Questions and Answers_Amendment 0004.pdf

Q&As

Q1- Do you know the breaker size feeding the electrical supply to the current compressor?

A1- 90 amp 3 phase 480volt fed from a siemens type BQD breaker

Q2- The disconnect before the existing compressor, is it fusible or just a knife switch?

A2- non fused disconnect

Q3- The disconnect before the existing compressor, is it fusible or just a knife switch?

A3- closed loop treated water ranges 42degrees f to 49 degrees f depending on season

Q4- The current compressor, did we see the normal operation or was there low production/usage today?

A4- Loading and unloading during site visit reflective of average air usage, note due to different experiments usage may increase

Q5: The specification calls out for 192 cfm at 125 psig. This is not the current capacity of the unit that is in place.

The current unit puts out 192 cfm at 100 psig, however, at 125 psig, it only puts out around 165 cfm. If replacing in kind, do you want a compressor that puts out 165 cfm at 125 psig, or actually 192 cfm at 125 psig?

A5: The current system is rated at 200 cfm at 120 psig (adjustable). It has met the facility needs for 30 years. 192 cfm at 125 psig is a desired target for the replacement.

Q6: When we were on site, we were told that the compressed air usage was normal and the compressor was only loaded for about 1/3 of the time, meaning that the facility was only using about 55 cfm while we were there. Does it make sense to data log the compressor to see actual operation over a two week period to see what the facility is actually using before making a purchase of this magnitude? Loading and unloading frequently is much harder on an oil free rotary screw compressor than it is on a double acting recip compressor. Oversizing an oil free rotary screw compressor can shorten its life.

A6: The current demand on the system is light due to several labs being idled during government budget negotiations. However, the government concurs that a “variable speed” unit will put less stress on the unit. Data log not required.

Q7: If oversizing the compressor, it would make sense to add more storage capacity to the system (receiver tanks).

Would you like us to quote appropriate storage capacity for an oil free rotary screw compressor?

A7: The government concurs more storage capacity is needed. However, that will be a future project. The goal here is to provide a reliable unit to replace the out of date unit currently on line.

Note: The goal of the procurement is to provide a reliable unit to replace the out of date unit currently online that has met the facility needs for 30 years. The Government is not intending to supersize even though the initial specs were for the wrong style replacement unit. If the contractor proposes a larger unit the wiring will need to be increased for a larger HP. Current feed for the compressor is #4thhn approx. 100 feet in 1 inch rigid conduit.