean-up.

Mixing Once the compound ingredients have been weighed out they are mixed together using specialised machines capable of dealing with the high stresses involved in shearing rubber. Mixing can be either by internal mixing or external/open mill mixing which have very different safety problems. Internal mixing (eg. Banbury or Intermix mixers) The compound ingredients are fed into an enclosed mixing chamber via a feed hopper and mixed by the shearing action of two winged rotors and the walls of the mixing chamber. There is therefore a continuous nip. A powered ram or floating weight in the feed throat forces ingredients into the mixing chamber, which is usually water-cooled. The mixed compound is discharged via a sliding or hinged door below the mixing chamber, usually onto a two- roll mill, roller die, twin-screw extruder, conveyor, skip hoist, or wheeled truck.