I'm rebuilding a Wabco control valve off our coach. I have the proper silcone based grease used on most of the valve already, but what is the best grease to use on the cut-out cock? The specs say #4 zinc based grease, but it does not give a specific brand or brand(s). Any suggestions? Thanks.

Just use Desitin Original Diaper Rash Ointment. It has 40% Zinc and is cheap at Wal Mart. You could spend a lot more for a product which has some high performance name but in the end, it's vaseline with zinc dust in it.

I think you meant zinc OXIDE. Zinc dust is actually very fine particles of metallic zinc and zinc oxide is a white powder used in paint, sun block creams and in Desitin. Zinc dust is sometimes used in anticorrosive paints but is mostly used in chemical processes.

You're right, I left off the Oxide. But it's still used as an anti seize/lubricant for parts in nuclear weapons system components.

Well if I ever have a squeaky atom bomb I'll try the Desitin. ;)

Have the cutout cocks been modified with o-rings? If so, petroleum based greases should be avoided. It would be nice if you could get WABCO to provided better information. They may be referring to the white (zinc oxide) lithium based greases, which are supposed to work well with wet air, but need to be renewed frequently as it will harden. Neither zinc or zinc oxide additives to grease would appear to be very appropriate for brass. I have used grease with Teflon additives. These will leave a Teflon coating behind when all the grease is wiped away. NLGI #4 is a stiff grease and is not common in modern greases. Wikipedia had an interesting write up on the NLGI consistency reading that I will try to post.

I would not recommend the use of Vaseline as a lubricant. It is not inhibited and tends to promote corrosion.

Please let us know what you learn. Finding proper lubricants for air brakes is a challenge.

NLGI consistency number
From Wikipedia, the free encyclopedia
The NLGI consistency number (sometimes called “NLGI grade”) expresses a measure of the relative hardness of a grease used for lubrication, as specified by the standard classification of lubricating grease established by the National Lubricating Grease Institute (NLGI). Reproduced in standards ASTM D4950 (“standard classification and specification of automotive service greases”) and SAE J310 (“automotive lubricating greases”), NLGI’s classification is widely used. The NLGI consistency number is also a component of the code specified in standard ISO 6743-9 “lubricants, industrial oils and related products (class L) — classification — part 9: family X (greases)”.[1]
The NLGI consistency number alone is not sufficient for specifying the grease required by a particular application. However, it complements other classifications (such as ASTM D4950 and ISO 6743-9). Besides consistency, other properties (such as structural and mechanical stability, apparent viscosity, resistance to oxidation, etc.) can be tested to determine the suitability of a grease to a specific application.
[edit]Test methodology

NLGI's classification defines nine grades, each associated to a range of ASTM worked penetration values, measured using the test defined by standard ASTM D217 “cone penetration of lubricating grease”. This involves two test apparatus. The first apparatus consists of a closed container and a piston-like plunger. The face of the plunger is perforated to allow grease to flow from one side of the plunger to another as the plunger is worked up and down. The test grease is inserted into the container and the plunger is stroked 60 times while the test apparatus and grease are maintained at a temperature of 25 °C.
Once worked, the grease is placed in a penetration test apparatus. This apparatus consists of a container, a specially-configured cone and a dial indicator. The container is filled with the grease and the top surface of the grease is smoothed over. The cone is placed so that its tip just touches the grease surface and the dial indicator is set to zero at this position. When the test starts, the weight of the cone will cause it to penetrate into the grease. After a specific time interval the depth of penetration is measured.
[edit]Classification

The following table[2] shows the NLGI classification and compares each grade with household products of similar consistency.
NLGI consistency numbers
NLGI number ASTM worked (60 strokes)
penetration at 25 °C
tenths of a millimetre Appearance Consistency food analog
000 445-475 fluid cooking oil
00 400-430 semi-fluid apple sauce
0 355-385 very soft brown mustard
1 310-340 soft tomato paste
2 265-295 "normal" grease peanut butter
3 220-250 firm vegetable shortening
4 175-205 very firm frozen yogurt
5 130-160 hard smooth pate
6 85-115 very hard cheddar cheese
Common greases are in the range 1 through 3. Those with a NLGI No. of 000 to 1 are used in low viscosity applications. Examples include enclosed gear drives operating at low speeds and open gearing. Grades 0, 1 and 2 are used in highly loaded gearing. Grades 1 through 4 are often used in rolling contact bearings. Greases with a higher number are firmer, tend to stay in place and are a good choice when leakage is a concern.

Why not use air brake cylinder grease? This is available from Interlube in smaller-than-5 gallon pail quantities. The stuff works just fine with rubber a/b gaskets, o-rings, etc., as well as with metal items.

Howard P.

WRM has used a lot of Brake Culinder grease for cocks in the past. But it is a soft grease and does not stay around very long. Also the stiffer greases do a better job of sealing. Where I use to work we used a WKM valve grease for traction motor couplings. It was a petroleum based grease with about 50% moly. But that still leaves open the question of o- rings or other rubber parts.

I have been using graphite grease for most metal on metal sliding and rotating valves in streetcar and interurban air brake (and door motor) work for several decades with good results. WABCO manuals for earlier equipments often specify this for various items such as rotary valves of brake valves.

My preferred brand is Dixon's Hy Heet GP, a product of Cummings-Moore Graphite Co. in Detroit. I have no affiliation with this company, I just like the product. A Toronto Transportation Commssion repair manual from the 1940's specified this brand and I was pleased to find it was still available.

This brand has EP additives, rust and corrosion inhibitors and resists alkalis and acids. I can't be 100% certain that long term use might affect "o" rings but have not observed any negative effects over several years. Graphite grease also tends to fill in pores of metal surfaces.

From their literature; "pumps like an NLGI-#1, has the body of an NLGI #3 and is an NLGI #2."

It also works well on pantograph shoes as graphite is conductive. We brush on an even coat roughly every seven operating days on our London & Port Stanley interurban car.

Gord