A plurality of scroll compressors with different fixed volume indexes are connected in fluid parallel circuit and configured to selectively operate to maximize isentropic efficiency at different condensing temperatures. Different quantities of scroll compressors of different volume indexes may be selected based upon typical climate or geographic location environmental conditions to attempt to maximize efficiency. A controller may selectively operate different combinations of the compressors of different volume indexes bases up load demands and condensing temperature conditions, which may be determined in a variety of ways.

An operating method for a conveying device with an eccentric screw pump for conveying viscous construction materials comprising sensing a pressure of the construction material at an outlet of the eccentric screw pump when the eccentric screw pump is running and automatically switching off the eccentric screw pump if the pressure exceeds an upper limit value, otherwise continued operation of the eccentric screw pump. The method includes sensing a characteristic variable of the running eccentric screw pump and comparison of the characteristic variable with a first comparison variable, which is characteristic of operation with an open dispensing device and/or with a second comparison variable, which is characteristic of operation with a closed dispensing device, and switching off the eccentric screw pump if operation with a closed dispensing device is detected, otherwise continued operation of the eccentric screw pump.

An operating method for a conveying device with an eccentric screw pump for conveying viscous construction materials comprising sensing a pressure of the construction material at an outlet of the eccentric screw pump when the eccentric screw pump is running and automatically switching off the eccentric screw pump if the pressure exceeds an upper limit value, otherwise continued operation of the eccentric screw pump. The method includes sensing a characteristic variable of the running eccentric screw pump and comparison of the characteristic variable with a first comparison variable, which is characteristic of operation with an open dispensing device and/or with a second comparison variable, which is characteristic of operation with a closed dispensing device, and switching off the eccentric screw pump if operation with a closed dispensing device is detected, otherwise continued operation of the eccentric screw pump.

In a method for operation control of a compressor, full-load running in which a gas intake control valve is fully open and a target rotation speed of a drive source is set to a full-load rotation speed that is a maximum rotation speed in a speed control band when pressure of compressed gas supplied to the consumption side is a datum pressure or less is carried out; then no-load running in which the valve is fully closed and a no-load rotation speed is set as the target rotation speed of the drive source when the supply pressure is a no-load running pressure or less that is a pressure higher than the datum pressure is carried out. The no-load running is started from the standard no-load rotation speed, however, after a transition time, the target rotation speed is reduced to a low speed no-load rotation speed.

In a method for operation control of a compressor, full-load running in which a gas intake control valve is fully open and a target rotation speed of a drive source is set to a full-load rotation speed that is a maximum rotation speed in a speed control band when pressure of compressed gas supplied to the consumption side is a datum pressure or less is carried out; then no-load running in which the valve is fully closed and a no-load rotation speed is set as the target rotation speed of the drive source when the supply pressure is a no-load running pressure or less that is a pressure higher than the datum pressure is carried out. The no-load running is started from the standard no-load rotation speed, however, after a transition time, the target rotation speed is reduced to a low speed no-load rotation speed.

The present invention is directed to a minimum pressure valve comprising a housing (13) with a valve inlet (11) and a valve outlet (12) which are connected by means of a chamber (16), said minimum pressure valve (10) further comprising a valve body (17) movable in said chamber (16) between a closed position in which said valve inlet (11) is closed off, and an open position in which said valve inlet (11) is open, whereby said minimum pressure valve (10) further comprises a regulation unit (18) for setting the value of the pressure at which the valve body (17) moves into an open position.

The present invention is directed to a minimum pressure valve comprising a housing (13) with a valve inlet (11) and a valve outlet (12) which are connected by means of a chamber (16), said minimum pressure valve (10) further comprising a valve body (17) movable in said chamber (16) between a closed position in which said valve inlet (11) is closed off, and an open position in which said valve inlet (11) is open, whereby said minimum pressure valve (10) further comprises a regulation unit (18) for setting the value of the pressure at which the valve body (17) moves into an open position.

Power systems and methods of controlling an engine driven air compressor include an air compressor driven by an engine via a clutch. A first pressure sensor configured to sense a pressure level at an outlet of the air compressor. An inlet valve configured to close in response to the first pressure sensor sensing a pressure level above a first pressure level. In addition, a second pressure sensor to sense a pressure level below a second pressure level at a housing of the air compressor, wherein the clutch is configured to disengage in response to the second pressure level, wherein the first pressure level is higher than the second pressure level.

Power systems and methods of controlling an engine driven air compressor include an air compressor driven by an engine via a clutch. A first pressure sensor configured to sense a pressure level at an outlet of the air compressor. An inlet valve configured to close in response to the first pressure sensor sensing a pressure level above a first pressure level. In addition, a second pressure sensor to sense a pressure level below a second pressure level at a housing of the air compressor, wherein the clutch is configured to disengage in response to the second pressure level, wherein the first pressure level is higher than the second pressure level.

A refrigerant compressor unit, including a compressor housing and at least one compressor element that is arranged in the compressor housing, is movable by bearing and drive parts, and operates in at least one compressor chamber, at least one lubricant supply point arranged in the compressor housing for at least one of the bearing and drive parts and/or compressor element, and a lubricant supply line to the at least one lubricant supply point, wherein the lubricant supply line has a lubricant storage chamber through which lubricant flows and in which a lubricant presence sensor is arranged for detecting the presence of lubricant in the lubricant storage chamber.