||Instructions for Layout and Tapping Stanley Boilers
By Don A. Bourdon, Woodstock, Vermont
Stanley boilers are shipped from Bourdon Boiler Works with two pipe tap openings on the top sheet only. One
is in the center and it is tapped to 3/8 NPT. It serves as the steam outlet for the throttle. The other tapping
is on the outside edge on the top sheet. This is tapped to 1/8 NPT.
When testing a boiler, water enters the boiler in the center as this serves as the inlet for the test pump. The
tapping on the outside edge lets the air out of the boiler while it is being filled and serves as a place to
attach the test gauge.
Boilers typically are tapped on the bottom sheet to ¼ NPT. I tap 20 HP and 30 HP boilers with 4 openings. 10 HP
or smaller boilers are ok with 3 openings. They all serve as bottom blow offs. One exception, however, may be
made in the case of a surface blow off used on condensing cars. One bottom blow off is connected to the water
level indicator which should be plumbed so it can be shut off from the top and bottom of the boiler, as needed.
Taps on the top sheet serve to connect the throttle, water feed, safety valve, siphon, steam automatic, steam
gauge, and whistle (optional). Tapping size ranges from 1/8 NPT to 3/8 NPT (boiler feed and throttle). A word
of caution - Do not place the boiler feed standpipe feed line tapping on the top of the boiler near the water
level indicator top and bottom tappings as water feed coming into the boiler will give you a higher water level
indication than actually exists.
In laying out for the tappings, I recommend that no edge of a tap hole be closer than 5/16” from a boiler
tube. No hole should be in contact with the edge of the welds on the bottom or top sheets. Space your hole
The tap hole size for 1/8” NPT is 5/16”, 7/16” for ¼” NPT, 9/16” for 3/8” NPT. I follow with a pipe taper
reamer. This makes the tap go easier into the hole. Next, I follow the taper reamer with an 82 degree
countersink to break the sharp edge of the hole. I drill the hole free hand. To aid in directing the drill
so that it penetrates the steel at 90 degrees to the tube sheet, it is best to have someone with a good eye
to spot you, looking at both the x and y axes to make sure the drill is vertical and remains so during the
operation. I suppose that if one had a super large drill press or mill, they could use it to drill the
holes, but this would be somewhat time-consuming and cumbersome, particularly for the larger boilers.
Following the drilling, reaming, and countersinking operations, I next set up for tapping the hole. To do
this, I use a HSS tap that is new or nearly so. I use a long tap wrench (21” or longer) to hold the tap.
The handles of the wrench need to remain parallel to the tube sheet. To aid in doing this, I place a
board on edge (4 to 5 inches wide by 25”long) which has a series of parallel lines drawn on it spaced
about ½” apart on top of the tube sheet.. By placing the board next to the wrench as it is started into
the hole, one can readily see if the tap handles holding the tap are parallel to the lines on the board.
A careful watch on the wrench handles relative to the lines on the board will ensure that the outcome is
what you want it to be.
Use a high grade of cutting oil. The boiler plate used in the construction of boilers is harder than
standard hot finished materials.
Don A. Bourdon.
Keeping Your Stanley Boiler Clean
By Don A. Bourdon, Woodstock, Vermont
Aside from the engine and burner, the boiler is the most important mechanical component to the Stanley: from the point
of view of safety, it is the most important part. A properly constructed and maintained boiler will give years of
faithful service with little expense. While much can be written about the technical aspects of boiler design,
efficiency standards, and operation, the attempt here will be to discuss a few of the more common practices that
owners of Stanleys may find useful for maintaining their boilers.
One of the most often asked questions is how and how frequently does one blow down a boiler. There are probably many
ways to answer this question and get similar results. Discussed below are a few experiences I have encountered and
learned from others over the past 45 years I have been operating a Stanley.
Blowing down is recommended every time following use of the car, regardless of the distance traveled. It should be
standard operating procedure. Without frequent blow downs, sediment, rust, and mineral deposits from the water will
settle on bottom tube sheet and around the tubes, eventually hardening into layer of scale. This can cause poor water
circulation which, in addition to reducing boiler efficiency, can subject the tube sheet to the full force of heat
from the burner. This will eventually cause overheating of the tubes, breaking the seal between the tubes and the
tube sheet, most likely resulting in leaky tubes, or scorching, even when the boiler has water in it.
As one early Stanley instruction manual pointed out, proper blowing off can actually reduce or eliminate sediment
formation not only by blowing it out, but by dissolving it. If a small amount of steam is left in the boiler
Blowing it down “the steam condenses into a small quantity of chemically pure water that falls into to the bottom
of the boiler and tends to re-dissolve any scale that has formed”.
Various boiler compounds are available to minimize sludge build-up and some operators use them in their cars with
the idea of prolonging the life of a boiler. However, I have never used a boiler compound. When driving a Stanley,
I get water anywhere it is readily available, be it a pond, river, or domestic water supply. The chemical properties
of water vary according to the region in which we live and travel with our cars. Accordingly, it can be hard to
adhere to a water treatment program that will work under these conditions. Logically, de-mineralized water or
soft water is preferred to hard water, but sometimes the choice is not there when you are traveling long
distances. Again, the best and most straight forward practice is frequent and thorough blow downs.
One thing I have done for years is to add a couple of tablespoons of Arm & Hammer household washing soda to the
water tank when it is first filled for the day. I find that this keeps the pumps and check valves free from dirt
It is good practice check the boiler feed standpipe on the top of the boiler. Standpipes can become clogged with
scale, restricting flow of water to the boiler; this places excessive stain on the pumps. To prevent this, make
it a habit to ream or drill out the feed stand pipe at least once a year. To do this, run a drill from the top of
the access plug down the full length of the pipe to open the tube to its original size. Also, I recommend adding
an extension to the top of the boiler feed fitting so that it projects out of top of the smoke bonnet, making it
easy to access for this purpose.
A hot boiler should not be blown down entirely or too quickly. This places undue stress on it due to sudden cooling
or contraction. This is especially true for an aging or older boiler. Latent heat in the boiler, superheater, and
burner can contribute to breaking the seal between the tube and tube sheet. As such, it is best to wait at least
one-half hour after everything has been turned off before blowing down.
For both non-condensing and condensing cars, all blow down valves can be opened simultaneously and can remain open
until wet steam is replaced by dry steam, and then immediately closed. At this point there will be 200 to 300 pounds
of steam pressure left in the boiler. If you have a tight throttle, enough water in the storage tank, and the pump
bypass valve closed, your boiler should siphon enough water for the next steam-up
For condensing cars, there can be a problem of sludge build up: cylinder oil returns from the engine to the condenser
with the steam, and then back to the water tank, eventually making its way into the boiler. Thus, special attention
needs to be given to remove as much of that oil as possible so that little or none gets into the boiler.
One of the most cost effective ways to cut down on oil build up is to adjust the oil pump or lubricator so that it
pumps the least amount of oil necessary to do the job of lubricating the engine. Most Stanleys pump too much oil. While
the old adage states “oil is cheap”, too much oil in a condensing Stanley is expensive. As a general rule, a
consumption rate of one quart or even less per one hundred miles will be adequate. Careful and modest adjustments
to the pump will get one to this point without too much difficulty. Just be careful not to cut the oil pump back
The Model 735 and later condensing cars were equipped with a boiler surface blow off valve. This consisted of a
vertical standpipe extending up from the bottom of the boiler about 8 inches which was connected to a valve next
to the boiler. During the cool-down period, oil will gradually rise to the top of the water line and separate from
the water. By using the blow-off valve first and before opening the bottom boiler blow offs, some oil can be “skimmed”
off the top and out through the valve. Of course, this only works if the water is above the top of the standpipe. While
not original for the earlier models, I would recommend a surface blow off as an aid to remove oil from a boiler. Also,
non-compounded steam cylinder oils are considered superior for condensing Stanleys as they are less likely to emulsify
Another effective and inexpensive way to keep oil out of the boiler is to let the tank overflow when filling. This will
allow any oil to float off the top, preventing it from become picked up by the pumps. Of course, a practicing
environmentalist should consider the consequences before doing this. Recently, owners have inserted an oil absorbent
sheet cloth type material in the tank. This cloth attracts oil, picking it up from the water while it floats around
in the tank. To do this, a small access hole needs to be made on the top of the tank with a cover to enable one to
insert and remove the sheet, when necessary. The sheets are not costly and carrying extras in the car for replacement
after a day or so of touring takes little space. Another way to cut down on oil is to add an oil separator device
between the engine and the condenser. These units have proven to be moderately effective and are presently in use
on our condensing Stanleys. Separators will need to be custom made to fit a Stanley and are expensive. These consist
of series filter cartridges or pads that serve to separate the oil from the hot condensate water.
Lastly, as reported in a 1923 Stanley Dealer Bulletin, another method of getting oil out of a boiler is to fill it
with kerosene, let it set for a time to loosen up any sludge, and then blowing it out. While I have not exactly
followed the recipe outlined in the Bulletin, it has proven successful as a means of getting a boiler cleaner.
Don A. Bourdon.
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