PUG Gas Cutting Machine

Introduction

          PUG Cutting Machine (used for Hot Work) is light weight, portable, cutting machine operated by fuel (i.e., compressed gas either acetylene or LPG). The PUG machine can easily be placed on the surface to cut with the track (i.e., aluminum track) can be used for the movement and help in straight cutting. Machine is designed to operate on magnetic effect in the roller shaft of gear box. Movement of gas cutting nozzle is directly linked with magnetic roller shaft which results in fine cutting of metal. 

          Oxygen cutting results from the exothermic chemical reaction of a jet of high purity oxygen impinging on sheet at the elevated temperature. The red-hot metal in the path of the oxygen jet is eroded as Iron oxide and the steel plate is severed.

          PUG machine is a powerful driven tool which cuts mild steel plate up to 75mm of thickness. Vertical cuts or bevels up to 45 degrees can be made by the following methods:

• Straight line cuts of any length with the machine running on an aluminum track (1.8 meters in length) and multiples.
• Circle from 75-114- mm diameter when using the circle cutting attachment.
• Free hand cutting of simple curves by hand steering (vertical cuts only).

Specification

Installation

          Place the machine on a steel/iron plate and connect the 3-pin socket to 220 volts, 1 phase, 50 Hz, AC supply line. An isolator should be used in the main line. Now connect the 3-core cable with the supply line and switch ON the isolator (if any) check its operation (i.e., forward, off, reverse) switch and speed control knob. “Do not push the machine by hand unless the front left-hand wheel is lifted off the surface.” Maintain electrical safety.

          Connect oxygen & acetylene hose to cutter. Connect the other ends of hose to the oxygen & acetylene supply line through the regulators.

Warning:
Do not use oil or grease on oxygen connections.

Always use two spanners while tightening or loosening the nozzle nut. This will prevent damage or distortion to the cutter assemble. Nozzle in the cutter is to high degree of surface finish and closed tolerance. Hence it should be cleaned properly before assembly otherwise gas leakage and backfire may occur during its operation.

Flame
Conditions

 (a) Access Acetylene

The inner cone is long without a distinct outline. If used, the top edges of cut will be badly melted.

(b) Excess Oxygen

The inner cone has the peculiar shape show and the whole flame is short. Liable to backfire. This type of flame may also be the result of a dirty nozzle.

(c) Correct Adjustment

The inner cone is from 2.5 mm to 6 mm long, according to pressure and thickness of steel being cut, and has a sharply defined outline.

How PUG Machine Works

PUG machine operating procedure are as follows:

• Choose your workplace and ensure safe work practice.
• Take Work Permit for concern Hot Work and get the necessary checks done by Safety Officer.
• Plug in the PUG machine and wear necessary PPE.
• Connect the PUG machine with Gas cylinders (Oxygen & LPG).
• Start the or turn on the gas cylinders and check its required pressure.
• Set PUG machine parameters prior cutting the metal.
• Ignite the torch with lighter.
• Start cutting.

Inspection & Maintenance

Daily Maintenance

• Wipe over the machine to remove any oxide dust. Lightly oil the flanged bushes of the wheel and castor wheel pin.
• Examine hoses and power cord for damage.

Monthly Maintenance

• Unscrew 4 cheese head screws and remove handle.
• Unscrew 2 hexagon head screw and remove heat shield.
• Unscrew 8 self-tapping screws and remove cover.
• Blow through motor ventilator holes at gear box and of motor with air 0.7 kg/cm. sq. Do not use oxygen.
• Re-assemble the machine.

Six Monthly Maintenance 

• Remove and examine motor brushes for wear and tear. Ensure that they are replaced in their original positions. Renew when only 6 mm of brush remains. Unscrew 3 screws holding the gear box and re-pack with light grease.

Note: It may be necessary to lightly tap the gear box with a mallet to free it.

PUG Machine parts are as mentioned in the given below picture:

Safety
precautions

          Fumes

• Fumes from gas cutting are not considered to be dangerous provided there is adequate ventilation.

        Gases

• Gases which are used in PUG machine are potential as explosion hazards.
• No naked flames should be near cutting blowpipes when purging house of making preliminary pressure / flow adjustments to blowpipes.
• Keep open flames away from storage areas i.e., gas cylinders, fuel, hoses, etc.
• Oxygen itself is not inflammable but in its presence, combustible burn more readily. Adequate caution must be exercised in preventing oxygen enrichment of the atmosphere, particularly in confined space situation.

Oxygen in contact with oil, grease or other hydrocarbons can cause spontaneous ignition resulting in fires or explosion. Oxygen must not be used to clear hoses. However, all new hose must be purged before bringing into service and this may be done with oil free are Nitrogen, Carbon-Dioxide.

          Blowpipe

• Use a friction or pilot flame as a source of ignition. Do not use matches or hot metal to light blowpipes. Always light and extinguish by the correct sequence.

         ON     Fuel gas on

                   Heating oxygen on

        Cutting oxygen on

         OFF   Cutting oxygen off

                   Fuel gas off

                   Heating oxygen off

• Use only approved blowpipes and nozzle for the process.

        Regulator & Gauges

• All sources from which gas supplies are taken must fitted with regulators capable of controlling the source outlet pressures to those recommended in the relevant cutting data for the equipment.
• Never use a regulator with other than the gas for which it is designed. Release the control pressure when shouting down, after the pressure in the hose has been released.
• Treat regulators and gauges are precious instruments.
• Do not subject them to sudden to pressure surges caused by the rapid opening of supply valves.
• Regulators that creep (pass gas when the pressure regulating screw is released) or build up pressure on the low-pressure side with the blowpipe tramlining valve is shut, should be replaced.
• Regulators, valves and pipework must be kept clean and free from oil and grease.

        Protective Clothing

• For the best protection cotton overalls should be worn when cutting and feet should be protected from slat and falling off cuts.
• Leather gloves should be worn at all times.
• A pair of goggles (as recommended by Safety Officer) with suitable filters to give best viewing of flame should be used for gas processes to protect eyes.

        Electric shock

• The equipment should be installed and maintained in accordance with the current issue of the Regulators for the Electrical equipment to maintain electrical safety.

• Servicing of the maintenance must not be carried out unless the apparatus is disconnected from the electrical supply.
• Do not ignore water, air or gas leakages.
• Ensure machine earthing.
• Water leakages are self-evident but should be taken up immediately to prevent damage of other equipment.
• Gas leaks at valve glands, joints and hoses can be detected by application of soapy water and remedied by tightening of gland nuts joints.
• Do not test for leakage with a flame.
• Particular care should be observed when changing nozzles, to the making of gas tight joints by ensuring that seating is clean.

        Hoses

• Do not expose hoses to heat, slag, sparks, oil or grease. Faulty hoses should be replaced or repaired by cutting out a faulty section of hose and inserting and approved coupling.
• Do not use wire to secure hoses. Use approved hose clips only.
• Where acetylene has is employed as the fuel, do not use copper tubing to connect hose.
• Hoses must not be linked or nipped in order to cut off gas supply temporarily.