#### Calculate Differential Pressure Sensed by Level Transmitter

#### Question :

Calculate the differential pressure sensed by the level transmitter at three different water levels in this boiler steam-drum level measurement system: The measurable points are 0%, 50%, and 100% of transmitter range.

Assume a density for (hot) boiler drum water of 36 lb/ft^{3} , a density for steam in the drum of 7 lb/ft^{3} , and a density for (warm) water in the “wet leg” of 61.8 lb/ft3 . If the pressure at the “low” (L) side of the transmitter is greater than the pressure at the “high” (H) side, be sure to express the differential pressure quantity as a negative number.

Credit will be given for correctly calculating each of the differential pressures:

- (6 points) Transmitter ∆P at 0% water level = _______”W.C.
- (6 points) Transmitter ∆P at 50% water level = _______”W.C.
- (6 points) Transmitter ∆P at 100% water level = _______”W.C.

**Answer :**

- (6 points) Transmitter ∆P at 0% water level = -38.832 ”W.C.
- (6 points) Transmitter ∆P at 50% water level = -31.864 ”W.C.
- (6 points) Transmitter ∆P at 100% water level = -24.896 ”W.C.

**Also Read : Boiler Drum Level Measurement Principle**

Instrument Range:

LV =[ [( 9″ x 36 + 40″ x 7) – 49″ x 61.8] x 0.0005787037] / 0.036127292000084 lbs/in3

= – 38.83 ” WC at standard condition

or LV = – 1.40289 psi

UV = [ [( 39″ x 36 + 10″ x 7) – 49″ x 61.8] x 0.0005787037] / 0.036127292000084 lbs/in3

=-24.896″ WC at standard condition

or UV = -0.89942129054 psi

Density water at 0.036127292000084 lbs/in3 standard conditions

Controller Range: -15″ to 15″ WC