Burners 101

[Mikey98118]

Mensi propane valves; the cheap path to 1/4" gas burners

A pair of 1/4” low cost Mikey burners can be constructed from two Mensi propane valves, which are sold as replacement parts for camper stoves at Amazon.com for $9. These are connected directly to fuel hose with metric hose fittings, which you can also buy for $9 a pair. These valves can employ

3D printer extruder nozzles for gas orifices. because their threads are so similar, the MK8 Ender 3 extruder .4 nozzles (available through Amazon.com) can be made to work properly on 1/4" burners. Extruder nozzles are your cheapest choice for a gas orifice; they are easy to find, and easy to install. I recommend extruder nozzles over capillary tube for gas orifices on this burner. The valve's M10x1 thread will tap into 1/4" water pipe, and you're off to the races

[Mikey98118]

3D printer extruder nozzles used as gas orifices are made with nozzles mounted on small brass or stainless-steel metric tubes; not that they make the very best gas orifices, but they are good enough; also, they’re the cheapest and easiest to use.MK8 Ender 3 extruder nozzles are available through Amazon.com); they have M6x1 male thread (Major thread diameter is 5.974mm; minor diameter is 4.596mm); this takes a 5mm drill bit, or will tap directly into 7mm x 5mm tubing. 5mm = 0.195” and 3/16” = 0.187” so any tube or fitting with a 3/16” inside diameter can be drilled and threaded for these nozzles.

[Mikey98118]

Before we get to far away from Trevor's 1/4" burner, I would like to make some closing comments about its flame. Normally I speak out against secondary flames, and strongly preach for 100% combustion in the primary flame envelope. However, miniature burners are the exception to this preference. The reason why is that the smaller the burner the more difficult it is to get fine control of its flame.

The smaller the burner the smaller its flame, or flames. The secondary flame on his burner  is so short as to make no difficulty in a forge. Frosty has taught me not to allow the perfect to hinder the practical.

My first 1/4" burner produced a perfect flame, but had no turn-down range to speak of. Being  a control freak, I hated that! This is a better flame, for my money.

[Mikey98118]

15 hours ago, Mikey98118 said:

will tap directly into 7mm x 5mm tubing.

I think Mikey got it wrong here. That wouldn't leave a whole lot of wall left...Maybe thicker tubing with a 3/16" inside diameter will have to do. Yeah, lets stop with that (bad Mikey. Bad, bad Mikey)!

[Mikey98118]

Any tube or fitting with a 3/16” inside diameter can be drilled and threaded for 3D printer nozzles; that includes schedule #80 1/8” pipe nipples.

[Trevor84]

When it comes to 1/4" micro burners and options for tapping thing I'll add that one can tap a 1/4" schedule 40 nipple to accept the 1/8"npt threads. 

If one takes the ACTUAL ID of the pipe nipple the sizes are way out to lunch! Inside of the quarter inch is like 3/8" inside the 3/8" is 1/2" id etc

I want to order some larger pipe taps.... To make a 3/8" pocket rocket I will tap the 3/8" nipple with the 1/4" pipe tap then tap up into the bottom of that 1/4" fitting (say a 1/4"npt - to 3/8"flare) to accept a piece of 1/8" sch 80 piple nipple (trim the last but of straight and the threads off a piece of sch80) to accept the mig contact tip or the 3d printer nizzle. 

I guess you could use a bushing but you'd want to file down the points on the nut portion of the bushing. 

 

Ughh sounds exhausting but really it's just 3 taps, trim the 1/8 and cut out intake ports. 

Tap the 3/8" sch 40 nipple,

Tap the 1/4" mnpt to 3/8" flare or something then

Tap a piece of 1/8"sch80

 

[Trevor84]

So the updated dimensions on the micro burner stand alone post but this is the latest version of the 1/4 inch pocket rocket's flame in open air unfortunately I can't get it to lock in place once in the micro forge, the gasses are moving way too fast. 

 

I have nothing to add along the rotory tool side, I haven't had one worth a bean so I don't use'em

[Mikey98118]

What I like best about your burners, OK, second best (first place goes to their flames). But a strong second best is their construction; they are very different from mine, and that is good! The more choices people have the better 

So, as to the forge; circumstances alters cases. Years ago, I was part of the home casting community, and we built our furnaces very differently from what forges (and furnaces) are made today; partly this was because we were mostly using homemade cast refractories. But the point is, that our equipment interiors were solid cast refractory, without insulating ceramic wool or insulating brick.

I discovered the joy of lite cast refractory, combined it with a layer of ceramic fiber blanket; it make a tough inner lining, which I have used every since. You have made a very hot burner, which you want to mount in a very small forge. This is all well and good. BUT, you now need a tougher, and larger interior in that very small forge, to deal with the flame output of that little dragon.

If you build a coffee-can forge, with a 1" layer of blanket, with a 1/2" hot face layer of insulating refractory, it will barely have enough interior space to run that burner. Two of those burners would adequately heat a Freon or helium canister forge (2" insulation). Are you going to end up with a lot less insulation in the coffee-can forge? Yup, and so what? Don't let the perfect interfere with your need for something practical.

Forge design is "where the rubber meets the road."

[Mikey98118]

Gas tubes for 3D Printer nozzles

Brass Round Tube; 8mm O.D. x 6mm I.D. x 300mm (12”) Length for $9.49 through amzon.com will take M6x1 thread for gas tubes:

I spoke too soon it didn't have enough thread left to hold the nozzle. Next, I try a 7mmx5mm brass tube.

[Mikey98118]

Simple gas assemblies for  1/8" burner size

1/8” burners are relatively simple to build, but the need for additional taps and dies increases their expense. The burner’s gas orifice is a 0.3mm 3D printer nozzle, which threads into a brass gas tube; this gas assembly is threaded directly into a 1/4” barb x 1/8” male NPT hose fitting. With this design, you delete the mixing tube’s spacer ring and up to six set screws in its installation. The short brass tube allows you to control the length of the three air openings on the burner’s mixing tube, and contributes to the length of the gas passage within the hose fitting, which replaces the long gas tubes in larger burners. Threading the rear of the mixing tube also greatly reduces layout and construction work, otherwise needed to mount a gas assembly onto this tiny burner.

    As mentioned elsewhere, extruder nozzles have many practical advantages over capillary tubes trapped in MIG tips, while the superiority of capillary tube gas orifices decrease along with burner size (they are superior in ½” and 3/8” burners, but only on par with extruder nozzles on ¼”burners). By 1/8” burner size, these nozzles outperform capillary tube; they are also far easier to clean. Cleaning becomes more frequent as gas orifice diameters decrease.

    1/8” burners can be connected to short lengths of hose, which are connected to “Y” fittings; then to a longer hose, to heat coffee-can forges, or jewelry furnaces. Single burners on two-brick forges can be connected directly through a single fuel hose, to a needle valve and canister, or a 0-30 PSI regulator and refillable fuel cylinder.

[Mikey98118]

Materials list for a 3/8" hose mount burner's gas assembly & mixing tube

(1)  A 1/8" NPT Female x 1/8"NPT Female Hex Nipple; this is a brass pipe fitting from your hardware store, or through Amazon.com. Carefully read through Step two in this chapter before deciding on a hex nipple.

(2)  A 1/4” Barb to 1/8” male NPT hose fitting bought through Amazon.com.

(1)  7mm x 4.5mm brass tube, 12” Length; $9.50 through Amazon.com:

(2)  0.4 MK8 Ender 3 extruder nozzles are available through Amazon.com); they have M6x1 male thread. The marking “0.4” on one of these nozzles stands for 0.4 millimeters, which is the diameter of its orifice; that comes to 0.016”.

(3)  The mixing tube is a #304 stainless-steel tube (part #469 from Onlinemetals.com); its outside diameter is 0.625”, and its inside diameter is 0.495”; 12” lengths are $17.60 and shipping. Or you can order it already cut to 8” long for the same price: 

 

[Mikey98118]

Because all the threading (except for the sets screws) is being done in brass, plug taps can be used in the gas assembly parts, BUT you must use a light oil, such as Pam, and you must start the threading with the tap in parallel to the part’s axis. If you don’t have a drill press and drill vice to accomplish this with, you must shim the part, and the tap body, at the inside corner of angle stock, to ensure that the tap is interring the hole straight; not at an angle. If you can’t manage that, you must buy taper taps (AKA starting taps). Otherwise, pass this gas assembly by, and choose another design.

[Mikey98118]

 

 

One method of mounting a gas assembly on small linear burners

 

It is necessary for incoming air to sufficiently mix with fuel gas. A swirling motion provides the most mixing for the least drag on mixture flow. Pipe reducer fittings and other funnel shapes provide convenient ready-made low-cost forms for this purpose.

    It has been well established that the gas pipe and whatever MIG contact tip, etc. is used for a gas orifice should be axially centered in the reducer's large opening by, whatever means is convenient. BUT the devil is in the details, because how you choose to mount the gas assembly, is your first and best chance, to gain that something extra that we all want to see in the flame; don't waste it!

    Why such emphases on a “minor” detail? You have an energy budget; it's limited to the air induction that your gas orifice supplies to the gas stream, which is the burner's air induction engine. It takes energy to get air moving, and also takes energy to change air direction. So. starting that change at the same point where the motion begins, will require the least energy from your tiny budget.

    So why not install a high-power fan or compressor at the opening? How much breath is required to blow out a candle? That is about the maximum power input—at the wrong place—It takes to blow out a burner flame too. You want burner magic? It comes from control.

    There is another important factor to consider; as with a whirl pool, nearly all of the air is going to inter near the opening’s periphery. No significant air will move down the center of the entrance. So what? So, this tells you where streamlining matters, and where it doesn’t.

    Mounting a gas assembly has two facets; what is easy versus what works best. There can be no "perfect” answers because, aside from tooling and skill levels, we all have our preferences; mine is maximum control of the parts being put together, having found you get the best results for the least work, if Murphy is never given a chance to muck everything up. For reducers needing a flat disc of up to 2-1/2” diameter, fender washers can be purchased, keeping your work at a minimum, by using only part of the instructions below. For larger openings than 2-1/2” you must completely fabricate your own part.

    So, why start with sheet metal, or a fender washer anyway? When you begin on a flat surface; all you need do, is to avoid bending it. Use a divider (best) or compass (workable), and a prick punch, to lay out a disc of the same diameter as the outer edge of the large opening in a pipe reducer or funnel. whether you want to silver braze, solder, screw, or glue it in position.

Cut a hole in the middle of the disc for your threaded gas tube to slide through. Mark out three equal spaces for ribs between the air openings, usint the divider or compass. Drill 1/4" or smaller holes between the areas of the ribs and well outside the area of a lamp thread nut. Remember that there is no significant air flow in this central part of the opening, so don't shortchange yourself on material in this area.

    The ribs would be fairly narrow if you kept their lines parallel, but that isn't desirable. You want them narrower at their outer ends, and  becoming wider toward the center of your disc. You can also cut a groove in their bottom face, and bend one side downward at a forty-five-degree angle; this will help encourage swirl in the incoming air, while helping to keep the structure rigid. You must cut the sections that angle downward small enough to fit inside the opening, leaving the rest of it still long enough to sit on the outside of the reducer or funnel. Why would you bother? To ensure that the gas tube’s mounting is diagonal with the air entrance; thus, helping to ensure that the gas assembly will remain axially true to the burner.

    The gas tube has an exterior thread, that allows it to run back and forth in a nut, or 1/2'” long brass 1/8 IP for lamp fixtures (to solder or silver braze on the mounting plate if your burner is positioned downward in heating equipment), for fine tuning burner performance. If your burner will be aimed upward, no choke is needed.

    For people who can’t afford “doing things the right way,” or find all these parts and tools, there are brass pipe, steel tube, etc. that can be slid into lamp thread from your hardware store, where it can be trapped in place with silver braze, solder, or even resin; it’s the lamp thread that has to move back and forth, for proper tuning. A nut snugged up on either face of the hole in the mounting plate can keep everything tight, so that tricky solder or brazing work, is not essential.

    You also don’t need to perfectly match up the inside of whatever you use for a gas pipe with the inside of the lamp part. Adding spacers are just fine so long as you solder, braze, or glue them, to prevent movement between lamp thread and gas tube. Even electrical tape can be used to provide an interference fit between the gas pipe and lamp thread.

    Gluing gas assembly parts? Anyone who has played around with air-fuel torch parts will have noticed that a few of them are glued together (mostly on old equipment) with some kind of black resinous substance. And anyone who has rebuilt an engine knows that gasket sealant is black and quite tough. Two and two makes…

    Thread-locker comes in hardening and non-hardening types; both kinds are resistant to vibration, and, like gasket sealant, thread-locker for fuel lines, are rated for use with petroleum products. LPG stands for liquid petroleum gas; that includes propane, butane, methane, and propylene fuels.  

 

What is an 1/8” IP thread? 1/8” IP or IPS (iron pipe, or iron pipe standard) thread dies and taps can be used to make lamp rod thread (1/8-27) on the outside of schedule #801/8” water pipe (designated size; actual outside diameter of 1/8” pipe is .405”). This is parallel thread, and is not to be confused with the tapered 1/8” NPT (national pipe thread); it can be used on the cut off ends of pipe nipples, with the other end used to mount your gas fitting or needle valve to. This means that your gas jet can be easily installed on your burner, with a flat washer for a choke included. Be sure to use an "S" letter drill bit; not an "R" bit, which is recommended for tapered thread; not for parallel thread.         

    1/8” schedule #80 pipe can be directly threaded with a 1/4-27 (best) or 1/4-28 (acceptable if you’re careful) tap, to accept a MIG contact tip.

    Lamp thread tubes at your local hardware store have external 1/8-27 IPS, and internal diameters of 0.0285” that will comfortably accommodate 1/4” O.D. gas pipe to be silver brazed, soldered, or glued in place. You will also find short tubes with internal 1/8-27 IPS thread, nuts, and flat washers in the same section.

Lamp thread is too large for use in micro-burners. Fortunately, the same mounting scheme can be carried out by threading brass tubing; thus, the right heavy wall tube, or nestled tubing in ever smaller gas assemblies can be installed in ever smaller burners. Brass tubing in millimeter sizes are available through Amazon.com in sizes from 2 millimeter (0.079”) up to 6 millimeters (0.236”), and in 5/16” x 3/16”  fractional sizes.

  

Three pieces of 7mm O.D. by 4mm I.D. by 300mm (11-13/16”) long seamless brass tube, with 1.5mm (0.058”) Wall Thickness are available from Amazon.com for $16.89. 4mm is 0.15748”. 1/4-27 thread for MIG contact tips have a minor diameter of 0.205” so this tube can be threaded for MIG tips at one end. 7mm is 0.275”; thus, accepting various 1/4” dies (fine thread is better than coarse thread for this). By stopping the outer thread short of the last 3/4” of length, you can use this heavy wall tubing for creating smaller versions of lamp thread gas assemblies. This tube can also be interference fit into standard lamp thread; or slid more easily into it, if the lamp thread is sanded just a little to smooth out its interior. it also fits fender washers, and other flat washers, for use in smaller burners as the only gas tube.

[Mikey98118]

So, why discuss tricks and tips on linear burners? The first time I got one-hundred percent combustion, it was on a linear burner, so there is nothing wrong with them on that score. At present, stainless-steel tubing and pipe is going for way too much money, so I'm all in favor of replacing any over priced burner parts I can with lower cost alternatives. And, by the way, linear burners are easier to build

[Mikey98118]

It is necessary to adjust how close the tip of your gas orifice is to the tube section at the small end of a funnel or pipe reducer fitting. Simply employ tape to keep the fender washer in place over the large opening during testing; permanently mount the washer and gas assembly in place afterward. Start with the end of the gas orifice at 3/8” short of the opening; its sweet spot will end up somewhere between 3/8” and 1/4” away from the opening.

[Mikey98118]

Mixing tube sources

While some SSTs have attached tubes of the right diameter and length to be used as your burner’s mixing tube, others need to be inserted in, or mounted on, longer stainless-steel tubes to work as burner parts. Kitchen funnels, and other air opening sources must be mechanically attached, silver brazed, or glued into or onto S.S. tubes, or steel pipe as mixing tubes.

While some U.S. built funnels have fractional tubing attached, many others use metric tubing. One of the advantages of metric tubing (sold in convenient lengths through Amazon.com) is that it is much easier to find compatible metric tubing to slide into or over it. Furthermore, this tubing is usually less costly than S.S. tubing or pipe sold in small amounts from regular steel sources, is seamless, and thinner than otherwise available at reasonable prices. 

[Mikey98118]

British thermal unit (Btu)

The British thermal unit (Btu) is a well-known unit of potential energy, which has long been used to compare fuels and/or burner sizes, but much is less legitimate for judging burner types; it’s a reliable measure when applied to equipment such as home heating furnaces. On top of this, you very rarely see it tied to burner turn down ranges, leaving us to ask questions like 140,000 Btu at what gas pressure; enough so that the burner was in danger of snuffing out sometime during the test? Was the burner tested so far over its normal top pressure that that its flame had long since started running rich?   

The problem is that actual energy potential is a slippery fish even in a saint’s hands, let alone a sales manager’s.  But, even if you do all the figuring for yourself, what does 140,000 Btu actually mean to YOU; at best it gives you a vague impression of what a burner should be able to do; and that’s where you were you were when you came in!

For instance, if two different burners are running the same gas pressure from the same gas orifice diameter, but one only puts out 2400

F flames, but the other one puts out 3800 F plus flame temperatures, their BTU consumption matches, but nothing else does.

[Mikey98118]

 Parting Tube

 Note: mixing tube lengths of linear burners follow the “nine diameters” rule of thumb, which states the mixing tube should be nine times as long as its inside diameter. When the burner is fan-induced, the mixing tube length jumps to fourteen diameters; these rules of thumb have exceptions. When your burner will mostly be used as a brazing torch, about 1” of added length will create a smoother flame; an advantage for better control of a forming bead, in braze welding. Subtracting an inch in mixing tube length will shorten the output flame, lengthening the distance between flame tip and the point of its impingement on the work’s surface; an advantage in smaller equipment.

Cutting parts to length is most easily done with an abrasive disc mounted in a cutoff saw (AKA chop saw); the cheapest of these are about $140. Harbor Freight Tools sells a 6” chop saw for $50 (mine has been very satisfactory), and there are various angle grinder chop saw stands available.

    On the other hand, surface cutting parts to length with a rotary tool or die grinder requires a proper cut line; this can be provided with an ink marker and sheet of paper rolled around the tube or pipe, instead of a pipe wrap. You then proceed to make the cut in the manner recommended in the Surface Cutting section below.

    Or, you can mark perfect cross lines, at true right angles, with a little pipe cutter; it can also be used to completely sever the parts. But for parting, you will need a quality tool; it will cost double the price of the cheapest pipe cutter, but with reasonable care, will do the job for years, without breaking (don’t attempt to cut deeply with each pass; take your time) Separating parts this way may (depending on what alloy, how thick, and how hard the blade is pressed against the part surface)compress the inside diameter, in the immediate area of the part line, several thousandths of an inch smaller; this can be quite handy with oversize spacer rings, and for leaving an indent in the end of the mixing tube, which can help to lengthen and sharpen the flame shape for torch work. Otherwise, the inside of the part area will need to be sanded to restore the original inside diameter. Even if you want to keep the narrowed area, it must still be sanded a very little bit to get rid of ragged edges, inside and outside.

Pipe and tubing aren’t perfectly round. So, start your cut by slowly turning the part under the blade, to feel where its diameter is greatest; then, gently roll the part back and forth under the blade to start forming the parting line in that area. Once, the part has the same feel between the largest and smallest areas, tighten the blade just a little bit, and roll the part its full 360 degrees. Then, tighten the blade a little more and roll the part in the opposite direction, once. You are looking to establish a single parting line, for the blade to be trapped in. Otherwise, you could end up with a wondering line that looks like a spiral. You will notice that the tool moves more easily over the work in one direction than in the other. Once the parting line is established, use the easier direction (to avoid broken blades).  

Note: Some imported stainless-steel tubing comes parted; not cut. So don’t expect internal diameters to match up with the advertised measurements, without some sanding or filing of their ends. Do to continuing supply problems, manufacturers have to “take what they can get.” Just because the tube section of an SST is supposed to be #304 series stainless-steel doesn’t guaranty that it actually is. After trying to part such a tube for more than an hour, I gave up and moved on. The very next tube I chose, easily parted in a few minutes. If the tool does no more than start a cut line, saw through it with a rotary disc.

RIDGID - CC247 RIDGID 40617 Model 101 Close Quarters Tubing Cutter (1/4” to 1-1/8”); $22.31through Amazon.com is recommended for parting:

[Mikey98118]

Passive Vortex Burners

    Let’s clarify just what is meant by the term “vortex burner”; it’s been miss-applied to any burner that swirls the fuel/air mixture at some point; that would describe most fuel/air burners—even some Bunsen burners. Often, the term is granted to burners that swirl the flames they make. But, causing a flame to swirl happens far too late in the mixing process to provide much benefit; used this way, the description is pure hype.

    Vortex is a fluid dynamics term, describing a region in which the fluid flow (gas, liquid, or plasma) revolves around an axis line.  The vortices generated on the tailing edge of a plane’s wing only generate drag. At the other extreme, a tornado’s funnel has terrible destructive power. The gentle current of a bathtub drain effectively employs vortex flow to good purpose.

    There are numerous ways to swirl incoming air and fuel gas, but only when the air passes through a restriction (ex. pipe reducer or funnel) can vortex movement become a practical air/fuel mixing aid. Nearly all home-built burners, whether linear or jet-ejector, create vortex flow.

    Any device that creates spin at the air entrance will increase vortex flow; this includes directly opposite openings on “T” plumbing fixtures, disc shaped choke plates near funnel entrances, or even still blade structures in front of a funnel opening. If you strip the blades from a computer fan, and mount them on a funnel burner’s gas pipe, they will significantly increase vortex movement in the funnel, even though they are still. Likewise, rib structures in mounting plates can be ground into fan like shapes, to increase vortex flow in the funnel. Installing computer fans on linear burners will supercharge flow, but this requires a complicated gas assembly, and an electrical power source. So, you are wise to move from passive to powered vortex burners in stages.

Before someone says "aw shucks; he's just talkin about linear burners"; well no, he is only talking about successful linear burners. I have seen lots of junk burner designs, that were linear, and others that were jet-ejectors, both powered and naturally aspirated.  Successful is as successful does; all else is dross.

[Mikey98118]

Stainless-steel pipe and tubing are becoming overpriced for small quantities, or when cut to length at the usual steel suppliers, but can still be purchased them at reasonable prices as millimeter tubing in small diameters and as pipe nipples in larger diameters, with free shipping, through Amazon.com.

[Mikey98118]

Pipe Nipples and Couplings

Due to the ridiculously high cost of small orders in pipe and tubing, as their sizes increase beyond 3/4” mild steel pipe nipples should be substituted for stainless-steel to make mixing tubes in the larger burner sizes. Schedule #40 pipe nipples of various lengths are available in hardware stores, and large size pipe nipples are available in plumbing supply stores.

    Because cutting fees make short parts used as the spacer ring and outer tube of a flame retention nozzle nearly as expensive as 12” lengths), male short nipples, or hex nipples (of mild or stainless-steel) can be cut in two, after being screwed into female S.S. pipe couplings (and then threaded for socket set screws) to become far less expensive flame retention nozzles; this can drastically reduce both costs and work to build your burner. This method will produce slide-over step nozzles, which work every bit as well as flame retention nozzles that are built from tube and pipe, but which will not last quite as long, because the female coupling is made of #304 stainless, instead of #316

[Frosty]

Not to intrude but pipe cutters are really common at yard/garage/etc. sales, 2nd hand and pawn shops for less than one cut charge at a plumbing supply. 

Frosty The Lucky.

[Mikey98118]

Intrude? You just pointed people to  bargain sources of good tools 

[Frosty]

When you don't need threaded ends why buy nipples when used pipe cutters are cheap or free bundle deals everywhere? I've only bought one small one for copper tubing and have a number of them. One 1" x 2" nipple for a burner mount probably costs more than a 1" x 12" unthreaded length and a yard sale cutter.

Sometimes these things are easier for someone other than the author to see. Even if its a good tip its still an intrusion into the narrative so I try to be careful.

Frosty The Lucky.

[Mikey98118]

You must remember that I am dealing with stainless steel tubing and pipe for most of my burner parts, and only resort to mild steel tubing when forced by high prices; and then only for mixing tubes. I try to compromise (ugh!) by using cut off threads from short S.S. nipples, screwed into  S.S. couplings to avoid ridiculous prices on 1" and 1-1/4" stainless steel pipe or tubing, to make flame retention nozzle parts.

Of course, anyone within driving distance of a big city can find reasonably price S.S. pipe and tubing in a salvage yard. But I live in a little city with big pretensions, and no more actual for real salvage yards. You can still buy some S.S. pipe and tube from legitimate salvage yards in Tacoma; but not in Seattle.