service pit

[lantraxco]

Consider this, I am in Northern Ontario Ca. (Canada, not California ) It is -33 deg C this evening so cold air from outside is not the simple answer for me. How do you blow in air and be sure the heavier than air fumes and vapors are removed.I have talked to many people about this and the consensus so far is not to build a pit. I am hoping to hear from anyone who lives in a cold climate who has come up with a solution to this issue.

I am thinking some sort of air in and air out system for the pit is required. Obviously any air pumped outside or fresh air pumped in will add to the heating bill.

Has anyone seen a good solution to this?

Heat exchanger

 

[norite]

Heat exchanger

Yeah, I've already thought about that. You still lose heat but it's better than drawing in cold outside air.

 

[hetkind]

Let's take a look at the ventilation issue...we need to have a floor level LOCAL exhaust of the pit to remove vapor, fumes and gases that settle. But we don't need much, probably less than 10 cubic feet a minute, because the source of contaminants is either from evaporation of a liquid, like gasoline or diesel fuel OR from a heavier than air gas dropping into the pit like exhaust gases/fumes.

But for ever cubic foot of air we remove, we need to replace with conditioned make up air, also at the same less than 10 cubic feet per minute rate, and want that placed at the breathing zone of the worker.

So a push pull system where we inject conditioned air for worker comfort at the top of the pit and pull air with a possible contaminant at the bottom of the pit. At those small amounts the cost is very reasonable.

Howard

 

[Randy88]

I've got a pit, which most know, I'm thinking your splitting hairs on your concern, for any gas, vapor or anything to settle to the lowest point, takes time, its not like spilling water and watching it run the lowest point, gas takes far longer to accumulate in the lowest point of any shop, unless your fogging the shop in such massive quantities of poisonous gas such as when an old Detroit is puking out massive amount of smoke and fumes from unburned diesel. If your running a Detroit or putting in massive quantities of poisonous gas of another source, the pit is the least of your issues. Aside from that, it takes far longer than just a few minutes for gas to accumulate, like a half hour or hours, with even the slightest air movement in the pit, your circulating the air and no issues of excess gas pocket accumulation should occur. Now unless you plan on circulating the air outside the shop as in a heat exchanger/scrubber/filtration system of some sort, your concern about a pit is what?? your only circulating the air that is already in the shop, if its toxic, I'm not wanting to bash anyone's concerns, but your still breathing the same air where is the concern with the pit come into play?? you've got far larger issues than the pit, as the insurance company rep explained to me, and which made sense to me and still does.

Not wanting to be negative, but the issue with putting air into one end of the pit, and a fan in the other, depending on how large and long your pit is and where the vents are located, why would the air be drawn from one end, when it can suck in from the open top of the pit, far closer to the exhaust fan or suction tube?? You need air inlets and exhaust along the pit length, but before anyone can tell you anything about where or how, you need to assess your dimensions and how air flows and where it will flow, every one is different.

Now let me ask a question here, since I've heard this a couple hundred times before about pit gas's, when your about to crawl under a machine on a creeper, where are your fans located?? how will you survive a gas issue, how do you plan to get out in case you'd spill some gasoline, after all, your at the lowest location in the shop at that point, what was your plan before you crawled under the machine, the air there is stagnant and toxic vapors could be accumulated waiting to kill you??

If you have a loft in your shop and your on the main floor, basically your in a pit of sorts, what's your plan then to survive and circulate the air so in case of gas vapors it won't kill you, do you have fans blowing on your constantly anywhere in the shop. Not sure if you have a house with a basement or not or an attached garage, but if you did, are you concerned with poisonous gas's in your basement every time you start your car or pickup and leave, how about coming back home hours later and entering your home?? Next question is, even if you don't have this scenario how many do you hear dying each year or being injured and hospitalized every year in the world from this issue??

If you were to walk into your shop, and feel sick, or see a fog or low hanging haze near your shop floor, what would you do, close the doors and stay inside or open all the doors and vent the fumes as safely as possible?? A pit isn't the issue, it how you handle the situation your given at any point in time is.

Yes circulation is important, air flows are really important, but its not just for the pit, its for the entire shop and work environment and for that you need someone who's up on those things to walk you through them on every aspect of the planned project. Now if you don't, don't get too shook up, you'll get to later on, you'll have condensation issues, frozen doors you can't open, same as windows you can't see out or open and it'll eventually get done, I'd suggest doing it up front, just keep in mind while doing it, as you add machines, shelves, tools, equipment in the shop being worked on and everything else, air flows change.

You only need a small amount of air movement to circulate gas's and fumes, if they are indeed toxic, you need to vent them somehow, not really sure yet how anyone gets those toxic of fumes into the shop and are ever willing to keep them in by not opening doors, windows or vents and turn on massive fans to blow it all out, but I'm told its been done before and usually where all the statistics come from on legal or deadly accidents.

When we bring machines in, we have a large fan sitting in the loft, keep the door open and turn it on, vent all the smoke and when its clear and fine, we shut the doors back up, can't say the pit was ever an issue or concern and the cost of heating never entered into the equation once at those times. As for gas vapors or any other vapors, whether its in the pit, shop floor or anywhere else, the doors come open, every fan in the shop comes on and the whole shop is ventilated massively, heating is the last of my concern, the pit is far below that on the list.

We do a lot of welding and fabricating in the shop, I need a heat exchanger but have not put one in yet, I have natural draft ventilation in the pit, never been concerned yet with working in it, when someone is next to the pit welding, does that mean mine is perfect, absolutely not, but if I can see, smell or taste something out of the ordinary, fans come on and it doesn't matter where I'm standing in the shop, in the pit or right next to the welder being run.

The last issue to keep in mind is this, your not laying in the pit floor, your usually standing upright, or at shop floor height or above, its not really any different than laying on the main shop floor where your head and nose are at, your not sucking up and breathing vapors laying on the pit floor unless your laying there unconscious for a long period of time. Most don't weld on or near the pit floor, when I'm welding in the pit, its usually on a machine above the pit or above the shop floor in essence, all you need is a small amount of air movement to circulate any air in the pit, is adequate to never have issues, the only better way is use common sense, just like anywhere else in the shop or with any situation. Not really a rant or downgrading anyone's concerns, heath is everyone's concern, just keep everything in perspective and don't let some peoples hysteria deter you from putting in a pit, common sense is still your best friend no matter the issue.

 

[bobcat1]

We have had a pit in our shop for 20 years. There is a 4 inch pvc line from 2 inches off the pit floor , under shop floor and up the wall to a 24 inch barn fan. The fan is boxed in with a trap door .When door is open fan draws exhaust from shop, door closed draws from pit. Fan has only been used for pit maybe dozen times in all these years. We have a 4 foot florescent light in wall and an electrical outlet for sump pump. Never had an issue with the pit. We do all our own fleet repairs , welding and fabrication. In our sewer side of the business we deal with confined space entry on a constant basis. As Randy88 has said, put things in perspective, use common sense and drop the doom and gloom. Our new shop will have longer pit to service tractor trailer units. Only change is 6 inch pipe for exhaust as per building inspectors request.

 

[Randy88]

 

[Randy88]

 

[Randy88]

 

[Randy88]

 

[Randy88]

Daro, you wanted some photo's of the pit, finally got some to come up on here, not in the right order, but took me most of the day, much easier to do the whole pit than post photo's.

The first photo is of the shop floor going over the pit walls, if you look at the end plank, you can see a couple two by's screwed together, when the forms get pulled, those are the recess for the planks to lay in, level with the shop floor. The forms are made up of two planks screwed together for the shop floor over the pit walls, the fist plank is red headed into the pit wall and the second is held in place with the 2x4's that are screwed on vertically. After the shop floor is done, we pulled the top plank off and left the bottom plank in place, that's where we screwed our air pipe air line to the length of the pit, it also serves as second place to put a plank across to have a drain pan holder lower into the pit.

The second photo is of the footing for the pit and pilasters, the tube sticking up is for the sump pump, below the footing about two feet i the length of the pit we hand dug in, one line in the center dumps into the pit sump, and two more one on each side the footings also hook up to the center line. On top of that and once the pit is poured, we ran another run of tile just a couple inches below the top of the footing. Then every two feet in height we ran another tile line for a total of four layers along the pit walls and below the floor, then the entire shop is pattern tiled every five- seven feet of width, and along the walls of the shop we have two layers of tile lines, one just below the shop floor and the other hand dug in near the footing of the building itself.

The third photo is of the finished shop floor on the left side of the photo, the right side of the shop floor left to do yet, the rebar's from the vertical's on the pit, are bent over and tied into the floor rebar's.

The last photo is of the forms coming off and before any tile or backfilling is done.

Air suction lines are also run near the footing's, just above the tile line and is going into the pit walls in about four places and go up the wall and into the attic and out the end of the building. All the rest of the lines under the shop floor to the pit are not in yet and I'm not sure I have photo's of those.

Once the pit was done, we laid insulation board in the pit, put in floor heat lines, and rebar and cemented in about 4 inches of concrete in the pit floor.

We originally planned on going about two feet deeper with the pit, but as we dug it, the dirt kept collapsing and we got concerned the building walls would collapse in, so we shallowed it up, nothing caused problems.

It took about two hours to dig for the pit, when we got to the end, we had two feet of water in the hole, took two sump pumps to keep the water pumped out so we could work. As for how many feet of tile, I recall about 2500 feet of dual walled tile under the shop floor and around the pit. The summer we did the pit, we were having a drought and it hadn't rained in a couple months enough to worry about, as soon as we got it done and the inside cemented, it started to rain a lot that fall, for a few months the sump never shut off to keep the water pumped away. The sump tube goes down about 8-9 feet below the footing level of the pit.

Not sure if it helps at all or what you wanted, if you want something specific you'll have to ask and I'll see what I can do to find photo's for you.

 

[Queenslander]

Very impressive Randy, should last a lifetime.
How do you think something like this would work?
Bearing in mind we don't have issues with subsoil water or freezing temps.
Cheers, Greg

http://jacobprecast.com.au/Vehicle%20Service%20Pits.html

 

[Randy88]

I don't know how thick the walls are for that, or what the dimensions are, but I do know of one guy that used a new septic tank without the lid for his pit, the walls were not very thick and it also wasn't rebarred very heavy, those only use mesh in them, for a septic they work fine, when he backed something over it, his walls buckled and it collapsed.

I'm not sure I'd want one unless you had pilasters installed in the walls to help give it support, but it depends on what you plan on driving over it all the time with, the more weight you have over it, the more inward force you have on the pit walls. Its not uncommon for me to put two 70-80k machines over the pit at one time end to end and my floor is tied to the pilasters and pit walls, the shop floor is 8 or so inches thick, with two levels of rebar in it, the pit walls are 10 inches thick and pilasters are far thicker still, can't recall off the top of my head how thick but 16 inches rings a bell.

I don't know anything about your ground, the wetter it is, the thicker you need to go on concrete, the heavier the machinery the thicker you need to go so the concrete won't crack or buckle.

I was told by many that I went far overkill on everything, the concrete guys in the area told me maybe 6-8 inches for the walls and 5 inches for the shop floor would be fine and when I sat down and did the math, the overall cost to go far thicker was minimal and the strength was far greater and I told everyone, someday someone can break it all out and cuss every moment of doing it, but until then, it wasn't going anywhere or cause me a moments grief no matter what I put over it, I planned on doing it once was all. I think we also used six bag mix on most everything, not four bag mix, and I also hunted up a concrete provider that actually put in what I ordered, no fly ash, not 3 and a half bag mix instead of four, or five bag mix instead of six type thing.

Before putting anything in to use as a pit, know how its build, what materials they put in for reinforcing and also how much, you still need a footing to set it on so it won't sink or be shoved into the ground deeper, I think my footing is two feet wider than the pit itself and a foot thick with a lot of rebar in it, like on six inch square's and two layers of them staggered.

If your ground isn't very wet, that also plays into the equation, you don't need as much footing thickness or wall thickness but with anything over 15 foot I'd still want at least one pilaster on each side, those don't have to be very wide the shorter the pit is, but if you noticed the pilasters on one side of the pit are longer than the other, I was up against the building foundation and could only dig back so far on one side, so those are shorter, the other side wasn't an issue, I'm thinking the shorter one's are also thicker in width as well to compensate for the length of them.

Queenslander, since I have idea of your area, climate or anything else, I'd suggest you go around and look in your area at pits, ask how they were done, ask what they drive over them with and compare it to you and what you plan on doing with it, and put over it for machines, that way you can tell if there are bows, cracks or whatever in the walls, floor and go from there ask questions to those local to you, most are more than willing to chat and tell you what they wished they'd have done differently or what they'd have changed.

In my area, there are plenty of farmers dump pits for grain to look at, building walls for two story buildings and also pits to look at, not only the service pits, but also manure pits of every size shape and form. I just asked a lot of questions as to how others did it and then guessed from there. But I can tell you this much, the work is the same no matter how you do it, the material cost is minimal to go far thicker and stronger. Best of luck

 

[DARO]

Randy thanks for the pics I'm still in planing stage so the info will help.

 

[hetkind]

Manure pits and service pits have different loads on them. A full manure pit has almost no side...And you can do virtually a static design load with FS on the pits since there is no dynamic load.

Howard

 

[Randy88]

When full and with ground around them your absolutely correct, when empty there is tremendous loads on them depending on how deep the pit is, when a pit is full and is sitting on top of the ground there is considerable loads to factor in to keep them from blowing out, like the several million gallon pit did near me two years ago, took out a road when it went, a couple buildings and killed a bunch of animals as they drowned, luckily nobody was killed in the ordeal, good thing experts designed it and the farmer wasn't held liable for it blowing or any of the millions in damage it did.

Then it depends on how close the pumping equipment gets to the edge of the pit, like one did when the tractor and triple axle tanker collapsed the sides of the pit and the whole thing fell in, guess nobody figured that scenario into the strength of the pit walls, then there are few that the operators had a brain fart and drove the skid steer into the pit, good thing the new skid steer already had the cab door broken out, or else the operator might have gotten trapped inside and drowned, this way he could swim to the surface of the pit and someone pulled him to safety, course the skid steer didn't fare too well, I was told they had to pump the pit a week or so later and went in and fished it out, was also told warranty didn't cover that one, who knew right??

But the absolute best one ever was when a neighbor built his, and when it was done going through the final inspection and it failed miserably, the reason for its failure to pass the inspection was...................................get this the inspector even wrote it down, I got to see the inspection forms personally or I'd have never believed it..................................the vertical rebar's were set in the walls upside down and the wrong end stuck up out of the pit walls, to be torched off later?? At first the owner thought it was a joke, turns out he was wrong the idiot was dead serious, which brought about the discussion of how to determine which end of a stick of rebar was the correct end to put down and which end goes up?? Well after a few days of discussion and the failed inspection with not one but two inspectors, the head of the local government office came out to save the day........................he had to call the main office in the state and have a fourth inspector sent out who apologized profusely to both the farmer and contractor for any misunderstanding and inconvenience the first three had caused. So for future reference, to determine the strength of the wall in question, one needs to know that all the vertical rebar's are put in the correct way, those that are put in upside down weaken the wall and that was a direct quote from three inspectors, I wrote it down so I'd never forget it, and some think life itself can't be entertaining, it helps to have inspectors in the mix, there are days you get to learn a lot.

 

[hetkind]

drainage and dewatering, with proper treatment is key...leachate is a terrible problem not only is silage or manure pits, but once you start building radioactive material waste cells the world get more complex.

but shear loading is not rocket science. It is terrible when walls fail. I am far more concerned with dynamic loads than static loads due to my particular industry,

Howard

Howard

 

[DARO]

Randy that is to funny. The sadness in that is that those inspectors are in charge of the infrastructure that we are paying for
DARO

 

[norite]

Randy, you have a real well built pit there by the look of it.

 

[td25c]

Randy's service pit & shop remodel turned out real nice . Additions like this really shine for aging mechanics that don't need to be crawling around on hands & knees for the experience anymore .

Myself approaching the age of aches & pains from this work look forward to an in ground service pit . I would like a combination style pit with traditional trench under the vehicle opening up on one end like an alignment pit for front end work .

http://www.beeline-co.com/Content/A...-Ground-Design/-T-Style-Center-Pit-Model.aspx

 

[Randy88]

Curious TD, what are you going to put in the T portion of the pit, tools??

You have a nice way of saying, we're getting old and fat and when laying on a creeper, tend to fall asleep instead of working.

So since nobody ever told me about my very best portion of owning a pit, let me be the first to tell you guys what it is, this is something I've had to learn strictly on my own, without any help from anyone. It caught me by surprise one day shortly after we got into the shop and using it.

Since it was "new" thing around the place, everyone had to try it out, which is fine, even before I got to try it out, everyone else beat me to it, which isn't surprising around here, but anyhow, when most everyone else was in the pit being totally amazed they asked me if I could hand them tools, which led to the new job of gopher, or simply translated can you "go for" this and that, at first it kind of ticked me off feeling like some kind of indentured servant and after about the third trip to go for something, it dawned on me, all I had to do was hand them tools and shut up and wait. Now this I could handle so while everyone else was being amazed by the pit, I was being amazed the work was getting done and I wasn't the one doing it per say, but then I got a promotion on my new found and created job, I located a five gallon pail, flipped it over and sat quietly and waited to be asked to go for more tools. Nobody said one word about sitting on a pail doing nothing, seems I had the most important job there was, to cater to their tool needs, after all I was doing something others considered important. So I'm going to take full credit creating a new job around my place with the creation of the service pit, its the go for guy and the job I like the most, its also the job you ask questions about if they can reach this or that, did they do this correct, didn't forget to do that, made sure they double checked this and tightened that and when on this job of the go for, nobody complains about the question asking portion, you can always say, I'm just wanting to know where your at on the job so I can have the tools you need "before" your going to need them.

Now when you get good enough at this new job, like I have already, with the promotion and all, you get to thinking, something I don't do often, I've also learned some need added motivation while on the job, so I made a few calls and did something I generally don't do, called in the boy's girlfriends to visit while they worked. So in they came no questions asked, faster than lighting and twice as dangerous. So while chatting and asking questions myself, the guys needing to show like their working and doing something, I got my second promotion in a matter of weeks no less, I got the girls to go get tools for me to hand to the guys, now this took some training of sorts, but the most important part is keep the conversation moving and discussion going so nobody notices what's going on per say, and within a few weeks, on weekends now, I have someone else do the go for job and I've graduated, I get to work in the machining section of the shop and only need to monitor to make sure nobody is slacking off on my former job. Now that's the best part of owning a pit, and not one single person told me anything about it, it must be a secret of sorts, so don't tell anyone else.

I've found wives can do the job, but catch on quicker as to what happened, but grandkids work too, they just take added monitoring to make sure they're doing the "go for" job correctly. I've also noticed you can hire people to do this job for you, depending on who's in the pit, you just have to put some thought to it first as to whom to hire and then work out scheduling. So before you invest in a pit, make sure your capable of managing all your newly created jobs, I'm learning it can be a stressor at times. LOL