RKI Instruments 35-3000RKA-H2S User Manual

Sample-Draw Hydrogen Sulfide Gas Detector for Use
With Generic Device

Specifications

Table 1 lists specifications for the sample-draw hydrogen sulfide detector. .

Table 1: Specifications

Target Gas Hydrogen Sulfide
Input Power 24 VDC
Output Signal 4-20 mA
Construction (housing) Fiberglass/polyester (NEMA 4X)
Dimensions 8.5 in. H x 6.5 in. W x 4.25 in. D
Weight 4.5 lbs.
Sampling Method Sample-draw
Sample Flow 1.5 SCFH (nominal)
Detection Range 0 to 100 ppm
Response Time 90% in 30 seconds
Accuracy ±5% of detection range
Repeatability ±2% of detection range

Sample-Draw Hydrogen Sulfide Gas Detection • 1

Description

This section describes the components of the sample-draw hydrogen sulfide gas detector.
The sample-draw detector consists of the housing, flow system, and detection system.

Mounting Foot,

Flow Adjust
Potentiometer

Pump/flow switch
terminal block

4X

Main Circuit Board

Flow Alarm Setpoint
Adjustment
Potentiometer

Fail LED

Pilot LED

Flowmeter
Bypass valve

Particle filter

Transmitter

Test Points
100 - 500 mV range

Factory Set Pot

Zero Pot
Span Pot

JUMPER PINS FOR
FACTORY USE
ONLY

ZERO

SPAN

TOXIC

Transmitter
Te rminal Strip

Interconnect Terminal
Strip

Exhaust

Inlet

Sensor
Connector

24VFB4/20BATT

Hydrogen Sulfide Sensor

OXY

TOXIC

OXY

G

BKRD W

Not Used

3/4" Conduit
Hub , 2X

Figure 1: Sample-draw Hydrogen Sulfide Gas Detector Component Location

Housing

The sample-draw detector’s fiberglass housing is weather- and corrosion-resistant. It is
suitable for installation where general purpose equipment is in use.

The housing door is hinged on the left side and is secured by two latches on the right side.
The flowmeter and status lights are visible through a window in the housing door.

Four mounting feet are attached to the back of the housing (one at each corner). Use the
mounting feet to install the housing to a vertical surface. Use the two conduit hubs on the
bottom of the housing to make wiring connections.

An aluminum subpanel is mounted to the interior of the housing. The sample-draw
detector’s internal components are mounted to the subpanel.

2 • Sample-Draw Hydrogen Sulfide Gas Detection

Flow System

The sample-draw detector’s flow system consists of the INLET fitting, filter, pump,
flowmeter, bypass valve, status lights, pressure switch, and EXHAUST fitting (see
Figure 1). Figure 2 illustrates how the gas sample moves through the flow system.

To

Exhaust

Bypass

Valve

Flowmeter

Inlet Filter Pump Sensor

Pressure Switch

Figure 2: Sample-draw Hydrogen Sulfide Gas Detector Flow Diagram

INLET fitting

The INLET fitting on the right side of the housing allows the gas sample to enter the
sample-draw detector. The INLET fitting accepts 1/4 in. rigid tubing. See the Installation
section on page 6 to connect tubing to the INLET fitting.

Filter

The dust filter is below the main circuit board. The filter prevents particulates in the
incoming gas sample from damaging the flow and detection systems. Replace the filter
when it appears dirty, discolored, or clogged.

Pump

The pump is behind the main circuit board near the top of the sample-draw detector.
The pump pulls the gas sample into the sample-draw detector. The pump operates on
24 VAC, which is generated from the 24 VDC supplied to the sample draw detector.

Flowmeter

The flowmeter is attached to the main circuit board near the top left corner (see Figure 1.)
You can see it through the window in the door. A ball in the flowmeter column indicates
the flow rate of the sample-draw detector. The flowmeter measures the flow in the range

0.2 to 2.0 SCFH (Standard Cubic Feet per Hour). The optimum flow rate is 1.5 SCFH.

Bypass valve

The bypass valve is to the left of the flowmeter. The bypass valve adjusts the flow rate to
the sensor. Use a flat-blade screwdriver to adjust the bypass valve.

NOTE: The bypass valve allows fine adjustments of the flow rate. For a wider range of

adjustment, use the flow adjust potentiometer (see Figure 1.)

Sample-Draw Hydrogen Sulfide Gas Detection • 3

Status lights

Two status lights are above the flowmeter. They are also visible through the window in
the housing door.

Pilot light

The green Pilot light is on when the sample-draw detector is receiving power from the
Pioneer.

Fail light

The red Fail light is on when the sample flow rate is below the low flow level.

NOTE: The default low flow level is 0.6 SCFH (±0.2). See “Adjusting the Low Flow

Setting” on page 13 to adjust this setting.

Pressure switch

The pressure switch is mounted to the opposite side of the main circuit board. The
pressure switch monitors the flow rate of the incoming gas sample.

If the flow rate falls below the preset low flow level, the pressure switch causes the fail
relay to interrupt the signal in the 4-20 mA line. This causes a downscale reading at the
monitor. The low flow level is factory-set at 0.6 SCFH (±0.2 SCFH).

EXHAUST fitting

The EXHAUST fitting on the right side of the housing allows the gas sample to exit the
sample-draw detector. The EXHAUST fitting accepts 1/4 in. rigid tubing. See the
Installation section on page 6 to connect tubing to the EXHAUST fitting.

Detection System

The detection system consists of the hydrogen sulfide gas sensor, the hydrogen sulfide
transmitter, and the main circuit board.

Hydrogen sulfide gas sensor

The hydrogen sulfide gas sensor is installed in a cavity block. The cavity block is mounted
to the aluminum subpanel on the right of the sample-draw detector. The hydrogen
sulfide gas sensor includes the sensor and the cable with connector.

NOTE: The cavity block includes a cavity for a second hydrogen sulfide or a carbon

monoxide sensor. This version of the sample-draw detector does not include the
second sensor.

Sensor

The sensor is pushed into the cavity block and held in place by two o-rings. Through a
series of chemical and electrical reactions, the sensor produces an electrical output that is
proportional to the detector range of the transmitter.

Cable w/Connector

The sensor has a two wire cable with a 4-pin connector soldered to it. The connector is
plugged into the sensor connector in the lower right of the Main Circuit Board.

4 • Sample-Draw Hydrogen Sulfide Gas Detection

Hydrogen Sulfide Transmitter

The hydrogen sulfide transmitter is mounted to the left of the hydrogen sensor. It consists
of the span pot, zero pot, two internally wired terminal strips, and the test points.

Span/zero pots

The span and zero pots are located at the left edge of the transmitter and are used for cali­bration. Use the span pot to make adjustments to gas response readings and the zero pot
to make adjustments to the zero reading

Termainal Strips

There are two terminal strips which are used for internal factory wiring.

Test points

The test points are located at the top of the transmitter and are labeled TP+ and TP- . A
100 mV - 500 mV output is available at these testpoints for use during calibration.

Main Circuit Board

The main circuit board includes the interconnect terminal strip, transmitter terminal strip,
pump terminal strip, and relay (see Figure 1).

NOTE: The flowmeter and status lights are mounted to the main circuit board but are

considered part of the flow system.

Interconnect terminal strip

The interconnect terminal strip is the nine-point terminal strip near the bottom edge of the
main circuit board. Use the interconnect terminal strip to connect the sample-draw
detector to power and an external device.

Transmitter terminal strip

The transmitter terminal strip is the nine-point terminal strip near the right edge of the
circuit board. Use the transmitter terminal strip to connect the transmitter to the main
circuit board.

NOTE: The transmitter is factory-wired to the circuit board. See the “Installation” section

on page 6 for all wiring procedures related to the sample-draw detector.

Pump terminal strip

The pump terminal strip is the four-point terminal strip near the top edge of the circuit
board. Use the pump terminal strip to connect the pump and pressure switch to the main
circuit board.

NOTE: The pump and pressure switch are factory-wired to the circuit board. See the

“Installation” on page 6 for all wiring procedures related to the sample-draw
detector.

Relay

The relay is to the left of the detector terminal strip. The relay is double pole, double­throw (DPDT) and is rated for 2 amps at 25 VDC (resistive). If the pressur e switch senses a
low flow condition, the relay interrupts the signal from the sensor. The interrupted sensor
signal causes a fail condition at the Pioneer.

Sample-Draw Hydrogen Sulfide Gas Detection • 5