Pump Room Airchange Rate 2

[aungkyawtun]

Gents,
Will glad if you lend me a hand to give an idea about the minimum airchange rate in offshore platform's pump room

 

[Zesti]

What are you trying to do: provide some cooling for the pumps or remove possible fumes? (or both)

 

[aungkyawtun]

Most likely to cooling down and there is not much fumes

 

[Zesti]

If it's cooling you need, then at least you need to know the heat load in the room and the maximum allowed temperature in the room.

 

[aungkyawtun]

Zesti,
Thks for your interset .We cant get the peak heat load cos even the end user cant estimate how many percent of equipment will running at the same time.The max allowable temperature is 45'C.

 

[Zesti]

What is the local highest possible outside airtemperature?

( If the customer can not give you the required information, then who is to blame if in the future the temperature rises above 45°C..? )

 

[aungkyawtun]

For the Marine we used 42'DB Normally we use ISO8861 to calculate for engine room ie based on the outsuide temp and equipment load and neglect the airchange.Now that we cant get the equipment so that I think we need to base on the standard airchange rate.

 

[Zesti]

Only three degrees temperature difference (45-42), which is not a lot to work with.

I am not familiar with ISO8861.

I would say, propose an air change rate to the end user and have him sign it that he agrees. After all he does not know how much heat will be generated so how can you?!

 

[sridhar1312]

Generally 15 to air changes per hour should reasonable and depending on the heat dissipation the temperature may be few degrees above ambient

 

[Zapster]

In addition to your concern for the temperature control, the electrical area classification may dictate a minimum ventilation rate to maintain the area classification. Review the design notes for the electrical area classification. Take a look at API RP-500 for some guidance.

 

[JohnnyHS]

If its any help the Shell requirements for online refinery process areas (GRP house i am doing at the moment) is min 12 changes per hour. I am designing for 15 (agree with sridhar1312). just enough to allow for any errors, but not too much in them thinking i've supplied a hovercraft!



Johnny H-S BSc(Hons) MInstMC

Engineers like to solve problems. If there are no problems handily available, they will create their own problems.

 

[vanduo]

Look in pump technical data. There must be two diferend pump powers: one from the net, other on the shaft. The diference is the heat that pump will submit to the the suroundings. Then you can calculate the heat income from the pumps. Then calculate other heat incomes (like sun radiation, computers, humans and so on). When you have all heat incomes then you can calculate how many air you need to absorb this heat.
Sorry for my engilsh. This is not my nativ language.

 

[aungkyawtun]

Thanks all,
Finally I settle with the airchange 22/hr since I cant get the peak load of individual pumps.

 

[Waramanga]

What is the room volume and approximate power of pumps?

 

[jphaymond]

I use the old sensible heat gain equation btu = 1.08 x cfm x delta T. I'm not sure what the SI version is, but it's used the same.

Use ASHRAE's heat gain for motor driven equipment, with motor and equipment in the air stream. Add up all the motor heat gains, along with any heat gain from other equipment. Use 25 degF for the delta T, and calculate the required air flow rate.

I've used this for 15 years and it seems to keep mechanical rooms fairly comfortable. If your mechanical room has a lot of equipment in it, the ACH will be 35+.