FLEET MAINTENANCE PART II
INTERIOR TANK TRUCK CLEANING

Background

The chemical industry touches every facet of American life: from housing, transportation and health to agriculture, industrial development and economic security. Because of their versatility, tank trucks have played an important role in making chemicals available everywhere. The commodities they haul very often represent a great deal of money to all the companies involved in the shipment.

First of all there is the manufacturer who after considerable investment in research, development, marketing and manufacturing must see that their product is delivered exactly as it was represented during the sale. Then there is the customer who has expensed time and money to set up his production lines to handle the product when it arrives. If the load arrives in a contaminated state, the tank truck operator faces considerable expense in terms of high insurance claims and nonrevenue operating cost for the drivers, tank trucks, dispatchers, tank cleaners and in effect, his entire organization.

With the present cost of equipment and labor, it is necessary for the operator to get as much use from his equipment and road time as possible, which means back hauling whenever possible. Without proper cleaning facilities on both ends of a routing, he is apt to unload in one city and deadhead the tank truck and driven several hundred miles before it begins to earn revenue again. These are some of the reasons why tanks need to be cleaned thoroughly the first time.

Basic Cleaning Methods

Interior tank truck cleaning is often considered to be a complicated procedure, but in essence the procedure is not much different than washing dishes, cleaning carburetors or other metal parts. Knowing exactly how a spinner or spray ball works, the chemical cleans, why heat is used, or for that matter, what is really happening inside the tank will help you overcome many of the difficult problems often encountered.

Interior tank truck cleaning evolved from the principles of immersion tank cleaning. First there are cold immersion tanks which hold cleaning solutions into which parts are dipped and permitted to soak until the soil is chemically loosened for final flushing with water. Recirculation or agitation features were later added to speed up the cleaning time. Agitation of the part or recirculation of the chemical brings fresh strong chemical into contact with the soil and gives mild flushing action at the same time which helps remove the loosened outer layer of soil. This permits deeper penetration of the chemical into the soil until the metal surface itself is reached. Cleaning time was further accelerated by the addition of heat which helps break down certain soils and serves to activate the cleaning chemical. Then impingement from spray jets was incorporated and spray washers were born. Hot impinging sprays coat the parts to be cleaned, provide penetrating agitation and flush the soil away in one continuous process. Obviously a tank truck cannot be placed in an immersion tank or a spray washer, but the principle is the same. Instead spray applicators are placed into the tank truck to accomplish cleaning.

Depending on the soil in the tank truck, cleaning can take one or more of several forms: steam only, heat or cold water only, or any one of these methods with a cleaning compounds added. in almost all cases the spray applicator will simply be one or more spray balls, discs or a high pressure spinner system.

Spray Ball Applicator

The spray ball applicator is a simple ball 2½" in diameter with small holes in it to create a spray pattern. A variety of spray balls with different spray patterns are available depending on the application. The most common type of spray ball available is the Vibra-Jet. These are designed to pass through the standard three inch clean-out opening(s) in the top of the tank.

The spray ball is placed approximately three feet into the tank truck from the top and hot chemical solution is sprayed through it which duplicates the agitated immersion tank or spray washer cleaning effect. The properly designed spray ball for tank truck cleaning will only have holes in the upper sphere of the spray ball to direct low pressure impinging streams of hot chemical to the top of the tank where they can cascade down the sides of the tank. The cascading downward action covers the entire interior tank surface and flushes away the soil as it is loosened by the hot chemical.

Spray balls, properly placed, will give infinite coverage of every single square inch of the tank's interior within five seconds after the supply pump is placed into operation. The area of coverage of one spray ball, placed three feet from the top of the tank, is six feet in all directions. Thus, each ball will cover a 12 foot section of the tank. Multiple compartment and baffled tanks can be cleaned in one operation, as long as there are enough clean-out openings along the top of the tank to handle the number of spray balls needed for complete coverage.

One important thing that must be noted is the whipping, vibrating action of the Vibra-Jet streams. You do not get the same action as a bathroom shower head. The solution flowing into the ball at approximately 25 pounds pressure, creates a strong turbulence that constantly changes the needle-like streams spray pattern, which assures infinite coverage with impingement. This whipping, vibrating action, when witnessed in the open, makes the ball look as if it is spinning, yet there are no moving parts to wear or give maintenance problems. Spray balls are effective on Bunker C, black oil, Bunker #6, etc.

Spray Disc Applicator

The spray disc applicator is a rotating device designed to distribute a dense spray giving a complete 360° coverage of all internal surfaces of a tank. Self operated by the cleaning fluid, the unit revolves in a slow controlled manner so providing quick and effective coverage of the tank interior. Depending on the type of disc, flow and pressure the spray disc can cover from 5’ - 22’ in all directions. The most common type of disc applicator is the Fury Turbodisc. It can be used instead of spray ball applications in 3" clean-out ports and offers these advantages:

- no small holes to get blocked
- lower water consumption - being rotational the disc applicators does not have to cover the whole tank at once
- no need for hole patterns drilled to suit the job

Spinner Applicator

The spray ball or disc type applicator is not the only, or always the best, style applicator to use. Where the spray ball or disc principle of operation is one of low pressure-hiqh volume, units such as the spinners, operate on the principle of high pressure-low volume. On clean bore tanks, these systems are especially effective since they are capable of cleaning the full length of a tank from a central position. on those tank trucks void of clean-out openings, the spinner system is a must, since the centrally located manhole is the only accessible opening to place the spray applicator.

This type of unit, employing two or four large nozzles, rotates on an axis that gives 360° coverage. The cleaning effect is much the same as can be accomplished if two men went into a tank with two fire-fighting nozzles. The entire unit is geared to give a definite pre-determined spray pattern and the speed is always controlled to prevent its operating so fast it would skip sections of the tank.

The driving force of this particular unit is the flow of the cleaning solution forced through it by the application pump's pressure. The pattern of operation is controlled by the pressure generated. Depending on the type of spinner used a liquid pressure of 20 psi or more will drive the spinner. In simple terms, the more gpm that passes through the spinner, the faster it will operate and clean, and vice versa. It should be noted here, generally speaking, the slower this type unit turns for a given nozzle pressure, the better the cleaning. It has an advantage over many other type applicators because of the high pressure chiseling action of the streams. However, rinsing can sometimes be slightly less effective than spray ball or disc cleaning, since the streams themselves tend to have limited coverage. Therefore, a burst rinse operation should be used on final rinsing. Burst rinsing is accomplished by stopping the pump and permitting a complete drainoff of solution, restarting the pump for 5 second intervals and again permitting drain-off, until perfectly clear water runs from the tank. Burst rinsing is effective for working such non-soluble soils as oil, grease, tallow, etc. down the sides of the tank and out the drain. Fury, Orbijet, Sellers, Butterworth, Hydrolance, Gamajet, Wellcojet, etc. are all common spinners to be found in the industry.

Pump and Hose Cleaning

The simple installation of valved pipe nipples to the solution tank permits the direct hookup of the pump to the solution tank and is the surest way to clean pumps and hose interiors. The operation of the pump automatically recirculates the cleaning solution through all parts of the pump and the hoses. This operation can be performed even while interior tank cleaning facilities are being operated.

Where both interior and exterior cleaning of hoses are required, several methods can be used. There is a simple device made from a 20 foot section of 12 inch flanged pipe. This pipe is mounted on the wall with piping running to one end from the solution tank, and piping running from the other end back to the solution tank. One end of the flanged pipe is permanently covered and the other end has a cover that can be easily removed.

Hoses are inserted into the tube and the end plate is locked closed. By starting the application pump, solution is pumped into the tube, passes through and around the hoses to the other end, where the return pump returns it to the solution tank. Rinsing is generally done manually.

More elaborate systems are built, consisting of a large open trough equipped with its own pumping system. The entire trough is filled with the desired cleaning solution and the pumps recirculate the solution from one end to the other. The hoses after cleaning, are removed and layed on a drain trough, and later rinsed with clear water.

Another method is to use an electric drill with a long shaft, equipped at one end with a heavy fibre or wire brush. The entire interior of the hose is reamed out during cleaning, but this method is seldom recommended. It does the job, but the hose life is reduced appreciably.

Recirculation Systems

Spray ball, disc or spinner systems can only be used economically by recirculating the cleaning solution. A recirculation system can be as simple as a self contained system or very elaborate incorporating the use of pumps, tanks and heaters.

The self contained system is only capable of working where spray ball applicators will do the job. This type of system consists of placing a spray ball and approximately 100 gallons of cleaning solution into the tank truck. The unloading line is then connected to the power take off (PTO) pump or Putt-Putt, whichever is available, and the discharge and is connected to the spray ball probe. Another line should be connected between the intake side of the PTO and the tank truck's drain valve to complete the system. Steam can be added for heat if necessary. Two spray balls can generally be used simultaneously with a single PTO. After cleaning, the solution can be pumped off to drums or a suitable holding tank for reuse or disposal. Rinsing can be accomplished by feeding fresh water from a fire hydrant to the pump's intake. Rinse water should be permitted to run to the drain and should not be recirculated. PTO pumps cannot operate spray discs or spinners.

A more elaborate system consists of a solution holding tank, supply pump to operate a spray ball(s), disc(s) or spinner, and return pump for recirculating the solution back to the holding tank. Additional tanks can be added to hold pre-rinse water; additional chemical solutions, such as strong alkalines for stainless steel tanks and inhibited type cleaners for aluminum tankers. Final rinse tanks are more often added as a reservoir for hot water. Heating systems, hose washers and catwalks with drop platforms may also be a part of the system.

Solution Tank Design

Heavy deposits in a recirculation system can clog spray applications, valves and piping. In-line strainers and/or baffled tanks are often used to separate out contaminates from the cleaning solution. The system must be periodically shut down so that the strainers can be cleaned out. Inline strainers can be located on the inlet side of the return pump.

All contaminates fall into three basic categories, the first of which are settleable solids which will sink to the bottom of the tank. The second is floating solids which will rise to the top of the tank. The third is suspended solids which remain suspended in the solution, and cannot be easily removed and cannot do damage through clogging of the system. By placing detention baffles in the line of flow in the solution tank settleable solids can be dropped to the bottom and floating solids raised to the top. As the solution life is used up, the tank is drained and flushed, thus ridding the system of bottom settlings. The floating material can be skimmed off as necessary.

Foaming Problems

Due to the nature of many chemical cleaners, especially when contaminated with other chemicals picked up during the cleaning process, foam can accumulate rapidly, both in the tank truck and the solution tank. Certain steps can be taken to either avoid this completely, or at least retard the foaming action. Since foam is simply air bubbles, the elimination of air will stop foaming, and cutting down on air entrainment into the solution flow will drastically retard its reaccumulation. The most important step in eliminating air entrainment is to balance the gpm output of the application pump with the gpm intake of the return pump. If the return pump is operating at a gpm capacity that is greater than the application pump's output, it will drain the tank truck quickly, thus whirlpooling the solution and eventually draw big gulps of air into the return line. When this air reaches the pump, it will whip the solution into a froth and can easily cause a vapor lock which can damage the pump. Most of this foam will be pumped into the solution tank.

By the same token, if the application pump puts out more gpm than the return pump can handle, a ponding will occur inside the tank truck. As the applicator's streams or rundown hits this pond of chemical, it can easily whip it into a heavy foam condition.

Pumps should be purchased as close to the same gpm rating as possible, and globe valves installed in the discharge side of each pump. These valves can be used to throttle the flow until the system is balanced. ONCE THE SYSTEM IS IN BALANCE, THE VALVE HANDLES SHOULD BE REMOVED TO ELIMINATE FUTURE TAMPERING.

Another source of air entrainment is where the return line feeds into the solution tank. If this enters the tank above the solution level, it will splash heavily into the tank, creating turbulence, which adds more air to the solution. Instead the return line should enter below the solution level to cut down on turbulence.

A foam depressant can be used for knocking down the foam, but foam depressants are not always effective. Its chances of success are better if the previous steps have been taken.

Chemical Cleaners

The above has emphasized the importance of the mechanical systems for cleaning. Yet these systems are merely the methods of applying the most important element of all, the cleaning agent. No system can clean tanks without the proper chemical, therefore, the selection of the chemical cleaner should be done with care. An error in testing and analyzing this part of the cleaning phase could cost manhours, money and can sometimes ruin a complete tank truck.

It is the chemicals' job to dissolve, disperse, loosen, melt, emulsify, or digest the soils to be cleaned from the tank's interior. It is chemically impossible for one cleaner to solve all problems. Everyday of the week researchers are working on paints that nothing can remove, and everyday we are given the task to furnish a chemical that will remove them anyway. So far, to the best of our knowledge, they have been successful only three times; with latex, sulphur, and a Polymer Resin. And we have latex and the resin on the run.

In the selection of chemical cleaners, the wise chemical salesman will make no recommendations, promises, claims or sales until he has thoroughly surveyed the tank truck operator's problems. The following method of surveying the job should not only be expected by the operator, but insisted upon by the sales representative.

1. Determine the capabilities of the mechanical system for cleaning.

2. Supply sample bottles to the customer, labeled, for gathering individual samples of the product that have proved difficult to remove.

3. Determine what metals, such as aluminum, steel, stainless steel, or artificially lined tanks are used for shipping these products.

4. Submit these samples to the laboratory for analysis. These samples can be applied to panels of similar metals. Cleaning agents can then be tested for their effectiveness.

5. Obtain a full written recommendation from the laboratory with concentration, temperature, safety factors and other pertinent data.

6. Take the time and effort to judge the recommendations carefully and follow the laboratory's suggestions whenever possible.

7. Forget the price per pound and base the purchase upon the number of tanks that can be cleaned per pound of chemical, without overlooking the better results, manpower savings, speed of cleaning, and safety of equipment and personnel.

8. Remember that Government agencies do not protect the operator from fly-by- night suppliers that would sell anything to make a buck.

9. Once a manufacturer has been decided upon; a product has been recommended and selected; give a full operational run and expect only the best, and above all, only the possible results.

Some of the more difficult cleaning problems you can expect to encounter are the removal of alkyd resins, acetate resin, acrylic acid, acrylics, adhesive, butylisocyanate, butyl acrylate, contamined PVA, caprolactam, DER resins, dectyl octyl methacrylate, ethyl acrylate, epon NOI, epon resins, flat lacquer, flexon, glacial acrylic acid, glue and liquid glue, lacquer sealer, lacquer, latex, methyl methacrylate, monomer, plastic material, plastic pellets, plastic resin, plastic synthetic, plastic material pellets, paint emulsion, polyether resin, polyethylene, reliance varnish, resin and liquid resin, mixed resins, spent lactum, stryene monomer, synthetic latex, synthetic resin and plastic synthetic resin, wet strings resins and waste chemicals. These and other hard to remove materials can generally be cleaned by one of the following methods. The method to use, again, can be determined by submitting samples to the Transportation Laboratory for testing.

The simplest method calls for using a caustic detergent at 180°F followed by a 180°F rinse and blow or air drying. Many shippers use a flake caustic for cleaning; however, a caustic compounded with wetters and emulsifiers is more effective, rinses better, lasts longer and does not cost much more to use. Clean Out between 8 - 16 oz. per gallon is an effective product to use. It can be beefed up for tougher jobs by the addition of Activate at the rate of 10 lbs. for every 100 lbs. alkaline powder used. Broco 5200W can be used in place of Clean Out for less demanding applications. In order to hold cleaning cost down make up solutions can be handled by adding a mix of Broco 5200W and Activate at the rate of 100 lbs. to 10 lbs. to the solution tank until the desired pH level is attained.

For harder to clean jobs a presolve method is often employed. The presolve method incorporates the use of a strong solventized chemical to penetrate and loosen the product to a point where it can go through the above cleaning process. Milanco has not developed a product for this application because the process is not always effective and it is very expensive. The truck is tied up longer and a good deal of chemical is used. These chemicals generally must run to waste rather than be recirculated since the active life of the solvent is short. After the presolve is rinsed from the tank the caustic wash process can begin.

A third cleaning method literally eliminates the presolve and can be used with most cleaning procedures. This method, a compounded caustic cleaner used with a solvent additive, eliminates downtime involved with using presolve procedures and gets the tanker through the turnaround period faster. This method requires using either Broco 5200W at concentrations of 6 oz. to 10 oz. per gallon with Rinse Aid LF added at the rate of 2.5 oz. per gallon. It has been further established that the addition of Rinse aid LF provides positive foam reduction during cleaning. Do not be turned off by the high price of the solvent additive; its benefits including low use concentrations far outweigh other options. Price objections should be handled by totaling up the cost of current cleaning methods used. Consider, for example, that over 95% of the cost is represented by labor, equipment, steam, water, electricity, fuel, etc. The true measure of an efficient cleaning operation is not the price per pound of a cleaning product. Actual cleaning results and unit cleaning costs provide a more accurate measure.

Most other products including petroleum products, vegetable oils, tallow, lard, etc. can be cleaned following these five basic steps for fast and effective interior cleaning---

1. Drain the tank as much as possible and pre-rinse with hot water at 1800F.

2. Spin with a cleaning solution heated to at least 180°F. Terj at 6 - 8 oz. per gallon can be used on aluminum tankers or one of the aforementioned products will be effective on stainless steel tankers.

3. Rinse with hot or cold water as the proper end operation determines.

4. Clean valves and hoses.

5. Blow or air dry the tank interior whenever possible.

If your account is cleaning some products with only hot water, cold water or steam, you cannot be of help to him.

You may also find vapor cleaning used which has undoubtedly proven to be an excellent and economical method of tank cleaning. It has its limitations, since it cannot clean behind a layer, or bubble of water. On asphalt or tar and similar products, it is practically the only true economical method of removal. Recirculation of a solvent type cleaner can be used, but safety precautions should be established, since the spraying of volatile solvents can spark at the wrong time and be dangerous.

Deodorizing and Sanitizing Chemicals

Once the cleaning process is completed, tank trucks which have carried offensive smelling chemicals must be deodorized and, in the case of food transports, sanitized. In many cases, tankers are rejected by the tanker's prospective customer because of contamination by offensive odors and/or residues "left over" in the tanker, even though it has been chemically cleaned. odor causing chemicals can penetrate the pores of the tanker skin and rubber hoses and in some cases, become locked-in valve chambers.

These odors can be eliminated by using Milanco Odor Killer after the tanker has been washed. This can be done by adding Milanco Odor Killer to the final rinse water at the rate of 1 lb, to 50 gals. Another method that is effective calls for adding one packet of Milanco Odor Killer to a five gallon pail of water. This is then dumped into the tank truck and a steam line Is hooked up to the bottom of the tank. Once the steam line is cracked open, the vapors will carry the deodorizer up the walls of the tank and into the pump and valves. This will also freshen up an account's treatment pond where the effluent eventually winds up. odors emanating from the ground where effluent gets dumped will also be eliminated.

Additional benefits from this final process include reduction of downtime and elimination of additional cleaning cost for tankers that are rejected at the pick up site. This final process is your client's assurance that his tanker will pass any test for pH, odor or surface bacteria administered at the pick up site.

After the tank interior has been cleaned and deodorized the disinfectant/ algacide should then be applied. This is only necessary with food transports. The FDA - the EPA - the DOT and others have all influenced regulations governing the sanitation of food transports.

Conclusion

This information constitutes only a small portion of the many problems confronting haulers of chemical products. There are many individual situations that demand different cleaning procedures and different equipment designs if the situation is to be approached in an efficient, cost-effective manner. Your presentation should be tailored to reducing the customer's cost by reducing cleaning time and tanker rejections. The combination of gallons per minute, temperature, pressure, and impingement with the proper cleaning compounds is the formula for correct cleaning at the lowest cost per unit washed.