HB Products SLCD-M1/25/Ex Linear Short-Stroke Position Transmitter

Overview

HB Products SLCD-M1/25/Ex is a linear short-stroke position transmitter engineered specifically for stop-valve and capacity-control feedback on screw gas compressor (SGC) trains and industrial refrigeration screw compressors. Manufactured by HB Products A/S of Hasselager, Denmark, the HB Products SLCD-M1/25/Ex converts a mechanical stroke of up to 25 mm into a standard 4–20 mA current-loop signal, giving the compressor control system continuous, real-time feedback on slide-valve or stop-valve position rather than relying on limit switches or open-loop actuator timing alone.

Backed by manufacturer datasheet documentation, Seven Star LLC proudly supplies the HB Products SLCD-M1/25/Ex to compressor packagers, OEMs, and end users across Oman and the GCC, backed by genuine manufacturer certification and local technical support. Screw compressor packages installed at refrigeration, LNG, and gas-processing sites in the Sultanate of Oman, Muscat, Sohar, and Salalah can be specified or retrofitted with this transmitter through Seven Star LLC with full confidence in traceability back to the original Danish manufacturer.

Measurement Principle

The HB Products SLCD-M1/25/Ex is a linear displacement transducer: a spring-loaded plunger or push-rod is mechanically coupled to the moving stop valve or slide-valve stem of the screw compressor, and as the valve travels through its stroke the transmitter’s internal sensing element tracks the plunger’s linear position. That position is converted electronically into a proportional 4–20 mA output signal, so 4 mA corresponds to one end of the calibrated stroke and 20 mA to the other, with intermediate valve positions reported as a linear current value in between. Because the sensing element has no external moving contacts exposed to the process gas, the transmitter is well suited to continuous duty inside a compressor’s oil-wetted or gas-side environment.

The unit’s intrinsically safe design uses the entity parameters marked on its nameplate (Ui, Ii, Pi, and Ci) to define the maximum voltage, current, power, and capacitance that can safely be supplied from an approved intrinsic-safety barrier without generating a spark or thermal effect capable of igniting a surrounding flammable atmosphere. The practical consequence for the compressor package designer is a continuous, high-resolution position feedback signal that can be wired directly into a PLC or compressor control panel located outside the hazardous area, without the step changes, wear, and maintenance burden associated with mechanical limit switches, and without introducing an ignition source into the classified zone around the compressor skid.

Engineering Design of the HB Products SLCD-M1/25/Ex

Mechanically, the HB Products SLCD-M1/25/Ex is housed in a compact stainless-steel/metal enclosure with a threaded probe mount that couples directly to the compressor’s stop-valve or capacity-control linkage, allowing it to be retrofitted onto existing screw compressor packages without major redesign of the valve actuator assembly. The nameplate-stamped intrinsic-safety parameters (type HB Products SLCD-M1/25/Ex, Ui 26.5 V, Ii 116 mA, Pi 950 mW, Ci 50 nF) are printed directly on the housing alongside the manufacturer’s Hasselager, Denmark address, allowing installation and maintenance technicians to verify compatibility with the plant’s certified intrinsic-safety barrier at the panel without needing to consult a separate datasheet.

Electrical connection is made via a factory-terminated, oil- and chemical-resistant cable exiting the housing through a strain-relief gland, supplied in a length long enough to route from the compressor skid to a junction box or control panel without an intermediate splice, reducing the number of potential ignition-relevant connection points inside the classified area. The transmitter’s short-stroke calibration range (adjustable down to a minimum span of roughly 5 mm within its 0–25 mm maximum travel) allows a single hardware variant to be field-calibrated to match the actual stop-valve or slide-valve travel of a given compressor model, simplifying spare-parts stocking for operators running mixed compressor fleets.

Key Features

The HB Products SLCD-M1/25/Ex was purpose-built for the demands of screw compressor capacity control, and its design reflects that specialization.

• Linear short-stroke measurement range up to 25 mm, field-calibratable down to a minimum span of approximately 5 mm for different compressor stop-valve travels.
• Standard 4–20 mA current-loop output for direct, drop-in wiring into PLC analog input cards and compressor control panels.
• Intrinsically safe design with nameplate-marked entity parameters (Ui 26.5 V, Ii 116 mA, Pi 950 mW, Ci 50 nF) for straightforward barrier matching during installation.
• Continuous, wear-free position feedback that eliminates the step-change limitations of mechanical limit switches on stop-valve and slide-valve linkages.
• Compact, robust metal housing designed to mount directly onto existing screw gas compressor (SGC) capacity-control linkages.
• Factory-terminated cable with strain-relief gland, reducing on-site wiring connections inside the hazardous area around the compressor skid.
• Purpose-built for retrofitting onto industrial refrigeration and process gas screw compressor packages already in service.
• Manufactured and certified by HB Products A/S of Denmark, a specialist supplier of compressor capacity sensors for the refrigeration and process gas industries.

Industrial Applications

Screw gas compressors are the workhorse of ammonia and industrial refrigeration plants, LNG and gas-processing trains, and large district cooling and process cooling installations, and every one of them depends on accurate slide-valve or stop-valve position feedback to modulate capacity efficiently. In Oman’s oil and gas gathering and gas-processing facilities, as well as district cooling plants serving commercial and hospitality developments in Muscat, screw compressor packages fitted with the HB Products SLCD-M1/25/Ex give operators continuous visibility into actual valve position rather than assumed setpoint, supporting tighter capacity control, reduced energy consumption, and earlier detection of a sticking or worn valve linkage before it causes an unplanned shutdown.

Working closely with plant engineers in the region, Seven Star LLC distributes the HB Products SLCD-M1/25/Ex to compressor packagers, OEM panel builders, and plant maintenance teams across the Sultanate of Oman, Muscat, and the wider GCC, supporting industrial refrigeration, LNG, and gas-processing sites in the Sohar and Salalah economic zones where hazardous-area classified compressor skids require intrinsically safe instrumentation with part-number traceability. Supply on request supports replacement on aging compressor fleets where an original sensor has failed or a plant is standardizing spares across multiple compressor models from different OEMs.

Technical Specifications

The table below summarizes the key specifications for the HB Products SLCD-M1/25/Ex short-stroke position transmitter, verified against the unit’s manufacturer nameplate and official documentation.

Hazardous-Area Installation Notes

The HB Products SLCD-M1/25/Ex short-stroke position transmitter is documented by the manufacturer in a combined Ex manual for its long-stroke and short-stroke compressor position sensors. The sensor is cULus approved with intrinsic safety according to UL, and the manufacturer data describes device category 2G for Zone 1, protection type ib and gas group IIC. It must only be connected to a certified intrinsically safe circuit, so the control panel side needs a suitable barrier or isolator before the signal reaches the PLC.

HB Products states that the SLCD-M1/_Ex series has been tested with the Pepperl+Fuchs special barrier KFD2-STC4-EX1 and recommends ordering this barrier together with the Ex sensor. The position is indicated over a range of 0 to 100 %, corresponding to a 4…20 mA analogue signal. Installers should follow the control drawing and the mounting instructions in the manufacturer's Ex manual and confirm the entity parameters printed on the nameplate against the barrier data.

Request a Quote for HB Products SLCD-M1/25/Ex

Compressor packagers, plant maintenance teams, and procurement leads in Oman and across the GCC can submit a formal RFQ to Seven Star LLC for the HB Products SLCD-M1/25/Ex, request the manufacturer’s technical documentation, and confirm current availability and delivery lead times. With fast quotation turnaround and technical support, our instrumentation division can advise on stroke-length calibration, intrinsic-safety barrier matching, and retrofit compatibility with your existing screw compressor capacity-control system, and can arrange genuine manufacturer support for every unit supplied.

Browse the full HB Products range or see more Encoders products supplied by Seven Star LLC in Oman and the GCC.