Dry Pipe Sprinkler System

Dry pipe sprinkler systems are systems in which the upper part of the dry pipe valve is continuously pressurized with compressed air or inert gas and the lower part of the dry pipe valve is pressurized with water. Dry pipe systems should only be used in rooms where there is a possibility of frost damage and in rooms with temperatures above 70 °C, such as drying ovens.

The following sprinkler types are allowed to be used in dry pipe sprinkler systems:

Vertical type sprinkler
Dry type sprinkler
Horizontal sidewall type sprinkler (in installations where there is no water in the pipe)
Pendent and sidewall type sprinkler (If sprinklers, main pipes or branchpipes are located in areas where the temperature is 4ºC and above)

A continuous air/inert gas supply must be fitted to maintain pressure in the piping. The Dry Pipe valve must be pressurized according to the pressure rating range recommended by the valve manufacturer. The source of air supply to the dry pipe valve must be continuous. The air supply must be capable of filling the system within 30 minutes. If more than one dry pipe system is supplied with a single compressor, the largest system should be taken as the basis for 30 minutes filling time. For areas cooled below -15ºC, the filling time can be taken as 60 minutes. The air pressure that provides the power to keep the valve closed is specified in the manufacturer’s catalogs according to the system water pressure. Approximately 1/3 ratio of air pressure to water pressure can be taken. Manufacturer’s catalogs should be consulted for exact values.

Categories: Dry Pipe Sprinkler Systems, Water Extinguishing Systems

Description

The size of the system controlled by a single dry pipe valve shall be determined in accordance with any of the following points. As an exception, points 3 and 4 are not applicable to residences.

When the test valve at the furthest point is fully opened, the time taken for the water to drain should not exceed 60 seconds.
The net pipe internal volume above the dry pipe valve must not exceed the values given in the table below.

Hazard Class	Maximum Pipe Volume (m³)
Hazard Class	With Accelerator	Without Accelerator
Low Hazard	4	1,5
Medium Hazard	4	1,5
High Hazard	3	–

In systems with a net pipe internal volume of less than 1.5 m³, the use of an accelerator is not required and the time limit for water discharge need not be observed.
If accelerator is used in systems with a net pipe internal volume of less than 4 m³, the time limit for water discharge does not need to be complied with.
System size should be calculated with a calculation software depending on the time taken for water to drain. The calculation software and method must be approved by a nationally recognized laboratory. The calculation must comply with the values given in the table below.

Hazard Class	Number of Sprinklers to be Opened at the Farthest Point	Maximum Water Discharge Time (second)
Residential Unit	1	15
Low Hazard Class	1	60
Medium Hazard Class	2	50
High Hazard Class	4	45
High Storage	4	40

The size of the system should be such that, when flow tests are carried out, the values given in the table above for the time taken for the water to drain are achieved. Flow tests shall be performed by simulating the number of sprinklers to be opened. For spaces where a single sprinkler is required to open, the test valve at the farthest point is opened. To simulate a larger number of sprinkler openings, a test manifold arrangement is required. In order to test the 4 sprinklers opening situation; two manifold arrangements suitable for sprinkler flow are made from both branch arms. If the required water discharge times are met by the tests performed, the requirements in Articles 1 and 5 are not required.

In dry pipe systems, grid piping installation should not be used.

It is recommended not to use dry pipe systems in high hazard class applications. The delay in water reaching the first sprinkler can seriously reduce the efficiency of the system.