Hydrocomponents & Technologies Inc.

General information, assembly, and mounting Instructions for pressure vessels

Vessel assembly and installation


  1. Un-wrap vessel carefully. Do not use blades to cut over wrap material.
  2. Inspect components for damage and cleanliness.
  3. Install fittings. Use Teflon tape on threads. Do not over tighten.
  4. Install “O” rings.
  5. Lubricate “O” rings lightly with Glycerin.
  6. Install one end plug aligning U-Pin with U-Pin holes in housing if applicable.
  7. Install U-Pin or Retaining Clamps.
  8. Install membrane (using adapters if required). Ensure it is properly seated into end plug receptacle.
  9. Install second end plug aligning grooves with U-Pin holes in housing.
  10. Install second U-Pin. Do not use excessive force.

It is recommended that the fitting be gently and squarely placed into the port chamfer and rotated clockwise by hand. Resistance should not be felt until the fitting has rotated 3 to 5 turns. Install fitting by hand until it firmly locks on the port thread. Do not over-tighten and do not use a wrench. Hook up system and slowly pressurize it. Carefully tighten fittings wrench until any leakage has stopped. This is enough; any further tightening may cause threading in the port or excessive stress on the end plug material. This will cause end plugs to crack even though it is not apparent during installation.


The most common cause of end plug failure is over tightening or cross threading of fittings during installation. If you have any questions regarding this process, call HCTI at 760-598-0189.



HCTI strongly recommends the use of Glycerin as a lubricant for installing end plugs and membranes. It is water-soluble and will not harm membranes and housings.

Other lubricants may cause damage to membranes and cause housings to leak. It is recommended that Glycerin be swabbed around the housing from the outer most chamber to beyond the U-Pin retaining holes and on the end plug “O” rings.

To ease end plug removal, it is recommended that Glycerin also be poured or sprayed around the end plug allowing it to flow down to the “O” ring. Using this method and an extractor tool will greatly ease the extraction process without damaging the housing or end plugs.

Inspection and cleaning


When installing or retrofitting a pressure vessel assembly, always thoroughly clean and inspect every component, never use or reuse a damaged, worn or defective component. A 4” diameter vessel pressurized to 225 PSI exerts a force on the end plug and locking system over 2800 lbs. using damaged components may cause severe bodily damage and or death.

After installing or retrofitting a pressure vessel, logically and deliberately check all components including the vessel assembly, mounting clamps, fittings and hoses as well as the rest of the system for proper fastening and functioning.

When assembling a HCTI pressure vessel, it is recommended that the “O”-rings on the end plugs be cleaned and installed so that they are not twisted and are seated properly in the “O”-ring glands. They should be lubricated using only Glycerin along with the housing as described in the LUBRICATION section of this manual. Place the end plug in the housing aligning the U-Pin grooves with the retaining holes. Firmly press the end plug into the housing using both hands. Ensure that even pressure is applied so that the end plug goes in evenly and square. Do not allow it to tilt. Once the end plug is installed so that the U-Pin grooves are beyond the retaining holes, you may align the grooves to the holes by placing the U-Pin into the grooves and gently rotating the end plug. The U-Pin may now be installed as per the U-Pin section of this manual. Follow the same process for the remaining end plug.

To extract end plugs, remove the U-Pin. Lubricate the housing by pouring or spraying Glycerin in between the housing and the end plug allowing the Glycerin to flow down to the end plug “O”-ring. Place an end plug extractor tool into the center most port of the end plug and pull outward evenly. Sometimes a slight clockwise rotation of the extractor tool while pulling outward will help to dislodge the end plug. Caution must be observed so as not to damage the port thread while using this procedure. Many end plugs are difficult to remove because the “O”-ring have swollen and deformed. If you cannot remove the end plug, call HCTI for further instructions. Never strike end plugs with an object that may cause damage to the end plug or the housing.


All HCTI end plugs contain Female National Pipe Thread ports. These ports are tapered and caution must be exercised so as not to over-tighten fittings. Caution must also be observed when installing fittings into end plugs so as not to cross-thread the fitting especially when using metallic fittings.

NOTE: When a system is being started up, leakage may occur through “O” rings seals until the excess lubricant is dissipated. Vessel should not leak after operating pressure is applied (200 PSI – 250 PSI). If leakage continues at this point for more than 5 minutes, discontinue its use immediately.

U-pin installation and removal


HCTI recommends that U-Pins be installed so that the legs point down toward the deck. Installing U-Pins should not require excessive force. Never use a hammer or strike a U-Pin during installation. Place the U-Pin in the retaining hole insuring that the end plug is properly aligned. Place your hand across the U-Pin back and gently “wiggle” it down to the bottom-retaining hole. The more pressure applied during this process the more difficult the installation will become. Once the U-Pin is aligned in the bottom-retaining hole, firmly press it into place until the radius on the U-Pin legs lock into the radius of the housing. At this point gently tap across the U-Pin back to ensure proper seating.

If the housings are not isolated from the vibration or the system cycles excessively, you may require a U-Pin lock kit available from HCTI to ensure that the U-Pin “Creep” does not occur. These kits are inexpensive and ensure positive locking of U-Pins in all situations.

To remove U-Pins, first insure that any locking kits have been removed. Then place a non-metallic flat object between the U-Pin back and the top of the housing and simply pry upward until the U-Pin has released. It may be necessary to lightly tap the bottom of each leg to unlock the U-Pin, if so, use caution so as not to damage the housing or the U-Pin. Once the U-Pin has unlocked simply remove it by gripping the U-Pin back and pulling it out.



Retaining clamp installation


  1. Both halves of the clamp must be properly aligned on the housing groove with equal spacing between the V-Clamp halves.
  2. Both 10-32 bolts must now be run down to the flat loosely.
  3. Check for equal spacing and tighten both bolts equally. 1/2 turn at a time, maintaining equal spacing between V-Clamp halves.
  4. Do not over tighten bolts. They do not effect clamping strength.
  5. If bolts do not run down to the flat easily, (finger only) the clamp is misaligned. Do not force bolts.
  6. It is recommended that a single drop of “lock-tite” be applied to each bolt prior to installation.
  7. Ensure that all components are properly aligned and installed (including end plug backing plates) prior to installing V-Clamps.

Mounting vessels


When mounting housing to the system, caution must be observed so as to isolate the housing from any undo vibration. Housings should never be mounted directly to any metal supports without a proper cushioning device, consequently this will cause damage to both PVC and Stainless Steel housings.

Mounting clamps for PVC housings must not be over-tightened. This will place excessive stress on the housing, causing it to fail prematurely. PVC housings expand slightly when pressurized and must be allowed to "breathe". Ridged non-cushioned mountings must never be used.

Over-tightening of Uni-strut type clamps will cause damage to even Stainless Steel housings usually causing the Uni-strut to dent thin wall Stainless Steel housings and to become out of round.

IMPORTANT: Housing clamps must be set and tightened evenly but not over-tightened to prevent them from stripping threads.


Stainless steel vessels

Stainless Steel

All metals and alloys are susceptible to corrosion in some environments therefore; no single metal or alloy is suitable for all applications. Fortunately, there are generally one or more materials that will perform satisfactorily in a given environment. The stainless steels are versatile in that they are resistant to corrosion in a wide range of environments.

The fundamental resistance of stainless steel to corrosion occurs because of its ability to form a protective coating on its surface. This coating is a "passive" film that is resistant to further oxidation or other forms of chemical attacks. This passive film may be monomolecular in thickness, usually invisible, but generally protective in oxidizing environments; e.g., air, nitric acid. The passive film will, however, tend to lose its protectiveness in reducing environments; e.g. hydrochloric acid. Whether an environment is oxidizing or reducing is not always just a function of it oxygen content. The oxidizing power of a given solution may change with concentration, temperature and impurity content.

Chromium is the most important element as far as maintaining the passive film is concerned. With free chromium in excess of about 11%, steels do not normally form red rust, and so they are called "stainless".

Fundamental to most types of corrosion to which stainless steels are subject is the fact that halogen salt, primarily chlorides, easily penetrates the passive film and allows the corrosion attack to proceed. Chlorides are soluble, active ions and the basis for good electrolytes-good conditions for chemical attack on corrosion.


The non-rusting properties of stainless steels are attributable to a very thin, invisible oxide film that completely covers the surfaces of the parts and helps prevent corrosion from taking place. Theoretically, a machined, polished or pickled part will acquire this film rather quickly from the atmosphere. In practice, however, such parts may be contaminated with small particles of foreign matter, which must be removed to impart full stainless properties. Under certain conditions, a thin coating of rust may appear on the part. This is corrosion of the foreign matter and not the parent metal. The primary purpose of a passivating treatment is to remove surface contamination, usually iron, so that the optimum corrosion resistance of the stainless steel will be returned. Passivation is not a scale removal treatment.

Passivation will only impede surface corrosion on stainless steels and will not prevent it.