scope:

This standard sets performance requirements for low water level controls used on boilers and feedwater vessels to protect against abnormal (below minimum safe) water level. They are intended to operate electrical contacts to provide an alarm and burner shutdown in the event of loss of primary water level. Low water level conditions may result in boiler destruction by overheating.

A high pressure low water level limit control is a device consisting of a sensor, alarm, and trip functions for use at an operating pressure of 250 psi (1725 kPa) or greater. A typical application of this control is its installation on a steam drum to sense drop in water level below the normal operating water level.

A low pressure low water level limit control is generally similar to the high pressure control except for lower maximum operating pressure. It may incorporate a time delay(s) which is activated when the water drops to the trip point before shutting off boiler firing.

The requirements of this standard shall be used to measure and describe the performance of low water level limit controls in response to exposure from heat, pressure, etc., under controlled laboratory conditions. The results of these controlled exposures shall not be used to describe or appraise actual exposure conditions, since such conditions will vary widely.

Purpose

This standard states testing and certification requirements for low water level limit controls for boilers.

Testing and certification criteria may include, but are not limited to, performance requirements, marking requirements, examination of manufacturing facility(ies), audit of quality assurance procedures, and a surveillance program.