{"id":987475009,"date":"2024-09-12T14:37:26","date_gmt":"2024-09-12T14:37:26","guid":{"rendered":"https:\/\/courses.asiascubainstructors.com\/lessons\/physics-4-the-ear-copy-copy\/"},"modified":"2025-01-26T11:20:11","modified_gmt":"2025-01-26T11:20:11","slug":"equipment-2-scuba-regulators","status":"publish","type":"lessons","link":"https:\/\/courses.asiascubainstructors.com\/de\/lessons\/equipment-2-scuba-regulators\/","title":{"rendered":"Restricted content"},"content":{"rendered":"

[et_pb_section fb_built=”1″ admin_label=”Classes Section” _builder_version=”4.23.1″ _module_preset=”add7fec1-62f1-4656-9396-e46e61dbc3b7″ background_color=”RGBA(255,255,255,0)” custom_margin=”||||false|false” custom_padding=”0px||||false|false” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_row use_custom_gutter=”on” gutter_width=”1″ make_equal=”on” _builder_version=”4.22.0″ _module_preset=”default” background_color=”#4E70C9″ background_size=”initial” background_position=”top_left” background_repeat=”repeat” max_width=”100%” module_alignment=”center” custom_padding=”3%|3%|3%|3%|true|true” locked=”off” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_column type=”4_4″ _builder_version=”4.22.0″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_text _builder_version=”4.22.0″ _module_preset=”8b1f8231-1210-4c64-bae4-d177be5c655c” text_text_color=”#FFFFFF” header_2_text_color=”#FFFFFF” header_3_text_color=”#FFFFFF” header_4_text_color=”#FFFFFF” locked=”off” global_colors_info=”{}” theme_builder_area=”post_content”]<\/p>\n

Equipment<\/h1>\n

 <\/p>\n

2. Scuba regulators<\/h2>\n

[\/et_pb_text][\/et_pb_column][\/et_pb_row][et_pb_row use_custom_gutter=”on” gutter_width=”1″ make_equal=”on” _builder_version=”4.22.0″ _module_preset=”default” background_size=”initial” background_position=”top_left” background_repeat=”repeat” max_width=”100%” module_alignment=”center” custom_padding=”10%||||false|false” use_custom_width=”on” width_unit=”off” custom_width_percent=”100%” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_column type=”4_4″ _builder_version=”4.22.0″ _module_preset=”default” custom_padding=”||||false|false” custom_padding_phone=”|5%||5%” custom_padding_last_edited=”off|desktop” global_colors_info=”{}” custom_padding__hover=”|||” theme_builder_area=”post_content”][et_pb_text _builder_version=”4.22.0″ _module_preset=”fd3255d4-f6f0-4f87-9821-9341db4eea8f” global_colors_info=”{}” theme_builder_area=”post_content”]<\/p>\n

Three types of scuba<\/h3>\n

Open Circuit Scuba<\/strong><\/em>: This is the most commonly used system. The diver inhales from a compressed gas cylinder. When the diver exhales, breathing gas vents into the water and bubbles to the surface.<\/p>\n

Closed-Circuit Rebreathers (CCRs)<\/strong><\/em>: The diver inhales from a bag (counterlung). The exhaled breath cycles through a system that removes waste carbon dioxide and replaces consumed oxygen, then returns it to the counterlung. There are no bubbles.
A computer monitors the partial pressure of the oxygen so that an ideal gas mix for whatever depth can be supplied to the diver. This greatly reduces the amount of nitrogen that the diver absorbs. Special training is required to use a Closed-Circuit Rebreather.<\/p>\n

Semi-Closed Rebreathers (SCRs)<\/strong><\/em>: The diver inhales from a bag (counterlung). The exhaled breath cycles through a system that removes waste carbon dioxide and returns it to the counterlung. It replaces consumed oxygen by letting a slow, steady flow of gas (Nitrox) into the counterlung. Excess gas is vented into the water, resulting in a slow, small stream of bubbles.
Compared to a Closed-Circuit system, Semi-Closed Rebreathers are technically less complicated but still require special training before use.<\/p>\n

<\/span><\/p>\n

[\/et_pb_text][\/et_pb_column][\/et_pb_row][et_pb_row use_custom_gutter=”on” gutter_width=”1″ make_equal=”on” _builder_version=”4.22.0″ _module_preset=”default” background_size=”initial” background_position=”top_left” background_repeat=”repeat” max_width=”100%” module_alignment=”center” custom_padding=”||||false|false” use_custom_width=”on” width_unit=”off” custom_width_percent=”100%” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_column type=”4_4″ _builder_version=”4.16″ _module_preset=”default” custom_padding=”||||false|false” global_colors_info=”{}” custom_padding__hover=”|||” theme_builder_area=”post_content”][et_pb_text _builder_version=”4.22.0″ _module_preset=”fd3255d4-f6f0-4f87-9821-9341db4eea8f” global_colors_info=”{}” theme_builder_area=”post_content”]<\/p>\n

Open circuit regulators – First stage<\/h3>\n

The first stage<\/strong><\/em> reduces high pressure air from the tank to an intermediate pressure<\/strong><\/em>.\u00a0The intermediate pressure is always approximately 10 bar above ambient pressure.\u00a0<\/p>\n

The most simple type of first stage is an unbalanced piston<\/strong><\/em> first stage. Most divecenters are using unbalanced piston regulators as rental equipment.
When the diver inhales from the second stage, pressure in the two main chambers is reduced. The piston is pushed to the \u201copen\u201d position by the main spring and the water pressure. High pressure air flows into the main chambers and pressure builds up untill intermediate pressure is reached. At this point, the force pushing the piston close becomes larger than the force of the spring and the water and the piston is pushed back to the \u201cclosed\u201d position.<\/p>\n

This system is \u201cunbalanced\u201d<\/strong><\/em> because high pressure from the tank is pushing on the pressure seat (red part in the picture), pushing the piston open. This means the tank pressure is affecting breathing resistance.<\/p>\n

A balanced piston regulator<\/strong><\/em> works similar to an unbalanced regulator. Again, breathing from the second stage will reduce the force on the piston and the piston is pushed open by the combined force from the spring and the water. With this system however, the high pressure from the tank is not pushing on the piston so breathing resistance is not influenced by the tank pressure.<\/p>\n

A Diaphragm first stage<\/strong><\/em> is also balanced. The working principle is not much different than that of a balanced piston regulator. Instead of a piston, it has a flexing diaphragm that pushes the valve open via a thin push rod.<\/p>\n

Balanced piston and diaphragm systems are both found in top-of-the line regulators.<\/p>\n

[\/et_pb_text][\/et_pb_column][\/et_pb_row][et_pb_row column_structure=”1_3,1_3,1_3″ use_custom_gutter=”on” gutter_width=”1″ make_equal=”on” module_class=” et_pb_row_fullwidth” _builder_version=”4.16″ _module_preset=”default” background_size=”initial” background_position=”top_left” background_repeat=”repeat” max_width=”100%” module_alignment=”center” custom_padding=”50px|0px|0px|0px|false|false” make_fullwidth=”on” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_column type=”1_3″ _builder_version=”4.16″ _module_preset=”default” custom_padding=”|||” global_colors_info=”{}” custom_padding__hover=”|||” theme_builder_area=”post_content”][et_pb_image src=”https:\/\/courses.asiascubainstructors.com\/wp-content\/uploads\/2024\/09\/padi-idc-divetheory-Unbalanced-piston.jpg” align_tablet=”center” align_phone=”” align_last_edited=”on|desktop” _builder_version=”4.16″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”][\/et_pb_image][et_pb_text _builder_version=”4.22.0″ _module_preset=”fd3255d4-f6f0-4f87-9821-9341db4eea8f” text_font=”||||||||” custom_margin=”-50px|5%||5%” custom_padding=”10px||” hover_enabled=”0″ global_colors_info=”{}” theme_builder_area=”post_content” sticky_enabled=”0″]<\/p>\n

Unbalanced Piston<\/p>\n

[\/et_pb_text][\/et_pb_column][et_pb_column type=”1_3″ _builder_version=”4.16″ _module_preset=”default” custom_padding=”|||” global_colors_info=”{}” custom_padding__hover=”|||” theme_builder_area=”post_content”][et_pb_image src=”https:\/\/courses.asiascubainstructors.com\/wp-content\/uploads\/2024\/09\/PADI-IDC-theory-Balanced-piston.jpg” align_tablet=”center” align_phone=”” align_last_edited=”on|desktop” _builder_version=”4.16″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”][\/et_pb_image][et_pb_text _builder_version=”4.22.0″ _module_preset=”fd3255d4-f6f0-4f87-9821-9341db4eea8f” text_font=”||||||||” custom_margin=”-50px|5%||5%” custom_padding=”10px||” hover_enabled=”0″ global_colors_info=”{}” theme_builder_area=”post_content” sticky_enabled=”0″]<\/p>\n

Balanced Piston<\/p>\n

[\/et_pb_text][\/et_pb_column][et_pb_column type=”1_3″ _builder_version=”4.16″ _module_preset=”default” custom_padding=”|||” global_colors_info=”{}” custom_padding__hover=”|||” theme_builder_area=”post_content”][et_pb_image src=”https:\/\/courses.asiascubainstructors.com\/wp-content\/uploads\/2024\/09\/PADI-IDC-theory-Balanced-diaphragm.jpg” align_tablet=”center” align_phone=”” align_last_edited=”on|desktop” _builder_version=”4.16″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”][\/et_pb_image][et_pb_text _builder_version=”4.22.0″ _module_preset=”fd3255d4-f6f0-4f87-9821-9341db4eea8f” text_font=”||||||||” custom_margin=”-50px|5%||5%” custom_padding=”10px||” hover_enabled=”0″ global_colors_info=”{}” theme_builder_area=”post_content” sticky_enabled=”0″]<\/p>\n

Balanced Diaphragm<\/p>\n

[\/et_pb_text][\/et_pb_column][\/et_pb_row][et_pb_row column_structure=”1_3,2_3″ make_equal=”on” _builder_version=”4.22.0″ _module_preset=”default” background_size=”initial” background_position=”top_left” background_repeat=”repeat” max_width=”100%” module_alignment=”center” custom_padding=”||||false|false” use_custom_width=”on” width_unit=”off” custom_width_percent=”100%” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_column type=”1_3″ _builder_version=”4.16″ _module_preset=”default” custom_padding=”|||0px” custom_padding_tablet=”” custom_padding_phone=”|||0px” custom_padding_last_edited=”on|desktop” global_colors_info=”{}” custom_padding__hover=”|||” theme_builder_area=”post_content”][et_pb_image src=”https:\/\/courses.asiascubainstructors.com\/wp-content\/uploads\/2024\/09\/PADI-IDC-theory-Environmental-seal.jpg” force_fullwidth=”on” align_tablet=”center” align_phone=”” align_last_edited=”on|desktop” _builder_version=”4.16″ _module_preset=”default” animation_style=”fade” animation_delay=”500ms” global_colors_info=”{}” theme_builder_area=”post_content”]   [\/et_pb_image][\/et_pb_column][et_pb_column type=”2_3″ _builder_version=”4.22.0″ _module_preset=”default” custom_padding=”||||false|false” custom_padding_phone=”10%|||” custom_padding_last_edited=”off|desktop” global_colors_info=”{}” custom_padding__hover=”|||” theme_builder_area=”post_content”][et_pb_text _builder_version=”4.16″ _module_preset=”fd3255d4-f6f0-4f87-9821-9341db4eea8f” global_colors_info=”{}” theme_builder_area=”post_content”]Some regulator first stages are fitted with an Environmental seal<\/strong><\/em>. The environmental seal keeps water from entering the regulator. The water pressure pushes on a diaphragm so that the intermediate pressure still rises with the ambient pressure (depth).
\nThe main advantage of an environmental seal is that the regulator is less prone to freezing in very cold water.
\nThe picture shows the same regulator with environmental seal (top) and without (bottom).[\/et_pb_text][\/et_pb_column][\/et_pb_row][et_pb_row column_structure=”3_5,2_5″ make_equal=”on” _builder_version=”4.22.0″ _module_preset=”default” background_size=”initial” background_position=”top_left” background_repeat=”repeat” max_width=”100%” module_alignment=”center” custom_padding=”||||false|false” use_custom_width=”on” width_unit=”off” custom_width_percent=”100%” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_column type=”3_5″ _builder_version=”4.22.0″ _module_preset=”default” custom_padding=”||||false|false” custom_padding_phone=”|||” custom_padding_last_edited=”off|desktop” global_colors_info=”{}” custom_padding__hover=”|||” theme_builder_area=”post_content”][et_pb_text _builder_version=”4.22.0″ _module_preset=”fd3255d4-f6f0-4f87-9821-9341db4eea8f” global_colors_info=”{}” theme_builder_area=”post_content”]<\/p>\n

Open circuit regulators \u2013 Second stage<\/h3>\n

The second stage reduces the intermediate pressure that comes from the first stage to ambient pressure for breathing.<\/p>\n

When the diver inhales, the water pushes a diaphragm<\/strong><\/em> inward. The diaphragm pushes on a lever<\/em><\/strong> that opens the valve<\/strong><\/em>. The diver can also push the diaphragm inward by pushing the purge button<\/strong><\/em>. When the diver exhales, a spring<\/strong><\/em> pushes the valve close.<\/p>\n

 <\/p>\n

[\/et_pb_text][\/et_pb_column][et_pb_column type=”2_5″ _builder_version=”4.16″ _module_preset=”default” custom_padding=”|0px||5%” custom_padding_tablet=”” custom_padding_phone=”10%|||0px” custom_padding_last_edited=”on|phone” global_colors_info=”{}” custom_padding__hover=”|||” theme_builder_area=”post_content”][et_pb_image src=”https:\/\/courses.asiascubainstructors.com\/wp-content\/uploads\/2024\/09\/PADI-IDC-theory-second-stage-1.jpg” force_fullwidth=”on” align_tablet=”center” align_phone=”” align_last_edited=”on|desktop” _builder_version=”4.16″ _module_preset=”default” animation_style=”fade” animation_delay=”500ms” global_colors_info=”{}” theme_builder_area=”post_content”]   [\/et_pb_image][\/et_pb_column][\/et_pb_row][et_pb_row column_structure=”3_5,2_5″ make_equal=”on” _builder_version=”4.22.0″ _module_preset=”default” background_size=”initial” background_position=”top_left” background_repeat=”repeat” max_width=”100%” module_alignment=”center” custom_padding=”||||false|false” use_custom_width=”on” width_unit=”off” custom_width_percent=”100%” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_column type=”3_5″ _builder_version=”4.16″ _module_preset=”default” custom_padding=”||||false|false” global_colors_info=”{}” custom_padding__hover=”|||” theme_builder_area=”post_content”][et_pb_text _builder_version=”4.16″ _module_preset=”fd3255d4-f6f0-4f87-9821-9341db4eea8f” custom_padding=”||5%|” global_colors_info=”{}” theme_builder_area=”post_content”]Second stages can also be balanced<\/strong><\/em>. Again, when the diver inhales, the water pushes a diaphragm inward and the diaphragm moves a lever. The lever moves the poppet assembly<\/strong><\/em> (yellow in the picture) and the valve opens.<\/p>\n

When the diver exhales, the valve is closed by a spring.
\nIn closed position, intermediate pressure air flows into a balancing chamber<\/strong><\/em> (red in the picture) and helps to push the valve closed. This reduces the \u2018cracking effort\u2019<\/strong><\/em> \u2013 the initial force needed to open the valve when the diver breathes in.[\/et_pb_text][\/et_pb_column][et_pb_column type=”2_5″ _builder_version=”4.16″ _module_preset=”default” custom_padding=”|0px||5%” custom_padding_tablet=”” custom_padding_phone=”10%|||0px” custom_padding_last_edited=”on|phone” global_colors_info=”{}” custom_padding__hover=”|||” theme_builder_area=”post_content”][et_pb_image src=”https:\/\/courses.asiascubainstructors.com\/wp-content\/uploads\/2024\/09\/PADI-IDC-theory-balanced-second-stage.jpg” force_fullwidth=”on” align_tablet=”center” align_phone=”” align_last_edited=”on|desktop” _builder_version=”4.16″ _module_preset=”default” animation_style=”fade” animation_delay=”500ms” global_colors_info=”{}” theme_builder_area=”post_content”]   [\/et_pb_image][\/et_pb_column][\/et_pb_row][et_pb_row use_custom_gutter=”on” gutter_width=”1″ make_equal=”on” _builder_version=”4.22.0″ _module_preset=”default” background_size=”initial” background_position=”top_left” background_repeat=”repeat” max_width=”100%” module_alignment=”center” custom_padding=”||||false|false” use_custom_width=”on” width_unit=”off” custom_width_percent=”100%” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_column type=”4_4″ _builder_version=”4.16″ _module_preset=”default” custom_padding=”||||false|false” global_colors_info=”{}” custom_padding__hover=”|||” theme_builder_area=”post_content”][et_pb_text _builder_version=”4.22.0″ _module_preset=”fd3255d4-f6f0-4f87-9821-9341db4eea8f” global_colors_info=”{}” theme_builder_area=”post_content”]<\/p>\n

Other features<\/h3>\n

The valves in the first and second stages are Downstream valves<\/strong><\/em> and open with the air flow. The air will push the valve open and a spring is needed to keep it closed.<\/p>\n

A malfunction will cause a continuous free flow of air rather than shutting off the air. This is known as a failsafe design<\/strong><\/em>.<\/p>\n

In some very old regulators you could find a pilot valve<\/strong><\/em>. A pilot valve is a small valve that assists in opening the main valve. This construction is not used in modern regulators.<\/p>\n

 <\/p>\n

[\/et_pb_text][\/et_pb_column][\/et_pb_row][et_pb_row _builder_version=”4.22.0″ _module_preset=”default” locked=”off” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_column type=”4_4″ _builder_version=”4.22.0″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”][et_pb_text _builder_version=”4.22.0″ _module_preset=”default” global_colors_info=”{}” theme_builder_area=”post_content”]<\/p>\n