Industrial Utility Efficiency

# A View From Southeast Asia. A Pharmaceutical System Assessment

### Supply-Side Overview

This plant was built and started-up in 2006. It has three 315 kW Atlas Copco ZR315 rotary screw ( non-lube ), water-cooled air compressors. One unit has a variable speed drive and it is used to control air pressure in the main 10” header that supplies the adjacent critical manufacturing process. A multiple compressor control system was included with the project. The installation was quite impressive. The equipment is robust and maintenance is very good.

The air compressor motors operate at 1,450 rpm (with 50 cycle power) providing about 1,700 scfm each. A 1,500 liter receiver tank supplies two 1,800 cfm regenerative desiccant air dryers installed in parallel. The dryers have an electric heated blower that uses 70 cfm of compressed air as part of the regeneration valve-sequencing operation. The facility operates on a 24-hour, 7 day a week schedule. Two machines are normally in service.

We conducted a comprehensive compressed air system assessment. Opportunities to improve the system were found in the main piping system, in reducing pressure losses in the mold machine piping, and with the high ambient temperatures found in the compressor room. We estimated energy savings of 403,500 kWh per year for a power savings of \$65,000 per year. The total projects costs were \$48,000 for a simple ROI of nine (9) months.

### Pressure Swings in the Main Piping System

The compressors were operating at 120-124 psig – a pressure well above the system pressure necessary for this type of facility. All crucial process equipment is designed to operate satisfactorily at 84-88 psig inlet to the machine regulators.

A “defective product” recall had recently resulted in raising system air pressure from a nominal 108 psig to 118 psig. We determined that the air compressors should be able to operate at 100-104 psig discharge pressure and adequately provide a minimum 90 psig in the 2” main lines that supply each of the ten critical-process molding machines.

Line pressure drop from the compressor room air dryers to these machines was calculated to be only 2-3 psig. When we also include filters and manifold valves, we saw a 5-6 psig pressure drop. This air treatment system is performing very well – providing high quality air with an appropriate pressure drop.

##### The heated desiccant air dryers, with pre- and after-filters provided a reliable pressure dew point of – 40 F, with a low system pressure drop, for this pharmaceutical plant.

The two main 4” air lines (located directly off of the 10” main header) supply the manufacturing bay with six molding machines on one loop and four machines on the second loop. Two additional machines are planned for the second area in 2011.

We determined that, due to a semi-loop configuration of these 4” air lines supplying the molding machines, it required only 50 feet of additional 4” pipe on each loop to connect back into the 10“ main header. This would eliminate all doubt of machines at the end of the loop experiencing low pressure. Due to the additional planned machines, plant personnel agreed to proceed with this modification. The cost for the piping changes was \$9,000.00. Process air demand was generally very uniform. Each key molding process machine uses between 75-100 scfm. Other plant compressed air uses (finishing, HVAC, maintenance, leaks, etc.) were determined to have no significant surge conditions. Nevertheless, the main 10” air header was experiencing pressure swings of 5-6 psig on a regular basis. We determined that the swings were due primarily to the be compressed air dryer tower regeneration sequencing valves and the slow-responding air compressor pressure controls. The air compressor load controls (both the direct drive units and the VSD unit) were not programmed to be able to maintain the system header pressure within the expected 2-3 psig range with a steady plant air load of only 2200-2400 scfm (with two units in service). To solve this, the decision was made to hire Atlas Copco service personnel to inspect the equipment and re-configure the air compressor and air dryer control systems and valving. The estimated project cost was \$18,000. Please note that this compressor control investment was necessary to capitalize on the system improvements detailed further on in this assessment.

### Pressure Drops in the Mold Machine Piping

The reported low air pressure condition in a key zone of each molding machine was determined to be due to local piping restrictions at the main air regulator valve. A ¾ inch size plastic air hose (with ½” I.D. pipe nipples) connected the 2” air supply pipe to the 1¼ ” size regulator on the machine. We recommended changing this 18” long hose to 1½” size on each machine and to also use less restrictive hose/pipe fittings. The cost was \$200.00 for each machine for a total project cost of \$2,000.00.

### Summary

A compressed air system assessment of this type is not unusual for us. All of the supply-side equipment (air compressors and dryers) was operating well and was well maintained. The over-all system had also been given considerable thought and investment.

The primary opportunities for improvement lay in reducing the 16 psig of pressure losses found in the hoses and piping in each of the molding machines. The second area of opportunity was to reduce the ambient temperatures in the compressor room by 30 F. Once these things were accomplished, modifications in the compressor controls were required to capitalize on the potential energy savings. We estimate energy savings of 403,500 kWh per year for a power savings of \$65,000 per year. The total projects costs were \$48,000 for a simple ROI of nine (9) months.