British Specifications covering the testing of compressors to verify guaranteed perform ance are to be found in BS1571 in a wholly metric form. Part 1 of that standard deals with type acceptance tests and Part 2 with simplified acceptance tests, calling only for measurements necessary to verify any guarantee given by the manufacturer to the purchase, in particular capacity, shaft input power or specific energy consumption and speed. Following is an outline of the procedure given in Part 2.
Preliminary tests should be taken for the purpose of:
• determining whether the compressor and associated systems are in a suitable condition for the acceptance tests to be conducted;
• checking of instruments;
• training of personnel.
After a preliminary test has been made, this test may, by agreement, be considered the acceptance test, provided that all the requirements for an acceptance test have been met.
The governing mechanism must be maintained in its normal working position.
During the test, the lubricant, the adjustment of the lubricating pumps, lubricators or other lubricating means must comply with the operating instructions. No adjustments other than those required to maintain the test conditions and those required for normal operation as given in the instruction manual shall be made.
Before readings begin, the compressor shall be run long enough to assure steady state conditions are reached so that no systemic changes occur in the instrument readings during the test.
The test report shall include the following information:
Type of machine
If reciprocating whether
vertical or horizontal,
single- or double-acting,
cylinders are air- or water-cooled,
intercooled or aftercooled,
single- or multi-stage.
the type of rotary elements employed,
if lubricated the type of lubricant used,
the type of filtration elements,
number of stages.
Name and number.
Date of manufacture.
Type of prime mover.
Name of manufacturer of prime mover and its number if applicable.
Type of speed increasing or reducing gear if fitted.
Name of manufacturer of speed gear and its number.
Type of coupling used during the test.
Guaranteed performance on test and/or performance on type test
Specific intake pressure and temperature. Capacity (FAD).
Power consumption. Speed.
Any other requirements of the standard, eg quantity of cooling water or tempera ture rise of cooling water.
Only those measurements necessary to verify any guarantee given by the manufac turer to the purchaser.
Diameter of nozzle (mm).
Barometric pressure (mm Hg).
Pressure at intake, absolute (bar).
Pressure drop across nozzle (mm H20).
Pressure on downstream side of nozzle (mm Hg).
Pressure at delivery, absolute (bar).
Temperature of air at intake (“C).
Temperature of air at nozzle (0C).
Any other observations that are required to verify a guaranteed quantity of cooling water, inlet and outlet temperatures of cooling water, etc.
Results derived from observations
If the speed for a specified FAD is not guaranteed, the correction does not apply provided that the machine gives the specified FAD at a speed which does not affect its service reliability (see also Table 2).
• Pressure at delivery. For positive displacement compressors no correction is necessary as it can safely be assumed that the specified delivery pressure can be obtained with specified intake conditions.
• Pressure at intake. For exhausters no correction is necessary within the permissible deviation, see Table I.
• Corrected power consumption
This is the only correction necessary provided that the deviations of test conditions from guarantee conditions do not exceed the values given in Table I.
Acceptance tests to Pneurop/CAGI test codes
Three codes have been published under the joint auspices of Pneurop and the American Compressed Air and Gas Institute. They define acceptance tests for compressors which are constructed to specifications determined by the manufacturer and are sold against performance data published by the manufacturer. The codes are:
• PN2CPTC1 for Bare Displacement Air Compressors
• PN2CPTC2 for Electrically-driven Packaged Displacement Air Compressors
• PN2CPTC3 for I C Engine-driven Packaged Displacement Air Compressors
The publication of these codes enables the user to verify and compare the stated performance of compressors from different suppliers. In general, because their purpose is limited, they are less detailed than the national standards.
They specify the permissible variations in test conditions and the acceptable range of deviations from the manufacturers’ claims in respect of flow rate, specific energy consumption and power consumption at zero flow. The permissible methods of determin ing the flow rate, shaft power, torque and electrical power are given.
They give the methods of calculating the correction factors that can be applied to the measured parameters when the test conditions do not agree with the specified conditions. These parameters include shaft speed, condensate formation, volume flow rates, power input and ambient pressure. These codes together form a useful guide to the measurement and comparison of compressor output.