Refurbishing major HVAC equipment

[stephanemunger]

My client operates a 15 year old, 20-storey condominium building. The mechanical equipment has been neglected maintenance-wise through the years. I have to write the specification to get a contractor to refurbish the following equipment :

- Water-cooled reciprocating chiller
- Firetube boiler
- Plate-type heat exchangers
- Cooling tower
- Inline pumps
- Indoor make-up air unit

I would like to know if anyone has information about the detailed scope of work involved in refurbishing these. Some of the manufacturers aren't being too cooperative since I am not giving them the contract to do the work. Thanks for the help !

 

[HVAC68]

That's a full-time job for a consultant !!!

HVAC68

 

[stephanemunger]

I am the consultant !!!

 

[TBP]

If they've neglected all of this equipment for a decade and a half, I'd bet refurbishing would be every bit as expensive as just replacing it.

 

[friartuck]

We do lots of boiler house refurbs. One thing to watch is cleaning the existing pipework. If you stick a new piece of kit onto a rusty old system, you are asking for trouble. Make sure you flush and clean properly. Don't over do it though as some chemical cleaning systems can find more leaks than you would like to.

We also fit high quality strainers or filters to keep the new kit clean.

We also use cyclone filters which we connect to the system to get it super clean.

Don't over pressurise either. Old systems are probably 'open tanked' and making them sealed or pressurised can have its draw backs...make sure the expension tanks are large enough so as not to over pressurise the pipework.

Also use inverter drives to control the pumps etc..this will reduce running costs and it will make pump selection easier.

Good luck

(PS..after 15 years, I might suggest replacement.......it might be more expensive but you will get less grief.)





Friar Tuck of Sherwood

 

[quark]

I fear the list will be exhaustive if the systems are not overhauled periodically. Here are few things which we generally go with(but not limited to),

Chiller

1. Descale the water cooling circuit along with jackets.
2. Rebuilding of crankshaft.
3. Replacing bigend, small end bearings, thrust collar and main bearings.
4. Cleaning crankshaft oil pathways.
5. Replacing connecting rods if necessary(if worn out near bearing)
6. Cleaning connecting rod oil pathways.
7. Replacing gudgeon pins
8. Replacing piston and oil rings.
9. Replacing cylinder liners(if the gap between two ends of piston ring is morethan required)
10. Lapping suction and discharge valve seats, changing valve plates and spring plates/springs.
11. Replacing unloading piston elastomers and thorough cleaning.
12. Replacing head gaskets.
13. Replacing lube oil pump(I strongly suggest)
14. Replacing refrigerant.
15. Pressure testing
16. Descaling of condenser and replacing cover gaskets.
17. Replacing damaged tubes(or plugging if not many)
18. Replace TEV.

Boiler

1. Replace all gaskets and ropes.
2. Descale shell and desoot the tubes.
3. Change bent and damaged tubes.
4. Lap, clean and hydrotest stop valves and safety valves.
5. Change electrodes, spray nozzle and diffuser plate.
6. Recast refractory.
7. Clean level switches.
8. Replace ID/FD fan bearings.
9. Cleaning fuel oil and feed water day storage tanks.
10. Hydrotesting boiler shell.

Cooling Tower

1. Replace fills and drift eliminators (I strongly recommend)
2. Clean/Replace spray nozzles.
3. Change fan and motor bearings.

Regards,

 

[lilliput1]

You have to survey the equipment and determine if it is worthwile to repair. Compare age of equipment with normal service life of equipment (see ASHRAE 2003 Applications Chapter 36 Owning & Operating Cost Table 3 Estimates of Service Lives of various system components). See Means for estimate on replacement. With labor cost being so high & difficulty factor involved with existing conditions for field repair, it may be better to replace units.

Field test of equipment may be required first before it can be determined if the unit can be repaired.

If water treatment was not practiced, you may as well scrap the equipment. You will never get rust out in time without possibly creating more damage.

 

[friartuck]

You might also have to bring the system up to current 'code' or regulations. If so, you are better replacing.

In the UK, major refurbs require you to bring the system up to the regs.

For boilers, the efficiency has to be a certain value. We also have to fit sub metering and the accessibility has to comply with CDM Regs.
Old plant in many instances quite often did not comply with anything.

We replace hospital AHU's for instance. The old AHU's are only 4m long because they dont have inspection panels. They also need stainless steel drip pans (On Theatre plant or clean areas). New AHU's are often 6 or 7m long (Or more) and simply won't fit in the old AHU position, so we have to move them (Usually onto a roof or on the outside floor)


Friar Tuck of Sherwood