Heavy Door Opener Lever 1

[Anthony_J]

Hello all,

I have a unique situation where I work at a plant that is equipped with air handling units that are so strong that it makes egress from some doors up to 100 lbs to open. Long story short, I've been tasked with providing assistance to drop this force down to NFPA-101 requirements of 30 lbs force to open it.

The device below is similar to what I'm looking at doing. You pull on the handle and it reacts with the wedge on the door frame, popping the door free. I preferable would like to start with a purchase item that I could modify but I can find nothing like this. Has anyone had to develop an item like this before?




~Anthony

 

[Snickster]

This is a HVAC issue. There is too much negative pressure inside the plant subject plant area. Typically a negative pressure is developed purposely inside areas where you want the air to flow in rather than flow out of. For instance in rooms or areas with chemicals (such as laboratories) you do not want positive pressure in those spaces that will push the air and chemicals out of the cracks of doors to hallways, etc, that have people in adjacent offices. Therefore the hazardous areas are always maintained at negative pressure relative to other adjacent areas.

That being said the typical negative pressure is only on the order of 0.1 inches of water gauge. To develop a force of 100 pounds on a door of say 3 ft wide x 7 ft tall you would need a negative pressure inside the room of about 1 inches water gauge. If you really have 1 inches water gage negative pressure this is a poor design and I believe against building codes.

In order to create negative pressure your building must be exhausting more air than is being supplied by ventilation through supply fans or through ventilation air from HVAC units. The exhaust fans will keep sucking air out of a room based on their exhaust flowrate. If not enough makeup air is supplied through the supply fans or HVAC unit to balance the exhaust flowrate, the extra exhaust air comes through cracks in the doors and window. In fact this is how a system is designed to have flow from adjacent spaces into the hazardous space and not the other way around. The exhaust air fans are purposely designed to have more flow than the makeup air to the room from supply fans or ventilation air from HVAC unit so the difference must flow though cracks in doors. However the design difference between supply air and exhaust air is maintains such that the room will maintain a negative pressure of only about 0.1 inches wg not 1 inches wg.

In your case there is not enough cracks in the room to let enough air into the room to balance the flow of the exhaust fans unless the pressure is reduced in the room to a very low value (1 inches wg). Therefore you need to install a louver in the wall to allow more air into the room, or increase the ventilation air into the room from the HVAC unit or makeup air fans, but not too much so you still maintain a negative static pressure of about 0.1 inches wg but not 1 inches water gage.

You need someone to do an evaluation of your HVAC, ventilation and exhaust system air flows to determine the required fix. For a HVAC engineer this is a very minor task. You should not correct the problem by trying to make the door easier to open with some type of lever. If someone gets hurt opening the door your company can be sued as the internal pressure in the room is against Codes.

 

[3DDave]

I was also worried about the door getting closing with the sudden development of differential pressure as the door neared being completely closed. Like, finger shearing kind of sudden.

I have seen similar problems for doors on inflated structures, which was solved by using three-blade revolving doors for getting in; they maintain the pressure balance to keep the force low, but would not be suitable for fire exit doors. What I really noticed with those was the slam to the eardrums when that segment with outside pressure (and me) opened to the inside pressure. The emergency exit doors opening were aided by the pressure differential and were conventional doors.

I know that it's also not going to be possible to put in a sliding door, so that the force is taken by good quality bearings rather than the users. Unlike an inflatable structure you have no worries that the building will collapse if the door is left open. Sliding doors are also more handicap friendly. I would not like to work against the door closer spring while confined to a wheel chair. I know buildings never have sliding emergency doors; cheap bast'ds but I do know a factory I worked in had sliding fire doors in the plant, held by electromagnets and set to roll closed on rails so they could not be blocked as easily with anything left in the exit path. They were indoors and not weather tight.

As Snickster writes, it's better to fix the source of the problem at this point.

 

[mfgenggear]

Reverse engineer the lever in your post.
Use mechanical advantage. The longer the handle, the less force is required.
I use mechanical advantage to loosen large
Stubborn nuts or bolts that have high torque values.

 

[Anthony_J]

This is a HVAC issue. There is too much negative pressure inside the plant subject plant area. Typically a negative pressure is developed purposely inside areas where you want the air to flow in rather than flow out of. For instance in rooms or areas with chemicals (such as laboratories) you do not want positive pressure in those spaces that will push the air and chemicals out of the cracks of doors to hallways, etc, that have people in adjacent offices. Therefore the hazardous areas are always maintained at negative pressure relative to other adjacent areas.

That being said the typical negative pressure is only on the order of 0.1 inches of water gauge. To develop a force of 100 pounds on a door of say 3 ft wide x 7 ft tall you would need a negative pressure inside the room of about 1 inches water gauge. If you really have 1 inches water gage negative pressure this is a poor design and I believe against building codes.

In order to create negative pressure your building must be exhausting more air than is being supplied by ventilation through supply fans or through ventilation air from HVAC units. The exhaust fans will keep sucking air out of a room based on their exhaust flowrate. If not enough makeup air is supplied through the supply fans or HVAC unit to balance the exhaust flowrate, the extra exhaust air comes through cracks in the doors and window. In fact this is how a system is designed to have flow from adjacent spaces into the hazardous space and not the other way around. The exhaust air fans are purposely designed to have more flow than the makeup air to the room from supply fans or ventilation air from HVAC unit so the difference must flow though cracks in doors. However the design difference between supply air and exhaust air is maintains such that the room will maintain a negative pressure of only about 0.1 inches wg not 1 inches wg.

In your case there is not enough cracks in the room to let enough air into the room to balance the flow of the exhaust fans unless the pressure is reduced in the room to a very low value (1 inches wg). Therefore you need to install a louver in the wall to allow more air into the room, or increase the ventilation air into the room from the HVAC unit or makeup air fans, but not too much so you still maintain a negative static pressure of about 0.1 inches wg but not 1 inches water gage.

You need someone to do an evaluation of your HVAC, ventilation and exhaust system air flows to determine the required fix. For a HVAC engineer this is a very minor task. You should not correct the problem by trying to make the door easier to open with some type of lever. If someone gets hurt opening the door your company can be sued as the internal pressure in the room is against Codes.

Your analysis is spot on. The plant will be going through an HVAC rebalancing in the not so near future to be the permanent fix for this. In the interim, I've been tasked with developing a stop gap device that provides assistance to getting these doors open (we had a small female worker get stuck in the plant due to not having the strength to open the door).

I learned on Thursday the NFPA-101 Life Safety Code requires the opening of any safety door to require only one motion. That means the device I showed would not work because our door has a crash bar that has to be utilized.

I'm currently developing a piston that will be installed towards the top of the door that will hopefully provide enough force to help push the door enough meet the 30 lb force requirement.

 

[Anthony_J]

I was also worried about the door getting closing with the sudden development of differential pressure as the door neared being completely closed. Like, finger shearing kind of sudden.

I have seen similar problems for doors on inflated structures, which was solved by using three-blade revolving doors for getting in; they maintain the pressure balance to keep the force low, but would not be suitable for fire exit doors. What I really noticed with those was the slam to the eardrums when that segment with outside pressure (and me) opened to the inside pressure. The emergency exit doors opening were aided by the pressure differential and were conventional doors.

I know that it's also not going to be possible to put in a sliding door, so that the force is taken by good quality bearings rather than the users. Unlike an inflatable structure you have no worries that the building will collapse if the door is left open. Sliding doors are also more handicap friendly. I would not like to work against the door closer spring while confined to a wheel chair. I know buildings never have sliding emergency doors; cheap bast'ds but I do know a factory I worked in had sliding fire doors in the plant, held by electromagnets and set to roll closed on rails so they could not be blocked as easily with anything left in the exit path. They were indoors and not weather tight.

As Snickster writes, it's better to fix the source of the problem at this point.

Yes, the tricky part of this task is that they are indeed fire doors, not only that is this is a Nuke II processing facility, so the doors are also barriers to contain radioactive contamination. If there wasn't enough reduction in options already...

 

[PersonalProfile]

The following may be options, despite that are apparently unlikely to be acceptable:
1. Balance duct in door - apparent unlikely to be fire resistant,
2. Sliding door - unlikely to good seal, or
3. Airlock by: new door, and "awning" etc.

 

[Anthony_J]

For anyone still interested in what was the solution to this problem, the attached pictures is what I proposed. Its essentially a piston that will push on the door while the personnel are engaging the Push Bar. Other concepts were proposed but due to NFPA-101 codes, majority of them were non-starters.