Steam Main Jargon Buster

Mach number

A measure of the speed of sound in a gas or liquid or solid, such that "Mach 1.0" is the speed of sound. The actual speed of sound varies, depending on the density and temperature of the substance in which it is being measured. The unit is named after the physicist Ernst Mach.

Maintenance

Maintenance of any system is critical to continued performance of the plant. A steam system is no exception to this. This might include, regular steam trap checking, strainer cleaning, boiler inspection, water treatment regime, pressure vessel strip down and inspection, heat exchanger cleaning, and safety valve testing.

Make up water

The name given to treated water (raw water that has been treated using a programmed water treatment system) which is fed to the boiler hotwell feedtank. The boiler hotwell feedtank will consists of condensate return water (condensed steam which has become water that is returned back to the boiler feedwater tank from the process) that is mixed with this treated make up water.

Mass flowrate

The rate of flow in which the quantity of medium being measured is expressed as a mass.

Maximum allowable accumulated pressure (MAAP)

The maximum pressure that a piece of equipment is allowed to reach in accordance with the specification of its design standard. MAAP will often be 10% higher than the maximum allowable working pressure (MAWP).

Maximum allowable working pressure (MAWP)

The maximum operating pressure of pressure equipment relative to its maximum operating temperature. This is the design pressure of the piece of equipment, and it must always be higher than or equal to the set pressure of the safety valve which is protecting it. It will always be higher than the 'normal working pressure' at which the equipment is rated to operate at. It can often be referred to as; 'maximum safe working pressure'.

Metal to metal valve seat

This is a valve which has the valve plug and seat both made of metal.

Modulating control valve

A control valve which is able to move and stop at any point between the full open and full closed position. This differs from an on-off control valve, which can only stop at the full open or closed positions.

Monel

A general purpose alloy which is corrosion resistant, strong, tough and has a silvery white colour. It is used for making abrasion and heat resistant valves and pump parts, propeller shafts, chemical processing equipment etc.

Muffs

These are cylindrical metal sleeves used for the protection of pipe lagging insulation. This could be on steam or condensate pipework.

Murray steam turbine

A type of steam turbine made by the Murray company in Iowa USA. Murray steam turbines are now part of the Dresser Rand company range.


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