What Field Data Is Required for a Rotary Screw Compressor?

Consistent and accurate field data is important for generating useful Enalysis reports. For rotary screw compressors, Enalysis uses field measurements together with the compressor model to evaluate performance and operating conditions.

This article summarizes the field information identified in Detechtion’s rotary screw compressor field data guidance and explains what each value represents.

What field data is required?

The following dynamic values are identified as mandatory to generate an Enalysis report for a rotary screw compressor:

• Report date and time
• Operator name
• Compressor speed (RPM)
• Suction temperature
• Discharge temperature
• Suction pressure
• Discharge pressure
• Slide valve position
• Vi position or port setting, unless fixed
• Oil injection temperature

 What additional field data is recommended?

The following values are identified as optional but highly recommended when they are available because they can add context and value to the Enalysis report:

• Runtime hours
• Compressor flow or station flow
• Station inlet pressure
• Coalescing filter differential pressure
• Oil filter differential pressure
• Bypass open position
• Suction control valve open position
• Engine boost or inlet manifold pressure

 What general information should I record?

• Operator Name: The name of the person collecting or entering the field data.
• Report Date and Time: The date and time the operating data was captured.
• Hour Meter Reading: The total runtime on the compressor. This can be left blank if it is not available.
• Scheduled Downtime: The number of hours the compressor was offline since the previous field data capture because of a planned event.
• Unscheduled Downtime: The number of hours the compressor was offline since the previous field data capture because of an unplanned event.

 How should I record maintenance information?

The field data workflow includes a section for recording preventative maintenance such as an engine overhaul, compressor overhaul, or oil change.

If no applicable maintenance has been completed, the section can be left blank. When maintenance has occurred, record the applicable date and time or the runtime hours since the work was completed.

What running-condition information should I capture?

• Speed (RPM): The current engine or compressor running speed.
• Compressor Flow: The compressor flow from a flow meter. The source guidance instructs users to enter 0 if no flow meter is present.
• Station Inlet Pressure: The pressure upstream of any suction control valve. If an upstream pressure is not available, the compressor suction pressure can be used.
• Turbo Engine Boost: Engine load indicated by turbo intake manifold air pressure or calculated panel load.
• Boost Units: Select the correct units for the boost value.
• Bypass Control Open (%): The recycle valve percent open. Enter 0 if the valve is fully closed.
• Suction Control Open (%): The suction control valve percent open. Enter 100 if it is fully open and is not restricting flow from the field.

The source guidance also notes that the Metric/Imperial unit controls can be used throughout data entry when field measurements are collected in a mixture of unit systems.

 What rotary screw operating-condition information should I capture?

• Coalescing Filter Differential Pressure: The pressure differential across the discharge coalescing filter element. The source guidance allows a value of 0 if no gauge is present.
• Balance Piston Pressure: The balance piston pressure that opposes thrust load due to compression. This value is only available on select compressors.
• Slide Valve Position: The current position of the slide valve.
• Vi / Port Setting: The current Vi setting for rotary screw compressors with a variable Vi.
• Suction Pressure: Ideally measured from the suction piping as close to the compressor inlet as possible.
• Discharge Pressure: Ideally measured from the discharge line upstream of the coalescing filter.
• Suction and Discharge Temperatures: Digital temperature transmitters are preferred. If digital transmitters are not installed, the source guidance recommends an IR temperature gun on the suction or discharge piping rather than an analogue temperature gauge.
• Oil Injection Temperature: The oil temperature immediately before the oil enters the screw compressor. The source guidance identifies the measurement location as downstream of the oil filter and toward the discharge end of the compressor casing.
• Oil Filter Differential Pressure: The pressure differential across the oil filter element. The source guidance allows a value of 0 if no gauge is present.

What should I include in Operator Notes?

Use Operator Notes to record additional information that may be relevant to the compressor or the field data set.

These comments are entered into the Operator Log in Enalysis and are also included in the body of the Enalysis report email.

Can I use a field data sheet?

Yes. Custom Detechtion Field Data Sheets for active rotary screw compressors can be downloaded from Enalysis.

These sheets can help field personnel collect the required operating information before entering it into the application.

Why does accurate field data matter?

Enalysis uses the field measurements together with the software model for the compressor. Accurate readings help ensure that the resulting calculated performance information reflects the compressor’s actual operating condition as closely as possible.