Myths and misunderstandings about workshop pressure pots

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Greg Davies takes a look at the pressure pot and how it can be used for a wide range of workshop applications.

Pressure pots are a versatile and durable piece of equipment that can be used for a wide range of applications including spraying polyester, sound deadening material, large two-pack spray jobs such as trucks, buses, boats or any situation that requires more than one litre of product.

Despite common misconceptions, pressure pots are easy to set up, easy to clean, provide excellent fluid control and due to product being consistently pushed to the gun head, the user can spray at any angle, including upside down.

To highlight some of the areas of confusion and set the record straight, we will walk through the process of setting up a pressure pot system.

Pressure pots come in a number of forms in terms of size, agitation (stirring) mechanism, and fluid delivery. Below is a quick overview or pressure pot types.

Size – Sizes can range from small pots (2L, 4L) up to larger pots (10L, 20L). The size of the job dictates the size of the pot required.

Agitation – Agitation is the ability to stir products which may separate over time. You can choose pots with no agitation, manual and air motor driven options.

Fluid Delivery – Fluid delivery is the method by which product is extracted from the pot. This is either via top or bottom outlet.

**NOTE – Bottom outlet systems are the easiest to clean.

Step 1 – Remove and inspect lid
Remove the top of the pressure pot and inspect the gasket. Look for cuts and make sure it is not distorted in any way.

Step 2 – Fill pot
Fill the pressure pot with product, ensuring you do not exceed the pot’s capacity.

**NOTE - Most quality pressure pots bigger than 2L will have a paint liner which makes for easy cleaning.

Step 3 – Sealing the pot
When sealing the pressure pot lid, ensure you do not over-tighten. The best way to ensure this is by tightening the securing mechanism (either screw lid or wing nuts) to the point where it stops with light to moderate torque pressure, and then give it one quick “nip” to secure. Over-tightening will likely damage the gasket.

NOTE – Larger pressure pots use wing nuts to secure the lid. The proper method to secure these is by tightening the two horizontally opposed nuts to the point where they stop, followed by the remaining two nuts; then one quick nip up on all four to secure.

TIP - If a leak is detected once the pot is pressurised, it will need to be de-pressurised before you are able to re-tighten.

Step 4 – Hose set up
Pressure pot hoses come with fluid and air lines. The fluid line is usually clear and has a larger diameter.

Connect one end of the fluid line to the fluid outlet on the pressure pot (3/8 bsp) and the other to the fluid inlet of the spray gun. The air line needs to be connected to the air regulator on the pressure pot with the opposing end connected to the air inlet on the gun.

DO NOT use thread tape. Most quality pressure pot systems use nut and tail air connections that have a conical (tapered) seat eliminating the need for external sealing products.

NOTE – A common misunderstanding: the air regulator on the pressure pot does not control the air atomisation pressure on the spray gun. It ONLY controls pressure going into the pressure pot.

One of the biggest issues with pressure pots is air getting into the fluid line. If you see bubbles in the fluid line check to make sure you have adequately tightened the fluid connection to the pressure pot and gun.

Step 5 – Air pressure
Before connecting the air, release the air regulator on the pressure pot all the way down (anti-clockwise). Connect your air line to your pressure pot ensuring you are using filtered air so that you do not contaminate the product. Close your relief valve and slowly turn the air regulator up (clockwise).

TIP – Normally you will only require between 2 and 5 PSI of pot pressure when spraying two-pack and enamel. Many users think 40 PSI is required; however you only need enough pressure to push product to the gun head. To test this turn off the atomisation control on your spray gun, remove the air cap of and pull the trigger. Correct pressure in the pot will produce a small arc of product that travels no more than 50 – 70mm out of the gun nozzle. If it shoots across the room your pressure is too high.

NOTE – Thicker products will require more pressure to get the product to the gun head. Therefore when spraying polyester or sound deadening material you will need to adjust your pressure up a few PSI to get the require product flow.

Step 6 – Begin spraying
Once you know you have the right fluid pressure, adjust your atomisation pressure at the gun to the lowest desired level and begin the spraying process.

TIP – A large plastic bag placed over the pressure pot while spraying will prevent over-spray getting on the regulator gauge, gumming up relief and safety valves and generally making a mess of your equipment.

Step 6 – Cleaning
Cleaning is easy. Firstly, release the air regulator on the pressure pot all the way down (anti-clockwise) and de-pressurise the pot via the relief valve. You can now safely disconnect the air line from the pressure pot. 

Remove the lid and empty any excess product from the pot, wipe the liner and pick up tube (if applicable) with some thinners, place two litres of used thinners in the liner, reconnect the lid and air line and turn up your pot pressure up to 30 PSI. 

Turn off the gun atomisation pressure and flush out the system. Repeat the process with two litres of clean thinners and clean you spray gun in the usual fashion.

Pressure pots are pressure vessels and can cause harm if not used properly. Regularly check your equipment to ensure safety blow-off value and pressure gauge are working properly. Safety valves should activate at approximately 40 PSI of pot pressure. To check this, set up empty pot in the manner we have described above. Slowly increase the pressure until the safety valve activates. If you get to 50 PSI and the safety valve has not blown, have the unit serviced. Quality pressure pot suppliers will have spare parts available and can service your equipment for you.

To get more information about pressure pots and their set-up, feel free to contact Garry Benson at GnG Sales.

To see a video detailing the steps described in this article, go to YouTube and search for ‘Pressure Pot Set Up’.

There are a  wide range of pressure pots available for every application, big and small.

Tech Tips is researched and written by Greg Davie of GnG Sales, suppliers of smash repair equipment and consumables under the brand names: Mako, Rupes, Star Sprayguns, Star New Century, Workquip, Autoglym and Tranmax. Head Office: 3 Foundry Road,
Seven Hills NSW 2147 Tel: (02) 9680 4464

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