SCUBA DIVING EQUIPMENT FIRST STAGE REGULATORS

SCUBA DIVING EQUIPMENT FIRST STAGE REGULATORS

Back again with some information regarding the first stage scuba diving regulator.

There are two basic first stage regulator designs the piston or diaphragm and then two versions of each design in the balanced or unbalanced.

With the Piston and Diaphragm first stage regulators the differences are:



In a diaphragm first stage, water pressure is transmitted to the valve through a flexible diaphragm. The valve itself is sealed against water intrusion, and the spring chamber can be easily sealed as well. Because water cannot enter the first-stage housing, internal corrosion is minimized. On the other hand, diaphragm first stages have more moving parts and may not lend themselves as well to swivel fittings for low-pressure hoses, because intermediate pressure comes out in the middle of the housing.




In a piston design, water pressure acts directly on the valve, making it simpler, with fewer moving parts. They are easy to adapt to swivel fittings, making low-pressure hose placement more convenient. But because water enters the spring and piston chamber, pistons are more sensitive to corrosion, especially if the owner neglects regular maintenance.



Balanced vs. Unbalanced

Both piston and diaphragm first stages come in balanced and unbalanced versions. A valve is balanced by extending the shaft beyond the pressure chamber so air pushes on both ends equally. A balanced first stage retains ease of breathing all the way down to the last few pounds of tank pressure, because intermediate pressure remains constant. These units are more complex and generally more expensive.

Until a few years ago, unbalanced first stages were severely affected by low tank pressures and would begin to breathe harder below about 700 psi. The reason was a 30- to 40-psi drop in intermediate pressure from full to near-empty tanks. But current models are less sensitive to supply pressure, with a pressure drop of only 20 to 30 psi. Therefore, the performance gap between balanced and unbalanced first stages has tightened. Unbalanced first stages are more economical, have fewer moving parts and are easier to service. But they will usually have fewer ports and lack the convenience of swivel mounting.

A simple description of the regulator first stage would be as follows;

The system operates like this:

1. You inhale, thereby lowering the pressure in the intermediate-pressure chamber to below the ambient water pressure.

2. The water pressure pushes inward, opening the valve or piston.

3. The open valve connects the high-pressure chamber with the intermediate pressure chamber.

4. Air flows from the high-pressure chamber into the intermediate-pressure chamber, thereby increasing the pressure in the intermediate-pressure chamber.


5. When the pressure in the intermediate-pressure chamber equals the ambient water pressure, the valve or piston closes.

6. The process repeats when you inhale again.

Look out for the next more detailed posts on Open Circuit SCUBA equipment Second Stages.

Please feel free to comment on any posts in this blog.


To find out more about SCUBA equipment available from Samui Dive Supply please contact us for more information.

SELF CONTAINED UNDERWATER BREATHING APPARATUS (SCUBA) (PART 1)

Self Contained Underwater Breathing Apparatus (SCUBA) (Part 1)

A month or so ago, doesn’t time fly when you’re having fun, we said we will introduce SCUBA equipment to you, attempt to explain what it is and what it does for you.

As an introduction there are three basic types of SCUBA equipment:

Open Circuit

When you breath in you use a two stage regulator that provides gas at the ambient pressure from a tank of compressed gas usually at 200 bar. When you breath out through your regulator second stage the exhaled air vents into the water as bubbles. Your SCUBA equipment would also consist of a Buoyancy Control Device (BCD) and weight system. This is the system we will focus on in more detail in the next post. An example of an Open Circuit Regulator would be the Scubapro Mk25 1st Stage witha S600 2nd Stage.

Semi-Closed Rebreathers (SCRs)

When you breathe in, you breathe from a counter lung in your SCR. When you breathe out your exhaled air passes through a scrubber that removes the excess carbon dioxide in the exhaled air. This air then passes into the counter lung where it mixes with oxygen that is flowing at a continuous set flow rate to produce your breathing gas. Any excess gas in the counter lung is vented off as a small stream of bubbles. An example of a SCR would be the Drager Dolphin.

Closed Circuit Rebreathers (CCR’s)

When you breathe in, you breathe from a counter lung in your CCR. When you breathe out your exhaled air passes through a system that removes the waste carbon dioxide in the exhaled air and replaces consumed oxygen then it returns to the counter lung. There are no bubbles. An Example of a CCR would be the Pelagian from RebreatherLab.

Look out for the next post on Open Circuit SCUBA equipment.

Please feel free to comment on any posts in this blog.

To find out more about SCUBA equipment available from Samui Dive Supply please contact us for more information.

BASIC EQUIPMENT FOR SCUBA DIVING AND SNORKELING (Part 4)

Basic Equipment for SCUBA Diving and Snorkeling (Part 4)

This week we have the second of two Blog posts covering the topic of the highly essential piece of diving/snorkeling equipment FINS.

Fins

To recap the basic function of a fin is to propel you the diver/snorkeler through the water with as little effort as possible for the most propulsion, to this end there are a multitude of designs now available on the market to suit everybody’s needs.

A fin consists of a foot pocket, either full foot “slipper fins” or open heel, and a blade which can be of many different designs.

In this Blog post we will cover the Open Heel adjustable design fins which are used predominantly by seasoned divers, dive professionals and in colder waters.


Open Heel Adjustable Fins

These fins are generally larger than full foot fins and provide more power which greatly assists the diver when wearing a full set of SCUBA diving equipment. We will introduce SCUBA equipment in the next Blog post, they have an Open Heel, hence the name, foot pocket with an adjustable strap to hold the foot in the foot pocket. The foot pockets come in a variety of sizes from extra small to extra large so they can encompass all foot sizes. The use of neoprene boots is also required.

The fin straps are generally made of rubber and are fixed to the fins using adjustable buckles some fin buckles also have a quick release mechanism to allow the diver to easily remove the fin strap and fin, especially useful when waiting to climb up the ladder of a boat. There is also the option to use spring heel straps such as the Saekodive Spring Strap with buckle. In place of the rubber strap a high powered spring is used to hold the foot in the foot pocket.

The blades are made from either rubber such as the Scubapro Jet Fin Classic or a mixture of rubber and techno polymers which encompasses the benefits on both materials.

The blades can incorporate channels to ease the flow of water across the fin but at the same time maximizing the thrust a good example of these would be the Seac Sub Propulsion fins and some fins have a split fin design which provides the diver/snorkeler with a propeller thrust effect, see diagram, such as the Scubapro Twin Jet fin or Max Twin Jet Fin.


You would normally find ribs down the edges of the blades, these tend to aid the flow of water down the length of the blade enhancing thrust and preventing the blade from twisting under stress.

To find out more about fins available form Dive Supply please contact us for more information.

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Own fins already? Why not take part in our poll to see which are the most popular brand fins used by our Blog readers.

Welcome to Samui Dive Supply

Samui Dive Supply is the leading retailer and wholesale supplier of quality diving, snorkeling and water sports equipment on Koh Samui. In this blog we will aim to provide you with information regarding dive equipment currently available in Koh Samui form new products to old favourites and some general information about dive equipment.

Supported by the largest warehouse facility for scuba diving equipment in Thailand we can offer an unsurpassed level of service to any dive centre, snorkel tour operator, hotel/resort or retail outlet on Koh Samui and Koh Phangan.

If you are in the area please feel free to visit our showroom on the Samui ring road in Chaweng located between the PTT gas station and the Bangkok Samui Hospital.

Stocking leading brands such as Scubapro, Suunto, Seac Sub, Bauer, Ocean Management Systems and Saekodive you can be sure to find what you want when visiting Samui Dive Supply.

If we do not currently hold stock of the dive equipment you want at the Samui Dive Supply showroom we can order most items of scuba diving or snorkeling equipment from our warehouse facility with a delivery time of between two and seven days.

We are open everyday from 9:00 am to 6:00 pm ready to serve you with our expert product knowledge.