Potassium Hydroxide
Safety & Handling Specifications

Methods of Shipping

ASHTA Caustic Potash (KOH) is shipped in a variety of containers. Liquid KOH is shipped in tank trucks and tank cars. Solid forms of KOH are shipped in non-returnable steel drums, 50 lb. bags, and 2,000 lb. super sacks.

Liquid KOH is shipped in ASHTA's fleet of tank cars which include 10,000 and 16,000 gallon capacities. Some cars are insulated for shipping 50% KOH.

Each ASHTA tank car is equipped with the following devices:
5" safety valve (resetting spring type) set at 25 pounds
4" inner valve with either a wheel or handle
2" steam coil with connections and caps
2" plug cock with cap on the bottom

The tops are either bolted or screwed shut and are sealed with a gasket. In addition to the above, the top unloading cars are equipped with a 1/2" air pressure connection and 2" unloading (eduction) line near the dome.

Before filling, each ASHTA tank car is given a thorough inspection. The inside of the car is washed and a final inspection is made after it has been filled. The car is then sealed.

Liquid KOH can be shipped throughout the entire United States by authorized trucking companies who deliver the caustic in 1,000 to 4,000 gallon quantities. The liquid KOH is unloaded by trucking company personnel and pumped into the customer's storage tank directly from the truck. Your ASHTA sales representative will be glad to discuss with you the possibility of tank truck deliveries in your area.

Flake KOH is shipped in full open-head non-returnable steel drums which are sealed tightly with a flowed-in gasket in order to prevent any moisture or carbon dioxide in the air from reacting with the contents. It is shipped in 50 lb. bags and 2,000 lb. super sacks. Walnut KOH is shipped in 2,000 lb. super sacks.

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Safety Precautions

KOH is one of the strongest alkalis known. Its ability to react quickly with moisture to liberate heat and to dissolve all types of animal tissue makes it very dangerous when improperly handled. All persons working with or near caustic in any form should be thoroughly instructed in the hazards, proper handling, safety precautions, and first aid treatment associated with this chemical.

KOH is a strong, primary irritant which quickly destroys human skin tissue. The necessity for immediate action in the treatment of caustic burns is imperative in order to avoid serious ulcerating and scarring. It is urgent that competent medical attention be obtained immediately following prompt First Aid treatment after caustic burns in the eye or ear or over large portions of the body.

Store KOH drums in a dry place to prevent rusting and provide liquid storage tanks with a sufficient number of overflow pipes. Install as short of pipe lines as possible, using flanged joints with rubber gaskets instead of screwed connections. Use only iron, nickel, or iron-nickel alloy in valves or fittings. Shield packing glands of pumps to prevent accidental spraying.

Agitate the solution constantly when dissolving dry forms of KOH in water. Avoid splashing. Install adequate ventilating equipment if there is much KOH dust or mist in the air.

Keep equipment clean. Wash away all deposits of KOH caused by spillage or leakage, using a hose instead of a broom. Drain and wash all equipment before disconnecting it for repairs. If compressed air is used in any equipment, make certain that it is released slowly to avoid spraying.

Make certain that all workers are acquainted with proper handling methods for KOH and with the use of protective devices. Display warning signs in dangerous working areas which tell what to do in case of an accident. Inspect safety and handling equipment frequently to see that it is in proper working order. Do not store food near KOH or permit it to be eaten in areas where the product is handled.

Since KOH rapidly disintegrates leather, wool and other animal tissues, all wearing apparel used should be made of cotton or rubber, which resist destruction to a greater extent. Employees exposed to KOH should be provided with the following protective clothing:

  • Wide-brimmed hats
  • Close-fitting safety goggles equipped with rubber side shields
  • Respirators or hoods
  • Long-sleeved cotton shirts or jackets with buttoned collars and buttoned sleeves
  • Rubber or rubber-coated canvas gloves (shirt sleeves should be buttoned over the gloves so that any spilled material will run down the outside)
  • Rubber safety toe shoe or boot
  • Cotton coveralls (trouser cuffs should be worn outside of boots)
  • Rubber aprons

Rapid-action safety showers should be installed at all points where KOH is handled. Special eye washing fountains of the bubbler type or a hose with a gentle flow of water should be available for eye irrigation. Make frequent inspections to insure the proper working condition of equipment and show its location by means of special lights or signs.

First Aid cabinets should be placed at readily accessible points within the working area and marked with special signs or lights. In addition to the normal equipment for cuts and burns, each cabinet should contain a gallon bottle of 1% acetic acid solution for caustic neutralization as well as other reagent specifically mentioned in the following section. Cabinets should be inspected frequently to see that equipment is clean and those first aid solutions are replaced as needed.

Speed in removing KOH from the skin is of great importance since severe burns may result from prolonged contact. Dilute solutions as well as the solid alkali exert a destructive effect on tissues. Specific instructions for first aid treatment follow. All contaminated clothing should be removed promptly and the affected areas washed with copious amounts of water as soon as possible. If a 5% solution of ammonium chloride or zinc chloride is available, wash the affected areas with these solutions. A 1% solution of acetic acid (or dilute vinegar) is also helpful in neutralizing KOH and several large bottles of it should be placed around the working area. A 1% solution of acetic acid may be prepared by mixing one quart of commercial 28% acetic acid with 7 gallons of water.

If neutralizing agents are not immediately available, continue applying large amounts of water. Use of a safety shower is recommended where large portions of the body are burned. Do not try to apply oil or ointment of any kind to the burn areas. Treat for shock by placing the patient in a prone position and by keeping him warm. A physician should be notified at the earliest possible moment even when the injury appears to be slight.

Even if minute quantities of KOH enter the eyes, they should be flushed with water immediately for a minimum of 15 minutes. Use of a bubbler-type fountain is recommended for the purpose. Make certain that the water contacts all the tissues of the surface of the eye and lids by holding the eyelids apart. Prolonged washing with water is usually less damaging to eye tissues than are attempts at chemical neutralization. An eye specialist should be called as soon as possible and any applications of ointment in the eye should be made by him/her. Do not try to remove burned tissue from the eyes.

If KOH enters the ear, flush the ear with water, followed with a 5% boric acid or citric acid solution. If the external part of the ear is burning, treat as described under skin and apply ice compresses to reduce any swelling.

Make the patient drink large quantities of water and administer dilute vinegar, a 5% solution of ammonium chloride, or citrus fruit juices to neutralize the caustic. Induce vomiting with large doses of olive oil, egg whites, or flour and water paste. After the KOH has been diluted or neutralized, follow with milk or mineral oil to soothe the burned linings. Treat for shock and call a physician as soon as possible. If there is swelling of the tongue or lips, apply a 2% solution of boric acid, or ammonium chloride. Hold a small piece of ice in the mouth or apply ice compresses.

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Handling and Storage

Set handbrake and block wheels after car is spotted. Unloading track should be level.

Metal "CAUTION" signs should be placed before and after car, locked to the track, preferably near the entering switch, as warning to persons and switching crews approaching the car. Signs should not be removed until the car has been unloaded and all fittings disconnected. Signs should be 12" x 15", painted blue, and bear the legend in white: "STOP. TANK CAR CONNECTED"; the Gothic letters "STOP" should be 4" high and the others 2" high.

When the unloading operation is conducted in close proximity to passers by, it is recommended that a safety rope be stretched completely around the car and at least 6 feet away from it. "DANGER - CAUSTIC" signs should be attached to the rope.

A derail attachment should be placed at the A and B ends of car, approximately one car length away.

Water in ample quantity must be immediately available at the unloading rack. A shower bath provided with treadle valve is recommended. Caustic burns should receive water treatment and medical attention immediately. Refer to the section on "Safety Precautions" for instructions on first aid.

Unloading operations should be conducted by properly instructed, reliable employees under adequate supervision.

Make sure that the storage that there is sufficient space in the storage tank to hold contents of the car and that it is vented before connecting the unloading line.

45% liquid kOH begins to crystallize at -30ºC (-22ºF) and is completely solidified at -33ºC (-27ºF). Under normal winter weather conditions, 45% KOH remains in a liquid state and no steaming is necessary. On the other hand, 50% KOH begins to crystallize at +9ºC (+48ºF) and solidifies at -33ºC (-27ºF).

To determine if steaming is necessary, open the dome cover after the internal car pressure has been released and take the temperature of the liquid in the car. If upon arrival, the 50% liquid is above 70ºF, the car may usually be unloaded without steam. The same is true where bottom unloading is planned. In this case if the car is equipped with a steam jacketed outlet leg, it is recommended that steam be applied at that fitting to make sure the caustic is in liquid condition around the bottom outlet valve.

Equalize car pressure with the atmosphere by opening dome air connection. Certain cars have the air connection on top of the dome, others on the side of the dome. In case the car is not equipped with such an air connection, remove all except one of the dome cover bolts to relieve internal pressure. Then remove the last dome cover bolt and open dome cover.

All ASHTA cars have heater coils, the ends of which are located either under the car near the bottom discharge outlet or at one end of the tank car at the bottom of the shell head. If cars have both heater coils and steam jacketed bottom outlet and ends of heater coils are under the car, the two steam connections farthest from the outlet leg are for the coils and the two nearest the outlet leg are for that fitting. In case cars have both provisions for heating, connecting steam to both will accelerate unloading. Where outlet is not connected to a condensate return line, it is advisable that a valve be connected to an outlet pipe, which should be opened sufficiently to relieve condensate. As contents liquefy, the condensate flow decreases and partially closing the valve will conserve steam. It is also advisable that the condensate outlet connection be extended beyond the running board and the steam directed toward the ground with a suitable length of pipe, or run to the sewer. If a trap is used on the outlet, steam pressure in the coil should be limited to 50 lbs. per square inch gauge pressure. Excessive steam pressures applied to jacket legs may crack either or both walls of this fitting, especially in cold weather.

Steam pressure should be built up gradually to avoid rupture of heating coil. Care must be exercised not to heat contents to the point where expansion results in the valve rod handle being covered or where liquid overflows top the dome. Continued heating after caustic is liquefied wastes steam, and accelerates contamination of the product with metallic impurities when shipments are in unlined cars.

When the caustic is completely melted (the entire length of the bottom of uninsulated car tanks should be warm) the car is ready for sampling and unloading.

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Materials of Construction

Pipelines should be constructed of welded Schedule 40 carbon for low temperature KOH service where impurity levels are not of concern. At elevated temperatures the iron pick-up, although small, becomes more appreciable. Certain alloys are resistant to such action. Nickel, high nickel alloys, and stainless steel are especially suitable. ASHTA Chemicals Inc. uses 316 stainless steel for low and ambient temperature applications, while Nickel 200 piping systems are used in high temperature product applications.

Pipelines in the open or lines exposed to temperatures below the crystallizing point of the KOH solution to be handled should be heat traced and insulated. ASHTA Chemicals Inc. uses a minimum 1½" thick fiberglass insulation, with PVC jacketing that is glued at seams and stainless steel banded. Pipelines should be installed with sufficient gradient to allow complete drainage after use.

Welded flange joints throughout the piping installation are preferable to screwed connections. Couplings do not hold up well in caustic service. It is advisable that as few joints as possible be used in the loading lines. Gaskets should be either Teflon® envelope or Taskline® types.

Stainless steel (316SS) and Nickel 200 lines are TIG welded in an argon atmosphere.

Lubricated plug cocks made of cast iron, carbon steel, or 316SS construction are recommended for low temperature KOH service. Nickel 200 and Monel 400 are more chemically resistant in hot KOH service or where impurity considerations are important. Alternatively, Teflon-lined valves can be used. ASHTA Chemicals Inc. uses only flanged valves with flange safety spray shields over the flanges in KOH service.

If a pump is required, either an open-impeller centrifugal or a rotary positive-displacement pump may be used. Piston type pumps are also satisfactory. Installation of either type of pump should include a bypass or circulation line arrangement. This reduces wear on the pump and in many cases can be used as a means of controlling rate of flow. For ease of operation the suction line must be as short as possible. A pump with deep packing gland should be specified. The packing material should be graphite-braided asbestos or equivalent. In ordering a pump, caustic potash should be specified.

ASHTA Chemicals Inc. uses open-impeller centrifugal pumps from the following manufacturers:

  • The Duriron, Inc. - The Pump Division
  • Goulds Pumps, Inc.
  • LaBour Pumps

ASHTA Chemicals Inc. uses EPDM o-rings and 316SS or Nickel 200 wetted parts within its pumps. Chesterton 255 seals are used, with the inboard seal made from sintered silicon carbide against sintered silicon carbide and the outboard seal made from carbon steel against sintered silicon carbide. More details can be gathered from the A.W. Chesterton Company.

Provisions should be made in all pipelines and pumps for easy draining or for blowing out the entire system with steam, followed by air. Lines, pumps and tank car connections should be blown free of caustic before disconnection. Caustic Potash Liquid should never be permitted to remain in pipe lines. Pipes of less than 2" diameter and having abnormal length and height in discharge lines should be avoided.


  • Cuno, Inc.
  • Filterite
  • Pall Process Filtration Company

Storage of caustic potash drums does not require unusual precautions. These containers should be placed in a dry location because the metal in non-returnable drums may be weakened by rusting. Liquid caustic potash drums should not be washed out with water.


Aluminum, zinc, brass, bronze and copper are readily attacked by KOH and are completely unsuitable for use with KOH solutions. Iron and steel are the two most common structural materials used for handling and strong caustic potash even though these materials are attacked by these solutions having high temperatures. However, 45-50% caustic potash solutions may be safely handled in steel up to temperatures around 130ºF (54ºC). Nickel resists attack better than most metals. Nickel-lined equipment is often used when minimum contamination of the caustic potash solution by metals is important.

Tank Linings
Certain rubbers can be used for lining caustic potash storage tanks. ASHTA Chemicals Inc. uses graphite-loaded rubber as a lining in carbon steel tanks. However, rubber does not withstand high temperatures and should be limited to a maximum service temperature of 185ºF (85ºC). ASHTA Chemicals Inc. also uses epoxy linings in storage service, specifically PLASITE 9570 Hi-Resistant Protective Coating. Information on PLASITE coatings may be provided by the Wisconsin Protective Coatings Corporation.

ASHTA Chemicals Inc. has utilized Duraline Systems, Inc. to fabricate tanks and provide linings of process and storage tanks.

Storage facilities must have adequate capacity to accommodate the shipments to be received. Provisions must be made for a reserve supply of KOH between shipments. In the case of 16,000 gallon tank-car shipments, it is suggested that total storage space be at least double the tank-car capacity (32,000 gallons).

In the construction of KOH storage tanks, the wall thickness should be at least 3/8" on the body of units larger than 10,000 gallon capacity and 1/4" for smaller capacities. The pipe connection for withdrawing the liquid should be located a few inches above the bottom of the tank. A drain connection at the bottom of the tank should also be included to facilitate flushing. Fill lines into the storage tank should be dip tubes. This arrangement will minimize the pick-up of carbon dioxide from air, thus causing a small portion of the potassium hydroxide to be converted to potassium carbonate.

If the storage tank for 50% KOH is located where the temperature will fall below 60ºF, it should be equipped with a steam coil near the bottom and close to the outlet. Alternately, a steam-supplied bayonet heater with a temperature regulator can be used. A small coil loop of 1 to 1¼" Schedule 80 steel pipe connected to a source of low pressure steam (12 to 15 PSIG) is adequate. Avoid storage temperatures above 130ºF. Insulation of tanks although desirable is not necessarily a requirement. The most economical thickness for common types of insulation is 2". ASHTA Chemicals Inc. uses fiberglass insulation with PVC jacketing held in place by glued joints and stainless steel banding for storage tank insulation.

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Tank Car and Drum Unloading

If liquid Caustic Potash is shipped in 55 gallon (660 pound) steel non-returnable drums, the following procedures are recommended:

  • Stand drum on end with plug at highest point and carefully loosen the end plug to equalize internal and external pressure. Replace bung with a standard pipe nipple provided with an all iron valve.
  • Return drum to horizontal position, with side-bung uppermost. Loosen side-bung sufficiently to prevent air-binding while emptying, controlling flow by the valve. Unloading by gravity is recommended. The use of compressed air is unsafe and should never be used.
  • To remove body plug, use a pipe wrench or plug wrench with a long handle. Face away during the operation. After plug starts, give one full turn. If internal pressure vents, allow reduction to atmospheric pressures. Loosen and remove plug.

All ASHTA tank cars may be unloaded through a bottom discharge nozzle.  Some cars, equipped with stand pipes, may also be unloaded through the dome by means of air pressure.

For bottom unloading, it is common to discharge by gravity flow through a pump, or directly to a storage tank at a lower level. Unloading through the bottom by gravity through a pump is the most common method used. There is a two inch plug cock on the outlet leg from the car. Compressed air is essential when unloading through the dome and may be used when discharging through the bottom outlet. Pressures up to 20 psig are permissible.  Note: the car safety rupture disc is set to relieve tank car pressure at 25 psig.  

The clearance between the bottom of the rail car and the bottom of the plug cock varies between 15 inches and 18 inches. This distance should be sufficient for the installation of a short nipple and elbow into the plug cock.

Before starting unloading operations, make sure that pressure within the car has been released, that caustic is completely liquid, and that delivery lines are thoroughly heated. Preheating of lines in cold weather will help prevent clogging and may be accomplished by blowing steam into lines through certain connections. Insulated lines are advisable if strong caustic is being hauled.

Unloading operations must be carried out strictly in the order listed under each method of unloading.

When compressed air is used for discharge of product, it is important that all dome fittings be checked for evidence of leaks or other defects before unloading. Should leakage occur, particularly at dome fittings, unloading operations should be suspended, pressure on the tank released, and the problem reported to the supervisor. When in doubt, contact shipper for instructions. It is advisable that the air supply line be provided with an oil trap.

  1. Securely fasten dome cover in place.
  2. Remove the protective housings from air inlet and from dome discharge fitting. On some cars the air inlet and dome discharge fittings are enclosed within a single housing, both being equipped with valves. On other cars the air inlet may not be fitted with a valve. Before applying air pressure to a car, make sure that the storage tank is well vented. The removal of the manway cover from the storage tank is advisable for this purpose.
  3. Connect unloading line (flexible steel chemical pressure or standard pipe with swivel joints) to dome discharge connection.
  4. Connect air supply line (high pressure hose or standard pipe) to air inlet on top of dome. Line should be equipped with release valve, safety pop valve set at not more than 23 lbs. pressure gauge, pressure reducing valve set at not more than 20 lbs. and air shutoff valve. These valves should be iron or iron and Monel trim construction.
  5. Apply air pressure slowly until there is a normal flow of liquid to storage tank. Eliminate all air or liquid leaks by tightening fittings. Adjust air pressure and maintain it until the tank car is empty. A drop in pressure and sound of air rushing through the discharge pipe indicates the car is empty. Continue air flow until the unloading line is completely empty. Shut off the air, open release valve to relieve all internal pressure, and allow the discharge pipe to drain. If, during this procedure, the frangible disc in the safety vent is broken in cars equipped with one, a new frangible disc of the same material and thickness must be installed. Use of other materials in this fitting may result in rupture of the tank.
  6. Close air inlet cock and disconnect plant air fittings from air on dome. Do not disconnect unloading line until the tank is at atmospheric pressure and unloading line thoroughly drained.
  7. Disconnect unloading line from discharge pipe fitting and tightly replace cap or plug, taking care that drainage does not spill on tank car. On cars so equipped, close valve on dome discharge fitting. If there is an accidental spillage, immediately wash it off with water to protect trainmen handling the empty car on its return and to minimize car damage.
  8. When inspecting car to determine whether it is empty, do not use an open flame as a source of light, as an explosive mixture, consisting of hydrogen and oxygen, may be present. Protect face, eyes and neck from caustic mist.


Unloading Through Bottom by Gravity Flow

  1. Open the dome cover and leave open during unloading.
  2. Remove plug from auxiliary cock attached to bottom discharge leg. Bottom plug is generally screwed into an auxiliary valve or cock which is attached to the discharge leg. In case there is no auxiliary cock and plug is screwed directly into bottom discharge leg, a pail should be placed in position to catch any liquid that may have leaked past the outlet valve. If leakage shows upon starting to remove the plug, the plug should not be entirely removed but sufficient threads should be left engaged, and sufficient time allowed permitting drainage of any accumulation of liquid from the discharge outlet before removing plug entirely. If leakage persists, showing that outlet valve is not properly seated, valve rod handle should be turned several times in both directions in an effort to reseat the valve. If it is impossible to reseat the valve with this procedure then it will be necessary to unload the car through the dome.
  3. Attach the unloading line.
  4. Return to dome and open bottom outlet valve by turning valve rod handle. If outlet valve handle or wheel does not move with a light pressure, it indicates that frozen material still remains in the bottom of the car and that further steaming is necessary. Do not attempt to force valve open. This may break the valve and make bottom unloading impossible. The valve handle may be located in the dome or the rod may extend through the dome head to the outside. In the latter case, examination of the dome will disclose the valve rod handle or a removable cap, which on being removed and inverted becomes an operating hand wheel when fitted back on the valve rod. If the valve handle is inside the dome, the operator should protect his/her face and head by holding them to one side while operating the valve.
  5. Open auxiliary cock, if car is so equipped, and allow contents to flow to storage tank.

Unloading Through Bottom with Pump
Follow the same procedure as outlined for gravity flow. The connection necessary at bottom outlet are the same as for gravity flow, but the discharge line will be connected to the inlet of a pump which may be primed by gravity flow. A centrifugal pump is recommended.

Unloading Through Bottom with Air Pressure
Make sure dome fittings are tight and not leaking and that tank is well vented

  1. Securely replace dome cover.
  2. Connect air supply line to air inlet on dome. Line should be equipped with release valve, safety pop valve set at not more than 23 lbs. pressure gauge, pressure reducing valve set at not more than 20 lbs. and air shutoff valve.
  3. Open auxiliary cock.
  4. Apply air pressure until car is empty. A drop in pressure and sound of air rushing through discharge pipe indicates that tank car is empty. Continue air flow until unloading line is completely empty. Shut off air, open release valve, and allow discharge line to drain.
  5. Close air inlet cock and disconnect plant air fittings from air inlet on dome.

Empty Car Return
Unloading Line - After blowing out with steam, followed by air, close bottom outlet valve, then disconnect line and securely replace bottom outlet plug or cap.
Heating Coil - Disconnect steam lines and blow coil out with compressed air. Do not replace caps on inlet and outlet connections; let caps hang by their chains. If the car is equipped with valves at these points, leaves valves open to permit drainage of coils in order to avoid freezing.
Steam jacketed outlet leg - If steam is applied through special fittings of this leg, do not replace caps after disconnecting steam lines. Allow them to hang by their chains to avoid freezing and possible cracking of the outlet leg. After removing connections, replace closures on all other tank openings. Close and securely fasten dome cover.

The four 10¾" x 10¾" D.O.T. caution placards on the sides and ends of the tank car must be removed or reversed. The empty tank car must be offered to the receiving carrier either without placard, or preferably with four placards reversed to show the "Residue" side, in conformance with D.O.T. Regulations. Return empty tank cars promptly in accordance with shipper’s instructions. Shipper's routing instructions must always be followed. If instructions for movement of cars have not been received, call shipper collect for them. Caustic cars are inspected by ASHTA after each trip, and are washed out, tested and repaired before being filled. Tank cars should not be washed out with water. Under no circumstances should anyone enter a car.

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