response time. Zero and span shall be adjustable. KELE Model PTXIE, or equal. Install with isolation valve.
4.Water differential pressure transmitters for flow measurement shall have stainless steel diaphragm construction,
5.All differential pressure transmitters for water service shall have a differential pressure gauges mounted at the point of application. Provide tees with ½” size,
6.Air differential static pressure transmitters: [Note to Consultant: For critical applications where the differential pressure can drop below 0.2" W.C. - such as
7.All differential pressure transmitters for air shall have
C.Transmitter Span Selection:
1.The span of each transmitter must be carefully selected by the Contractor. Typical spans are shown above in Section 2.11 B. General selection procedures are given below.
2.The selection of the appropriate transmitter span is a crucial step in the design of a functional control system. In general, the span of the transmitter should match the normal ranges of the variable to be controlled. For example, the measurement of system pressure where the normal operating pressure is 20 psi and the peak system pressure is 35 psi, the correct span selection would be 0 to 50 psi. A 0 to 100 psi span, while workable, would be operating in the lower third of the span under normal conditions. This decreases the controller’s ability to detect small changes in pressure. Ideally, the control setpoint should be at approximately 75% of the transmitter’s span. However, expected maximum and minimum values encountered during normal operation of the system must be accounted for.
3.Particular attention to transmitter span must be taken with airflow monitoring sta- tions. The recommendations of the
4.Transmitters found operating in the lower 33% or upper 20% of their span, during normal conditions of system operation, shall be replaced, at the Contractor’s expense, with units having an acceptable span.
JANUARY 2008 | UCCS STANDARDS |
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