KRAL hermetically sealed pump with magnetic coupling, ATEX

A pump with a magnetic coupling is a design in which torque is transmitted from the motor to the impellers via a magnetic field, without a shaft passing through the casing. There is no mechanical seal, and therefore no point through which the fluid can escape. KRAL offers magnetic drive pumps for the K, L, C, F and W series, as well as for single and twin pump stations.

How does a magnetic coupling work, and why is there no leakage?

The outer rotor, with permanent magnets, is mounted on the motor shaft, whilst the inner rotor is mounted on the pump shaft. Between them is a sleeve made of non-magnetic stainless steel, which hermetically seals the flow path. The magnetic field passes through the sleeve, torque is transmitted, and the fluid remains sealed inside.

There are three practical implications. No mechanical seal means no more of the most common cause of unscheduled downtime. No contact between the rotors means no friction or wear in this assembly. No air can reach the product, so substances that oxidise or crystallise when exposed to oxygen retain their properties.

The screw pair itself operates in the same way as in the standard version — how a screw pair works.

For which KRAL series is the version with a magnetic clutch available?

The series	Models with a magnetic clutch
KRAL K Series	KF, KV, KFT
KRAL L Series	LFT, LVI, LVT, LFI
KRAL C Series	CGF, CG, CL
KRAL F Series	standard magnetic clutch
KRAL W Series	magnetic clutch (optional)
EK / EL stations	EKL/EKS 11–14, ELL/ELS 11–14
Twin DKC / DLC / DS-L stations	DKC, DLC, DS1, DS3, DS4, DL2, DL3, DL4

Technical specifications by series

The operating limits for models with a magnetic coupling are determined by the basic series, not by the coupling itself. Consequently, there is no single table covering all series — the data below is taken from the manufacturer’s documentation, with the source cited.

The series	Capacity	Pressure	Temperature	Viscosity	Source
K	5–668 l/min	16 bar	up to 300 °C	2–10,000 mm²/s	the table on the ‘with magnetic clutch’ page
L	not specified separately	not listed separately	not specified separately	not specified separately	The page lists only the models
C (CG)	15–3,550 l/min	up to 40 bar with a relief valve; up to 100 bar with a steel casing	180 °C standard coupling · 250 °C high-temperature coupling	3–7,000 mm²/s	CG manufacturer’s instructions
F	25–180 l/min	120 bar	−40…+300 °C	0.2–500 mm²/s	F series page
W	15–118 litres per minute	120 bar	up to 300 °C	1–100,000 mm²/s	W series page

Materials according to the manufacturer: housing — high-strength EN-GJS-400 cast iron, steel or aluminium; screws — nitrided steel; coupling sleeve — non-magnetic stainless steel. In the F series, the wetted parts are made of stainless steel.

K-series size range with magnetic coupling

Size	Qth flow rate (1450 min⁻¹, 0 bar)	Pressure	Inlet pressure	Frequency: 50 Hz	60 Hz
5-42	5–43 l/min	16 bar	16 bar	2,900 rpm	up to 3,500 min⁻¹
55-118	59–119 litres per minute	16 bar	16 bar	2,900 rpm	up to 3,500 min⁻¹
160-275	166–282 l/min	16 bar	16 bar	2,900 rpm	up to 3,500 min⁻¹
370-450	368–448 litres per minute	16 bar	16 bar	2,900 rpm	up to 3,500 min⁻¹
550-660	543–668 litres per minute	16 bar	16 bar	1,450 rpm	up to 1,750 min⁻¹

Up to what temperature does a magnetic coupling pump operate?

The answer depends on the design of the coupling, and the manufacturer’s documentation specifies different limits.

When selecting a coupling for a specific operating temperature, the specification must be agreed with the manufacturer on a case-by-case basis: the choice between the standard and high-temperature versions determines both the price and the lead times.

Certificates and explosion protection

Classification societies: ABS, BV, CCS, DNV, GL, LRS, MRS, NK, RINA.
Explosion protection: ATEX II 2 GD b/c, Group II, Category 2.
The CG manufacturer’s instructions refer to Directives 2006/42/EC, 2014/68/EU, 2014/30/EU, 2014/35/EU and 2014/34/EU.

The specific set of certificates depends on the series and variant and is confirmed upon ordering.

Where are magnetic coupling pumps used?

Selection and service from Steiner Ukraine

The specification of a magnetic coupling is selected based on the sealing requirements: first, it is determined whether any leakage is permissible and whether ATEX compliance is required, and only then is the basic series selected according to flow rate, pressure and viscosity. The operating temperature determines the type of coupling – standard or high-temperature. We coordinate the specification with the manufacturer, supply the unit fully assembled and ensure service and spare parts. Steiner Ukraine has been operating in the industrial equipment market since 2006.