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Regulating Laser Water Supply In a Club Installation
L. Michael Roberts

Abstract

Water cooled lasers require a proper supply of clean, pressure regulated water for correct operation. A two stage water regulation installation in a club with water pressure problems is described and diagrammed.

Complex plumbing under construction

Introduction

Recently AVM of Toronto installed a laser projection system at "Club Energy" in Regina Saskatchewan. The installation presented some problems with water supply to the laser which was solved in a novel way using a two stage system.
The Laser projection system consisted of a six position beam table, two grating positions, and a graphics projection head with colour-box control. The controller for the system was New Method Lasers FullAuto controller running on a 233 MHz PII computer. The laser was a Spectra Physic 168 White Light laser by Cambridge Laser Labs. The laser was located on a platform suspended from the roof girders approximately 16 feet above the floor near the DJ booth.

Initial Installation

The water supply for the laser was located in the kitchen area which entailed running some 75 ft of 3/4 inch supply and drain pipes to the laser position. Initially a single stage, standard water handling and regulation system was installed (see diagram 1).
This consisted of a 3/4 inch shut-off valve, followed by a cartridge type water filter, a Watts 3/4 inch pressure regulator, a pressure gauge and a second 3/4 inch shut-off valve. Once the laser was installed, this was found to provide an adequate pressure of 40 PSI to the laser system.

Diagram 1 - Initial Installation

The club was a victim of the "john effect". During installation and testing of the laser, it was discovered that if more than one toilet was flushed, the pressure dropped below the critical level and the laser would shut off. This entailed climbing up to the laser platform to re-start the laser which would be unsatisfactory during normal club operation when multiple toilets might be flushed simultaneously and water was also required for the dishwasher and bar.

Booster Pump Added

The solution was to install a centrifugal type booster pump (see diagram 2). A suitable half horsepower pump with a pressure gauge was located and installed in the line between the first 3/4 inch shut-off valve and the filter. Once the air had been bled out of the lines, the pump was activated. Almost immediately the seals on the pump began to leak and the on-pump pressure gauge indicated a pressure of over 100 PSI, well above the recommended operating range of the pump.
The water pressure to the laser was correct and no amount of water use in the club caused it to cut out, however the leakage was unsatisfactory and the pressure in the pump lines and pump housing was dangerously high.

Diagram 2 - Booster pump added to system

Dual Stage Regulation Installed

To keep the pressure in the primary supply loop from exceeding the pump’s recommended operating pressure, a bypass with a second pressure regulator was installed (see diagram 3).
The second pressure regulator was set to 80 PSI.
The bypass allowed water to flow from the output of the pump back to the input via the regulator to keep the pump pressure within operating parameters. Since the pump could now potentially force water back into the main supply line, a check valve was installed to prevent this.

Diagram 3 - Two stage pressure regulation installed

The final installation, while more complex than usual, allowed for good primary pressure to the filter and the second regulator, which provided the correct pressure to the laser. Higher input pressure to the system than the laser requires is important to compensate for reduced pressure in the replaceable filter element as the filter ages and collects particulates from the water.
The club is able to use as much water as is needed for the dishwasher, bar and toilets without affecting the operation of the laser system.

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