Maintaining Different Pressure in Different Rooms

Keep the door between them closed, perhaps?

Even if door closed, How we can maintain, How i can know the difference in pressure in each space

Hello maglak@mail.com

Yours truly is a large question. Can you tell us just which parts you have figured out, and which parts are giving you troubles?

This pressure transition space; is it for the product inflow/outflow or personnel in/out?

Seriously, you cannot figure out how to maintain a relative pressure differential?

After I set up a little thought experiment, I will ask you a couple of simple questions. You have two volumes of space; chambers A and B. These two volumes of space have the same convenient inert gas of air in them but at different pressures; A' and B'. A>B A'>B'. Initially these two volumes are isolated from each other by a closed valve. At the moment that this valve opens what are the pressures of chamber A and B? What happens to the gas in chamber A and B over time? What happens to the pressure in A and B over time?

With the exception of the first question, I do not want an exact answer.

I think his question was not really understood.

He has different rooms and each room has a leak (continuous or discontinuous), what he wants is to maintain in every room despise the losses the required pressures.

part of the answer was done: limit the leaks as low as possible

second part of the answer is :supply for each room enough gas (air or other kind) to compensate the losses.

So that you need a pressure measuring device to monitor the pressure in every room and second a gas source from which you obtain the leak compensating flows. The supply is function of the losses so that the system should be able to supply for the compensation of the maximal leak and stop when the pressure has reached the prescribed level. Your supply should thus be able to supply as well >than the highest requested pressure in a room.

Hi guys this is a serious question. These recent years Pharmaceutical rooms, and clean rooms in general such as operating theaters in hospitals are required to have positive differential pressure with respect to corridor or other adjacent rooms. The purpose is keeping out side air from contaminating the room when a door is opened. This is achieved usually by a DDC, a Fresh air fan ( Optional VFD driven motor), and a differential pressure switch (DPS) or a differential pressure transmitter (DPT). I will describe how I achieved this in some medical and pharmaceutical rooms. A PID loop is configured in a DDC such that it will keep the reading from the DPT at the setpoint variable by applying the output of the PID to the VFD of the fan. It is this simple. All you need is 1 Analog Input 1 PID loop and 1 Analog Output. In this way you can control the pressure in a room at any degree desired by changing the setpoint. Of course you can have an external unit for the setpoint in which case you need 1 more analog input. I hope this will illuminate you.

Good morning MOURADIG. Nice to meet you.

You are correct, this IS a serious question, and I believe it to be even more involved and complex than your description. The worm 'pharma' in the OP tells me that we might be talking about a Pharmadule module, and he/she is asking about the varied airlocks or security interlocks that are required for operation.

The OP (original post) sounds more like a homework question than an engineer's inquiry. If this a student, I hope to help him/her think it through, so he/she might arrive at some version of an enlightened conclusion. If it is some design professional, we need a lot more information regarding the stumbling block.

Here is a graphic for a radiopharmaceutical room.. with differential pressure sensors across the doors, to show when they were open. of course these are wired to digital controllers and show as alarms on the HMI.

Overall, to simplify, the air handlers pulled air through the massive HEPA filter banks, which drew air from the central zone of the building. The building was designed to have concentric rings of decreasing pressure zones, so the lowest air was in the center. All air was drawn through the stainless steel nuclear exhaust (filter) system. As radioactivity in this case is airborne, then controlling the air largely controls any leakage, and ensures all passes through the filters. The output of these filters was less than the backround radiation, which made the entire building a nuclear filter.

Chris

In our various biomedical manufacturing facilities this is purely routine. The room with the highest cleanliness level is also at the highest pressure. Any leak when a door is opened is from a cleaner to a less clean area. Additional air curtains are used where critical. Each such space usually has its own air handling + AC units. Even temperatures/humidities may be different. Wherever there is a differential, Low Differential pressure sensors (1 mm water gauge accuracy) are used. The problem is that in use the filters tend to choke reducing delivered pressure. Each filter unit also has differential pressure monitors to enable early cleaning. Bioramani

Maintaining pressure in any vessel or room is accomplished with a closed loop, electronic proportional pressure regulator. This is the type of precise control that we do. You would need to know what pressure range you want to control and what analog signal you wish to use to control it with, such as 4-20 mA, 0-5 VDC, or 0-10 VDC. This could then be controlled through a plc or even through a simple potentiometer.

It is hard to believe that your question is a serious inquiry, but on the off chance that it is;

First, the purpose of maintaining differential pressure between rooms is to prevent contamination from migrating from the surroundings to the cleanest room, or to prevent contamination from migrating from the dirtiest room to the surroundings. The first case would apply to keeping pharma products clean and the second would apply to keeping the surrounding free of toxic/radioactive material.

Let's assume that there are two rooms in the system. The first room is totally contained within the second room, and access between the two rooms is by way of an air lock. Access from the surroundings to the first (outer) room is also by way of an air lock. The objective is to keep the material in the second room free of outside contamination.

The design concept would be as follows;

An air supply fan provides HEPA filtered air to the first room at slightly above the pressure of the surroundings. The differential pressure is maintained by regulating an exhaust vent damper which vents excess air to the surroundings. This vent can be from the room to the surrounds or from the supply duct to the surroundings; however, I prefer that it be from the room to the surroundings to take advantage of the damping effect of the room volume. Obviously, you want to minimize the amount of spilled air. Access to the room is only by means of the air lock so as to avoid large swings in the filtered air demand.

A exhaust fan removes air from the second room which is kept at slightly negative pressure relative to the first room by regulating a damper between the first and the second rooms. A second set of HEPA filters located in the duct between the two rooms insure that the air moving from the first to the second room is at least as clean as the air in the first room.

And finally, an exhaust fan removes a constant quantity of air from the second room, passes it through a set of HEPA filters, and exhaust the air to a suitable abatement device to atmosphere.

Each of the HEPA filter sets can be just high efficiency filters only, or they can be chemically treated filters to remove vapor contaminants as the situation requires. The filters can be single elements or parallel lines of three of more elements in series. Depending on the need for continuous operation and the difficulty of system decontamination prior to maintenance and reestablishing a clean environment. In most cases 3-5 series filter elements piped to allow lead-lag configuration between the on-line filters is sufficient. The dirtiest filter element is always piped as the first in series.

Also the control system can be relatively simple or very complex depending on the tolerances that need to be maintained.

In most cases, the design needs to be done by a firm that has experience in clean room design (or contamination control) and has access to the dynamic computer models that allow off line testing of the design concept.

Hope this helps.

"Each of the HEPA filter sets can be just high efficiency filters only"

Ga overall.. but just for clarity, HEPA means High Efficiency Particular Air.

Chris

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